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Old 06-17-2002, 10:02 PM   #1
malichite
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Default Can't create more than 3lbs of boost.

I just put a super 16G turbo on my 2.5 RS. When I first ran it I could only get 3 lbs of boost. I made a manual boost controler for it and tried to boost it up more. Even when it was cranked all the way down it still wouldn't get above 3 lbs. I then completely shut the valve and it still wouldn't change. Then I unhooked it completly. Still nothing. I am wondering what the chance is that I may have a air leak. When I stick my finger in my blow off valve I can feel i chattering. Also if I stick my hand over the end of it I can feel it sucking in a little bit I think. Is it possibe it could be my blow off valve causing my problem??? Does it take positive or negative pressure on the acctuater to create boost??? Also what are the consequences of unhooking the blow off valve and caping the hole to see if that is where the leak is at???
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Old 06-17-2002, 10:15 PM   #2
STiTuner
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does it sound like you have an exhaust leak?

try capping off the wastegate and trying to give it a little bit of boost ie not full throttle but just a little down the street when the boost goes of 14 psi and you have blown your engine you then know that your wastegate was not set right. maybe your wastegate was not closing right? how long does it take you to build boost?

and alos I could check your BOV first.. maybe its opening up early.

Brad
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Old 06-17-2002, 11:04 PM   #3
T-WRX450
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malichite,
Try taking off the BOV to make sure the valve seats in the housing and then try to adjust it with the set screw on top by backing it out and turning it in while it is off to see if anything changes. You will have a vacuum at idle but air shouldn't be coming in thru the BOV.
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Old 06-18-2002, 08:16 AM   #4
malichite
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I completly unhooked the acctuater on the wastegate and it still will only go to 3 lbs. I tried moving the swing valve by hand while I had the acctuater off and it moves freely. Also I can't adjust this piece of crap blow off valve. It is the stock one off of a 3000 gt. I can definatly feel air being pulled in from the blow off valve though. Can I just cap that off and see if that in turn puts enough pressure back to the acctuater to create more boost with out having any problems?
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Old 06-18-2002, 08:18 AM   #5
malichite
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I forgot. The boost does comes up a little slugish. I can't create posotive pressure either while I am ideling or trying to tune from under the hood so there is no way to feel if air is also being blown out from around the blow off valve.
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Old 06-18-2002, 08:28 AM   #6
yebokmj
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It will run fine without a BOV. BOV are there to prevent compressor surge with in the long run damages the turbo, short term effect will be nill and help you diagnose the problem. I ran mine without a BOV for awhile.
Joshua
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Old 06-18-2002, 11:39 AM   #7
malichite
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That makes sence. So there is a possobility that it is the blow off valve causing the problem though?
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Old 06-18-2002, 11:48 AM   #8
Jewbaru
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Quote:
Originally posted by malichite
That makes sence. So there is a possobility that it is the blow off valve causing the problem though?
Yea, sounds like it might be the BOV to me too. Do you hear any funny noises when driving?
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Old 06-18-2002, 12:00 PM   #9
RallyNavvie
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That BOV should be screaming if you opened up the vac line to the wastegate and let the turbo run at whatever pressure it felt like.

However don't most BOVs use the vac line to judge when to let off boost? My first thought would be that this is a wastegate issue. You could have your vac line to your BOV pinched somewhere as well.

~Garrett
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Old 06-18-2002, 10:07 PM   #10
STiTuner
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if it was pinched wouldn't it be staying closed instead of open and it would be able to get much more boost unless he had a BOV problem.

brad
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Old 06-20-2002, 02:32 AM   #11
T-WRX450
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Default Your BOV is the problem

malichite,
Your BOV is the problem. You can cap it off to test, however, I would not run it for long like that because the blow off valve releases the pressure shock wave which is generated as you rev the motor under load and shut down the throttle plate suddenly such as between shifts. The shock wave goes back thru the intake to the turbo and actually jars the vanes putting undue stresses on the turbo bearing eventually causing the turbo to fail. This was the biggest problem with the 90-94 Legacy Turbo, besides no intercooling, that caused them to fail even though they only ran about 6 psi stock.
The vacuum line to the BOV allows it to be controlled externally but an internal spring will open it at a set level if the vacuum control is not hooked up or the vacuum control is set higher than this level. There should not be air going in or out at any time other than out when these boost limits are reached.
I would get a new BOV as soon as possible.

Troy
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