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Old 10-10-2012, 02:28 AM   #1
151sti
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Default sti wont keep tune?

first off heres a little info about the car, 2006 sti, has headers full catless exhaust(perrin dp, cobb cat back) spt intake, and a pro tune. so heres the deal recently ive been having an issue which seems like the tune fades on the car? i can flash it and for a few days the car will hit target boost which is 18.5 psi, then one day it wont go over 12-13. im getting no trouble codes or anything other than the car not boosting its running fine.

if once i realize it dosnt hit target boost i can flash it and the car is back to target boost again. has anyone else ever heard of this? its very strange to say the least
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Old 10-10-2012, 03:01 AM   #2
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As weird as this is going to sound, check your coolant reservoir for your turbo and radiator. If they are low or empty, top them off with 50/50 coolant. From my understanding when the coolant is low, the DAM of your car will drop below the value of 1.0 and therefore reducing the target boost level. Then reset your ECU with Cobb AP

That is what I was told to do when I had the same problem and it worked for me. Once I datalogged the car it all made sense. Datalog it and post up the file and it will narrow down some possibilities. I'd also perform a compression test to be on the safe side -$30 kit from AutoZone, about 2-3 hours to do it yourself with some instructions from NASIOC/IWSTI wouldn't hurt.

-Jason
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Old 10-10-2012, 03:02 AM   #3
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Also, when did you perform those mods and when did the problem start happening? Do you have a bigger fuel pump?

-Jason
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Old 10-10-2012, 03:49 AM   #4
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Are you tuning your car yourself ?
If when you reflash the car it seems to recover power, it's only because you have a problem with the learnings. I bet that instead of reflashing the car if you perform an ECU reset, you will recover power as well.
So it's just a bad tune, or eventually a leak somewhere.
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Old 10-10-2012, 04:19 AM   #5
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I would almost bet that your IAM is just dropping over time. That will cause the ECU to cut your boost roughly in half.

Maybe you need higher octane fuel, or maybe your tune is just too aggressive for the fuel that you have.
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Old 10-10-2012, 05:00 AM   #6
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My $.02, the ecu is learning, it sees something it doesn't like and is pulling power to be safe. Could be knock form different fuel, heat, aggressive tune, etc. Data log.
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Old 10-10-2012, 11:40 AM   #7
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If you keep re-flashing over your learned tune you will be purchasing a new engine soon. You need to data log and find out why your engine is not happy and rectify the problem.
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Old 10-10-2012, 11:40 AM   #8
151sti
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Quote:
Originally Posted by ARiSTA Performance View Post
As weird as this is going to sound, check your coolant reservoir for your turbo and radiator. If they are low or empty, top them off with 50/50 coolant. From my understanding when the coolant is low, the DAM of your car will drop below the value of 1.0 and therefore reducing the target boost level. Then reset your ECU with Cobb AP



That is what I was told to do when I had the same problem and it worked for me. Once I datalogged the car it all made sense. Datalog it and post up the file and it will narrow down some possibilities. I'd also perform a compression test to be on the safe side -$30 kit from AutoZone, about 2-3 hours to do it yourself with some instructions from NASIOC/IWSTI wouldn't hurt.

-Jason
ill check the coolant today, that would be an easy fix. the motor has about 10k on it from a recent rebuild

Quote:
Originally Posted by ARiSTA Performance View Post
Also, when did you perform those mods and when did the problem start happening? Do you have a bigger fuel pump?

i never realized it was happening untill i hooked my ap up to see the boost on it. i noticed it wasnt pulling hard anymore so i wanted to check and see if it was just me being used to the power or if it really was lacking i have a walbro255 fuel pump, from what i can tell the afr's are good under wot

-Jason
Quote:
Originally Posted by FRWRX View Post
Are you tuning your car yourself ?
If when you reflash the car it seems to recover power, it's only because you have a problem with the learnings. I bet that instead of reflashing the car if you perform an ECU reset, you will recover power as well.
So it's just a bad tune, or eventually a leak somewhere.
i had my local shop do a dyno tune on it, im going to call him today a see if he has any ideas.

Quote:
Originally Posted by NSFW View Post
I would almost bet that your IAM is just dropping over time. That will cause the ECU to cut your boost roughly in half.

Maybe you need higher octane fuel, or maybe your tune is just too aggressive for the fuel that you have.
ill look into the fuel but i only run shell or 76 91octane would octane booster help or would i need to mix in race gas?

Quote:
Originally Posted by k mier View Post
My $.02, the ecu is learning, it sees something it doesn't like and is pulling power to be safe. Could be knock form different fuel, heat, aggressive tune, etc. Data log.
what things should i data log to get good info?
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Old 10-10-2012, 12:04 PM   #9
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you need to log:

A/f learning
A/f correction
Engine Load
Feedback Knock Correction
Fine learn knock correction
IAM
MAFv
MAP (corrected)
Throtle open angle
Vehicle Speed
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Old 10-10-2012, 03:44 PM   #10
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Quote:
Originally Posted by NoGraffix View Post
you need to log:

A/f learning
A/f correction
Engine Load
Feedback Knock Correction
Fine learn knock correction
IAM
MAFv
MAP (corrected)
Throtle open angle
Vehicle Speed
Also add "Knock Sum" to the list, if the ECU supports it.
AFR would be helpful too, preferably from an aftermarket wideband setup.
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Old 10-10-2012, 10:02 PM   #11
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yep.. logs. Need to see the data.
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Old 10-11-2012, 12:55 AM   #12
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https://docs.google.com/a/folsombike...BR0dSNEE#gid=0

heres the log 3rd gear pull, seems like some knock?
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Old 10-11-2012, 02:05 AM   #13
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Quote:
Originally Posted by 151sti View Post
https://docs.google.com/a/folsombike...BR0dSNEE#gid=0

heres the log 3rd gear pull, seems like some knock?

