Okay guys its me again, I'm the guy who is hitting over 22 psi on a Cobalt SS/SC that SHOULD NOT be hitting that much boost. The only mods i had at the time were an Injen CAI and GMPP Stage 2.

Many of you advised me that it was a clogged catalytic converter or that my exhaust was too restrictive.

So i took your advice and had the GMPP catback exhaust and a magnaflow hi-flow cat installed.

But i'm still overboosting at 22psi. I have taken it to two different mechanics, one was a very good GM mechanic and the other guy was a western auto head mechanic, and both of them cannot figure it out.

The stock boost gauge has been replaced and a new boost solenoid has been installed. (under warranty), so i know its not a bad gauge/read.

The car runs fine and my gas mileage is awesome. Occasionally after running it hard the blower whine will start to surge at around 6-7K RPM. But it does not seem to be a problem and acceleration does not suffer.

Please help! I love my Cobalt and do not want to melt the blower/blow the engine.

 

damn... I got a guy over here having the same problem... still can't figure it out... he was supposed to come by today so I could spend some time going through and running some scans.... but... oh well

 

Please keep me updated! I would go buy the Aeroforce Interceptor but well, i'm kind of out of money since i just bought $700 worth of exhaust mods.

The Interceptor reads directly from the OBDII port, so if theres something wrong with the wiring in my gauge, then i will find out.

But if ANYBODY has any suggestions, let me know. But make sure there at least educated guesses, cause i tend to take advice from here seriously.

 

once I find something I"ll def let you know man

 

overboosting... sounds like a clogged cat...

 

He just said he bought a brand new High flow cat.

 

I saw that... perhaps the new cat he bought is defective...

could also be something wrong with the exhaust manifold too... anything blocking airflow out of the engine will cause overboosting.

If he's boosting that high... he should seriously take it in to a dealership... as far as I know, the stock head gasket can only handle like 20PSI.

 

I actualy had the hi-flow cat installed today, and i highly doubt both the stock and turbotechracing cat were defective. I cant be THAT unlucky.

As of right now, the only stock parts of my exhaust are the exhaust manifold (header) and the downpipe.

I don't imagine the downpipe could be defective/clogged because.....well, its just a pipe. And if the exhaust manifold was clogged, I imagine I would be having significant power loss and i have never really heard of people having clogged headers. But hey, ya never know.

The car performs beautifully, everybody who rides in is impressed so like i said before, there is no noticable power loss. Once again, thanks for the comments and anybody who has a suggestion please speak up.

 

I was thinking it might be something in the exhaust too.... maybe header... or crap blew outta the cat into the muffler...

 

That's probably what it is bro. Don't go out and buy a new one yet. Remove it and check it first.

 

I know of something that would cause you to boost that high on an M62 with a 2.8" pulley. But I doubt it highly.

 

darksuns is doin that with a 3.0.... wierd and we just tried 2 different high flow cats

 

Does he have a header or stock manifold? It sounds like it could be the manifold getting blocked up by the carbon from this very rich running GM tune.

 

stock manifold... thats what I tried to get him over here to change today... I got a spare header and was gonna try that out

 

One of my guys here in AZ is seeing about 20 PSI with the GM Stage 2. That's a ton of boost for those few mods, but he was seeing 15PSI stock, and he had his boost guage replaced too.

 

omfg.. ur complaining cause u got 22 PSI under warranty.. theres something wrong with you

 

While 22 PSI sounds like it's a good thing, he's not doing that on purpose. He doesn't have any "big-time" power-adders that should give him the 22 PSI so it's actually a problem for him. It's better to be honest with the dealer, anyway, than to just get away with it, allowing him to keep his warranty, because the second the dealer asks why you were boosting at 22 PSI and never mentioned anything about it, the argument that you didn't know why it was doing that won't stand. That position could leave you with a voided warranty.

 

factory freak?

 

This message is from GM the car u have was a prototype and somehow got sent out to a dealer for sale. Please return the car asap.

 

take out the O2 sensor and go for a quick run. see if the boost comes down. this is one way to tell if the cat is pulged. also is there not a vac pot on the supercharger that limits boost? i just got my car 2 days ago and havent realy looked through it yet. but could that cause the problem?

 

do you have the boost bypass mod done? If so the car can't bleed boost properly if you got the system rigged.

 

Thanks for the help guys and let me state a few things.

1) It cannot be the cat or the exhaust system from the cat back. They have both been replaced this week. The only stock exhaust components are the downpipe and exhaust manifold.

2) I'm worried because the car is not capable of handling 22psi without significant supporting mods. It is still under warranty, but running a car with a problem is just stupid, this is a daily driver. I'm a college kid with my own place and vehicle, if the car breaks, i'm screwed.

3) The boost bypass mod has NOT been done on this car. Only me or certified mechanics touch under the hood. The stage 2 pulley (3.0") is still on the car.

So you guys are saying that it is possible to have a clogged/restricted exhaust manifold? Is it possible for me to just jack up the car and unbolt the exhaust mani and inspect it without having to cut anything?

Thanks

 

I boosted:
13.1 PSI stock
16.5 PSI w/S2 + CAI
18.0 PSI w/2.8
and now thinking my DP should bring my boost down to 17, thinking it was a clogged cat.
19.0 PSI w/ XTC 3" DP

I have no clue whats going on, i dont think i should be seeing this much boost, wondering if the boost guage itself is malfuncationing.

 

My GM mechanic originally thought it was the gauge, so he replaced both it and the boost solenoid, but neither helped the situation.

I knew it wasn't the gauge because at 7K rpm, you can hear the blower literally at its max.

If i can get into my header without having to cut anything, then i'm gonna try and give them a good inspection tomorrow. I'll keep you guys posted.

But please, any other suggestions are welcome. The problem with this car is that NOBODY KNOWS ANYTHING ABOUT IT. Everytime i mention the word "over-boosting", mechanics just stare at me like i'm an idiot.

 

hahaha same with thte guy over here... but unfortunatly I got a phone call at 3:30 am last night that it droppped a cylinder... so I"m on my way to go look at it now... so my advice.. do not drive it hard to you find the problem.