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Old 11-13-2018, 09:48 AM   #1
nyev
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Post Fluctuating AF Correction

I am currently having my WRX tuned by Ron @ Phatbotti, and I seem to have some sort of leak and strange AF correction spikes, leading to my fuel trims being off.

Every time I get on the throttle during a normal cruise my AF correction spikes drastically between +-20% and steadys down between +-10%. During idle, the correction does not surpass +-5%.

I am currently stage 2+

Mod list
- Custom Muffler Delete 4" Quad Tips
- Cobb Big SF Revised Intake
- Boomba Bypass Valve
- Invidia Catless J-Pipe w/ Extra O2
- iAG TGV Delete
- iAG EGR Delete
- Grimmspeed 3-Port EBCS

I have gone and checked my turbo inlet, the boomba bpv is installed correctly and fastened properly/securely. The boost controller is installed securely and both wastegate hoses are secured and zip tied at the connection port.

The jpipe is installed securely to the turbo with new gs studs, and has the proper 3" to 2.5" adapter to stock cat back, there are no exhaust leaks. Soapy water test has been done.

TGV's are sitting on the gasket and tightened down to spec. EGR delete block off plates are tightened down to spec. Both recirc. elbows are attached and fastened. All plugs are zip tied to avoid false knocks.

The intake filter is sitting exactly 1 inch on the tube, the rubber coupler is fastened properly, even tried to match the exact location the hose clamps sit on the coupler by the pictures.

Here are my logs. I have no idea what could be off. Thoughts?

Cruise log:
https://datazap.me/u/nyev/log-154207...ta=1-2-3-25-33

WOT:
https://datazap.me/u/nyev/log-154207...=1-2-3-9-25-33
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Old 11-13-2018, 11:39 AM   #2
Stija
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What did Ron say? That you have a leak?

If so, that’s as far as we can diagnose it too, most likely a leak somewhere. Can you do a smoke test?

Just peaked at your logs, what’s the highest boost you get? If I’m reading the chart correctly barely ~5psi?? There’s your leak.
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Old 11-13-2018, 12:46 PM   #3
Craigster08
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@Stija, yes you did read the log incorrectly. He was hitting 18-19 psi in his WOT log.


@nyev, have you tried cleaning your MAF? Also, if possible, it may not hurt to put the stock intake back on and see if the AF corrections are still spiking.
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Old 11-13-2018, 01:00 PM   #4
Stija
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Wow I just realized that the data is down in the table and i can look through it. It was hard to see on my phone.

If you put stock intake have Ron send you an adjusted map for the stock intake.
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Old 11-13-2018, 01:25 PM   #5
nyev
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Quote:
Originally Posted by Craigster08 View Post
@Stija, yes you did read the log incorrectly. He was hitting 18-19 psi in his WOT log.


@nyev, have you tried cleaning your MAF? Also, if possible, it may not hurt to put the stock intake back on and see if the AF corrections are still spiking.
Just cleaned my maf sensor with the crc electronic cleaner, adjusted the inlet a tad. Going to reset ECU and send some new logs.

And regarding the smoke test, I was debating it. If I still have issues I'll be sure to try that.
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Old 11-13-2018, 05:31 PM   #6
tegxsi
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I really don't see an issue...WOT looks fine.
AF correction is going to jump all over the place which is normal. AF correction is real time short term fuel trim based on o2 sensor feedback.
AF learn is long term fuel trim the ECU learns over time based on AF correction.

Keep in mind your total fuel trim applied = AF correction + AF learn.
You have varying weather, temperatures, fuel quality...etc. If you are expecting near 0 AF learn/correction all the time, that is impossible. You'll even see the AF learn/correction shift after an oil change since the fresh oil will have no fuel dilution yet.

It's probably as good as it gets with the Cobb intake.

Last edited by tegxsi; 11-13-2018 at 05:38 PM.
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Old 11-13-2018, 05:52 PM   #7
GlarryHoodDIT
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Quote:
Originally Posted by tegxsi View Post
I really don't see an issue...WOT looks fine.
AF correction is going to jump all over the place which is normal. AF correction is real time short term fuel trim based on o2 sensor feedback.
AF learn is long term fuel trim the ECU learns over time based on AF correction.

Keep in mind your total fuel trim applied = AF correction + AF learn.
You have varying weather, temperatures, fuel quality...etc. If you are expecting near 0 AF learn/correction all the time, that is impossible. You'll even see the AF learn/correction shift after an oil change since the fresh oil will have no fuel dilution yet.

It's probably as good as it gets with the Cobb intake.
AF Correction and Learn are based on accurate MAF scaling, how would an oil change do anything to affect air going from the scoop to the airbox to the MAF.
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Old 11-13-2018, 08:11 PM   #8
X49
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On your WOT log, you're holding boost just fine, and your AFRs are perfect. You don't seem to have a leak.
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Old 11-13-2018, 08:19 PM   #9
nyev
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Quote:
Originally Posted by tegxsi View Post
I really don't see an issue...WOT looks fine.
AF correction is going to jump all over the place which is normal. AF correction is real time short term fuel trim based on o2 sensor feedback.
AF learn is long term fuel trim the ECU learns over time based on AF correction.