Quote:
Drive



You need permission to access this item.
Looks like you need to make that file public...
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Old 10-11-2012, 11:25 AM   #14
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Quote:
Originally Posted by 151sti View Post
ill look into the fuel but i only run shell or 76 91octane would octane booster help or would i need to mix in race gas?
Stating the obvious here, any STI owner would be smart enough to not run 91octane or mixed fuel or octane booster or any of that crap. you should be running 94octane. mixing fuels will only confuse your ECU. it could be that you had 94octane when you went for your protune.
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Old 10-11-2012, 11:47 AM   #15
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i live in california. 91 is the highest we have here thank for the input tho
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Old 10-11-2012, 11:55 AM   #16
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In some areas 91 is the top grade. The ecu should learn the fuel, which it sounds like it's trying to do. It doesn't like what it's seeing. And yes, from experience, you can damage a motor with peemix quicker than the ecu can pull timing/ boost. Liked mentioned, if you got tuned on a higher grade fuel you should be using that fuel all the time.
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Old 10-11-2012, 12:37 PM   #17
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Old 10-11-2012, 12:47 PM   #18
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Quote:
Originally Posted by coalslaw View Post
Stating the obvious here, any STI owner would be smart enough to not run 91octane or mixed fuel or octane booster or any of that crap. you should be running 94octane. mixing fuels will only confuse your ECU. it could be that you had 94octane when you went for your protune.
And I'd figure most STI's owners would know that not every state carries above 91 octane in most gas stations. Way to prove me wrong.

91 is perfectly fine, not ideal, but it works fine stock or if tuned for it.
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Old 10-11-2012, 01:21 PM   #19
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Quote:
Originally Posted by 151sti View Post

According to this log you're peaking boost @ 16.87 at ~4600rpm. If you are still on the stock vf39 then you are peaking boost really late in your powerband and you likely have an exhaust leak, malfunction bcs, or wastegate actuator. There are also some instances of some fairly substantial knock events (the -6 and -5). More concerning is that your DAM started off at 0.75 which means you either had just flashed the map or your ECU has been experiencing knock consistantly and has lowered this value to reduce timing and boost in order to protect your engine.
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Old 10-11-2012, 03:06 PM   #20
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Quote:
Originally Posted by s2ktosti View Post
And I'd figure most STI's owners would know that not every state carries above 91 octane in most gas stations. Way to prove me wrong.

91 is perfectly fine, not ideal, but it works fine stock or if tuned for it.
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Old 10-11-2012, 04:47 PM   #21
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Quote:
Originally Posted by s2ktosti View Post
And I'd figure most STI's owners would know that not every state carries above 91 octane in most gas stations. Way to prove me wrong.

91 is perfectly fine, not ideal, but it works fine stock or if tuned for it.
Zing!

Quote:
Originally Posted by NoGraffix View Post
According to this log you're peaking boost @ 16.87 at ~4600rpm. If you are still on the stock vf39 then you are peaking boost really late in your powerband and you likely have an exhaust leak, malfunction bcs, or wastegate actuator. There are also some instances of some fairly substantial knock events (the -6 and -5). More concerning is that your DAM started off at 0.75 which means you either had just flashed the map or your ECU has been experiencing knock consistantly and has lowered this value to reduce timing and boost in order to protect your engine.
I agree. And those knocks were in boost and at high load, so they're legit knock, not the false knock that everybody gets when cruising at low loads from time to time.

18 degrees of timing at 2.5 g/rev and 5600 RPM is pretty high, I think the tune probably needs to be mellowed out.
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Old 10-12-2012, 01:11 AM   #22
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Quote:
Originally Posted by NSFW View Post
Zing!



I agree. And those knocks were in boost and at high load, so they're legit knock, not the false knock that everybody gets when cruising at low loads from time to time.

18 degrees of timing at 2.5 g/rev and 5600 RPM is pretty high, I think the tune probably needs to be mellowed out.
the car is going back in on monday for a check up and re-tune if necessary, in the mean time im going to check for exhaust leaks or boost leaks as well
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Old 10-12-2012, 08:55 PM   #23
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change the front o2 sensor
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Old 10-13-2012, 02:31 AM   #24
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o2 sensor is no more than 6 months old, but it definitely could be the problem ill look into it! thanks!
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Old 10-13-2012, 02:44 AM   #25
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heres one more data log that i did today with a 4th gear pull, lots of knock apparently. some thing with the tune? or could it be a faulty sensor?

https://docs.google.com/spreadsheet/...yUkhqLWc#gid=0
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