exhaust manifold pressure in speed density calculation?
 

I've been monitoring exhaust manifold pressure (EMP) for some time, and now that DynoTech Tuning has a simple adapter to attach a pressure sensor monitor exhaust flow, its pretty easy for almost anyone to log EMP. Besides using it as a tool to more intelligently tune a turbo charged car, it also can be used to more accurately estimate air mass for speed density calculations. Nimpoc and I started a conversation in a different thread, but Nimpoc suggested starting a new thread so, here it is.

Intuitively, I can imagine that EMP could be used in an SD air mass calculation, but the form of the most reasonable dependence is not really obvious to me. I found a few SAE papers by Delphi, but I haven't had a chance to thoroughly read and consider them. Curious if anyone has insight or experience with using EMP for and SD calculation.

Can you please link me to the most current SD ROM thread so I can catch up on what's state of the art? I'm looking at a couple and not sure what the most desirable variant is at this point.

jscbanks SD is what probably 95% of the people are using. master load is calculated from two tables - The first table produces a base load from the MAP sensor reading, and then that value gets multiplied by a 2D RPM VE table. Temperature and baro compensation are already built into the Evo load calculation code because it is needed with the Karmen Vortex MAF sensor.

Would it be reasonable to use it not directly in load calc but as a modifier to another parameter ?

Such as back pressure increases decrease mivec? Either open loop or closed loop ? 2/3d

You are suggesting it as a way to redundantly calculate load though right ? Or can a primary load be calculated by the emp/map type of arythmitic ?

Map(ve)=load: emap/map(ve)

The scale of the two ve numbers is not equal. But would something like this be reasonable?

The VE wouldn't really be affected until there was actual back pressure being logged IMO. So until the ratio exceeds 1:1 it would just use the standard VE calculation. Perhaps have a multiplier table that would begin to lower the active VE as back pressure increases?

-Jamie

Okay, so you're saying this:
https://www.evolutionm.net/forums/ec...y-patches.html
https://www.evolutionm.net/forums/ec...ched-roms.html

Rather than this:
https://www.evolutionm.net/forums/ec...bles-baro.html

Good point

Interesting to see where this goes !

Is this a way to implement your idea?

Or
Wouldn't you need a combustion efficiency table?

Please excuse my lack of background with the Mitsu ECU / Tephra ROM, I'm new to the platform and trying to catch up.

As an FYI, here's the original thread that started all this:
https://www.evolutionm.net/forums/ve...ure-plate.html

Why consider EMAP?

Speed Density systems estimate the flow through the engine rather than measure it directly (MAF). Observing the pressure only on one side of the system gives an incomplete picture of what's happening. This is especially true on engines where the pressure ratio can vary dramatically, such as high powered turbocharged powerplants.

It is proposed that by measuring EMAP, a more accurately estimate of engine flow can be made to potentially make tuning easier.
Where typical SD system load is calculated with:
Load = Disp*n*p(IMAP,IAT)*VE(IMAP,n)

Something like this might be better:
Load = Disp*n*p(IMAP,IAT)*VE(p(IMAP,IAT),n)*PR(IMAP,EMAP)
PR(IMAP,EMAP) = Table with dimensionless coefficients output as a function of IMAP/EMAP to influence effective VE. The table may or may not be the same as the ratio of IMAP/EMAP. This needs to be investigated; unlikely true. It's also likely that one would want to apply an averaging filter to the EMAP signal. Not sure if this is currently done for IMAP.

IMAP & IAT could be thought to reflect air filter, compressor, and intercooler performance.
VE map reflects the intake manifold, head & cams.
EMAP would reflect exhaust manifold, turbine, exhaust system.

Currently the VE map tries to characterize most of this together. It really isn't that bad of a method, but may need to be adjusted significantly when part changes are made. Adding EMAP may or may not make the process of tuning easier.

This is similar to what MrFred proposed:
"load = MAP/IAT*(1 + A*pr)*VE where A is an adjustable value and pr is the pressure ratio."

One thing (of many?) that's missing is accounting EGR flow. Are there issues with EGR flow falsing the MAP based load calc and adding excessive fuel today? Is the EGR flow normally calculated through comparison of MAF vs. MAP readings?

EMAP may be able to help compensate in an SD tune for changes in backpressure due to altitude relative to the tune altitude.

211ratsbud makes a good point that one may want to make changes (if they can) to valve timing as a function of EMAP.

I'm thinking Jamie meant to post this here: