Boost leak??
Thread Starter
Instructor
Joined: Jan 2011
Posts: 176
Likes: 1
From: Buffalo Grove Illinois
Boost leak??
I have an STS remote twin turbo setup. I noticed recently that boost was building very slow. I usually get 9 -9.5 PSI boost. I am barely hitting 5 and it is taking a long time to spool. I was thinking it is related to one of two issues:
1) a Bad Tial 38 MM Wastegate. If this is not sealing it would be leaking pressure to the dump tube all the time. I found a 1/2" dent in the Tial aluminum housing where it looks like the WG hit the swaybar on a bad bump. I was thinking bent valve or loose valve seat.
2) a single seized turbo. I had both turbos rebuilt 2 years ago. They are not making any noise or any other indication that they have failed.
Except for the slow spooling and lower boost the car runs and sounds fine. The BOV works fine as well if I build up some boost PSI and let off the gas.
Anyone have any ideas? I have a new Tial WG coming.
1) a Bad Tial 38 MM Wastegate. If this is not sealing it would be leaking pressure to the dump tube all the time. I found a 1/2" dent in the Tial aluminum housing where it looks like the WG hit the swaybar on a bad bump. I was thinking bent valve or loose valve seat.
2) a single seized turbo. I had both turbos rebuilt 2 years ago. They are not making any noise or any other indication that they have failed.
Except for the slow spooling and lower boost the car runs and sounds fine. The BOV works fine as well if I build up some boost PSI and let off the gas.
Anyone have any ideas? I have a new Tial WG coming.
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
Get a PVC cap the same size as the pipe where it enters the throttle body. Drill a hole in it to insert an air chuck into and clamp it to the charge pipe and force air through the intercooler, pipes, turbos. Cap off the turbo inlets and listen for leaks. Spray soapy water on couplings.
Thread Starter
Instructor
Joined: Jan 2011
Posts: 176
Likes: 1
From: Buffalo Grove Illinois
Today I noticed that my boost guage which was showing 12 inches vacuum normally since I got the car out of storage was down to 9 inches at idle. Then it was at 3 inches. I checked the vacuum lines and found that the little rubber step-down adapter that connects the nylon vacuum line from the boost guage to the T-fitting was cracked. Stopped at O'Reilly and got a new vacuum fitting. The Autometer Cobalt now has 22 inches of vacuum at idle which sounds right for the Lingenfelter cam I have.
The BOV isnt venting after I let off the boost so next step is a new diaphragm for the BOV. I had 6 psi boost when I hit it in 2nd today but usually I hit 9.5 psi,
I have a new 38 mm wastegate going in this week and the diaphram for the BOV and hopefully that gets things back to normal. I am suspecting the valve seat in the WG may be decayed as it is like 5 years old.
The BOV isnt venting after I let off the boost so next step is a new diaphragm for the BOV. I had 6 psi boost when I hit it in 2nd today but usually I hit 9.5 psi,
I have a new 38 mm wastegate going in this week and the diaphram for the BOV and hopefully that gets things back to normal. I am suspecting the valve seat in the WG may be decayed as it is like 5 years old.
Thread Starter
Instructor
Joined: Jan 2011
Posts: 176
Likes: 1
From: Buffalo Grove Illinois
Two things I found. One the Wastegate fire ring wasnt making a good seal. When you held the wastegate up to the light you could see light come through in a gap between the valve and the valve seat all the way around the valve seat. Replaced wastegate. I also found one of the rubber couplings on the air dam between the intercooler and the throttle body was not tight enough. I dripped some soapy water on the edge of the coupling while the car was idling and watched the water get sucked right into the dam. So fixed that by adjusting clamp position and tightening with a wrench - not a screwdriver. Bad seal is probably from when I R & R the intake manifold for a oil pressure sensor previously.
I also replaced the Tial 50 BOV diaphragm which was kind of gunked up from when I blew my scavenge pump a long time ago. BOV works nicely now.
I also replaced the Tial 50 BOV diaphragm which was kind of gunked up from when I blew my scavenge pump a long time ago. BOV works nicely now.
Last edited by TwinTurboZ51; Jun 15, 2014 at 09:44 AM.
