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2g MAF with Evo 8 Ecu - Scaling

knochgoon24

DSM Wiseman
6,136
89
Jan 29, 2008
Troy, Michigan
DISCLAIMER: This may all be a load of crap. I'm just thinking out loud. Hence, all the edits. - Wes

After scaling my MAF the other night, I've been stumped with why my MAF Scaling is so different that the one suggested. I may have figured it out using and an alternative method for scaling a 2g MAF for the Evo 8 Ecu.



There has been talks on the evolutionm about how the MAF Smoothing/Compensation tables factor into the airflow calculations. If you compare roms, some of them have different values. I then compared these values to what the DSM roms have on them. As expected, it's also different. (Go figure, different sensors completely).

Someone on evolutionm decided to add them together and saw that the 9055 rom (Evo 7 Ralliart) has higher numbers compared to the 9653 rom (EDM Evo 8?). The fuel injector scaling is also higher for the 9055 compared to 9653, and it happens to be just about right to offset the different in MAF Scaling. (6% bigger injector scaling. 8% Larger "MAF Total" - Fuel Tables also different)

I propose that MAF Scaling is nothing more than a generic baseline.
MAF Compensation/Smoothing is where the fine tuning was done. Seems they started at 128 and added/subtracted to tune. Which makes sense: 256/2 = 128. That gives you your +/- room to adjust.
After testing - Hypothesis Rejected - Stick with tuning the MAF Scaling.

9653 Smoothing -> 9055 Smoothing -> 2g Smoothing
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The Evo tables for MAF Scaling are all the same. It seems that it's a generic curve for the Evo 8 sensor, and that instead of using the MAF Scaling to 'tune' the Ralliart rom, they may have used the table we now call MAF Compensation or MAF Smoothing.
Not sure about this now... The larger value for the same injectors is compensated somehow though.

When I scaled my MAF the other night, the only correction I had was the difference in MAF sizes (2g uses 286 instead of the Evo 357.46). I came up with a MAF Scaling that was very different from the suggest one. -Read on: MAF Size has no effect as far as I can tell.

From left to right:
Suggested(Just MAF adder difference) -> Mine (9653) -> My Calc. for 9653 rom -> My Calc. for 9055 rom

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My calculated values are closer to what I actually ended up with.
This also explains why I had to set my injectors to 713 while running 9055 with the suggested scaling when I was supposed to set them to 609. And I still ran rich. I pulled the rest of the fuel through the fuel maps because my load was way off.

If anyone else would like to post what then ended up with for a MAF scaling so we could compare and test my hypothesis, I'd appreciate it.

As before, don't just copy my MAF Scaling and expect it to work on your car.
There are still too many variables.

I got my values by:
Taking the Evo MAF Scaling,
Adding the Evo MAF Adder,
Adding the Evo MAF Compensation,
Subtracting 20% (the difference in size between the 2g and the evo maf),
Subtracing the Evo MAF Adder,
Subtracting the Evo MAF Compensation.

By using this method, the only table I had to change is the MAF Scaling.

I'll have to try with and without changing the MAF size and see if it makes a difference. - I'm back - No difference. This seems to work.

EDIT: Back with after some testing.
MAF Size has NO effect in regards to calculating how much fuel to inject.
It does however directly affect the value output to Air Volume (MUT request 2C). A 20% change in the MAF Size made a 20% change in Air Volume, but no change in the AFR or fuel trims.

I'm heading out for more testing. If I'm right, I should be able to change the MAF Compensation tables by the same amount I changed the MAF Scaling table, then set the MAF Scaling table back to stock, and still have it run the same. - No go.

EDIT 2: Back again.
The car won't start if you do what I just tried. Apparently, the MAF compensation factors in somewhere else. My battery is to low to flash again (from the door being open and a crappy alternator) an I'm stuck with a flash that won't start. I'll have to hook up the battery charger tomorrow. :ohdamn:

This would be a lot easier to figure out if I could disassemble code.

Please post up your MAF Scaling and any fueling related oddities (like extra large injector scaling, odd latency values, etc.
 
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clockworktoy

Proven Member
315
2
Jul 22, 2006
long beach, California
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This is my scaling with evo injectors, 2g maf, FP intake and a small air filter. Not perfect but my trips seem to be +-10%
 

hediki12

Proven Member
347
0
Oct 13, 2008
mt vernon, New_York
heres mines. stft 0% ltft lo +2/+3 % ltft mid -2/-3% . i haven't touched anything over realy 400 hz because i dont drive that fast for long. LOL. btw this is on 9417stock injectors 2g maf...
 

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knochgoon24

DSM Wiseman
6,136
89
Jan 29, 2008
Troy, Michigan
Ok, so the trend here, is that no one is anywhere near the one made by just subtracting the difference in MAF adders (the first one out of the 4 I posted).

If people are trying to use that scaling to get their car setup, this may be why they are running into problems.
 

hediki12

Proven Member
347
0
Oct 13, 2008
mt vernon, New_York
what i did was look at the trims... and change the and changed it to percent 128 and just subtract the trim percent form the value in the table.... worked pretty well some guy on the evom did it so i gave it a try.
my table in unit8 wich i think is what both of your are in is .....
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knochgoon24

DSM Wiseman
6,136
89
Jan 29, 2008
Troy, Michigan
You don't go over 400Hz that often? That's about the point where I just start to break into positive pressure while cruising.

Ceddy, I see you're looking at this. Hopefully you can shine some light. I haven't learned any of the assembly stuff yet, so I was just going by trial and error.
 

hediki12

Proven Member
347
0
Oct 13, 2008
mt vernon, New_York
You don't go over 400Hz that often? That's about the point where I just start to break into positive pressure while cruising.

Ceddy, I see you're looking at this. Hopefully you can shine some light. I haven't learned any of the assembly stuff yet, so I was just going by trial and error.

what do you mean break into position? i cruise in 5th @ 3-3.5 k which isnt 400hz
 

knochgoon24

DSM Wiseman
6,136
89
Jan 29, 2008
Troy, Michigan
what do you mean break into position? i cruise in 5th @ 3-3.5 k which isnt 400hz

No, break into positive pressure. Crossing from vacuum, past 0psi, into boost.

I don't hit 400Hz at cruise, but I do hit it as soon as I give it some more gas while cruising, like when I'm going up a steep hill. When I'm at ~2.5k-3k RPM and 3psi or so.

I really need to get a MAP sensor wired in.
 
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