Understanding what kPa is for tuning

[Steve Cole]

Since it seems some would like to believe that tuning requires things to be done in TPS versus a kPa measurement I think people need to learn and understand what kPa measurement really is. Who out there understands what kPa is and how it's measured?

[glens]

(k)Pa is an SI unit of pressure measurement.  It's usually measured with a pressure transducer.

[Tsani]

As I understanding it on my bike, it is a derived reading using various sensors like the Map, CKP, Tp and possibly the ET and IAT sensors. Not sure if the VSS is involved. Used help set fuel requirements at certain rpms for the derived value.

[Steve Cole]

It is a measure of absolute pressure and it does not matter where you are it will give a reading of what the absolute pressure at that point in time. It is from a MAP sensor on a HD motor cycle that is placed in the intake manifold after the throttle blade.

Now with that understanding what is the difference in say 50 kPa manifold pressure if the throttle blade is 1/2 open, 3/4 open or WOT?

[Tsani]

Engine is working harder at 1/2 compared to 3/4 or WOT to develop the at pressue or vacuum and require more fuel compared to less at a higher opening, but wouldn't RPM play into it as well? I don't think it's linear either, more like a bell curve function.

[Tsani]

Lets just go with a curve. Definately not linear.

[Tsani]

And since we are talking about it, excuse my ignorance on the subject. But it's my understanding that the Map sensor doesn't directly the pressure in the manifold on a Harley, that there is another type of sensor in use on cars that do that or very similar job. Or am I just wrongly informed? EFI is new to me so I am going to enjoy this.

[Steve Cole]

All the MAP does is measure absolute pressure, nothing more or nothing less. MAP stands for Manifold Absolute Pressure.  It has no idea nor does it care what position the throttle is in, it just reads the pressure that is in the manifold at any given time. The units that it gives to represent that pressure in this case are kPa.

So again, I ask what is the difference in say 50 kPa manifold pressure if the throttle blade is 1/2 open, 3/4 open or WOT?

[Tsani]

As far as the pressure is concern, nothing. It's pressure.

[glens]

So again, I ask what is the difference in say 50 kPa manifold pressure if the throttle blade is 1/2 open, 3/4 open or WOT?

In this case the pressure outside the manifold is nominally twice that of the pressure inside.  The outside pressure will be aggressively trying to fill the void and hopefully will only be able to do so through the throttle plate opening.  If the engine is pulling half the atmospheric pressure from behind a 1/2-open throttle plate, it will be moving less air than when it's pulling that same pressure at 3/4 throttle, which will be allowing the pressure to (try to) equalize at a more rapid rate than 1/2 throttle will.

But I think what you're getting at is that the MAP sensor doesn't know or care how much air is moving through the manifold, what speed the engine is turning, what position the throttle plate is, or even whether/where the sensor's mounted.  The sensor itself is merely seeing and reporting the absolute pressure at it's location.

[mayor]

So again, I ask what is the difference in say 50 kPa manifold pressure if the throttle blade is 1/2 open, 3/4 open or WOT?

it's highly unlikely that you will be able to be at 50 kPa in all those throttle positions...in fact,  I doubt that keeping the map to 50 kPa at 3/4 or wide open could even happen unless you found a really really steep hill to ride down. 

From what I've seen, steady state Map is very coralate ble to throttle position...at least with in a reasonable range.  I just don't think that range is +/-  50 kPa. 

[saddle tramp]

All the MAP does is measure absolute pressure, nothing more or nothing less. MAP stands for Manifold Absolute Pressure.  It has no idea nor does it care what position the throttle is in, it just reads the pressure that is in the manifold at any given time. The units that it gives to represent that pressure in this case are kPa.

So again, I ask what is the difference in say 50 kPa manifold pressure if the throttle blade is 1/2 open, 3/4 open or WOT?

the KPA would be lower at the larger (wfo) opening than at the 1/2 open throttle position. I'm still trying to learn this stuff so I could be wrong, but I think thats how it works ? Am I close Steve ?

[Steve Cole]

The correct answer is that it is just PRESSURE and there is no difference in the pressure regardless of where the throttle blade position is as long as the reading is fixed at 50 kPa. So once you know the manifold pressure it no longer matters where the throttle blade is. I'm not looking for what can and cannot happen here, but yet to get people to understand the basics of how and why first, then we can move from there. There is just to many of you that do not seem to understand/know the basics.

Question #2

If you increase the load on the engine at a fixed throttle opening what do you think the MAP reading will be provided you hold the RPM fixed?

[FSG]

As far as the pressure is concern, nothing. It's pressure.

  but it's a loaded question

[mayor]

Question #2

If you increase the load on the engine at a fixed throttle opening what do you think the MAP reading will be provided you hold the RPM fixed?

if the load increases, the Map increases.

[rbabos]

The correct answer is that it is just PRESSURE and there is no difference in the pressure regardless of where the throttle blade position is as long as the reading is fixed at 50 kPa. So once you know the manifold pressure it no longer matters where the throttle blade is. I'm not looking for what can and cannot happen here, but yet to get people to understand the basics of how and why first, then we can move from there. There is just to many of you that do not seem to understand/know the basics.

Question #2

If you increase the load on the engine at a fixed throttle opening what do you think the MAP reading will be provided you hold the RPM fixed?

You can't keep a fixed rpm without opening the throttle if the load is increased. Once the load is applied and throttle opened to keep the fixed rpm the kpa reading will increase due to less engine vacume. The higher the kpa reading the less vacume inside the manifold. 0 vacume would be 100kpa at sea level or whatever your air pressure is at elevation or atmospheric highs and lows would be in a given day.
Ron

[glens]

He didn't say a fixed engine speed.  He said fixed throttle position.  The MAP goes up because the engine speed decreases with more load, thus giving more time for the pressure outside the manifold to get 'round the throttle plate and better-equalize the differential pressure.

[FSG]

Seems to me he did. Read the question again, taking note of the  provided you hold the RPM fixed.

[rbabos]

He didn't say a fixed engine speed.  He said fixed throttle position.  The MAP goes up because the engine speed decreases with more load, thus giving more time for the pressure outside the manifold to get 'round the throttle plate and better-equalize the differential pressure.

The way I read it he said both at the same time in the same load condition. No wonder it's so hard to figure out stuff.
Ron

[glens]

Damn!  How'd I miss that?  Well, then, it's an unanswerable question, because if you increase the load you have to either lose engine speed or increase throttle position.  MAP is the man behind the curtain there.

[mayor]

interesting, was thinking the same...but didn't think he meant to word it the way he did.  I would suspect that Map would increase just before rpm would drop though, since the throttle position is fixed. 

[rbabos]

Damn!  How'd I miss that?  Well, then, it's an unanswerable question, because if you increase the load you have to either lose engine speed or increase throttle position.  MAP is the man behind the curtain there.

I thought it was a test to see if we could read accurately. A form of a trick question. I'd hope so or I'll be doomed following this directions.
Ron

[Tsani]

Question #2

If you increase the load on the engine at a fixed throttle opening what do you think the MAP reading will be provided you hold the RPM fixed?

If it was possible to acheive this, then the map would not change at all is the way I see it.  However, I do not see how this can be done in a real world engine. Kind of how we were taught stuff in the mil. Theory is theroy, real world is another matter. I think the point here is map is map no matter what. It is just simply a reading of pressure or lack of.

[hotroadking]

sure you can, going from a flat road to a hill, why couldn't you hold the  throttle steady and rpm steady, you'll just slow down
like using the old throttle lock, the engine speed (rpm) won't change but the vehicle speed reduces.  it's why cruise advances the throttle
to maintain speed, question wasn't how do you maintain speed when load increases - ie more throttle.

[Steve Cole]

BINGO, MAYOR is a winner! The MAP will increase as soon as the load changes when throttle position is held constant and RPM stays fixed.

So MAP or kPa is much quicker responding to load changes than throttle position and is much more accurate! This is why it is used in near ALL automotive applications. Take a look at any automotive application and you will find a MAP sensor to measure the kPa along with any other system. The reason a MAP is used is due to accuracy and response at low engine speed in a MAF application.

So now that we understand how the MAP shows what is happening in the manifold let's move on.

Question #3

What is the difference if the manifold measures 100 kPa at 1/2 throttle or 100 kPa at WOT in sea level conditions? Sea Level conditions means a Baro reading of 100 kPa for this case.

[rbabos]

Load is higher at the 1/2 throttle 100 kpa.
Ron

[Tsani]

Well, on question 2, I was leaning towards higher, but just couldn't get around the idea of a fixed rpm-throttle- dealie with a load change...till hotrod brought up a real worls situation. And BTW, MAF is the other sensor I was thinking about.

As far as Q3,
No difference, 100 is 100 is 100 if all we are talking about is pressure. But if we are now including other things, I am with rbabos on this one.

[Scotty]

Question #3

What is the difference if the manifold measures 100 kPa at 1/2 throttle or 100 kPa at WOT in sea level conditions? Sea Level conditions means a Baro reading of 100 kPa for this case.

