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Old 05-08-2017, 10:46 AM   #1
romanboy
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Default When do you rescale your MAF?

When would you want to rescale your MAF?

The common response I get is when you change your intake system. Does this include changing the intercooler?

On my 2011 wrx I recently put on 38mm ewg, 1000cc injectors, pump, PW verticooler, colder spark plugs on top of full 3" dp.

I got my injectors latency and scalar dialed in, my A-D learning values are all within +-5%. On WOT runs, my 1/3 corrections and learning values are zero.
Thus, do I have to rescale my MAF?
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Old 05-08-2017, 10:47 AM   #2
romanboy
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If I don't see much change between the commanded AFR and the actual AFR can I also ignore rescaling my MAF?
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Old 05-09-2017, 07:53 PM   #3
86Dreams
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No you should not have to rescale your MAF. If you change anything in the intake tract before the compressor then you will need to rescale.

Last edited by 86Dreams; 05-10-2017 at 03:04 PM. Reason: poorly worded
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Old 05-10-2017, 01:46 PM   #4
Joshfl420
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I had to scale mine when I put the K&N drop in. Anything intake wise needs it scaled
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Old 05-10-2017, 08:58 PM   #5
romanboy
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Quote:
Originally Posted by Joshfl420 View Post
I had to scale mine when I put the K&N drop in. Anything intake wise needs it scaled
Wow you had to scale it for the drop in alone??

How did you know you had to? Were your fuel learning trims edging away from your norm?
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Old 05-11-2017, 04:13 PM   #6
Joshfl420
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Yes. Showed the car running lean. EJ's are super sensitive to any air changes.
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Old 05-15-2017, 09:40 PM   #7
romanboy
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Thanks Josh,

My next question would be how do you differentiate between having to change the injector values vs. maf calibration? If all of my learning values are within +- 5% then when do I decide my maf needs to be rescaled granted I changed nothing before the compressor?

I understand that the voltage-airflow relation needs to change if the correspondence is wrong, but conceptually because I put a different intercooler will this change the actual airflow going through the sensor itself to warrant a change?



Random questions
1. If there is an air leak after the compressor, does it make the engine run rich on WOT and lean at idle?
2. And if there is an air leak before the compressor, does it make the engine run lean?
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Old 05-15-2017, 10:12 PM   #8
CarmelValleyWRX
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here is a LV of my car. (2005 wrx) stock inlet up to the turbo, vf48 with a big intercooler. injectors are from a 06-07 wrx using stock scaling and latency from a 2006-2007 wrx. the front O2 and MAF sensor are only a few months old.


as you can see if you leave the intake stock you should not have to scale the MAF, at least not the low end. if your pushing way more air than stock the top end might need some work.

now if you have leaks it will throw your readings way off and will be pointless to use as a tool to scale the injectors.

the reason you have no corrections at WOT is because you are in "open loop" which ignores the o2 sensor. you need a wideband to tune the higher flow ranges of the MAF.

Last edited by CarmelValleyWRX; 05-15-2017 at 10:17 PM.
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Old 05-16-2017, 06:40 AM   #9
romanboy
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Thanks CarmelValleyWRX:

So do people rescale their MAF for closed loop only?

I have a wideband and based off my logs it looks like the commanded fuel final and actual O2 readings are exactly spot on. My AFR's are a bit wacky apart from WOT (I just blame that on how sensitive the AEM UEGO seems to act)
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Old 05-17-2017, 10:31 PM   #10
CarmelValleyWRX
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you can adjust the whole maf scale if you want. if your wideband matches the ECU commanded fuel through the entire range of MAF voltage thats good and you dont need to rescale it.
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Old 05-18-2017, 03:41 AM   #11
goldfingerfif
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If you change your intake you'll need to rescale / calibrate the MAF. You want your total corrections (AF Correction 1 + AF Learning 1 = Total Correction) to be +/- 5 % for closed loop (Generally up to ~2.77v depending on your year and settings).
You want your open loop to be +/- 1-2% of commanded fuel final.
You'll want to change load compensations after you get your MAF scaling and this includes changing things such as
Intake
Turbo Inlet
Turbo
TVG Deletes
Intake Manifold
After market TMIC
FMIC
BOV
Cams
Porting and polishing of anything in the intake path including heads

Things that would allow for a larger pressure differential such as FMIC, throttle body, etc would almost certainly require a change with Tip-In Enrichment.
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Old 09-29-2019, 02:09 PM   #12
wingman358
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Quote:
Originally Posted by goldfingerfif View Post
If you change your intake you'll need to rescale / calibrate the MAF. You want your total corrections (AF Correction 1 + AF Learning 1 = Total Correction) to be +/- 5 % for closed loop (Generally up to ~2.77v depending on your year and settings).
You want your open loop to be +/- 1-2% of commanded fuel final.
You'll want to change load compensations after you get your MAF scaling and this includes changing things such as
Intake
Turbo Inlet
Turbo
TVG Deletes
Intake Manifold
After market TMIC
FMIC
BOV
Cams
Porting and polishing of anything in the intake path including heads

Things that would allow for a larger pressure differential such as FMIC, throttle body, etc would almost certainly require a change with Tip-In Enrichment.
Just curious why you say "change load compensations after you get your MAF scaling and this includes changing things such as (...list...)" - is that due to possibly different volumetric efficiency? or what?
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Old 09-23-2020, 08:44 PM   #13
sebastian323
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So I bought a base MAP from XPT tuning. My car more or less completely matches the build list for the XPT tune EXCEPT the intake. I am thinking of borrowing the MAF scaling from another tune I have that was setup for my specific intake. I am copying and pasting the whole MAF section in ECU flash. How does this idea sound ?
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