Boost issue during transition. Help!
09-08-03, 03:47 PM
#1
Boost issue during transition. Help!
I know this is a worn out subject and I did search and find some usefull pages but wanted to see if anyone has had the same problem and what they found wrong. Here goess:
I was going down a curvey road last week end, pushing it pretty good. Back
and forth from full boost when all the sudden I loose all boost after
4500rpm (right at the transition). I can her a sound kinda like the bypass
valve or just a leak of all the boost being let out ?? Car runs great and
pulls hard right to the transition then its 5-6lbs after that.
I have spent a few hours checking things out to no avail. I "think"
I have checked most of the vacuum lines, remove and tested the bypass and
relief valves also. I have read the page on 3rd gen turbo trouble shooting
( www.autosportracetech.com ) I have one question. The test for the
actuator ( one right below and towards the firewall from y-pipe) was too
start car, let idle then turn off and check arm coming out of actuator,
should be in. Remove vacuum line from front chamber and arm should come
out. Mine comes out as soon as car is shut off? Does this mean it is bad? Could this be my problem? When I use the minivac it will open and close it just fine!!
It's like something is causing my relief/ bypass valve to open during the transition???
If anyone has had this problem or experience with this matter please let me
know. I plan tonight to start the last stage of take every F&%&ing thing
apart down to the turbos.
Thanks, Mike
I was going down a curvey road last week end, pushing it pretty good. Back
and forth from full boost when all the sudden I loose all boost after
4500rpm (right at the transition). I can her a sound kinda like the bypass
valve or just a leak of all the boost being let out ?? Car runs great and
pulls hard right to the transition then its 5-6lbs after that.
I have spent a few hours checking things out to no avail. I "think"
I have checked most of the vacuum lines, remove and tested the bypass and
relief valves also. I have read the page on 3rd gen turbo trouble shooting
( www.autosportracetech.com ) I have one question. The test for the
actuator ( one right below and towards the firewall from y-pipe) was too
start car, let idle then turn off and check arm coming out of actuator,
should be in. Remove vacuum line from front chamber and arm should come
out. Mine comes out as soon as car is shut off? Does this mean it is bad? Could this be my problem? When I use the minivac it will open and close it just fine!!
It's like something is causing my relief/ bypass valve to open during the transition???
If anyone has had this problem or experience with this matter please let me
know. I plan tonight to start the last stage of take every F&%&ing thing
apart down to the turbos.
Thanks, Mike
09-08-03, 04:24 PM
#4
Lives on the Forum
Yeah, my charge control actuator rod releases as soon as I shut off the motor. The important part is that it holds vacuum, which apparently yours does based on your Mityvac results.
Check turbo control solenoid connection. This solenoid is located under the intake extension manifold right by the air control valve. You'll see two vacuum hoses connected to this solenoid. One is under pressure from the primary turbo, and the other is under vacuum. Both need to be securely connected. The whooshing sound might be coming from a leaking or broken vacuum hose connection to the turbo control solenoid. If these hoses are ok, check the solenoid, and see if it holds vacuum. If you have voltmeter, you can check the voltages on the solenoid.
Check your one-way vacuum chamber check valve. If this is leaking your vacuum chamber will not store vacuum for the turbo control and charge control actuators to work properly. Both are key in the 4500-rpm transition from primary turbo to twin turbo operation.
Check your turbo control actuator. These rarely go bad, but you can check with the Mityvac and actuate the rod with the Mityvac applied to the vacuum nipple on the actuator. If you have a portable air pump with a pressure gauge, apply pressure to the pressure nipple of the TCA and watch the rod actuate. Of course you should check to see if the C-clip is attaching the TCA rod to the exhaust flapper. If the C-clip is missing the TCA will not open the flapper to add secondary boost pressure to the primaries.
Check your vacuum chamber for oil. Hook up your Mityvac vacuum pump to the vacuum chamber. It should take 40 to 45 pumps to create 15 inches Hg vacuum. I use a NAPA vacuum chamber tester pump. Each pump stroke creates ~1 inch Hg (Mercury) vacuum. Thus it takes 25 pump strokes to create 25 inches Hg vacuum. If it takes only 15 to 20 with the Mityvac or 4 to 5 with the NAPA vacuum chamber tester, the vacuum chamber is full of oil, and your vacuum chamber will not provide the vacuum needed for any of the solenoids and actuators to work properly during the 4500-rpm transition from primary turbo to twin turbo operation.
Good luck!
Check turbo control solenoid connection. This solenoid is located under the intake extension manifold right by the air control valve. You'll see two vacuum hoses connected to this solenoid. One is under pressure from the primary turbo, and the other is under vacuum. Both need to be securely connected. The whooshing sound might be coming from a leaking or broken vacuum hose connection to the turbo control solenoid. If these hoses are ok, check the solenoid, and see if it holds vacuum. If you have voltmeter, you can check the voltages on the solenoid.
Check your one-way vacuum chamber check valve. If this is leaking your vacuum chamber will not store vacuum for the turbo control and charge control actuators to work properly. Both are key in the 4500-rpm transition from primary turbo to twin turbo operation.
Check your turbo control actuator. These rarely go bad, but you can check with the Mityvac and actuate the rod with the Mityvac applied to the vacuum nipple on the actuator. If you have a portable air pump with a pressure gauge, apply pressure to the pressure nipple of the TCA and watch the rod actuate. Of course you should check to see if the C-clip is attaching the TCA rod to the exhaust flapper. If the C-clip is missing the TCA will not open the flapper to add secondary boost pressure to the primaries.
Check your vacuum chamber for oil. Hook up your Mityvac vacuum pump to the vacuum chamber. It should take 40 to 45 pumps to create 15 inches Hg vacuum. I use a NAPA vacuum chamber tester pump. Each pump stroke creates ~1 inch Hg (Mercury) vacuum. Thus it takes 25 pump strokes to create 25 inches Hg vacuum. If it takes only 15 to 20 with the Mityvac or 4 to 5 with the NAPA vacuum chamber tester, the vacuum chamber is full of oil, and your vacuum chamber will not provide the vacuum needed for any of the solenoids and actuators to work properly during the 4500-rpm transition from primary turbo to twin turbo operation.
Good luck!
Last edited by SleepR1; 09-08-03 at 04:35 PM.
12-15-04, 03:34 PM
#6
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I'm having the same problems too sk8world. I did a quick check on my pressure chamber, and when i disc. the two hoses from it, the hose that connects to a check valve right under it was cracked(hairline -_-). So i replaced it hoping I would have a change in boost but I don't. I'm still on the hunt for the culprit and am anxious to read your results.
Jeremy
Jeremy
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