[BiturboS4] Rumor(s) Behind The New S4

Chip Goetzinger chip at auguricorp.com
Thu Sep 26 11:39:44 EDT 2002


To your forced induction point...i would tend to disagree. Yes you can
supercharge or even turbocharge the V8, but in the case of the new S4 --
"Houston we have a problem". Nameley it's the 11:1 compression ratio on
that motor. Have you ever seen a superchared E46 M3? Ever wonder why? In
order to make boost happen on this motor you'll have to replace the rods
and pistons, as well as modify the cams. Otherwise you're in severe
detonation land... To this point take a look at the 4.2 liter in the rs6
with its 9.2:1 compression ratio. So without MAJOR work the new s4 will
not be going anywhere near as fast as stage 3 cars we have right now.>>

Interesting, I wasn't aware that the compression ratio was that high.
You're correct, that does create a problem in forced induction - though not
an insurmountable one.  The Chevy LS6 (Vette Z06 engine), for instance, has
10.5:1 compression, and Lingenfelter offers a number of S/C and turbo
packages for the engine starting at ~$5k (the lower-powered ones - ~490hp -
require no internal engine changes).  The other option, of course, is to
install lower-compression pistons.  This does increase the cost/difficulty
of a forced induction install, but Stage 3 is hardly cheap and easy either,
especially when supported by the appropriate intercooling and fuel mods
necessary to make it a reliable track package.  So, yes, the high
compression does make adding forced induction harder (except at low boost
levels), but not impossible.  You emphasize MAJOR in that conversion, but I
would consider Stage 3 to be MAJOR as well, so it's a fair comparison.

'96 Mustang Cobra Convertible - 435 RWHP (Laser Red, Saddle, Saddle - shhh,
it's sleeping)
'02 Audi S4 6-speed (Santorin/Onyx/Silver Alcantara sport)
'02 Nissan Xterra XE-SC 4x4 AT (Black)

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