Jllewan

NCLA951

fast951

Which chip are you running? It could be overboost protection or many other things. We need more information.

Humboldtgrin

Jllewan

fast951

Start by getting a boost gauge to monitor boost.

You can check for error codes (ex Knock, Overboost...) by connecting an Led to the test port. Search for the procedure on how to do it. Overboost will give you a "3 - 2" code.

If you can boost in lower gears through the Rpm range, but not in 3rd or 4th, then it could be overboost.
Basically, the stock overboost kicks in when you the engine load (air flow / rpm) exceeds the programmed value (per rpm) , and it remains for a predetermined period.
In lower gears you go through the Rpm fast enough, you may not trigger overboost. In higher gears, you spend more time per Rpm which could be it.

If you removed the cat converter, raised boost, mismatch KLR chip (assuming cycling valve is used for boost control) or your AFM is off; any or all could cause it.

When you hit overboost, it's a fuel cut as in Rev limit. The engine will not die, but you cannot hit the gas. It remains for 30-60 sec, then it clears itself. Or if you cycle ignition.

Jllewan

fast951

That's probably it. Regardless, to get the most out of your turbo you need a performance chip, and turn up boost a bit. The other option is to get factory 951S DME and KLR chips, but may still risk overboost without the cat.

Jllewan

fast951

Obviously I recommend the Vitesse chip. It works and performs great.

A manual boost controller is the easiest way to turn up boost. Keep in mind, the boost and engine management (chip) work as a system.

Jllewan

John & Forum,

I installed the Vitesse chip, boost/vacuum gauge & went from 2.5 to 3 bar fuel pressure regulator. The over boost issue is gone !

I do have a Lindsey racing boost enhancer hooked up and I'm not sure if it needs adjusting? removed? or left on? Any suggestions? How do I test? It was on the car when I got it.

thanks!