difference between us and jap spec turbos?

[joff]

I think I remember hearing the newer models used some sort of coating on the inside of the compressor housing that was designed to be eroded away by the compressor blades during breakin. Supposedly would make for really tight clearances that were part of the secret to acheiving 80+% peak adiabatic efficiency.

[GorillaRE]

Originally Posted by joff

I think I remember hearing the newer models used some sort of coating on the inside of the compressor housing that was designed to be eroded away by the compressor blades during breakin. Supposedly would make for really tight clearances that were part of the secret to acheiving 80+% peak adiabatic efficiency.

The units you're speaking of are the '99s.

The 96-98 twins were rated at 265hp instead of the 255hp US spec S6. The '99s were rated at 285hp. The only real visual difference besides the already stated waste gates color, is the compressor inlet. The compressor inlet on the '96-98s have a "step" or mechined "restrictor" of sorts, if you can even call it that, about 5mm before the compressor inducer. Now, to me, that means the inlet flow wouldn't be as efficient as the US spec S6s but they say that they're 10hp higher. I remove and reshape the step any way...