Quote Originally Posted by ttboost View Post
Yep, factory manifolds and turbines just. don't. flow. enough.
This is a side effect of the "Eco Boost" (just done by Audi 30 years earlier) of using the turbo to supplement low/mid torque by adding it to a highly efficient naturally aspirated car. In order to spool up (until recently, it was unheard of that a turbo spools up fast and peak torque arrives at under 2k rpm), small turbos (hot and colds side) are used. And in order to provide better response, fairly restrictive exhaust manifolds (and again small 'snails' in the turbine) were used.

This general concepts applies to other VAG turbo engines (1.8T, 2.7T). Over the last few years, those "K04" framed turbos' performance have been pushed quite a bit, first on the 1.8T, later the 2.7T to provide an alternative to the "big and slow" "Big Turbo" that are readily available, but tend to provide a fairly narrow, peaky power band. It appears that not a lot has yet been done for the RS6 in this respect, probably because there are simply not that many around (and the limitation of the transmission).

I hope to have an upgraded engine (rods!) installed in my TT this summer. The TT225 turbo is similar (turbine and compressor wheel) as the RS6 turbo, and we have built a much less restrictive turbine and a big, 67mm billet compressor cold side. The turbo is already installed and running with only minor loss in spool up, but is curently heavily detuned in light of the stock rods (18-20 psi).

I am hoping for 450 cHP on E85 from this 1.8T and a 3000-7200 power band.