Keep in mind your total fuel trim applied = AF correction + AF learn.
You have varying weather, temperatures, fuel quality...etc. If you are expecting near 0 AF learn/correction all the time, that is impossible. You'll even see the AF learn/correction shift after an oil change since the fresh oil will have no fuel dilution yet.

It's probably as good as it gets with the Cobb intake.
After spraying my maf sensor with cleaner, and moving the intlet around exactly to cobbs instructions.

Drove around 120km/75miles, mixed city, traffic, and highway.

WOT pull after cleaning:
https://datazap.me/u/nyev/log-154215...=1-2-3-9-25-33

Last edited by nyev; 11-14-2018 at 08:14 AM.
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Old 11-14-2018, 10:19 AM   #10
X49
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Another WOT log doesn't really help. The last one was fine. This one is too.
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Old 11-14-2018, 11:58 AM   #11
anarekist
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your log is way smoother than mine, getting tuned by ron too, dyno date this monday. but hes been sending me maps and asking me for logs.

https://datazap.me/u/anarekist/2nd-3...=0&data=3-9-26
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Old 11-14-2018, 02:32 PM   #12
nyev
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Quote:
Originally Posted by anarekist View Post
your log is way smoother than mine, getting tuned by ron too, dyno date this monday. but hes been sending me maps and asking me for logs.

https://datazap.me/u/anarekist/2nd-3...=0&data=3-9-26
Can't seem to access your log. Also, Ron has been telling me my logs seem to be throwing fuel trims around and a little strange, but everyone I have shown seems to say they are normal.

Not sure if we are missing something or not looking at the right things, or what.
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Old 11-14-2018, 02:37 PM   #13
anarekist
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Quote:
Originally Posted by nyev View Post
Can't seem to access your log. Also, Ron has been telling me my logs seem to be throwing fuel trims around and a little strange, but everyone I have shown seems to say they are normal.

Not sure if we are missing something or not looking at the right things, or what.
ah sorry corrected that.

have you tried a smoke test?
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Old 11-14-2018, 03:16 PM   #14
nyev
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Quote:
Originally Posted by anarekist View Post
ah sorry corrected that.

have you tried a smoke test?
I've went over everything on my car, I doubt I have a leak post/pre turbo.
If it comes to it, and I really need to, I will.
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Old 11-14-2018, 03:32 PM   #15
Stija
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It’s probaby that intake of yours that’s doing it. It’s probably as good as it will get.

Added: Had you asked Ron beforehand he’d most likely advised you to spend money else where.

Last edited by Stija; 11-14-2018 at 04:16 PM.
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Old 11-14-2018, 07:51 PM   #16
nyev
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Quote:
Originally Posted by Stija View Post
Itís probaby that intake of yours thatís doing it. Itís probably as good as it will get.

Added: Had you asked Ron beforehand heíd most likely advised you to spend money else where.
Yea honestly, it can't get perfect. I doubt even with stock intake it would be the be any better, just smaller margins that's all.

Ron doesn't recommend intakes by taking a glance at his website.
"Intakes are mostly just noise makers on these cars."
Although he says if you were to get one, it would be the GS CAI, the filter fitment is the same for every customer as there is a threshold notch it can not surpass. Making margin for error smaller.

I only got the Cobb Big SF intake because of their customer support, it had an OTS tune for it back when all I had was an intake, and everyone in the local community seemed to have one. Also, I was in contact with Cobb at the time and they told me they would be releasing a revised intake "fixing" the turbulence, as well as fitting the 2018/19 models better. You can see this with the two models having slightly different tubes & brackets.

Will most likely be swapping to the GS CAI on my next tune, along with a CP and GS TMIC.
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Old 11-15-2018, 11:51 AM   #17
Stija
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I was watching mine today, not logging though, a1 was 0 and the b1 was the one with largest changes as big as -4.4/1.1% recorded in slow moving hwy traffic on my way to work. B1 stayed mostly -1.78 or something, all others were fractions of 1.00.

I’d get a clearer picture if I logged it, but I went into this with the decision not to be one of those people looking at logs constantly and chasing dragons and stressing. Unless I notice a big swing in af learning or my car acts funny I don’t log and analyze.

Last edited by Stija; 11-15-2018 at 02:08 PM.
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Old 11-15-2018, 03:12 PM   #18
nyev
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Quote:
Originally Posted by Stija View Post
I was watching mine today, not logging though, a1 was 0 and the b1 was the one with largest changes as big as -4.4/1.1% recorded in slow moving hwy traffic on my way to work. B1 stayed mostly -1.78 or something, all others were fractions of 1.00.

Iíd get a clearer picture if I logged it, but I went into this with the decision not to be one of those people looking at logs constantly and chasing dragons and stressing. Unless I notice a big swing in af learning or my car acts funny I donít log and analyze.
Your setup?
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Old 11-15-2018, 04:43 PM   #19
Stija
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TGVEGRGEBCS GS TMIC GS J-Pipe and 91oct tune by Ron. (Egr unplug only).
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Old 11-16-2018, 12:50 PM   #20
arghx7
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Pressure test for boost/vacuum leaks.
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