Difference in what? .................... 100 kpa is 100 kpa  no matter what the throttle position

[Jeffd]

i am voting with rabos  in order to be a 100kpa at 1/2 throttle must be under high load.

[thumpn]

Absolutely nothing as long as it reads 100% it doesent matter whether the throttle blade is at 50% or 100% the manifold is at atmospheric pressue

[hotroadking]

Or the engine isn't running at all 100 at sea level presuming that is the pressure
of the atmosphere at sea level and at 1/2 and wot would nothing be happening ie
the pistons are not moving and valves not opening changing pressure.


Isn't the MAP actually measuring the drop in pressure?  Can Pressure increase
above the max pressure out side the engine in the atmosphere ie if it's 100 KPa outside
the engine, wouldn't that be the max you could have?

[Steve Cole]

Tsani has got it! When you measure Absolute pressure it is what it is. If it's 50 kPa at 25 % throttle or 50 kPa at 50% throttle it doesn't matter, just the same as if it's 100 kPa at 20% throttle or 100 kPa at 100% throttle the pressure is what it is.

Question #4

So if your tuning a VE table @ 1500 RPM that is in RPM and TPS, what is the difference going to be if you reach 100 kPa at 40% TPS all the way out to 100% TPS? Again in sea level conditions

[hotroadking]

Apparently - None..

[thumpn]

I would say nothing would change the motor is all ready atmopheric so the is no inprovmemnt. The motor isn't capable of of any more. I think

[glens]

BINGO, MAYOR is a winner! The MAP will increase as soon as the load changes when throttle position is held constant and RPM stays fixed.

I'd like to see a load change where both the throttle blade and engine speed remain constant.  I don't think it can be done.  If you've got a load change, in order to maintain RPM the throttle is going to have to move, and in order to maintain throttle the RPM is going to change.

Question #3

What is the difference if the manifold measures 100 kPa at 1/2 throttle or 100 kPa at WOT in sea level conditions? Sea Level conditions means a Baro reading of 100 kPa for this case.

No difference.  The engine is taking as much air as it can and it ain't fast enough to overcome what the atmosphere can push through the throttle plate.  Now if the engine speed is different between the two conditions that's another matter in terms of what'll become fuel requirements.  If the engine's the same speed both ways, no fuel difference.

[mayor]

Question #4

So if your tuning a VE table @ 1500 RPM that is in RPM and TPS, what is the difference going to be if you reach 100 kPa at 40% TPS all the way out to 100% TPS? Again in sea level conditions

so, if a bike reaches 100 kpa at 1700 rpm at say 28% throttle...we can assume that the pressure can not go up, but is the amount of air traveling through the heads linear regardless of the increased throttle? what if your bike is capable of reaching greater than 100 kPa, due to increased cylinder fill abilities? 

[glens]

Question #4

So if your tuning a VE table @ 1500 RPM that is in RPM and TPS, what is the difference going to be if you reach 100 kPa at 40% TPS all the way out to 100% TPS? Again in sea level conditions

No difference.  All the table cells to the right of 40% are redundant in this particular case.

[Steve Cole]

Question #4

So if your tuning a VE table @ 1500 RPM that is in RPM and TPS, what is the difference going to be if you reach 100 kPa at 40% TPS all the way out to 100% TPS? Again in sea level conditions

so, if a bike reaches 100 kpa at 1700 rpm at say 28% throttle...we can assume that the pressure can not go up, but is the amount of air traveling through the heads linear regardless of the increased throttle? what if your bike is capable of reaching greater than 100 kPa, due to increased cylinder fill abilities?

There is always if's, and's or butt's but you need to first understand the basics. So I'm working in theory first and will get to real world after you can get your head around the basics. Now as far as getting better than 100 kPa it isn't going to happen as the head/port cannot push the air in. All it can do is restrict it less!

[glens]

what if your bike is capable of reaching greater than 100 kPa, due to increased cylinder fill abilities?

How are your phenomenal cylinder fill abilities ever going to be able to increase the air pressure outside of the manifold?

[Tsani]

Question #4

So if your tuning a VE table @ 1500 RPM that is in RPM and TPS, what is the difference going to be if you reach 100 kPa at 40% TPS all the way out to 100% TPS? Again in sea level conditions
[/quote]

Well if the RPM is staying the same but the throttle plate is changing, it would seem to me that there will lees restriction and the pressure would decrease.

[mayor]

what if your bike is capable of reaching greater than 100 kPa, due to increased cylinder fill abilities?

How are your phenomenal cylinder fill abilities ever going to be able to increase the air pressure outside of the manifold?

simple Glen, not all bikes are stock.    How do you think that one build of a certain cubic inch might out produce another by 15 ft-lbs?  that's all based on cylinder fill...it literally is like putting 6 lb's of crap in a 5 lb bag.  I have seen bikes pull 107 kPa, and I'm sure that's not a record...and I'm at 1,000 asl.   

[Steve Cole]

Question #4

So if your tuning a VE table @ 1500 RPM that is in RPM and TPS, what is the difference going to be if you reach 100 kPa at 40% TPS all the way out to 100% TPS? Again in sea level conditions

Well if the RPM is staying the same but the throttle plate is changing, it would seem to me that there will lees restriction and the pressure would decrease.

One you reach the point where the manifold reach's atmospheric pressure there is no more air entering the cylinder unless there is something pushing it in like a supercharger or turbo charger. So as you've learned 100 kPa is 100 kPa and your not getting any more regardless if the throttle is at 40% or 100%!

[Tsani]

Mayor, that is milli bars correct?
The other day we were at 30 inches mercury which is 102 kPa which is 1020 mb. I am at 68 ft asl.

[Tsani]

One you reach the point where the manifold reach's atmospheric pressure there is no more air entering the cylinder unless there is something pushing it in like a supercharger or turbo charger. So as you've learned 100 kPa is 100 kPa and your not getting any more regardless if the throttle is at 40% or 100%!

In theory, correct?

[Steve Cole]

As the weather changes your going to have number changes so that is why for this discussion I've called out sea level as 100 kPa. Here at the shop we see 102 - 103 kPa most of the winter months when it cold out, but the principal is the same. Whatever the Baro reading is, that is the best your going to get.

[mayor]

on reply #19 on this thread is a screen shot showing 33 inHG:
http://harleytechtalk.com/htt/index.php/topic,45734.0.html

so, how would the 100 kPa limit work with a bike that hits over 110 kPa?     I guess we could assume that a hi pressure area was around during this run.   

[Tsani]

I got cha on that Steve. Max is max unless aided. However the opposite is not true and comes into play in an engine. Carburators rely on it. So I assume so do EFI systems in a manner of speaking. But I will wait. As on of my old instructors used to say"For all you guys with time in the field, shut up, I have to teach this a certain way!"

[akjeff]

Seems to me that if you have 100k/Pa(basically atmospheric ppressure) at 40% throttle, the only way you can maintain that same pressure at 100% throttle, is for the volume of air to increase? That being the engine increasing in RPM in order to move the increasing mass of air?

Jeff

[hotroadking]

so the MAP is really only measuring the decrease in potential pressure

[glens]

what if your bike is capable of reaching greater than 100 kPa, due to increased cylinder fill abilities?

How are your phenomenal cylinder fill abilities ever going to be able to increase the air pressure outside of the manifold?

simple Glen, not all bikes are stock.    How do you think that one build of a certain cubic inch might out produce another by 15 ft-lbs?  that's all based on cylinder fill...it literally is like putting 6 lb's of crap in a 5 lb bag.  I have seen bikes pull 107 kPa, and I'm sure that's not a record...and I'm at 1,000 asl.   

Don't listen to Jim.  I never said or implied that all bikes are stock.  He's the one that keeps trying to make it seem that's what I'm saying.

Okay, so do you believe that reading in the screenshot?  It's only for informational purposes as the TMax uses that sensor for nothing otherwise, right? 

The only way I can envision a good-cylinder-filling arrangement could possibly cause a MAP sensor to go above atmospheric pressure would be to get the column of air moving so fast, then slam the door shut on it at the intake valve.  The mass of air might still be moving into the intake, hit the dead end, and get packed in by the tail of the column.  This is theory only, but if the MAP sensor was polled at just the right time it might capture a smidgen above atmospheric.

Maybe a long-overlap cam with exhaust anomalies could slightly pressurize the manifold, too.

Neither of those possibilities are what I would consider to be beneficial to the engine's running characteristics, though.

