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01-21-2010, 11:28 AM | #1 |
Scooby Newbie
Member#: 205807
Join Date: Mar 2009
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Boost pressure starting at -20 psi, peaking at 5 psi...whats wrong?
i have an 03 wrx that didnt have a boost gauge on it when i bought it, i only recently got a gauge and it is only giving me a maximum reading of 5 or 6 psi. im wondering if its the boost controller thats holding it back, but its the stock controller, and my utec has the stock settings on it... it also takes a while for the boost to get to positive psi. my mechanic said to take the wastegate hose off and see if the pressure builds fast, in which case get off the gas. thats fine, but how do i fix it then if that happens.
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01-21-2010, 12:00 PM | #2 |
Scooby Newbie
Member#: 204177
Join Date: Feb 2009
Location: Blacksburg VA
Vehicle:2000 OBS with EJ205 |
is it a decent boost gauge cause the gauge you got could be bad.
any other mods on the car? and is that 5 psi at full throttle? if i stay under 1/4 throttle or so it stays right about 5psi |
01-21-2010, 04:15 PM | #3 |
Scooby Guru
Member#: 4414
Join Date: Feb 2001
Location: Dublin, CA
Vehicle:2002 WRX Sedan Midnight Black |
Wastegate boost should be at least 8-10 psi. Sounds like your gauge is screwed up. Especially if it's really reading -20psi at any time (-20psi is physically not possible,) though I suspect you're misreading the units, it should be +20mmHg vacuum, not -20psi.
If you have a UTEC, presumably someone tuned it at some point? They should have calibrated the MAP readings when they did it. Log the UTEC and what does it say for boost pressure? If you're at approx sea level, even the UTEC's default calibration should be close enough to tell the difference between 12 psi (stock boost) and 5-6 psi. Log and look at WOT ~4kRPM. |
01-21-2010, 04:17 PM | #4 |
Scooby Guru
Member#: 118209
Join Date: Jun 2006
Chapter/Region:
MWSOC
Location: North Dakota
Vehicle:2015 WRX Limitec |
stock boost controller? you mean the ecu? sounds like you are dealing with someone else's halfass returned to stock hack job.
I wouldn't take the wastegate hose off and run. It only takes a split second to ruin an engine. one thing to consider, with the stock turbo, the wastegate spring is at least 7 psi. you should hit that no matter what your controller (either the ecu or standalone) is trying to do. There is simply no way to open the wastegate at a lower pressure. |
01-21-2010, 06:56 PM | #5 |
Scooby Newbie
Member#: 205807
Join Date: Mar 2009
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i thought about it being a bad gauge, but aparently its supposed to make vaccuum at idle, but 20? 5 psi at full throttle and no, the boost controller is separate from the ecu, ecu controlls the boost controller. anyway, wats the probable cause for it? more than likely the gauge?
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01-21-2010, 07:03 PM | #6 |
Scooby Newbie
Member#: 124720
Join Date: Sep 2006
Location: MD
Vehicle:2009 WRX Hatch Black |
Can't believe no one's asked the obvious yet..
How's the car running? If your engine was actually only getting 5 psi of boost from the turbo, you would know. It would be slowwwww... |
01-21-2010, 07:10 PM | #7 |
Scooby Guru
Member#: 21808
Join Date: Jul 2002
Chapter/Region:
E. Canada
Location: National Capital Region
Vehicle:02 GroceryGettAr Nonemore Black |
It would help if you could post some details:
o what brand and type (mechanical? electrical?) of gauge is it? o where did you tee off? o what units does your gauge read in? a value of -20 would be about right for vacuum at idle in inches of mercury (in-Hg) o what conditions are you measuring the boost? you need a good bit of load (e.g. a hard 2nd gear pull) to hit full boost |
01-21-2010, 07:22 PM | #8 |
Scooby Newbie
Member#: 205807
Join Date: Mar 2009
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I have headers, upipe, tbe, intake, turboxs utec, thats about it. i hope its just the gauge, so its easy and cheap
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01-21-2010, 07:26 PM | #9 |
Scooby Newbie
Member#: 205807
Join Date: Mar 2009
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the engine runs fine, its just as you said slow at higher rpms, 3500+. its a prosport mechanical gauge, measuring boost in all gears, reaches max psi in 3rd, 4th, and 5th. yea sorry, just easier to write -20 psi lol, yes, 20 in-Hg
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