KKK RS2 race turbo charger

[Dave Eaton]

well i'm running an rs2 turbo on my 20v, with higher boost, modified exhaust
cam, modified airbox, inlet and exhaust manifolds, and exhaust system.  it
has a larger intercooler, uprated fuel pump, slightly lower compression and
an uprated motonic, and uses only 98 ron gas.  throttle response and lag are
still not good, and cannot compare to the 3b w/k24.  great top-end though.
no, not great, wonderful - far better than the k24.  but around town, even
many times on the motorway, i'd trade the top-end for the "stomp" of the
k24 - in the rs2, "stomp" almost always means changing down at least once.

i've also had seat time in an uprated rs2 (w/mtm 340hp upgrade) and found
exactly the same issues, although the top end is better.  i've also had 3
years in an s2 (3b w/k24) with similar weight as the rs2 - again much better
throttle response and less lag than the rs2.

i know what the hp charts say, but the reality is that the rs2 is not giving
serious boost until over 3,000 rpm, 3,200 is "nice", and this is almost
1,000 rpm higher than the same "boost point" in the k24 ur_q application.
read any road test of the rs2, or post on the rs2 list, and you will find
the same comments.

charts are one thing, but i believe the stopwatch (courtesy of autocar) - so
lets compare.

5th gear in the ur-q is 4% higher than 6th gear in the rs2, yet despite
this, the 20-40mph time is 9.4s vs 14.8 sec for the rs2.  for the 30-50mph
time, read 7.1 against 12.5!  even at 50-70mph, the ur_q is faster with 6.5
against 7.7sec.  so despite a slightly higher gear, the rs2 is on average
over 50% *slower* than the ur_q - at any legal speed in top gear.

what happens when you change down a gear?  4th gear in the ur-q is 6% higher
than 5th gear in the rs2, yet despite this, the 20-40mph time is 6.2s vs
10.4 sec for the rs2.  for the 30-50mph time, read 4.9 against 8.4. the
50-70mph time are identical. so, again, despite a slightly higher gear, the
rs2 is on average over 40% *slower* than the ur_q.

chop down another gear?  3rd gear in each car are comparable (3% lower in
the ur_q), here 20-40mph takes 3.7s in the ur_q vs 5.2 in the rs2.  30-50mph
takes 3.2 against 3.7sec.  once again, the rs2 is slower, this time by an
average of 30%.

but what about weight you say?  well, lets look at the heavier s2 (3b
w/k24).  comparing 4th gear in the s2 with the rs2 in 5th gear (5% higher
ratio in the s2) yields 20-40 in 5.8s (s2) and 10.4 in the rs2, 30-50 in 6.0
to 8.4, and 40-60 in 5.4 to 6.3.  so, again, despite a higher ratio, the rs2
is over 30% slower than the s2.

so the stop watch says to forget the rs2 turbo and get a k24 if you want
low-end grunt, and minimal lag.

but what the hell would i know?  i don't sell modified turbos for a living
;-)

dave
'95 rs2
'90 ur-q
-----Original Message-----
From: QSHIPQ at aol.com
Date: Fri, 7 Jun 2002 08:31:04 EDT
Subject: RE: KKK RS2 race turbo charger
To: quattro at audifans.com

I'm not sure I agree with that statement Dave.  It would depend on what the
application is.  IME, the RS2 turbo on the 2.1L urq would plain suck, and
the
k24 unit is much better matched in terms of spoolup and output (BTDT).  The
RS2 turbo on the 2.2/2.3 liter motors *can* be a different story.  I've run
RS2 turbos on 10vt cars for 8years now, and with some attention to the
application, it can be a fine "all around turbo", and far outperforms the
k24.  Currently, my '87 t44tqw runs the RS2 (7200 comp), and my 83 urq runs
the k24.  I've also installed 15 or so of the RS2/7200comp in a variety of
20vt applications.

Here's my thoughts on the RS2 in the 10vt application.  The RS2 chokes on
the
stock exhaust, a 3in turbo back makes a great addition.  Minimally the RS2
needs a single pass IC, ideally a biger IC.  The RS2 will *kill* the CIS
meter without a bypass valve install (btdt).  Larger exhaust valves help the
RS2 turbo spool up faster.  The RS2 can run a constant 22psi at a really
high
efficiency, the K24 is beyond peak, and can only run this for short burst.
The RS2 needs to be agressively WG controlled at lower boost levels, as it
tends to cause Wastegate Cracking that will slow the spoolup noticeably.

WRT the RS2 turbo in the 20vt application.  The RS2 exhaust cam helps low
end
greatly.  So does the 3in turbo back exhaust system.  The 91 200 with the
RS2
stuff on it just smokes the k24, btinstalledthat.  I think the reasoning is
that the 91 200/urq is the only 20vt application without the dual mass
flywheel.  That dual mass really dogs off the line.

The RS2 turbo power output exceeds the k24 by 2250rpm (from your own comparo
chart Dave).  Although you 'own' both, a direct comparo to your two
applications isn't fair.  The RS2 has a serious weight disadvantage to the
urq, and the urq has a much lighter reciprocating mass.  Since you run both
cars in stock trim, I too might conclude the k24 is a better driver.
Tweeking either car, the RS2 turbo give the 24 a hard punt.