car just will not hold set boost level
car just will not hold set boost level I've run through all common troubleshooting steps now. No intake leaks, no audible exhaust leaks. Car will build to what ever boost is set initially, but then fall off by redline. If it's set for 5 it will drop to 3, if it's set for 10 it will drop to 6.
Wastegate has been off and apart, bov doesn't leak when pressure tested to 12 psi on the car. I'm out of ideas.
67 turbo, .81 housing. I had an equivlent 67 on the car previous and it worked great.
Wastegate has been off and apart, bov doesn't leak when pressure tested to 12 psi on the car. I'm out of ideas.
67 turbo, .81 housing. I had an equivlent 67 on the car previous and it worked great. 
It's the boost drop across the intercooler. 
Fairly easy to fix.Don't use the turbo unit for the vacuum port that controls the wastegate.Plug that off.Run a 1/4" brkeline from the engine bay to the Turbo.On the engine bay side hook the 1/4 line to a manifold vacuum source.At the turbo use the 1/4 line instead of the turbo port. Problem solved
Fairly easy to fix.Don't use the turbo unit for the vacuum port that controls the wastegate.Plug that off.Run a 1/4" brkeline from the engine bay to the Turbo.On the engine bay side hook the 1/4 line to a manifold vacuum source.At the turbo use the 1/4 line instead of the turbo port. Problem solved
Originally Posted by Slowhawk
It's the boost drop across the intercooler.
Fairly easy to fix.Don't use the turbo unit for the vacuum port that controls the wastegate.Plug that off.Run a 1/4" brkeline from the engine bay to the Turbo.On the engine bay side hook the 1/4 line to a manifold vacuum source.At the turbo use the 1/4 line instead of the turbo port. Problem solved
Fairly easy to fix.Don't use the turbo unit for the vacuum port that controls the wastegate.Plug that off.Run a 1/4" brkeline from the engine bay to the Turbo.On the engine bay side hook the 1/4 line to a manifold vacuum source.At the turbo use the 1/4 line instead of the turbo port. Problem solved
I could be wrong, but I'm pretty sure that it was working in this config with the intercooler before. It's been so long now though that i'm not really sure.
I don't see how it could make a difference, but i'm willing to give it a shot. When the 76 was on it, it would not drop, but it also would not make full boost (i'm pretty sure because I couldn't build the pressure ratio needed due to the R exhaust wheel).
If this stuff doesn't work I guess I could always toss my greddy profec b II on there to force it to hold the boost i set.
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Joined: Nov 2001
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From: Bellevue, Wa
I mentioned for you to move that in the first post you made.
Suprised you did not try it.
The wastegate doesn't know you have a pressure drop accross the IC so it doesn't compenstate. when you take the reading out of the turbo it is different than what makes it into the TB. so the wastegate is doing what it should, it thinks you have X amount of boost (which you do at the outlet of the turbo) but not at the engine so it never adjusts to keep your boost level up.
make sense? not the best worded explanation I know, but hopefully good enough.
takes 10 minutes to run a vacum line from the front to back, try it and let us know.
Suprised you did not try it.
The wastegate doesn't know you have a pressure drop accross the IC so it doesn't compenstate. when you take the reading out of the turbo it is different than what makes it into the TB. so the wastegate is doing what it should, it thinks you have X amount of boost (which you do at the outlet of the turbo) but not at the engine so it never adjusts to keep your boost level up.
make sense? not the best worded explanation I know, but hopefully good enough.
takes 10 minutes to run a vacum line from the front to back, try it and let us know.
I will try it for sure, it just seemed to work correctly on the original 67 turbo before. I'll be running that line later tonight or tomorrow to see if it resolves the issue. One of the few things I have not tried yet.
