car not making boost ??
Thread Starter
Joined: May 2004
Posts: 6,492
Likes: 6
From: Back in the Burg
car not making boost ?? I just finished my d1 install with the race bypass. The car runs but when i crack the throttle the boost seems to just get bypassed and the boost gauge wont break 0psi. The by pass is in the Y pipe before the intercoolers, and I have the bypass vented to the atmosphere and the vac line hooked from the bypass to the vac line that my boost gauge is connected to. Need some help I have to leave to get the car tuned first thing in the morning.
Thread Starter
Joined: May 2004
Posts: 6,492
Likes: 6
From: Back in the Burg
I'll check for a leak now. Can any one tell me how the race bypass should be installed? Scott from sdce told me to install before intercooler and connnect vac fitting to constant vac line behind throttle body, is this correct? Is there any need to adjust bypass? Higher throttle position the more open(more air blowing out)of the bypass valve.
On The Tree
Joined: Sep 2004
Posts: 117
Likes: 0
wait...
are you saying that it wont break 0 psi when you crack the throttle?
ur car wont start boosting until there is pressure created (like going WOT or almost WOT) it wont create boost when u touch the gas or give it a rev...
or i misunderstood ya
are you saying that it wont break 0 psi when you crack the throttle?
ur car wont start boosting until there is pressure created (like going WOT or almost WOT) it wont create boost when u touch the gas or give it a rev...
or i misunderstood ya
Thread Starter
Joined: May 2004
Posts: 6,492
Likes: 6
From: Back in the Burg
No thats what I am saying, I am working all the air out of the engine now(i pulled the raidatior) and Im going to go for a ride. I havent gone wide open throttle yet. just holding the rpms at 3k and giving it a blast.
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To get boost you must go full wot to the floor, then things start to happen.You do need a strong vacuum source to make the raceready shut completely, also I adjusted mine to where the bolt is flush with the nut on the adjuster. The vacuum is critical i had to redo mine to a diff location to get it to shut completly. I would adjust the adjuster before you tune and leave it.
Last edited by BOONE; Sep 16, 2005 at 01:24 AM.
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Teching In
Joined: Aug 2005
Posts: 16
Likes: 0
I pulled the lines on the check valve and hooked up a vacuum gauge to make sure I had the right one. You'll find the two wrong ones are weak and sluggish. The one you want will be responsive. It'll drop instantly as you tap the throttle and then pull a high vacuum while the engine spins down. Also like someone else suggested, you won't get boost at low rpm. A centrifugal blower does not build boost linearly. The blower has to be putting out more air than the engine can flow N/A...AND... you need to have the throttle open big enough to expose the manifold to the boost. You probably won't get any boost (even at WOT) below 2500-2800, after that it will start building up as RPM increases.
You can not use a vacuum port that has a check valve between the port and your bypass. The bypass needs to see boost as well as vacuum. If the bypass never sees boost, any boost can push the bypass piston open as soon as your motor starts to build any boost, so it basically dumps it as you are trying to build it.
To test, disconnect the bypass vacuum line and plug it. Crank up the adjuster so that it puts some pressure on the back of the bypass piston. If you have a datalog, turn it on, then go from 5-10mph and pin the throttle to the floor. After it shifts to 2nd, let off, then check your data.
Also, if your belt is not tight enough, you won't build decent boost. I had that problem cuz I adjusted it like a regular serpentine belt. Guys here told me that if you can turn the belt 90degrees with your fingers, it's not tight enough. Tightening my belt made it go from 4lbs boost to 7.5 right away!
Jim
Jim
To test, disconnect the bypass vacuum line and plug it. Crank up the adjuster so that it puts some pressure on the back of the bypass piston. If you have a datalog, turn it on, then go from 5-10mph and pin the throttle to the floor. After it shifts to 2nd, let off, then check your data.
Also, if your belt is not tight enough, you won't build decent boost. I had that problem cuz I adjusted it like a regular serpentine belt. Guys here told me that if you can turn the belt 90degrees with your fingers, it's not tight enough. Tightening my belt made it go from 4lbs boost to 7.5 right away!
Jim
Jim
