Understanding what kPa is for tuning

[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.