[BVHOG]

I think I see where this is going and what your final point to be made is that at whatever throttle vs rpm cell that reaches 100 MAP then anything after that is redundant and should end up at the same VE, making V-tune accurate by interpolating the data out to the right (high map) areas of the tp vs rpm type tuning tables.
However, we have a definitive shape change and change of air flow in the intake tract at different throttle blade angles(alpha) which can affect the air velocity even at 100 MAP and can have a definite influence on how well fuel is atomized or as the case may be properly mixed within the combustion chamber and can result in requiring a different pulse width to the injectors to keep the emissions (exhaust gas, (02, NoX  CO etc) at the desired level for best power and/or cool running.  This is why interpolation of numbers for un-sampled areas works marginally at best.
As far as tuning using feedback from MAP for VE tables I feel it is the best thing that has happened to the Harley/Delphi system.
One more thing, it has always been stated that if the throttle blade is wide open then you should never see anything other than the absolute pressure that is outside the motor, but, if these engines are capable at high rpm due to inertia to have better than 100% true VE than how can that be?

[Steve Cole]

What or how that Tmax sensor is calibrated or what it may have been reading I do not know but the Physics of it is that you are only going to get very close to atmospheric pressure Unless you introduce something to force or push the air in. That is NOT going to happen on a HD intake tract, it's to short and too screwed up. The laws of Physics do apply no matter how much a few people want to believe they do not.

BVhog

There you go assuming and making up a story. How about we stick to how things work so people can learn the correct way instead of jumping in with your assumptions again and again. This thread is for people to learn and understand how things work!

[mayor]

Okay, so do you believe that reading in the screenshot?  It's only for informational purposes as the TMax uses that sensor for nothing otherwise, right? 

no  and yes.  it doesn't matter if the reading is right or not, because right or wrong it is being supplied to the ecm (and the ecm is never wrong, at least that is what the ecm thinks).  In the TMax's case, it does very little to change anything..it's mostly a reference point.  I have never been able to pull that high on my TTS bike, and that's likely due to not having enough actual atmospheric pressure.     I have seen momentary times at 102-103 kPa on my tts bike though.  My guess is the Delphi system has a much better grasp on how to report Map, since it uses that reading.   

The only way I can envision a good-cylinder-filling arrangement could possibly cause a MAP sensor to go above atmospheric pressure would be to get the column of air moving so fast, then slam the door shut on it at the intake valve.  The mass of air might still be moving into the intake, hit the dead end, and get packed in by the tail of the column.  This is theory only, but if the MAP sensor was polled at just the right time it might capture a smidgen above atmospheric.

Maybe a long-overlap cam with exhaust anomalies could slightly pressurize the manifold, too.

Neither of those possibilities are what I would consider to be beneficial to the engine's running characteristics, though.

I don't disagree, but where the build it self matters is how well it uses all available atmospheric pressure.  I have seen where I have been able to reach full Map on my little mouse engine bike (96" 48h's), and as the speed goes up in the higher gear the bike starts loosing map (very high actual load on the engine).  How I would explain this is the more efficient the build is in delivery air, the more likely the engine can use all the available pressure it has.  I would think that air cleaners alone would have an affect on an engines potential for reaching full map.   

[BVHOG]

What or how that Tmax sensor is calibrated or what it may have been reading I do not know but the Physics of it is that you are only going to get very close to atmospheric pressure Unless you introduce something to force or push the air in. That is NOT going to happen on a HD intake tract, it's to short and too screwed up. The laws of Physics do apply no matter how much a few people want to believe they do not.

BVhog

There you go assuming and making up a story. How about we stick to how things work so people can learn the correct way instead of jumping in with your assumptions again and again. This thread is for people to learn and understand how things work!

No assumptions, just observations while tuning.  One more thing that is interesting is that during a wot dyno run on a build that have a throttle body  or a/c that is too small you can watch the timing trace go back a row from 100 KPA toward the end (high rpm)of a run.  Now consider what a shop like GMR that works at high altitude must see during dyno tuning never reaching 100 kpa but knowing that once the bike travels back closer to sea level it will be running in areas he has no chance of actually seeing on the dyno.
Sorry Steve C, hope I didn't derail you too bad, carry on please.

[lonewolf]

What I like about the maps where the ve tables are kpa/rpm is the lower the rpm the more break points horizontally. If tuning at 2500 rpm and I reach 100 kpa by 30% throttle I only have 8 break points. Kpa based I have at least 12.

[Steve Cole]

So now we have two different way that HD has the VE tables to be adjusted. One uses TPS and RPM the other MAP and RPM.

Question #5

Why would one or the other be better?

[mayor]

Question #5

Why would one or the other be better?

I believe the answer can be found in reply#24.   

[Tsani]

I don;t see the answer in #24 at all. This question about VE, which is shown as a percentage of? , I say cylinder fill. And the varibles ther are RPM and TP(s) which are mechanical factors. The Map is what it is. So VE is a mechanical measurement or setting in my opinion. VE is about a pump and it's efficiency to fill with it's charge. Yes, Map plays a function, but for the most part it is being treated it seems as a non varying factor to fill performance in this example.

Or am I looking at this all wrong?

[saddle tramp]

The MAP is tied into the timing, so when the map sees a change it will adjust your timing correctly, more load less timing, less load more timing.

[Jeffd]

ditto on reply #24

[mayor]

Or am I looking at this all wrong?

I think you may be confused of the question, either that or I am.     I think what Steve is asking is which way of populating the ve tables is more accurate, dividing them by throttle position of dividing them by MAP reading.  If that is indeed the question, the answer is in reply #24. 

[Tsani]

Or am I looking at this all wrong?

I think you may be confused of the question, either that or I am.     I think what Steve is asking is which way of populating the ve tables is more accurate, dividing them by throttle position of dividing them by MAP reading.  If that is indeed the question, the answer is in reply #24.

Well, where in TTS is the VE table using a MAP value? On one axis we have RPM, on the other, TPS, the cells are Volumetric Efficiency, i.e. air fill or how well they can be filled which along with the MAP will be used else where to determine fuel requirements. Using RPM along with throttle is a lot easier to predict fill than bring in a varible like MAP which can vary according to altitude amongst other things.

[Coyote]

Or am I looking at this all wrong?

I think you may be confused of the question, either that or I am.     I think what Steve is asking is which way of populating the ve tables is more accurate, dividing them by throttle position of dividing them by MAP reading.  If that is indeed the question, the answer is in reply #24.

Well, where in TTS is the VE table using a MAP value? On one axis we have RPM, on the other, TPS, the cells are Volumetric Efficiency, i.e. air fill or how well they can be filled which along with the MAP will be used else where to determine fuel requirements. Using RPM along with throttle is a lot easier to predict fill than bring in a varible like MAP which can vary according to altitude amongst other things.

Try an MT8 file for late model bike.

Question #5

Why would one or the other be better?

I believe the answer can be found in reply#24.   

So this is the reason for the change, faster.

[Tsani]

ok.

[mayor]

Tsani, the MAP based ve tables are in the lambda systems only.  The afr based systems still have ve tables based on throttle position (which is what your bike is).

[Tsani]

Thanks. I just looked at that. Which now means I am in trouble. What determines using Lambda?
The ECM? I am still struggling with my setup!

[glens]

So now we have two different way that HD has the VE tables to be adjusted. One uses TPS and RPM the other MAP and RPM.

Question #5

Why would one or the other be better?

They're both good for different reasons, though overall the MAP/RPM scheme makes better use of the tables, resulting in a greater number of useful/meaningful cells, especially in the lower RPM range.

It's a shame it has to be "one or the other".

At lower RPM the MAP-based table covers a greater number of nuances while at higher RPM/load the TPS-based table gets the nod in that respect.

[glens]

What determines using Lambda?  The ECM?

The low-level programming in the ECM determines which is used.  The breakpoint is pretty much the location and type of O2 sensors you have, with the older, larger, unheated sensors going with the TPS/RPM VE tables and the newer, smaller, heated sensors going with the MAP/RPM VE tables.  I believe it's only the 009 and 044 calibrations which have MAP-based VEs.

[Tsani]

So it would seem.
So for the sake of simplicity, maybe we should pick an example cal for this discussion.
That being said, function of the VE table is still the same, pumping effects, just different
methods of measurement.

[Steve Cole]

What I am asking is with what you all understand now from this discussion of MAP (kPa). Why you would think one way or the other way is better or worse. Another words is one better or worse than the other?

There is a reason Spark has always been done with MAP and if you can understand why it will help you with the above answers. None of this is met as a trick question, I just want you all to learn and think things out on your own once you understand the basics.

[TXP]

I think what makes this so challenging to grasp is our system is a hybridized alpha/n speed density system. It uses many inputs to arrive at the calculated pulse width. CKP/TP/MAP etc. The real interesting thing is the ECM reads the Global MAP signal and applies different correction factors for Front & Rear cyls. The actual commanded pulse width is determined not only by commanded afr or lamda and the corresponding closest interpolated ve tables, but also the programmed correction factor for each cyl. As well as several other underlying programs such as AE, DE, PE, etc. So arriving at set in stone perfect tables doesn't seem very probable as you are always shooting at a moving target which is constantly changing direction and speed.  The scratch is there are so many things going on in the program which we can not and will likely never be able to see in the field. And from what I see in the field, much of what we already have available and can see is not used. So, I wonder, how much more is needed if much of what we now have goes unused by many if not most? Just wondering?

