acceleration problem

[moe]

I have 87 gn that I have installed afpr ,thrasher 92, and adjustable wastegate. I have also done spring cleaning and also new autometer boost gage. My problem is the car stutters at 10psi on gradual acceleration to just about half throttle then seems to be fine the rest of the way to wot. But from dead stop wot the car woofs right away.

 

[scottyb]

10psi is gradual acceleration? That's humpin it pretty good in my book.


Anyhoo, do you have scantool numbers?
Does it run well under light acceleration, (no boost)?

 

[moe]

yes it cruises around well with no boost and up to 8psi but soon as 10,11 psi it starts to stumble. I have no scan tool but do have fuel pressure gage under the hood, set at 45psi line off.

 

[UNGN]

If the car truly is stock, don't run a thrasher chip or additional boost until you have replaced the fuel pump with an aftermarket one. It may not be your problem, now, but it will be in the future if it's not changed.

The stock fuel pump can't maintain pressure/volume at the high fuel pressures needed for high boost operation (It maybe could when it was new...)

 

[TurboDave]

Sounds more like you're suffering from compressor surge, not engine stumble. This is a complicated function of airway sizes, turbo compressor size, throttle opening, etc.
This happens at part throttle, right? While you're holding the throttle at one particular setting, Maybe even letting out of the throttle so very very imperceptably?
Did I guess right?

But my vote is for compressor surge.