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Old 01-03-2013, 06:57 PM   #1
mhughes
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Default 05 sti stg2 over boosting

I have an 05 sti with an invidia bellmouth dp/ N1 street exhaust(no cats), also have a grimmspeed uppipe and a K&N typhoon intake.

My question is i currently am running the stg2 91oct map from cobb AP which is set at 17.5lbs of boost, i having been hitting upwards of 21.5lbs and i was wondering what could be causing this or how can i fix it??
i recently installed a grimmspeed mbc and my boost will hold around 15.5lbs but if i keep on it, it will then start to increase and is peaking near 20lbs

Please any advise would be very helpful!!! my only thought is to go get a pro tune to see if they cant get my boost under control
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Old 01-03-2013, 08:31 PM   #2
veel86
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The intake you are running will not work for your tune. My guess is that it is cause your A/F ratio to be lean. Also a tune is needed for your MBC. You need a tune for both of them. Also do you have a wide band o2 sensor gauge? If not, then this would be your next step before you get a protune.
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Old 01-03-2013, 09:17 PM   #3
mhughes
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I dont not have a wideband o2 sensor gauge. the tuner i was talking to said he has his own that he would use when he tunes
but ok thanks for the input
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Old 01-03-2013, 10:14 PM   #4
Airboy
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Cat-less exhaust + intake + cold winter air is a recipe for boost creep for the stock STi turbo. The wastegate port of the turbo doesn't flow enough to prevent the turbine from building boost. This would be why the manual boost controller didn't help.

A catted downpipe will help as would porting the wastegate port on the turbo.
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Old 01-03-2013, 11:28 PM   #5
mhughes
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Airboy, that is basically what i have come to, im going to talk to a tuner and see if he cant smooth it out a little bit so it doesnt spike so much
another thing i have thought about it going to an ewg uppipe but at that point i would still need a pro tune
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Old 01-04-2013, 09:42 AM   #6
Cobb Tuning
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Quote:
Originally Posted by mhughes View Post
Airboy, that is basically what i have come to, im going to talk to a tuner and see if he cant smooth it out a little bit so it doesnt spike so much
another thing i have thought about it going to an ewg uppipe but at that point i would still need a pro tune
I wouldn't do any more wide open throttle (WOT) pulls with your combination. The intake is not supported by the map, you are obviously overboosting (possible boost creep), and an MBC is not compatible with these OTS map either. If you have the stock intake, you could remove the MBC and replace the intake then do a WOT run with our fuel economy map. This will disable boost control and tell you if there is any chance of tuning out the overboost at all. This probably won't be worth it, though, if you are planning to get a tune anyway with this combination of mods. So, you could just drive very conservatively until the tune, but it may not possible for the tuner to help with the overboost if this is boost creep. As mentioned, that may require a mechanical change - 1. catted bellmouth DP 2. ported WG w/ tune 3. EWG w/ tune.

Bill
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Old 01-06-2013, 01:58 AM   #7
mhughes
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decide to go with an ewg and 3port ebc, about to order parts and have a tune schedule for feb 8th, thx for the help
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