Average PW for a given Mafload varies by drive

[shauer]

I only tested the code over the past few weeks. Ambient temperature range from 50 deg F to about 90 deg F. I noticed a shift of up to 2%-3% in mafload value. For me this was significant because I have an area of low RPM / high load where I make use of trim table bins that are only 2.5% apart from each other. Maybe I don't need them that close but it did help me understand that mafload was not consistent relative to MAF.

My vote is also for configurable inclusion of the IAT in mafload calculation.

[muythaibxr]

Yeah, we originally didn't include it, and that caused people problems... so we put it back.

[shauer]

Yeah, we originally didn't include it, and that caused people problems... so we put it back.

I sympathize...

I think MAF tuning has matured a lot since then. Effects like this one we are talking about would not have been as visible in older versions of code before the MAF signal was cleaned up at least for the voltage based MAF sensors. In theory you want the IAT incorporated into the mafload to make it mathematically correct as a "load" variable. However, the problem experienced here is that the MAF value already incorporates a temperature sensitive component as measured at the MAF sensor (air density), and the IAT sensor could be in a completely different location with completely different thermal characteristics. The two air temp sensitive components will converge and diverge based on a bunch of installation specific variables and introduce a few percent of extra variability in the mafload as documented in this thread. In a perfect world you would use an IAT sensor that's incorporated into the MAF sensor but many sensors do not have air temp available as a separate sensor output.

I would request that making this a configuration option in the MAF setup dialog be added for consideration in V1.4 code at least.

I would be more than happy to make the required source code changes based on the publicly available V1.3 source but I don't think that would really save you or James' time since the 1.4 code is most likely already different in many of the same areas I would need to touch.

[Kzcleve]

How large are the temperature swings you have tested over yet? Over the course of a year, I see IATs from -25°C to +40°C, that could make quite a difference in MAFload.

My vote is C: configurable.

I tested from about 12°C to 30°C.

I agree that an option to not use MAT in mafload would work well, at least for my application..

[mr_minnis]

MS3x firmware 1.3.2
I have noticed some inconsistencies also depending on air temperature. MAF as fuel MAFload as load.

I am running a PMAS HPX sensor (has IAT in the MAF), I also am using VE1 as a trim table with idle VE. I started using the VE because I wanted a way to see how far off things were.

I can the car idling at 14.7 on a cool day with the VE set to 93. Later on that day I take the car out for a drive to Walmart get back in and the afr is now like 15.5. The air intake temperature is about 120.The air density correction is at 90%. I bump the ve up to 102 and the afr shoots back to where it needs to be. Of coarse when it cools back off the afr goes down to 14.0.

My meter is large for my needs (1300 g/s for 230 hp) and I thought maybe the mafload was lower than it should be.

questions:
1) If the load parameter was set to map or %baro would the problem exist?
2) I would be interested in trying the firmware you guys are testing.

[subwoofer]

Are you saying that you are using the MAT correction curve option? A film-type MAF is temperature compensated by nature, so disable it.




1300g/sec is too much overkill for a 230BHP application, 1/4 of that would have been more than sufficient. What happens is that you lose resolution at idle and cruise, with no benefit at the top end. Size things right, not as big as possible, that way it is easier to get good results.

[mr_minnis]

Are you saying that you are using the MAT correction curve option? A film-type MAF is temperature compensated by nature, so disable it.


1300g/sec is too much overkill for a 230BHP application, 1/4 of that would have been more than sufficient. What happens is that you lose resolution at idle and cruise, with no benefit at the top end. Size things right, not as big as possible, that way it is easier to get good results.

no I am not using the MAT temperature correction table.

I bought the smallest housing PMAS offered and I think all their sensors flow above the 650 g/s (smallest choice in MAF settings). I am going to be modifying my engine soon. Drive-abilty of the car is fine. The O2s are adjusting for the differences in temperature.

I don't have a log,(I can get one) but it is strange seeing the "Air Corr" value at 90% and then see the "total fuel correction" at 100%. I wondered if it was pulling fuel. especially when I am looking for reasons why the engine is leaner on hot start ups. Before the O2s kick on

Attached is my MSQ.