NordicSnow

I bought an S4 Turbo II and have always had an issue with the car stuttering whenever it got on boost. Someone (the previous owner probably) installed a stainless steel 3" turbo back exhaust system, although did not do any other modifications to the car. From my understanding this will cause issues, altho I'm not sure what issues it could cause or if its even causing my particular issue. My guess is that the boost levels go above the ECU's threshold and therefore is causing a fuel cut, which makes sense. Racing Beat suggests just using an FCD to handle the higher boost levels, but that seems like an overly simplistic suggestion.

So assuming this is an issue, what would be a potential solution for me to fix it? I don't particularly want to port the wastegate, and finding a stock exhaustto replace my current one has been somewhat difficult, let alone one in good condition.

Any ideas would be appreciated, thanks

Mlammert

You can get a FCD to deal with the over boosting but it wont adjust your fuel or spark for the extra boost like you should do when increasing boost levels. Granted a few PSI over stock probably wont do anything bad.

I've heard people suggesting cutting out a piece of metal to the shape of your exhaust gasket and cutting a smaller, stock sized hole to simulate the restriction a stock exhaust system puts on your car to limit boost. This is probably the quickest and cheapest way to cure your issue and it's easily reversible but I cant speak for it's effectiveness.

I have a large street ported S4 motor and 3" ID turbo back exhaust and even porting the internal wastegate ports to their max didn't help but I did find a small crack in the line going from my turbo to my wastegate when I took the turbo off. Checking the current operation of your internal waste gate would be a smart thing to verify.

If you want to keep the aftermarket exhaust on and keep the stock turbo system as is you can buy an Apexi Power FC or similar stand alone ecu and get the car tuned but this is one of the more expensive options. A Power FC or other stand alone will allow full modification of your car if you want to keep her and plan on going further in power levels.