ABeasst

iTrader: (5)

I have had this problem ever since I put the turbo on. It will ramp up to where I want it at around 5K and then by 6500 is will have dropped 3#. For example yesterday I wanted to run 15# and it would ramp up to 15 at 5K and then by 6500 it would be at 12-13#. It does it on every boost setting.

I have a T76GTS on a 8.5" 383 (LS1). The boost controller is a HKS EVC. Cant find any boost leaks either.

Any help would be appreciated.

98turbls1

iTrader: (17)

What is the A/R on the exhaust housing?? Does it act like it's running out of steam up top?? Do you know if you're floating your valves??

b00sted

iTrader: (7)

Sounds like the a/r is too small on the exhaust housing...It'll start choking the motor up because it can't flow enough.

What size is it?

ABeasst

iTrader: (5)

its a .96 the biggest you can get on that turbo. I wouldnt think I'm floating the valves I've got big isky toolroom springs, but I guess I could.

Slowhawk

iTrader: (12)

Are you getting the boost reference for the wastegate setup off the intake?

Ryan K

iTrader: (11)

Also, is it an on center exhaust housing?

And what wastegate?

It sounds like the boost controller is not compensating for the increased back pressure which acts on the wastegate valve...

Ryan K.

ABeasst

iTrader: (5)

The wastegate is referenced off the intake manifold and its a JGS40. Also its a tangential.

1Love_369

Check your settings on your boost controller and play with your gain. if it drops off at peak, add gain, if it spikes during building boost, lower the gain. Bottom line, check the manual and work it out in low boost. Also, check your limits, warning limits, etc.., they will come into play.

jeejee

iTrader: (3)

i had something simular, it turned out that wastegate was too small, so in midrange it was wide open and still the boost was increasing, at higher rpm the wastegate was able to do it's work again because the turbo needed all the exhaust gasses it could get to supply the engine with sufficient air.....