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Old 03-01-2008, 04:11 PM   #1
dbrunner
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Default Low boost readings

Always thought my car felt so strong (never driven any other subie but mine), until I pay a shop to install a boost gauge. I've done some 3rd and 4th gear pulls beyond 4500rpm and I'm not even hitting 10psi; more like 9.5psi. The boost likes to sit around 6-7psi at 3500-4500rpm until it gets beyond 5000rpm where it creeps to around 9. As of right now I'm hoping it's just an inaccurate reading from the gauge...

There is an orifice (pill) in the line coming off the wastegate actuator, I thought for sure that was the problem after some of the threads I've read. Everything seems fine, maybe a vacuum leak of some kind. I don't know. The car was tuned after I had my turbo-back exhaust installed, tuner even told me he would increase the boost a little but nothing to make it unreliable.

It's a mechanical boost gauge and I'm pretty sure there isn't a restrictor in the line off the BPV, shouldn't I do this? When in full throttle, I'm hearing a lot of metal rattling noise coming from the BPV area, I've read that the restrictor gets rid of this and makes the needle on the gauge smoother. Would it also fix a gauge from reading incorrectly?

CN: Car runs strong (or so I thought), had boost gauge installed, reading around 9.5psi MAX, hearing lots of noises near the BPV is located (needs restrictor?).

Car: 2002 WRX
Mods: 3" turbo-back exhaust, catless uppipe, Perrin TI, APS intercooler hoses
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Old 03-01-2008, 04:29 PM   #2
Mulder
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The restrictor in the wastegate line needs to be there, otherwise you will only get wastegate pressure.
Is the gauge installed properly? It sounds like it is, since you mention the line from the BPV which is where it should be connected. Usually a restrictor is used in that line with a mechanical gauge, not for accuracy but for damping so the needle doesn't oscillate or buzz.
Does the gauge read zero with the engine off? If it doesn't the gauge won't be accurate, the readings will be offset by the amount it varies from zero.
You could have an intake leak that is bleeding off some boost, check all your hoses and fittings.
If everything checks ok you may want to try a different gauge if you have access to one, yours could just be way off. If the readings with a different gauge are the same, that would confirm a problem.
One final suggestion, if you don't find anything else you could try removing and cleaning the BCS, they do get sticky sometimes.
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Old 03-01-2008, 04:52 PM   #3
dbrunner
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Thanks, all good information I can use to look over again.
With the engine off and the key in the ON position, the boost gauge is just barely below zero (.5-1 HG). As far as any intake leak I don't see anything noticeable, and I haven't cleaned the BCS ever for the time I've had my car so that might be something I could do.
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Old 03-01-2008, 05:05 PM   #4
dbrunner
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After looking at my uppipe from above, it doesn't look like the installer blocked off the EGT bung with a bolt since the EGT probe isn't there anymore. This can't be that good can it?
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Old 03-01-2008, 05:31 PM   #5
whtlegacy
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Quote:
Originally Posted by dbrunner View Post
After looking at my uppipe from above, it doesn't look like the installer blocked off the EGT bung with a bolt since the EGT probe isn't there anymore. This can't be that good can it?
So he left a hole open in the up pipe? Yeah, that's bad and will prevent exhaust gasses from spooling the turbo up properly.

More importantly, I would imagine this leaves the turbo open to particles/dust/gravel/etc that could really mess it up. Don't drive anymore until you plug that.
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Old 03-01-2008, 05:49 PM   #6
dbrunner
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I just went and grabbed a M12x1.25 since that seemed to be the bolt everyone uses and it wouldn't fit.
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Old 03-01-2008, 07:57 PM   #7
dbrunner
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Okay, after sticking something through the "hole" to see if it really was just left open, it feels like something is there to block it. Can't tell what they used, but there definitely isn't an opening now.

I'll have my tuner look at the car eventually to get some help, I've done everything I can think of that I feel confident enough being able to fix.
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Old 03-12-2008, 11:09 PM   #8
dbrunner
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Just a little bump. I had my tuner hook up his laptop and drive around for a bit and his conclusion is that it's a bad turbo. My car has 113k miles so I wouldn't doubt him, lol. This sound common though? I already bought a replacement TD04, so we'll see. I just always thought of turbos going bad that they would be more noticeable.
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