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Old 07-17-2019, 11:24 AM   #1
gw7
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Member#: 490887
Join Date: Aug 2018
Vehicle:
2007 STI
Urban Grey Metallic

Default Laggy, choppy at low RPM ó cause for concern?

Hey guys.

Bought a 2007 STI tuned on Speed Density with a built EQ Stage 1 block, bowl bend valves, BC cam, 1000cc top feeds, Grimmspeed TGV deletes, ATP GT3076R, Tial 44mm EWG, KS Tech 73mm CAI, Perrin FMIC, etc. etc. etc.

The car rips at WOT on both the 18psi 93 oct tune and the 21psi e85 tune.

However, at low RPM (at idle in neutral, for example) the throttle response is REALLY slow/laggy and "chops" or "stumbles" a bit when revving in neutral.

Similarly, if I'm coasting to a stop (car is in neutral) and I give it a little "blip", it's choppy and hesitates to rev back up if I want to rev match, for example.

Both of these things only really happen under 3k RPM. Driving around in low RPMs, it can be a little wonky/choppy at light throttle until the car is fully, FULLY warmed up. I baby the car until it's been driving around for at least 10 minutes, and even then, I RARELY get into boost. I drive slow 99% of the time.

Even once it's smooth at low RPM and fully warmed up, it still feels "hesitate-y" in low RPMs until it's up around 3.5k.

Do I just chalk this up to "big turbo, CAI/FMIC, speed density tune" probs?

Had a compression/leakdown test done before buying the car about a year ago and everything came back good.

However, the motor was built YEARS ago (I think like 9-10 years ago). It was re-tuned in the last 3-4 years. Does this sound like something a re-tune or adjustment could fix?

I'll be moving to a higher-elevation state soon, so I was going to have the car retuned anyway, but don't want it going on the dyno if **** could potentially blow up.
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Old 07-17-2019, 12:45 PM   #2
GravyRobber
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Join Date: Mar 2009
Location: West TN
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2017 WRX STi
WRB

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Would you be able to post a data log? That would be a fairly easy way to check on the general health of things.
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Old 07-17-2019, 01:00 PM   #3
JSR84
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Logs....
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Old 07-17-2019, 05:16 PM   #4
gw7
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I can certainly post a log! Didnít know you guys were able to decipher them. Iím certainly not. What parameters should I log, and what kind of driving should I do?
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Old 07-17-2019, 05:17 PM   #5
Fahrezz
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Quote:
Originally Posted by GravyRobber View Post
Would you be able to post a data log? That would be a fairly easy way to check on the general health of things.
+1
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Old 07-17-2019, 06:53 PM   #6
Haevn
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Do you have TGV deletes? I know after i did my deletes my car studders sometimes between 2-3k rpm at light throttle

nvm just re read your post and seen you do have them lol
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Old 07-17-2019, 07:17 PM   #7
JSR84
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Quote:
Originally Posted by gw7 View Post
I can certainly post a log! Didn’t know you guys were able to decipher them. I’m certainly not. What parameters should I log, and what kind of driving should I do?
AF Correction 1
AF Learning 1
AF Ratio (Both the factory sensor and a wideband if you're able)
AVCS (Exhaust and intake if you have dual)
Boost
Calculated Load
Dynamic Advance Mult.
Knock Learning
Feedback Knock
Injector PW
MAF
MAF Voltage
MAP Abs
Primary Ignition
Throttle Position
VE

That's all I can think of now. Do a couple of sweeps through the problem areas.

Last edited by JSR84; 07-17-2019 at 07:31 PM.
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