[s-cars] More dyno results

[Djdawson2 at aol.com]

Today we spent some time testing the lightly modified S4 again.  For those of 
you who read the last round, you're aware that we tested a car equipped with 
the RS2 EM, injectors, MAF, and software, along with the ITS RS2 killer turbo. 
 The RS2 killer did not fare well against the RS2 turbo.  It did make 12 more 
peak hp, but the cost was power delivery that was delayed about 650rpm, and a 
torque peak that was 30ft/lbs shy of the RS2.

We decided that we needed to experiment with a different turbo.  Our goals 
were pretty straightforward:
300+ hp ATW
400 ft/lbs of torque
Power delivery similar to, or sooner than the RS2

We based our new turbo on the 46 trim Garrett.  The results were not quite 
what we had hoped for, but better than the RS2 killer by a significant margin.

Peak hp came in at 323, only 2 short of the RS2.  Peak torque, however, was 
367ft/lbs.  This was well short of our goal, and 35 less than the RS2 
delivered.  While power delivery was about 400rpm sooner than the "killer," it was 
still 250rpm later than the RS2.  So, by and large, this is still not the perfect 
solution... but a significantly improved solution over the RS2 killer.  Bottom 
line... the standard RS2 turbo ain't too easy to kill.

Other tests we ran:

We dynoed the engine in a "stage 1" format.  The engine was still fitted with 
the RS2 EM, and the 46 trim Garrett.  The injectors and MAF were replaced 
with the stock units, and the ECU was swapped with a typical stage 1 unit, 
producing about 20psi of boost.  This setup yielded a very respectable 298hp, and 
323ft/lbs.  Not bad for just a turbo and EM.

Our final test was done with the full RS2 setup.  Our goal was to see what 
gains might be expected by improving the exhaust system.  The car in this 
configuration had previously recorded 323hp/367ft/lbs with a full stock exhaust.  We 
removed the car from the dyno, and then disconnected the entire exhaust 
system.  The only element in place was the downpipe... and yes, it was loud.  Our 
theory was that it would be pretty difficult to build any system that would 
flow as freely as only the downpipe.  Why not see what the engine would gain by 
running wide open?

This is where class participation begins.  Since everyone has been happily 
speculating on the "turbo spool" issue, I'm curious to hear what speculation 
exists concerning the Audi stock exhaust system.  As soon as we have 10 guesses, 
I'll post the results.  Doesn't that suck?  I just want opinions....  Anyone?  
(NOT Hap or Mike Pederson please!!)
Take care,
Dave in CO