[glens]

Okay, so do you believe that reading in the screenshot?  It's only for informational purposes as the TMax uses that sensor for nothing otherwise, right? 

no  and yes.  it doesn't matter if the reading is right or not, because right or wrong it is being supplied to the ecm (and the ecm is never wrong, at least that is what the ecm thinks).  In the TMax's case, it does very little to change anything..it's mostly a reference point.  I have never been able to pull that high on my TTS bike, and that's likely due to not having enough actual atmospheric pressure.     I have seen momentary times at 102-103 kPa on my tts bike though.  My guess is the Delphi system has a much better grasp on how to report Map, since it uses that reading.   

I believe the TMax gets a barometer reading from the MAP at startup.  It would need to know that information for its fuel calculations.  But since it doesn't (likely) use it any other time, it's not going to be careful/critical of when it polls the sensor for its display/informational purposes.  It does matter when the sensor is polled, however, since the manifold pressure at the sensor's location is not a steady-state condition, hence the cam-tune settings in the .mt8 files.

The only way I can envision a good-cylinder-filling arrangement could possibly cause a MAP sensor to go above atmospheric pressure would be to get the column of air moving so fast, then slam the door shut on it at the intake valve.  The mass of air might still be moving into the intake, hit the dead end, and get packed in by the tail of the column.  This is theory only, but if the MAP sensor was polled at just the right time it might capture a smidgen above atmospheric.

Maybe a long-overlap cam with exhaust anomalies could slightly pressurize the manifold, too.

Neither of those possibilities are what I would consider to be beneficial to the engine's running characteristics, though.

I don't disagree, but where the build it self matters is how well it uses all available atmospheric pressure.  I have seen where I have been able to reach full Map on my little mouse engine bike (96" 48h's), and as the speed goes up in the higher gear the bike starts loosing map (very high actual load on the engine).  How I would explain this is the more efficient the build is in delivery air, the more likely the engine can use all the available pressure it has.  I would think that air cleaners alone would have an affect on an engines potential for reaching full map.

If you look at a number of TTS calibrations you'll see that the VEs decrease a little at the far right.  It's just a matter of the way cams and the other stuff work together.  They cannot be "right" for every possible engine speed.  If you want to be able to carry full MAP all the way out, you're going to have to give up some of that capability on the other end of the spectrum, and vice versa.

[Tsani]

The map along with other varibles is going to determine the fuel charge.
Some of the other varibles such as RPM and TPS will have some effect on
MAP, but depending on where you are at as far as engine speed, etc, Map
is MAP and that is why is used, it's simple. Less to calculate. But you really
can't one is better than the other. You can say one is better is a certain area
or range than the other. So it would depend on how you use the machine.
If you are always spending your time going balls to the walls, then the
RPM/TPS based VE setup may be best for you. But most riders spend their
time below 4000 RPM, heck 3500 RPM, and The MAP based table would be
as accurate if not more realistic. This will effect the timing because the
fuel charge needs a certain amount of time to burn. MAP affects the amount
of fuel delivery and thus Spark Timing.

I think.

[akjeff]

What I am asking is with what you all understand now from this discussion of MAP (kPa). Why you would think one way or the other way is better or worse. Another words is one better or worse than the other?

There is a reason Spark has always been done with MAP and if you can understand why it will help you with the above answers. None of this is met as a trick question, I just want you all to learn and think things out on your own once you understand the basics.

My WAG is that MAPxRPM based is better, as it can take into account the load the engine is under, at a particular time. Whereas TPSxRPM has no idea if you're going uphill or down. All it knows is the TPS is at X % and the engine is turning at Y RPM?

Jeff

[Steve Cole]

While there is plenty of things going on I believe you first have to understand the basics. Once you understand the pieces of the system then the rest of it is not to hard to understand. What I think everyone knows and understands turns out not to be the case and what I'm trying to do now is get you all to understand the pieces of the system first. Then we can move on to how they work together.

A HD is is not your normal engine but the EFI fuel system is the same and works the same as most automotive systems did back in the 90's. Absolute pressure is absolute pressure and there is not much any of us can do about it. The pressure does vary based on where your located but for the sake of this you need to just understand what it is and what can effect it.

[akjeff]

Would the MAPxRPM based table also better compensate for changes in altitude and/or just plain variations in day to day barometric pressure? It wouldn't care if you were in Death Valley or on Pikes Peak.

Jeff

[BVHOG]

The simple answer to why the MAP based VE system is superior would be a simple test,  Set the dyno brake at 2500 rpm (example only) now put the bike in 3rd gear and go through the table stopping at each throttle postion, if you can ,note the MAP along the way at each cell, now do the test in 4th gear and while the throttle postion/rpm  stopping points stay the same for the test the MAP readings are much different at each stop.

[Steve Cole]

Would the MAPxRPM based table also better compensate for changes in altitude and/or just plain variations in day to day barometric pressure? It wouldn't care if you were in Death Valley or on Pikes Peak.

Jeff

This is a very good answer and why the automotive manufactures use MAP based readings. MAP is the first thing to respond when ANY load change happens to the engine. This is also why Spark has always been done based on MAP readings. You can see a real change long before a rider may twist the throttle! By using Absolute pressure we now do not have to wonder what area your in, what the air is doing or not doing or what the engine is doing. If gives us much faster control over what is going on, all good things when it comes to tuning.

So when you go back to question # 2,3 and 4 does it all start to make some sense to you all now?

[choseneasy]

Yup, makes perfect sense to me. Good thread!

[Steve Cole]

Now that you understand that MAP is just a reading of Absolute pressure and that once you reach an equal Absolute pressure in the intake to outside (Baro) NO more air is going to enter the engine. This is the way that it works and there is nothing you nor I can do to change than short of installing a forced induction unit.

With this in mind we can look back to another way HD has done the VE's and that is to base it from TPS and RPM. I think most everyone understands what these are and it is pretty easy to now compare the two methods of doing it.

Question #6

Why use TPS instead of MAP for VE's?

[BVHOG]

Now that you understand that MAP is just a reading of Absolute pressure and that once you reach an equal Absolute pressure in the intake to outside (Baro) NO more air is going to enter the engine. This is the way that it works and there is nothing you nor I can do to change than short of installing a forced induction unit.

With this in mind we can look back to another way HD has done the VE's and that is to base it from TPS and RPM. I think most everyone understands what these are and it is pretty easy to now compare the two methods of doing it.

Question #6

Why use TPS instead of MAP for VE's?

The biggest reason that tp vs rpm would be used is due to intake tract reversion on the uneven firing v twin and the difficulty of getting a steady map reading at lower rpm operation. Some systems even advertise the advantage of tp vs rpm for timing tables with highly modified motors.

[glens]

That problem can be sorted out with careful timing of the MAP sensor polling.

I touched on the answer to this question #6 in my earlier response to question #5. 

[Steve Cole]

TPS readings are a poor way to predict how much air is entering the cylinder for any given case.
TPS readings typically respond after the airflow has already changed in the engine.
TPS will give you different readings for the SAME airflow entering the engine.

The engine needs the fuel air mixture to be correct................right?

[BVHOG]

Makes sense but KPA will also give you the same reading for different amounts of air, consider a wot run on a dyno, it will go to 100 kpa (sea level) and stay there as the bike runs up the rpm scale  progressively taking in more air along the way.

[hrdtail78]

I think that's is why it's rpm/ map based instead of just map. Also we have seen higher rpm's drop a little kpa with keeping the throttle at 100%.

[glens]

So now we have two different way that HD has the VE tables to be adjusted. One uses TPS and RPM the other MAP and RPM.

Question #5

Why would one or the other be better?

They're both good for different reasons, though overall the MAP/RPM scheme makes better use of the tables, resulting in a greater number of useful/meaningful cells, especially in the lower RPM range.

It's a shame it has to be "one or the other".

At lower RPM the MAP-based table covers a greater number of nuances while at higher RPM/load the TPS-based table gets the nod in that respect.

Like I'd said...

[Steve Cole]

Makes sense but KPA will also give you the same reading for different amounts of air, consider a wot run on a dyno, it will go to 100 kpa (sea level) and stay there as the bike runs up the rpm scale  progressively taking in more air along the way.

I think that's is why it's rpm/ map based instead of just map. Also we have seen higher rpm's drop a little kpa with keeping the throttle at 100%.

Exactly, Steve did bring up some excellent points however in regards to MAP specifically this is a limitation of a speed density system as it uses modeled airflow and we cannot rely soley on MAP as it becomes much more difficult to accurately model airflow once you effectively reach max Kpa. This is why most Jap 4 cyl bikes are Alpha N based (even though most are speed density by definition) as they can easily reach max Kpa at 60% TPS and only half way to redline, they use the MAP sensor for low speed cruise only. Ducati for example uses full Alpha-N systems: 160Hp off the showroom floor with no MAP sensor. This is also the reason why most modern automotive control systems use Mass Air (measured airflow) systems.

