boost?
02-17-2005, 02:58 PM
#13
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Re: boost?
There could be several reasons for the boost drop, if there are no boost leaks.
The boost controller is a bad design, hooked up wrong or has too small of a bleed off. I am assuming the factory boost solenoid has been eliminated from the equation, if not start there.
Exhaust restriction could cause a boost drop, although using the correct boost control science it can be overcome(to hold 15psi), but not advised.
If the turbo spools slow it may have a cracked housing or damaged wastegate actuator causing the problem.
I could probably come up with a few more causes, but without physically inspecting it personally I cannot speculate any further, so try the the #1 and #3 suggestion and post back. If the info I posted is confusing, PM me and I will give more detailed info.
The boost controller is a bad design, hooked up wrong or has too small of a bleed off. I am assuming the factory boost solenoid has been eliminated from the equation, if not start there.
Exhaust restriction could cause a boost drop, although using the correct boost control science it can be overcome(to hold 15psi), but not advised.
If the turbo spools slow it may have a cracked housing or damaged wastegate actuator causing the problem.
I could probably come up with a few more causes, but without physically inspecting it personally I cannot speculate any further, so try the the #1 and #3 suggestion and post back. If the info I posted is confusing, PM me and I will give more detailed info.
Last edited by 4SFED4; 02-17-2005 at 03:02 PM.
02-17-2005, 03:03 PM
#14
Big Dick Playa
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Re: boost?
stock boost control solinoid is still in place cause i dont have an after market controller yet.
im still runnin the stock dp and o2 housing with the stock t25
i didnt check my vacuum lines or whatever
but sometimes at idle my gauge will read 0 like im gettin no vacuum at all i dunno
fuck it i will figure it out eventually
im still runnin the stock dp and o2 housing with the stock t25
i didnt check my vacuum lines or whatever
but sometimes at idle my gauge will read 0 like im gettin no vacuum at all i dunno
fuck it i will figure it out eventually
02-17-2005, 03:19 PM
#15
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Re: boost?
If the vaccum gauge is reading zero you have a leak somewhere. A healthy 4G63 should pull between 15-18in/hg at an idle.
The factory O2 and DP should not pose a restriction for a T25 @ 15psi.
After locating your vaccum leak, you can pull the hoses off of the boost solenoid, but leave it electrically connected. Then put an 1/8" T connector between the boost source and w/g actuator and run the extra line off the T connector to the air canister/MAS. With that you should be able to sustain 15psi, if not you will need a boost controller, but be sure to check and make sure the boost does not go to high. If the boost spikes to high you can lower it by restricting the hose going to the canister. I have used pellets(the type for a BB gun) and drilled a 1/16" hole in it.
The factory O2 and DP should not pose a restriction for a T25 @ 15psi.
After locating your vaccum leak, you can pull the hoses off of the boost solenoid, but leave it electrically connected. Then put an 1/8" T connector between the boost source and w/g actuator and run the extra line off the T connector to the air canister/MAS. With that you should be able to sustain 15psi, if not you will need a boost controller, but be sure to check and make sure the boost does not go to high. If the boost spikes to high you can lower it by restricting the hose going to the canister. I have used pellets(the type for a BB gun) and drilled a 1/16" hole in it.
02-17-2005, 03:45 PM
#18
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Re: boost?
The bcs doesn't have to stay connected as far as I know, but I don't want to tell someone to completely remove it, then blame me if a check engine light comes on.
The only thing the bcs does is regulate the amount of air that is bypassed from the w/g actuator. That is how the ECU prevents you from overboosting, unless the w/g actator becomes damaged.
The only thing the bcs does is regulate the amount of air that is bypassed from the w/g actuator. That is how the ECU prevents you from overboosting, unless the w/g actator becomes damaged.
Last edited by 4SFED4; 02-17-2005 at 03:49 PM.
02-17-2005, 04:26 PM
#19
Ivy Tadita
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Re: boost?
You're definately leaking. If you have a mechanical boost gauge with a thin nylon hose make sure tat s not kinked up or a hole in it as well cause if it gets cracked it will show 0 vacumn and still show boost just not full boost.You'll figure it out. if you are not idling bad then it can't be a real lage leak.
Oh and it is common for the t25 to loose boost a about 5k rpm. It should not ccompletely loose it though.
Oh and it is common for the t25 to loose boost a about 5k rpm. It should not ccompletely loose it though.
02-17-2005, 07:06 PM
#20
Big Dick Playa
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Re: boost?
Originally Posted by cootees
You're definately leaking. If you have a mechanical boost gauge with a thin nylon hose make sure tat s not kinked up or a hole in it as well cause if it gets cracked it will show 0 vacumn and still show boost just not full boost.You'll figure it out. if you are not idling bad then it can't be a real lage leak.
Oh and it is common for the t25 to loose boost a about 5k rpm. It should not ccompletely loose it though.
Oh and it is common for the t25 to loose boost a about 5k rpm. It should not ccompletely loose it though.