Boost problems... - Subaru WRX Forum
 
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post #1 of 12 Old 08-29-2004, 12:45 AM Thread Starter
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Unhappy Boost problems...

Ok, so last week i ran 14.5 @ 93 mph on 15psi boost. Today, I installed my Vishnu Downpipe. Car sounds great, you can hella hear the turbo and all, but when i ran it at the tracks, i am running 15.3's, and theres a problem with my boost. I didn't change it or anything, and now it runs 17psi, then spiked (at around 5k+rpm) to 20 psi....so i turn down the boost, same, turn down boost, same, turn boost all the way until it stops, so, no boost until 4K+rpms, where boost goes back up into 16+psi. So i turn the boost up a little....still same thing. So now, on the way home, I'm in 5th, spool it up, at 3k rpm i get 8 psi (what it's set at i guess), but then around 4-5k rpm, boost hit's VTEC and goes up into 18+psi... IS WRONG?!?!??! Seriously, i didn't have problem yesterday, btw i have turbo xs MBC, what should i do? also, because i bought mbc used, no instructions, so another q, if i turn boost all the way down until it stops, how many turns is 1 psi? 1/2 turn? full turn? i dunno... SO like if i turn boost all the way down, how many turns with allen wrench until 15psi is reached?
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post #2 of 12 Old 08-29-2004, 08:10 AM
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First of all, when you install a new downpipe your boost goes up by 2psi by itself because of the increase flow. Secondly, what boost gauge do you have? Thirdly, do you have a catless up-pipe, because if you don't turn the boost down to 15psi. Fourthly, to set the boost you keep the MBC open all the way then you close it little by little until you get the desired setting. Fifthly, don't boost more than 15psi with the stock up-pipe and injectors. Sixthly, getting lower boost in 5th is fine.

Che
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post #3 of 12 Old 08-29-2004, 10:17 AM
 
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And I hope you are joking about that VTEC thing.
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post #4 of 12 Old 08-29-2004, 02:12 PM Thread Starter
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lol, that's just what it "acts" like. so do i turn boost all the way down and open little by little? just keep making runs until i get it set right? i have an Autometer ultra light boost gauge. HKS SSQV BOV, stock up pipe still, and the vishnu downpipe. I got the turbo xs up pipe, i just dunno how to install that so i'm having someone help me. not a shop, just someone that's done it before, they said they'll help me. but what would cause my boost to stay at 8 psi then go waaaay up when i get into higher rpm's?
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post #5 of 12 Old 08-29-2004, 02:52 PM
 
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Something might be wrong with your wastegate.
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post #6 of 12 Old 08-29-2004, 03:38 PM Thread Starter
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how do i find out? Someone said maybe it's stuck open. how do i find out? would i have to kick it or something, or take off DP and kick it? I wanna kick it cause it isn't working!!!!! :-/
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post #7 of 12 Old 08-29-2004, 05:01 PM
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It's generally not a good idea to start kicking parts of your car because they aren't working, either due to 1) Your lack of knowledge on this particular subject regarding vehicle tuning or 2) An apparent malfunction due to unknown causes.

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post #8 of 12 Old 08-29-2004, 05:01 PM Thread Starter
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could it be boost creep? do i need bigger wastegate flapper? someone said that might work?
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post #9 of 12 Old 08-29-2004, 07:38 PM
 
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There is a way to check the wastegate. There is a vacuum line going into the wastegate actuator. If you remove that, you should uncontrolled boost. But that test is usually done to see if the wastegate is stuck open. It sounds more like yours is stuck closed or is opening later than it should. Actually it doesn't even sound like a wastegate problem to me. But I would recommend doing that test, but BE CAREFUL. The boost will go crazy. It sounds to me like somethign is wrong with your MBC. If possible try to get the stock boost controller back on and see what happens. You should hit around 14.5-15 psi with the stock boost controller and a aftermarket downpipe.
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post #10 of 12 Old 08-30-2004, 01:39 AM Thread Starter
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if i can hit 15 psi with no boost controller, then why do i need a boost controller? lol. it's coming off, but because i didn't see how the stock hoses went, i can't do it alone. my friend did it at 10 o clock at night, so i didn't see what hoses he pulled and what not. does anyone have pics on how the stock hoses went?
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post #11 of 12 Old 08-30-2004, 12:08 PM
 
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You don't until you start upgrading turbos and ICs when you can raise boost more. People get MBC's and set them to the stock level to reach boost quicker. Or you can do the 3/16 mod. But first off, I reocmmend getting the FBC back on and seeing what happens.
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post #12 of 12 Old 08-31-2004, 02:11 PM Thread Starter
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well, i threw my car on the lift, took off the downpipe, checked everthing, turns out, there is a ####ing bolt or something that the downpipe was rubbing on, therefore not getting a secure connection, and air leak was there, so i sanded the downpipe where it was rubbing and scraping along, got it down just enough to clear, bolted it back on, and now perfect boost. :-D
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