There is NO modeling needed when you measure MAP and RPM in a Speed Density system. It is straight physics and you have your answer. As RPM increases that provides the missing part of what MAP does not give you............. end of story.

Let's talk about what is going on as you go up in RPM and you can see why. Each cycle of the engine air enters into the cylinder and that is what needs to be measured and fuel provided for. As RPM goes up NO more air enters the cylinder per cycle but the amount of cycles goes up, in a fixed amount of time. This is what RPM (revolutions per minute) tells the ECM! This along with the MAP reading takes care of it just fine. Doesn't matter if your at 3000 RPM or 15,000 RPM it works just fine with no guessing or modeling involved.

Alpha-N is a cheaper style system and that is the main reason that a few manufactures and I mean very few still use it and it will NOT provide near the accuracy of a Speed Density system. MAF systems are the most accurate way to measure but they also have some problems that must be overcome and guess how they do it, they use a MAP sensor to tell them what is going on!

A MAF system needs to be sized to measure the total amount of airflow the engine can ever use or it is going to choke the intake of airflow. So depending on how much air you need to measure the meter gets fairly large. Now when you get a large meter to measure the high end airflow it does not measure low flow very well, if at all. So a MAP is used to handle the low end up until the MAF reading is stable and it takes over from there. Another issue with the MAF sensor is that it cannot tell the direction of the airflow, so in the case of a HD the air would be pulled in and measure but the same air would then get measure a second time when it gets pushed back out of the intake. If you look at a carb'ed bike this was called stand off and it still occurs on an EFI HD as well. So, since it cannot tell, it doubles the airflow during stand off and would make the engine run way too rich. (A MAP sensor see the absolute pressure rise when this occurs and cuts back the fuel delivery.) This occurs on all engines but is handled with long intake track length and a large plenum in the intake track. None of which is possible on a motorcycle application let alone a HD intake system. This is just why a MAF is NOT used on a HD or most any other short intake track engine applications.

As I stated back in post #12 people need to learn and understand the basics and these are just a perfect example of people that donot understand the basics. Once you do the rest of it will come along much easier.

[TXP]

Just wondering Steve, as far as I know the Lambda cals are only available with the DBW bikes/Freebird ECM. Is there a reason its not been made available on the cable bikes? Even the CAN bus Softail/Dyna stuff is still rpm/tp based in the VE section and still has the CLB tables. At least thats what I've seen so far on the SESPT version. Since the ECM is controlling the throttle inputs electronically at the throttle blade does that make a big difference in how the MAP is seen or applied or is it just the HD has chosen to handle it?

[Steve Cole]

The new 2012 CAN calibrations are still TPS based VE's and I do not know why. They switched most everything else in the code to be very similar to the 2010 and later Lambda based calibrations. There is no CLB's in these calibrations. 2011 Softail is a bastard year as the ECM's were new for them and it's a one year deal. They used the large O2 sensor just like the 2010 Softail but with the new CAN buss calibrations. You've got two sets of code basically one for the DBW CVO bike and the other for the cable bike version. The cable version still has CLB's but the CVO version did not. My only guess would be that two different groups of people at Delphi are writing the based code and each one is doing it the way they have in the past. After all it's the same engine being run with the same parts except for the throttle body. At that they have run the Electronic throttle body both ways.

Also the Dyna and Softail are in one group at HD OEM and the Touring bikes are in another group at HD OEM. So it could be that as well.

2007 - 2011 Cable throttle BT use TPS VE's
2008 - 2009 DBW bikes had TPS VE's.
2010 - 2012 DBW Lambda based and MAP based VE's
2012 Dyna and Softail use TPS VE's but with Lambda type tuning

[akjeff]

Would the MAPxRPM based table also better compensate for changes in altitude and/or just plain variations in day to day barometric pressure? It wouldn't care if you were in Death Valley or on Pikes Peak.

Jeff

This is a very good answer and why the automotive manufactures use MAP based readings. MAP is the first thing to respond when ANY load change happens to the engine. This is also why Spark has always been done based on MAP readings. You can see a real change long before a rider may twist the throttle! By using Absolute pressure we now do not have to wonder what area your in, what the air is doing or not doing or what the engine is doing. If gives us much faster control over what is going on, all good things when it comes to tuning.

So when you go back to question # 2,3 and 4 does it all start to make some sense to you all now?

It is beginning to make sense. Also wanted to thank you for taking the time to do this kinda stuff! On my Evo bagger, all I did was swap jets in my S&S carb till the plugs looked good, and the bike ran and sounded "right", and that was it. Now, with this fuel injected TC, I think about this "Potty mouth" all the time! Very interesting stuff!

Jeff

[BVHOG]

Yes the events happen more often but as you get higher in rpm in areas that run above ACTUAL 100% VE (not cal VE) you WILL be taking more air in per event due to inertia.
As for the CAN cals being the way they are, I thought TTS made their own cals, am I wrong?

[Steve Cole]

There is NO modeling needed when you measure MAP and RPM in a Speed Density system. It is straight physics and you have your answer.

Which is why I stated "we cannot rely soley on MAP" in reference to hrdtail78's comment that you need MAP and RPM.
No modeling needed? measured MAP and RPM give you just that and nothing more, we also need IAT and volume to calculate air mass.
Very good detailed explanation on increasing RPM, as it is easily misunderstood that as engine speed increases, airflow itself does not increase,
the events just happen more often.

Alpha-N is a cheaper style system and that is the main reason that a few manufactures and I mean very few still use it and it will NOT provide near
the accuracy of a Speed Density system. MAF systems are the most accurate way to measure but they also have some problems that must be
overcome and guess how they do it, they use a MAP sensor to tell them what is going on!

Few MAF systems also use a MAP sensor. In fact very, very, few of them. I do agree however that a MAF system is not practical on on motorcycle for many reasons including those you listed. I am proponent of Speed Density systems and MAP based HD calibrations, however there are several very good OE Alpha N system used on Japanese and European bikes that few will argue their accuracy, most notably the the Magneti Marelli systems Ducati is using, they even have traction control and other complex strategies. Saying they are cheap or that they cannot provide the same accuracy is simply your own opinion. Have you actually ever worked on or tuned one of these modern Alpha N bikes? If not how can you speak for their accuracy?

Jamie
Again there is no modeling necessary nor used. Do you understand what modeling is? Modeling is not just a calculation for values received. As for other corrections to be used in the final MASS air calculation there are several but we are not discussing those yet as you first have to learn and understand the basics. You cannot go on to the advanced portion of a subject until you understand the basics and it clear here that people do not.

Alpha-N is cheaper and it is less accurate and that is just why very few use it anymore. If all you want to look at is a few Japanese and European bikes you limited yourself to a very small segment of engines and fuel systems. Try looking at any GM, Ford, Chrysler, BMW, Audi, Toyota ect. automotive application where the requirements are much tighter. It's the manufactures duty to make things work as cheap as possible to get the job done, thats how they make profit! It only needs to be just enough to get by and no more. None of this has anything to do with the basics of how the engine works! Alpha-N or Speed Density has nothing at all to do with traction control, that's handled by the power of the micro-controller being used and has nothing at all to do with this discussion.

This is the same argument you tried to make about BroadBand sensors versus true Wide Band sensors, you were wrong then just as you are now. It all boils down to what is accurate enough, not what is more accurate.

Yes the events happen more often but as you get higher in rpm in areas that run above ACTUAL 100% VE (not cal VE) you WILL be taking more air in per event due to inertia.
As for the CAN cals being the way they are, I thought TTS made their own cals, am I wrong?

First off there is no inertia in the intake but what you are trying to talk about is a column of moving high speed air. So let's assume for a moment that the air is flowing at a high rate of speed being pushed by Absolute Pressure as that's all there is.
In order to get greater than Absolute pressure the speed of the air, uninterrupted, must enter the cylinder and before the pressure wave bounces back out of the cylinder the valve has to be closed. Now let's look at a HD intake track where the column of air hits the back side of the valve and what happens? It has to stop! As it stops it creates a rebound effect and the air begins to move in any direction it can, but also a pressure wave travels back up and out of the intake and back out through the throttle body. Commonly called "Stand Off" in the HD world. As it does this it slows the incoming air and cylinder fill is reduced. As this rebound air goes back into the intake the MAP sensor will see a pressure change. Because of this intake track a HD engine will never see 100% let alone over 100% cylinder fill due to its design unless you add a supercharger or some type of forced induction.

As for our calibrations, yes we make them but we do not rewrite ALL the base operating code. Two completely different things.

[BVHOG]

There is NO modeling needed when you measure MAP and RPM in a Speed Density system. It is straight physics and you have your answer.

Which is why I stated "we cannot rely soley on MAP" in reference to hrdtail78's comment that you need MAP and RPM.
No modeling needed? measured MAP and RPM give you just that and nothing more, we also need IAT and volume to calculate air mass.
Very good detailed explanation on increasing RPM, as it is easily misunderstood that as engine speed increases, airflow itself does not increase,
the events just happen more often.

