Understanding what kPa is for 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

[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.