[urq] RE: RS2 turbocharger

[QSHIPQ at aol.com]

In a message dated 6/12/02 6:40:26 PM Central Daylight Time,
deaton at tranzrail.co.nz writes:


>what you cannot seem to grasp (is it really so difficult, or is it just that
>you don't like admitting that you're wrong?) is that the stopwatch numbers
>posted from the low-engine-speed road tests of the rs2 and the aby s2 are
>for cars with:

Stick with this Dave...

>the only difference is in the wheels and tyres, and these are basically the
>same rolling diameter and, i would wager, very similar weight.  the end
>result, as posted, is that the s2 w/k24 comprehensively outperforms the rs2
>at low engine speeds.

That just doesn't appear to be a turbocharger issue Dave.  Both turbos put up
the same numbers wrt output, and are well within the surge line for the lower
boost levels vs engine air demand.  No disagreement that something isn't
working the same.  The RS2 turbo however, does work the same (albeit slower,
it doesn't NEED to be faster).  I'm not sure what you are arguing.  The MAPS
are published, so are the numbers from the turbo unit "up/down/sideways" on
the 20vt application.

>i have not posted the numbers taken at higher engine speeds which show, as
>expected, that the rs2 starts to perform significantly better than the k24.
>thus, incidentally,  if your "rotational dynamics" argument were true,
>surely the effect would be felt everywhere in the rev range?

Not necessarily, but we're not there yet.

>wrt high engine speed performance, that is not at issue.  the issue is the
>lag of the rs2.

CAR, as delivered from the factory

>also you insist on reading the torque charts as gospel.  clearly they don't
>take regard of turbo spool-up time (latency), also clearly more of a factor
>with the rs2 setup.  surely this is also a consideration?

Lag is a factor, which was addressed quite well with a spec'd design of the
hot side of the turbo by porsche for ONLY the RS2 car.  In that design,
Porsche obviously wanted both the quickness of the k24 output, as well as the
high end of the k27 fitment in the SQ.  Overlapping the three turbo MAPS and
the corresponding "up/down" engine testing, success is measured, confirmed by
the maps, and the car output.  What's MISSING is the rest of the equation,
specifically, why can't this turbo application IN the RS2 automobile reflect
the 300rpm differential.  Rotational inertia?  Timing/boost tables?  Cam
timing?  Big ass IC?

Dave, I enjoy a good discussion, it doesn't have to be this heated.  The k24
is faster to spool than the RS2.  But for engine demand, the RS2 can be
slower and produce the same output.  IF indeed the S2 and the RS2 share the
same dual mass flywheel, BOTH could be faster without it. Do you have tables
comparing the 3B S2 to the ABY S2?  Might be interesting to see what the DMF
did to the "overboost" performance 'gain'.

My claim is that RS2 turbos can be quick to perform.  The turbo maps indicate
they don't need to be as fast to get the same output.  The engine output
numbers indicate that to be true as well, a 300rpm differential in fact.
Which means ANY reduction in rotational inertia will result in performance
gains on the RS2 equipped turbo motor.  It also means that the RS2 will
respond very well to any performance tweeks to the motor, including turbo hot
side, ECU mapping, Reciprocating Mass (lightened engine components),
rotational inertia, and optimizing airflow.

All anecdotes aside, the RS2 turbo POTENTIAL is damn close to the k24, even
at low boost levels.  Execution appears to be a tough nut, as Dave has so
dilegently tried to present.

Again, anyone wanting to trade their RS2 POS for a awesome k24, let me know.

still lagging behind in class
Scott Justusson