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Old 09-04-2005, 06:09 PM   #1
peters14gc
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Default underboosting in a jdm sti v.5 motor.

Hey guys... just wanted to inquire upon your wisdom regarding underboosting.

I've searched the forums and could not find anything specific to my problem but close, and i have looked into the few possibilities that were laid out but have yet to solve the problem

I have a jdm v.5 sti motor, 2 days it ago it was making 17psi-19psi max boost depending on gear and rmp.

Yesterday while driving down I270 and hitting WOT i noticed it was a lil slower.

I checked the boost and i was only getting about 10psi or so.

So what ive checked so far is driving until i hit full boost, i hit full boost right now at 10psi around 3500-4000 rpm which was normal when i was able to boost at 19psi. But instead of the boost climbing it stops at 10psi.

Driving up until then 10psi and up the rpm feels normal, the motor still pulls like before. its just the boost stops at 10psi.

So we visually checked the vaccum hoses, no disconnections or visual leaks. Intercooler and everything looks fine.

I even emptied the oil catch can, but the can didnt seem clogged or anything, air can freely move in it. I then check the intake and noticed that the clamp from intake to turbo was broken, so i tighten it. check everything else. Reset the ECU and drove...

Since there was no intake leak anymore the cars response was better, but then the underboost issue is still there.

I know that underboosting can be caused by wastegate, blow off valve or bad boost solenoid other than vacuums. Is there any else i can do to check or any other factors i can look into and ways to check these mechanical issues so that i get my boost back?

any help is appreciated, thanks guys.

-peter.
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Old 09-04-2005, 11:30 PM   #2
DuoMaxwell
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What type of ECU are you running. Has it been reflashed or do you have a piggy back or a stand alone. The ECUs are pretty smart and will retard timing and limit boost if the gas does not support it properly.
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Old 09-05-2005, 02:28 AM   #3
peters14gc
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Quote:
Originally Posted by DuoMaxwell
What type of ECU are you running. Has it been reflashed or do you have a piggy back or a stand alone. The ECUs are pretty smart and will retard timing and limit boost if the gas does not support it properly.
runny stock jdm ecu, no reflash no piggy back.
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Old 09-05-2005, 05:31 AM   #4
DuoMaxwell
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I would get a reflash on the ECU because I am pretty sure the octane you run on a regular basis is not the same as JDM gas!
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Old 09-05-2005, 05:58 AM   #5
SaabTuner
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Hmmm ... faulty wastegate control solenoid leaving you with only base-boost?
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Old 09-05-2005, 08:10 PM   #6
rishoboy6
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Quote:
Originally Posted by DuoMaxwell
I would get a reflash on the ECU because I am pretty sure the octane you run on a regular basis is not the same as JDM gas!
+1 on that. . .i'm pretty sure the JDM ECU expects 96 octane gas
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Old 09-06-2005, 09:59 AM   #7
peters14gc
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Its a jdm ecu so i dont know what i can use for the ecu reflash.... but i will check to see if there is a bad wastegate solenoid, because it seems like it only running base boost from the wastegate.
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Old 09-06-2005, 11:26 AM   #8
rishoboy6
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i think u can ship your ecu out to kingpin and they can reflash it for you.
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Old 09-06-2005, 05:21 PM   #9
peters14gc
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Quote:
Originally Posted by rishoboy6
i think u can ship your ecu out to kingpin and they can reflash it for you.
is there a website.
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Old 09-06-2005, 09:26 PM   #10
peters14gc
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thanks for all the advice guys... im actually boosting normally now. I guess sundays ECU reset took some time to figure things out after i fixed the intake issue.

feels good around 17-20psi again.
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Old 09-07-2005, 12:02 AM   #11
rishoboy6
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Old 09-07-2005, 12:11 AM   #12
jamesfacts
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Quote:
Originally Posted by peters14gc
thanks for all the advice guys... im actually boosting normally now. I guess sundays ECU reset took some time to figure things out after i fixed the intake issue.

feels good around 17-20psi again.
I would run octane booster, just to be safe. JDM ecus come from the factory running insane timing, up to 4x*

I know they're smart and will pull that, but driving a JDM car on 93 is kinda like driving a US WRX on 87. Why take chances with a rare, expensive motor?
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