I have an 94 Z28 with a built for boost LT1 and the 4L60E tranny, also built for more HP. Am running a single turbo at 7psi. I presently have a problem where boost comes up to 7psi in 1st gear, dies off completly when it shifts to 2 and then comes back on when it shifts to 3rd. This seems to only happen when I go WOT as I can roll into the throttle while in 2nd and it will spin the tires but if I continue to increase the throttle till I hit WOT then boost rapidily bleeds off again. I have looked at my programming (I use LT1 edit) and do not see anything unusual. Could it be that the tranny is slipping in 2nd gear when the torgue load gets to high?
Any ideas?
Thanks,

 

I guess it could be if it's slipping bad?? Falling off at high rpm sounds like the turbo is going into choke.

What are the details of your setup?

 

Turbo is load based - so we would have to be talking a lot of slip, but if the motor is free spinning it won't build much boost if any.

 

OK, the turbo going into choke sounds interesting, What would cause that?

 

Sounds like it could be a wastegate issue.
Are you sure the wastegate is operating smoothly? Pull it off and check for binding or sealing issues.

Is your wastegate referenced close to the throttle body?
Are you sure theres no exhaust or bewst leaks?
Was the setup working before?
Is the turbo large enough for the application?
Where do babies come from?
Is the tranny for sure slipping?
You can observe the 'slip rpm' in Datamaster.

 

Been doing some searching on choking and that may be an issue with my setup? I am running an old 60-1 Hi-Fi turbo which I have had on my stock then rubuilt 355LT1. This last winter I had the engine stroked, so now with a383 stroke and the 40 over it has been bored out, I believe it is basically a 394 now. Anyway, I never had any boost issues with the other setups but is the larger cubes now to the point that the turbo can't keep up so it "chokes", (or quits flowing air), when I go WOT? Does this make sense?

 

350 to 394 is only about a 12% increase... Thats probably roughly equal to a 12% percent increase in pressure from 7psi, which is less than 8psi. So I doubt that's the issue. Granted, there are alot of other factors (i.e. flow) but a 60-1 compressor flows around 60lbs/min, which is probably at least 12psi (?) on a stock motor no problem.

 

Sounds like turbo is maxxed