Alpha-N is a cheaper style system and that is the main reason that a few manufactures and I mean very few still use it and it will NOT provide near
the accuracy of a Speed Density system. MAF systems are the most accurate way to measure but they also have some problems that must be
overcome and guess how they do it, they use a MAP sensor to tell them what is going on!

Few MAF systems also use a MAP sensor. In fact very, very, few of them. I do agree however that a MAF system is not practical on on motorcycle for many reasons including those you listed. I am proponent of Speed Density systems and MAP based HD calibrations, however there are several very good OE Alpha N system used on Japanese and European bikes that few will argue their accuracy, most notably the the Magneti Marelli systems Ducati is using, they even have traction control and other complex strategies. Saying they are cheap or that they cannot provide the same accuracy is simply your own opinion. Have you actually ever worked on or tuned one of these modern Alpha N bikes? If not how can you speak for their accuracy?

Jamie
Again there is no modeling necessary nor used. Do you understand what modeling is? Modeling is not just a calculation for values received. As for other corrections to be used in the final MASS air calculation there are several but we are not discussing those yet as you first have to learn and understand the basics. You cannot go on to the advanced portion of a subject until you understand the basics and it clear here that people do not.

Alpha-N is cheaper and it is less accurate and that is just why very few use it anymore. If all you want to look at is a few Japanese and European bikes you limited yourself to a very small segment of engines and fuel systems. Try looking at any GM, Ford, Chrysler, BMW, Audi, Toyota ect. automotive application where the requirements are much tighter. It's the manufactures duty to make things work as cheap as possible to get the job done, thats how they make profit! It only needs to be just enough to get by and no more. None of this has anything to do with the basics of how the engine works! Alpha-N or Speed Density has nothing at all to do with traction control, that's handled by the power of the micro-controller being used and has nothing at all to do with this discussion.

This is the same argument you tried to make about BroadBand sensors versus true Wide Band sensors, you were wrong then just as you are now. It all boils down to what is accurate enough, not what is more accurate.

Yes the events happen more often but as you get higher in rpm in areas that run above ACTUAL 100% VE (not cal VE) you WILL be taking more air in per event due to inertia.
As for the CAN cals being the way they are, I thought TTS made their own cals, am I wrong?

First off there is no inertia in the intake but what you are trying to talk about is a column of moving high speed air. So let's assume for a moment that the air is flowing at a high rate of speed being pushed by Absolute Pressure as that's all there is.
In order to get greater than Absolute pressure the speed of the air, uninterrupted, must enter the cylinder and before the pressure wave bounces back out of the cylinder the valve has to be closed. Now let's look at a HD intake track where the column of air hits the back side of the valve and what happens? It has to stop! As it stops it creates a rebound effect and the air begins to move in any direction it can, but also a pressure wave travels back up and out of the intake and back out through the throttle body. Commonly called "Stand Off" in the HD world. As it does this it slows the incoming air and cylinder fill is reduced. As this rebound air goes back into the intake the MAP sensor will see a pressure change. Because of this intake track a HD engine will never see 100% let alone over 100% cylinder fill due to its design unless you add a supercharger or some type of forced induction.

As for our calibrations, yes we make them but we do not rewrite ALL the base operating code. Two completely different things.

Makes sense but I am not sure I agree  that you never get more than 100% cylinder fill, for some of these high end combo's to make the power they produce wouldn't they have to be doing over 100% fill. I remember seeing formulas for that years ago on another site.

[ultraswede]

It is a fact that many cars/trucks use both MAF and MAP sensors.
For example all GM gen III V8 engines. A "few" of those have been manufactured.....
In MAF auto applications the MAP sensor is used to take care of the transients where the MAF would be to slow to react Due to the time it takes for the column of air to change speed after a change of the throttle blade position.

Another fact is that MAF sensors of the HFM type CAN detect the reverse flow taking place and only
report air flow in one direction to the ECU.

[Jeffd]

this helped at least understand some of the of the lingo on a basic level.
http://www.oldfuelinjection.com/?p=4

[Steve Cole]

Jamie

I have never stated that Wide Band sensors do not work, nor have I stated that Broad Band sensors do not work. As a matter of fact when you use them as they were designed and intended to be used they work very well. What I have stated is that they do NOT work when you try to use them for something they were not designed to do. So let's get your stories straight. Again, you need to learn the basics first then maybe you will understand the advanced stuff. Most MAF systems today do use a MAP with them and as stated if you look outside the motorcycle world you will find it to be very common and the normal application. If I were to venture a guess I would say it applies to about 75%.

As for over 100% fill on a HD I do not see it happening with the intake track as it is today on any production bike. Now maybe in a race application where the intake tract has been completely changed it might be possible, not likely but possible. This conversation was intended to talk about what people are using and riding around daily and the theory behind it all.

Ultraswede

What does HFM stand for and what automotive application is it used on. Would love to look into it more as the reverse flow has been the major draw back to them.

[Jeffd]

I for one am glad this thread started I have learned a lot.

[War Horse]

If I may, been dealing with these for some time, copied the information as my explaination would confuse.

A hot wire mass airflow sensor determines the mass of air flowing into the engine’s air intake system. The theory of operation of the hot wire mass airflow sensor is similar to that of the hot wire anemometer (which determines air velocity). The General Motors division (GM) was the first car company to use the hot wire sensor.[citation needed] This is achieved by heating a wire with an electric current that is suspended in the engine’s air stream, like a toaster wire. The wire's electrical resistance increases as the wire’s temperature increases, which limits electrical current flowing through the circuit. When air flows past the wire, the wire cools, decreasing its resistance, which in turn allows more current to flow through the circuit. As more current flows, the wire’s temperature increases until the resistance reaches equilibrium again. The amount of current required to maintain the wire’s temperature is directly proportional to the mass of air flowing past the wire. The integrated electronic circuit converts the measurement of current into a voltage signal which is sent to the ECU.

If air density increases due to pressure increase or temperature drop, but the air volume remains constant, the denser air will remove more heat from the wire indicating a higher mass airflow. Unlike the vane meter's paddle sensing element, the hot wire responds directly to air density. This sensor's capabilities are well suited to support the gasoline combustion process which fundamentally responds to air mass, not air volume. (See stoichiometry.)

This sensor sometimes employs a mixture screw, but this screw is fully electronic and uses a variable resistor (potentiometer) instead of an air bypass screw. The screw needs more turns to achieve the desired results. A hot wire burn-off cleaning circuit is employed on some of these sensors. A burn-off relay applies a high current through the platinum hot wire after the vehicle is turned off for a second or so, thereby burning or vaporizing any contaminants that have stuck to the platinum hot wire element.

The hot film MAF sensor works somewhat similar to the hot wire MAF sensor, but instead it usually outputs a frequency signal. This sensor uses a hot film-grid instead of a hot wire. It is commonly found in late 80’s early 90’s fuel-injected vehicles. The output frequency is directly proportional to the amount of air entering the engine. So as air flow increases so does frequency. These sensors tend to cause intermittent problems due to internal electrical failures. The use of an oscilloscope is strongly recommended to check the output frequency of these sensors. Frequency distortion is also common when the sensor starts to fail. Many technicians in the field use a tap test with very conclusive results. Not all HFM systems output a frequency. In some cases, this sensor works by outputting a regular varying voltage signal.

Some of the benefits of a hot-wire MAF compared to the older style vane meter are:

responds very quickly to changes in air flow
low airflow restriction
smaller overall package
less sensitive to mounting location and orientation
no moving parts improve its durability
less expensive
separate temperature and pressure sensors are not required (to determine air mass)
There are some drawbacks:

dirt and oil can contaminate the hot-wire deteriorating its accuracy
installation requires a laminar flow across the hot-wire
[edit] 

[glens]

C'mon Jamie, please don't pull your posts like that.  I was at the tail end of 'page 4', where Steve asked about "HFM".  Then clicked the link to 'page 5' and thought "what the hell?  I've already seen these posts..."  A quick review and all Jamie's posts are gone.  Really messes things up when that happens.  At least we've still got some of the information in posts that quote Jamie.

[Steve Cole]

War Horse

That's good description of the current MAF sensors out there. I understand those but the HFM is one that I'm not familiar with that senses the air direction along with the air measurement, as this has been the problem with them when used with higher performance and shorter intake tract systems. If that issue can be overcome then I would think engines like a HD could make use of them.

[War Horse]

I really don't know about air flow direction with the HFM, but believe that intake runner length has to be somewhat more than a stock H-D intake. Cant remember what their called but the air filters/runner that sit at a 90° to the intake forward may be the answere to the intake runner needed for the HFM, mounted just behind the AC , but I'm just speculating and can offer no concrete proof. I'll leave that to better minds . I'm just a guy in the trench's that's getting rusty.

[glens]

Perhaps there are two elements in "series" (in the air flow) and the ECM can tell by which one changed first which direction the flow is?

