RomRaider

Be honest, I don't buy in the concept of modifying MAF scaling to compensate for error in AFR ratio.

Subaru engineer carefully measured, calculated and scaled the air that pass through the MAF so that the MAF sends the the right signal to make the engine work properly as they originally designed.

Now one day, we think something is wrong about our AFR being too rich or too lean and we adjust MAF scaling instead of Injector scaling or Fuel Map.

All that I say is not to attack anyone, sincerely. Just want to point out my opinion if we are going the right direction.

The statement above is not applied to anyone who has changed their intake system though.

i have to agree with you on this. If you adjust the scale of the maf sensor your not changeing the amount of air going into the cylinders (unless you've changed boost) therefore your not making power. You increase output when you increase input, i would do like he said and adjust the fuel map but do a little at a time, log, and watch your knock.

I dont believe in modifying the MAF to correct AFR values specifically, but I do actually have a homemade intake and it affects the way the ECU determines incoming air/fuel mixture information. And, for everyone who wonders ANY changes in the structure of your intake due actually create a margin for error; even simply removing the stock airbox/snorkus can have a slight impact on your airflow. It may not be enough to require recalibration but I guess it just depends on how easily satisfied you are with a tune with a few flaws.

The 07 sti has different maf scaling than previous years and unless the intake was changed, it seems Subaru decided to make changes in that case.

Use the injector scaler to get closer ratios. This is if you have a stock intake system. The MAF tables should be left alone because they are set from Subaru(which are pretty smart engineers) to work very well with the current/stock MAF tube/intake tract.

see the problem here is when you put a cone filter on with a stock diameter housing it still jacks everything up. the way the air flows past the maf changes and now my car is pig rich on factory settings... i had to go up to 500cc on the injector scaling to get close...

easy fix for that: put a panel filter in instead

Exactly. Pay attention to this point. It is very important. SOA changed the injector scalar and then modified the MAF tables!

not as easy as it sounds when you are adding a turbo to the one you already have in there and all the supporting piping to go along with it...

Could somebody please post these? I don't recall seeing any '07 ROMs yet.

Thanks!

http://www.romraider.com/forum/viewtopic.php?t=694

Also, the newest definition file has support for this rom.

i believe that once your fuel trims are stable and <10% (the closer to zero the better obviously), then you're done with injector scaling.

now, one issue that MAY affect other people and not myself is the possibility of the oem fpr getting overrun, particularly with an aftermarket high flow fuel pump. this will shift afrs rich in the higher rpms because the fuel pump duty is mapped to rpm.

on my ecu with defs from xmlwrite i have another compensation map for target afr wrt load and rpm. why would they put yet another load/rpm/afr map in the ecu? i suggest that it is to compensate for non-linearities in the fuel delivery system, and this one would be great for a fuel pressure regulator that isn't quite up to snuff.

another example of a map that i suspect is for the same correctional type purpose plots MAP and target afr offset. this could/would be used to compensate for a fuel pump that trails off as its output pressure rises.

in a nutshell the ONLY way to know for sure that a given amount of air is entering the engine would be to run two mafs in series, with the second as a control. it would obviously have to be well-calibrated.

i would be very wary of shifting the SHAPE of the mafv-g/s transfer function too much. if you're needing to then your answer is probably buried in one of these other compensation tables.

other than that, things are in accordance when your target afr is close to your actual afr. if it deviates in the same area time and time again and you can correlate it to a particular mafv, then change your translation table. if it correlates to higher boost pressure, then look at the MAP compensation. if it correlates to fp duty (you can log this directly) then look at an RPM based compensation.

I have an uprated fuel pump fitted with the stock fpr. I find that the closed loop afr is rich by about .2 AFR and I also get some afr correction and some learning.

In closed loop I find that AFRs are leaner than in the fuel map, particularly at high revs, and believe at least some of this may be attirbuted to the learning. Whilst the correction goes to zero when it goes in to closed loop the learning is still there.

When I reset the ecu or flash a new map that causes a reset the correction and learning go to zero but as soon as the engine is revved it returns. I have previously just took this into account and set the AFR as I want it using the wideband. The fuel table doesn't look very smooth but the actuals are ok.

I believe the answer is a better adjustable fpr. This should allow me to set the pressure properly and get me closer to target, reduce correction and learning and therefore allow me to have a more accurate fuel map. In the meantime though, I will see if my ecu also has some compensation maps.