RE: S4 upgrades

[QSHIPQ@aol.com]

Dwaye writes:
>I spent the weekend at Mosport at a BMW driving school. My instructor is
>the owner of a major tuning shop in the Toronto area (Mantis Racing). He
>suggests that the car (94 S4) could be made much more responsive by
>porting and polishing the exhaust manifold (cheap about US$200),
>installing a bigger turbo intake impellor, blueprinting the turbo, and
>removing the exhaust resonator. 
>Any comments? I've been considering a port and polish job on the stock
>manifold for a while now. 

How many turbo cars has he done?  A couple of things to consider.  1) the 
stock S4 manifold is a restriction, not one that can be improved by porting 
and polishing IMO, it's a design problem.  The best thing to do to a S4 is to 
get either the stock RS2 unit, or Ned's knockoff of the RS2 unit (Extrude 
honed).  Porting and polishing what would be my question.  I can see 
practically porting at the head, but how would you polish or port the 
runners?  2) Regarding the turbo....  Going larger on either the intake or 
exhaust impellor with a k24 is a schrapnel proposition, btdt.  The shaft will 
break, that k24 is taxed in stock trim.  Again, a better solution, would be 
either the RS2 turbo, the RS2 competition turbo, or the RS2 hot/hybrid cold 
side turbo, btdt.  The reason you do this, is that the RS2 turbo was 
specified for the AAN designed motor, including flow and rpm.  3)  Removing 
the exhaust resonator will give you some midrange power (and a LOT more 
sound), but really isn't the biggest restriction to exhaust flow (the 
downpipe and cats are).  Better to go with a 3in turbo back, or a dual 2.5 
(or bigger) with some high flow cats.  You get better flow and weight savings.

The 20vt motors are some of the easiest to tweek IMO.  The parts are 
available from the RS2, which has a very flat torque band from 2500-redline.  
This would include the turbo, EM, IM, and exhaust cam.  The intake is ala 3B 
so some other issues await you if you are going after the intake, but the 
throttle body is the same.  Tweeking the k24 or the stock EM is throwing good 
money after bad (or "stock car optimized") design.  The stock S car is 
supposed to have the feel of v8 torque, trying to make more out of those 
stock components will lead you and your checkbook down a frustrating road, 
IMO.  Get a better intercooler, and all that money spent on the Mantis 
suggestions couldn't get close.  Sounds like a N/A dude without much turbo 
experience to me.

My .02

Scott Justusson
QSHIPQ Performance Tuning
QSHIPQ@aol.com
'87 5ktqwRS2-10vt
'84 UrqRS2-20vt
'87 4Runner turbo