[Steve Cole]

While I am sure that something will come along sometime in the future that allows them to get it figured out I was just unaware of it at this time. That's why my interest in it. The long runner with a large plenum is what settles it down in automotive applications, as it acts basically like a shock absorber does on suspension. The plenum is typically 4 times the volume of the total of the intake runners to make it work out and there is no where near that amount of room on most motorcycle applications.

[ultraswede]

The HFM stands for Hot Film Measurement, but the original abbreviation is in German.
But it works in English as well.

The reason the HFM can detect air flow direction is; (grossly simplified)

There is a piece of silicon/chip area that is exposed to the air flow.
This chip is in the center heated by a resistor that draws a current = Heat produced.
There is a temp sensor on the upstream side of the silicon/chip, measuring the temp of the chip upstream the heating resistor.
The air flow is calculated by measuring how much current is needed to maintan temp X at the temp sensor.

There is also a temp sensor DOWNSTREAM of the normal airflow direction, measuring any flow in the opposite direction, in the same way as the upstream temp sensor.
(if the down stream temp sensor see a lower temp than the upstream sensor = air flow has changed direction.)


The built in electronics in the HFM does the math and sends out an air mass signal that corespond to the air mass that has passed through the HFM in the direction towards the engine.

How fast this is done I don't know (its OK for the pulsations in automotive applications but fast enough for a HD?), the technology has been around at least 10 years.

[Steve Cole]

The Hot film has been around for a long while but I just have not seen one as you describe. It sounds like a good idea with the dual temp. sensors to try and determine airflow direction. Do you have any links to them being discussed, ie. who makes them? Would love to find out more about them and what year model automotive applications use them.

[War Horse]

Steve , if it helps, the Mercedes Benz uses a NTC resistor along with the HFM.

[ultraswede]

Steve, try this link
http://rb-kwin.bosch.com/en/powerconsumptionemissions/electric_controls/sensors/enginemanagement/hfm.html

I think you can get the detailed answers I am sure you are looking for by contacting Bosch.

[hrdtail78]

Now that you understand that MAP is just a reading of Absolute pressure and that once you reach an equal Absolute pressure in the intake to outside (Baro) NO more air is going to enter the engine. This is the way that it works and there is nothing you nor I can do to change than short of installing a forced induction unit.

With this in mind we can look back to another way HD has done the VE's and that is to base it from TPS and RPM. I think most everyone understands what these are and it is pretty easy to now compare the two methods of doing it.

Question #6

Why use TPS instead of MAP for VE's?

So what is the correct answer and whats the next question?

[War Horse]

I would venture that MAP is a more accurate information input....

[Jeffd]

tps reacts to throttle changes quicker but then you better have a calibrated wrist.

[hrdtail78]

Maybe we are still on 6th.

MAP is the best way to figure out the engine's condition in the term of load. 100% kpa is the most load that the engine is going to be under. 

[akjeff]

Now that you understand that MAP is just a reading of Absolute pressure and that once you reach an equal Absolute pressure in the intake to outside (Baro) NO more air is going to enter the engine. This is the way that it works and there is nothing you nor I can do to change than short of installing a forced induction unit.

With this in mind we can look back to another way HD has done the VE's and that is to base it from TPS and RPM. I think most everyone understands what these are and it is pretty easy to now compare the two methods of doing it.

Question #6

Why use TPS instead of MAP for VE's?

So what is the correct answer and whats the next question?

I'll take a stab at it. Maybe the MoCo used/uses TPSxRPM for reasons unrelated to total engine performance. Perhaps when the engine gets tested to meet EPA standards, it's done at known, and very repeatable parameters. i.e. 20%, 50%, 100% throttle etc at XYZ RPM, and at a standard altitude density. All they have to do is make it run dead nuts on 14.7 AFR at these settings, pass the test, and make it run as well as possible across the board???

Jeff

edited to correct the dyslexic "ARF" to what I meant to say...."AFR" !

[hrdtail78]

Now that you understand that MAP is just a reading of Absolute pressure and that once you reach an equal Absolute pressure in the intake to outside (Baro) NO more air is going to enter the engine. This is the way that it works and there is nothing you nor I can do to change than short of installing a forced induction unit.

With this in mind we can look back to another way HD has done the VE's and that is to base it from TPS and RPM. I think most everyone understands what these are and it is pretty easy to now compare the two methods of doing it.

Question #6

Why use TPS instead of MAP for VE's?

So what is the correct answer and whats the next question?

I'll take a stab at it. Maybe the MoCo used/uses TPSxRPM for reasons unrelated to total engine performance. Perhaps when the engine gets tested to meet EPA standards, it's done at known, and very repeatable parameters. i.e. 20%, 50%, 100% throttle etc at XYZ RPM, and at a standard altitude density. All they have to do is make it run dead nuts on 14.7 ARF at these settings, pass there test, and make it run as well as possible across the board???

Jeff

On top of that.  I would have to think.  TP/RPM is a lot less complicated and easier to deal with.

[glens]

It's easier to v-tune by blind feel...

[Steve Cole]

To me the answer to #6 is what's good enough? We know the problems it causes and we know it's not accurate but is it accurate enough for what's currently being done? I know without a doubt that MAP is more accurate but as I said before, you need to look at what's going on in the intake manifold while the engine is running. If TPS is believed to be good enough and in someone's mind easier to do then why change it. Since there are two different groups at HD in charge of it, that could be the answer but I just do not know.

What I do know is that if you run a bike on the dyno with a steady load on it you will find that the TPS reading in each gear is different, for the same load and RPM. So that means when tuning what gear are you going to use, as it matters. So the mixture is going to be different based upon the gear your in and yes it can be measured! By using MAP, 40 kPa is 40 kPa regardless of the gear! Just as 100 kPa is 100 kPa. Now TPS gives a measurable error based on the gearing of the bike and the heaviest bikes all get MAP referenced tables starting in 2010. So it could be that due to the weight of the bike and gearing they needed to switch and the lighter bikes can get away without it. Lot's of guessing as to why but no solid answers as to why.

The EPA test are very close to being a tight set of conditions but there is a rider on the bike and there is some room for him to influence the test results. The rider has to control the bike by following a speed trace on the dyno which has been setup for the test. In this test there is a high and low trace on the screen and the rider must keep it between the lines. Now the trick comes from how smooth the rider is on the throttle, if he varies a lot between the lines with little throttle movements (long slow changes)or does he vary a lot with big throttle movements (quick large changes). It all plays in to a pass or fail. Rider57 can probably give a better description of the EPA test schedule than I've done here.

What you all need to learn here is the basics of how it really works and then you can makeup you own minds as to why, knowing what's really going on. The whole reason for me to start this was for you to learn and while I'm not the best at doing it as a teacher I keep seeing the same problems over and over because people just do not understand how things work. It's not only the DIY guy either.

This is just the easy stuff so far and it gets more complicated when we start going into all the interactions that occur in a running engine, that have to be handled, but I'm not sure if you guys want to get into it that far? If you do I can try and explain more of it but it's up to you all.

[Tsani]

Bring it Steve. I like learning new stuff.

[akjeff]

Bring it Steve. I like learning new stuff.

+1

This thread has convinced me to quit mooching, and make a donation to the site. Was beginning to feel the need to wear a ski mask when I logged on for free! Thanks again for the education Steve!(and everyone else, for that matter)

Jeff

[tunaman]

Please do keep it going Steve. As a truly uneducated person on these subjects, I am not qualified to offer any opinions or contributions to the discussion. I have, however, been following along with keen interest and am learning thanks to your lead.
Extremely interesting subject and discussions!
Roger

[War Horse]

  Please do keep it comming, getting back to the basics sometimes gets lost along the way of overcomplicating the simple.

Thank you, Steve, for taking the time.

[wurk_truk]

I have NOT posted until now, because I do NOT want anything I say to derail threads like this.  Thank you Steve, and all the other members for posting up.  I too like learning.

[FBRR]

I didn't read the "whole" thing so forgive me if these answers have been adressed.
First many Speed density CAR systems do not use MAP as a VE table axis. ( Map or more correctly Vacuum is always used on fueling.) Vacuum is the difference between current MAP and Baro.
( Baro can be derived even if the system ONLY has a MAP sensor. Many vehicles have both, MAP and Baro, but some make due with only a MAP Sensor and derive Baro at key up where MAP=Baro when the engine is not running and then use a correction scheme to adjust Baro based on engine load and speed during engine run.)

The last Speed density I calibrated used IACTPS, as a VE breakpoint. That is a percentage of the IAC position vs. TPS. ( At small throttle openings and IDLE IAC has more "effect" than TPS. As throttle increases IAC becomes less of a factor.) And at any given MAP with different Throttle positions, VE is effected again as turbulence about the throttle blade changes flow. You can have the same MAP, ERPM with varying throttle posistion during an engine cycle due to changes in ROAD Load. i.e. hills and valleys. So MAP varies alot at the SAME TPS AND RPM while running down the road.
The problem with using either "all TPS" or MAP is precisely becasue YOU can get different reading for MAP at the SAME TPS ERPM load point. If you accelerating/steady state cruise/UP HILL/or DOWN
you will not get a consistant reading vs. MAP alone! And conversely, using only TPS and ERPM as table points means the MAP is not consistant at each speed and load! Nether (MAP or TPS)  Based VE are perfect, but I have used BOTH on different applications.( and additional "corrections" factors need to be used depending on which is choosen as base! )



Using only TPS also presents the same problem. But by using MAP as an input to the base fueling and using an "adjusted" TPS( in this case by also using IAC counts for expected air rate) you can get "closer." But!! BIG BUT, using speed density you will NEVER be correct 100% of the time! There are simply too many variables that effect the VE other thna MAP! If you use a given VE at even IDLE, as the INTAKE heats up ( with engine heat) the air lag time in the manifold will walk the fuel control up as well! There are tables to "try" and negate some of those effects but it is never perfect!

All that said, there was a question regarding AIRFLOW through a MASS airflow sensor.
Reversion in the intake track ( s valves open and close and overlap effects are present) does cause an INCORRECT reading in the MASS sensor output. Some neww sensor are working on "directional flow" but the older sensors need to be corrected for this reversion!!
Guess how "they/we" did THAT!The engine application is run with the correct induction parts and connected to a STANDARD AIR MACHINE ( measures all air in and out! Of the intake)
( I might add as an aside, fewer cylinders produce MORE reversion in a common plenum. There is more time for the airflow to be effected between cylinder event as th enumber of cyclinders goes down!)
So back to the problem of reversion with MASS air sensors.! The area of reversion is related to speed load and throttle, so you can map ( as in MODEL and KNOW where reversion is taking place)
and choose ignore the MAF SENSOR. That is why MOST MAF sensor application also HAVE SPEED DENSITY! Tables. When the SENSOR reading in an area of KNOW reversion ( as well as some engine acceleration events)  is outside of a calibrated "window" the Sensor output is ignored and Speed density calculations are used instead of the sensor input! So any application without a bidirectional MAF sensor still uses speed density "sometimes."!!

[FBRR]

And to answer Steve's first question "what is kPa" it merely the UNIT of measure for MAP. Just as a speedometer can be used to measure MPH or KPH or ft/sec, kPa is a unit of measure, and nothing more! In this instance it is the unit of measure for the "converted" output of the MAP sensor. The OUTPUT of a MAP sensor is voltage! That voltage is converted inside the ECM software to a UNIT of measure.
And any unit measure of PRESSURE could have been used, it just happens to be kPa in this software.

[HV]

Very interesting thread  THANK YOU Steve  and FBRR and ALL that have posted in keeping this a civil and educational thread ...

[Steve Cole]

FBRR

I think it would be nice if you could join in here if you have the time and help to teach those that want to learn the basics. At some point we can get into all the reversion that goes on in the intake tract as well as how fuel sharing and correction terms go on in a HD application but I'm not so sure how fast people can understand it all. Both you and I have been doing this for a very long time and I know that I assume people understand what I'm trying to say here. I've been told by a few people that they do not understand, so I'm trying to start with the very basic things of a Speed Density system and then work forward. I think you would be a great help in explaining things and it would give people possible another way to have it explained.

Just so everyone understands no system is perfect but the better you get it the better it will run in the long run. Doing this at a factory level allows plenty of ways to test and create correction terms that get things closer but remember that those were all done based on how the equipment was when it got built. Most all of you have changed something on your bike and that is what you are trying to correct for, so you cannot expect all the factory presets to be calibrated correctly and some never will be. So it all boils down to what you as the bike owner feels is good enough in the long run.

[Herko]

FBRR...thanks!
'Effective' communication.   

[Jeffd]

I think it is awesome to be schooled in this.  I can not think of 3 better professors to do it Steve, FBRR and Herko

[TXP]

I would certainly like to see this thread continue. As Steve eluded to its not just the DIY guys that benefit from discussions like this. I would submit that those Professional Tuners who read this and don't think they already know everything gain more from this kind of discussion than most. One of the greatest benefits IMHO for using TTS product is the unparalled support Steve offers. Every other manufacturer of tuning products including the MoCo could be offering direct support and educational advice on this or any other forum. And, I wish they would. I'm fortunate enough to get to talk with those in the know at trade shows and HD Dealer Meetings and get the "different takes" different companies pursue on tuning products. Its difficult at best to try to keep up with the changes made with just one product, much less the plethrora of products offered today. When someone shows up with one of the upper level tuners from whomever (no pot devices) I try to help rather than saying you bought a piece of junk and the only way I can help is if you buy my preferred tuning product. So the more we all learn about the basics as well as the more complicated, the better off we all are. Your tuner gets better by applying himself and learning. The retail customer can at the very least learn how not to be taken advantage of, and the DIY guys can have a good time learning and tinkering. I appreciate the explanations Steve provides here. It takes up a lot of time to follow the boards and try to educate those who want to learn as much as they can about how/why things work the way they do. Thanks!

[Herko]

I think it is awesome to be schooled in this.  I can not think of 3 better professors to do it Steve, FBRR and Herko

Thanks Jeff for the kindness of placing me in this parallel, but I have to humbly remain in my league.

[fatboy]

Now that you understand that MAP is just a reading of Absolute pressure and that once you reach an equal Absolute pressure in the intake to outside (Baro) NO more air is going to enter the engine. This is the way that it works and there is nothing you nor I can do to change than short of installing a forced induction unit.

With this in mind we can look back to another way HD has done the VE's and that is to base it from TPS and RPM. I think most everyone understands what these are and it is pretty easy to now compare the two methods of doing it.

Question #6

Why use TPS instead of MAP for VE's?

So what is the correct answer and whats the next question?

Did this thread die..........Question # 6 still open ?

[blusmbl]

Most of the new stuff I've worked on has been map breakpoint based exclusively.

So back to the problem of reversion with MASS air sensors.! The area of reversion is related to speed load and throttle, so you can map ( as in MODEL and KNOW where reversion is taking place)
and choose ignore the MAF SENSOR. That is why MOST MAF sensor application also HAVE SPEED DENSITY! Tables. When the SENSOR reading in an area of KNOW reversion ( as well as some engine acceleration events)  is outside of a calibrated "window" the Sensor output is ignored and Speed density calculations are used instead of the sensor input! So any application without a bidirectional MAF sensor still uses speed density "sometimes."!!

The speed density tables are needed for anticipation and failure reactions, too.  Without calibrating the speed density model on a mass air based system, the vehicle will be undrivable with a disconnected or faulty air meter.    I also don't see any easy way to package a mass air meter in the Harley intake tract, they're terribly sensitive to noise, and have to be placed in areas with little to no flow disturbance on either side, otherwise you may as well disregard it's signal completely.

Many of the naturally aspirated gasoline engines I've worked on don't have a map sensor anymore, but map is still being inferred based on the voleff calculations and load derived from the air meter.

[emxgarcia]

Excellent topic / thread.

[Sam45]

ok ready for some more

[fatboy]

Me too!

[Paul in Alaska]

Still waiting....

[glens]

Most of the new stuff I've worked on has been map breakpoint based exclusively.
...
Many of the naturally aspirated gasoline engines I've worked on don't have a map sensor anymore, but map is still being inferred based on the voleff calculations and load derived from the air meter.

A little confusing when the middle section is disregarded...

Certainly there's a pressure sensor at least to determine atmospheric pressure else how could anything get derived outside of closed-loop operation?

[blusmbl]

A little confusing when the middle section is disregarded...

Certainly there's a pressure sensor at least to determine atmospheric pressure else how could anything get derived outside of closed-loop operation?

Nope, it's all inferred.  It isn't that bad to do with a naturally aspirated engine.  You obviously can't do it without measuring the air meter signal, and you calibrate modeled airflow (and pressure) across the throttle plate.  Both MAP and BP is inferred, and it works pretty well.  That being said with an air meter in place, the fueling is not done by speed density/ve calculations anymore unless the maf sensor has failed.

[FBRR]

A little confusing when the middle section is disregarded...

Certainly there's a pressure sensor at least to determine atmospheric pressure else how could anything get derived outside of closed-loop operation?

NOPE! Speed density is USED on most MAF systems. The reason being there is reversion in the intake side that changes the direction of flow, and MAF sensor (most bt some newer ones do read direction!) need speed density as a back up to compare current signal vs. KNOWn reversion. When the signal from the MAF is "out of range" the speed density calibrations are used, And that happens under NORMAL operation!

Nope, it's all inferred.  It isn't that bad to do with a naturally aspirated engine.  You obviously can't do it without measuring the air meter signal, and you calibrate modeled airflow (and pressure) across the throttle plate.  Both MAP and BP is inferred, and it works pretty well.  That being said with an air meter in place, the fueling is not done by speed density/ve calculations anymore unless the maf sensor has failed.

[Thumper Buttercup]

OK,

   I missed this when it came up but have read it all now, so far I'm with you and
learning here.

I hope you guys continue this thread.

[N-gin]

Thank you Steve