[torsen] RE: RS2 turbocharger

David Eaton deaton at tranzrail.co.nz
Wed Jun 12 20:41:52 EDT 2002


scott insists on stating:

<<"Reduce rotating inertia (Ok Bernie?). That would include, those big heavy
wheels/tires/brakes the RS2 sports, the clutch assembly mass.  You might
also consider looking at the OTHER known differences:  the intercooler
efficiency (larger IC's tend to be less efficient at lower PR), even the
intake manifold is different, exhaust manifold is different, so is the
exhaust cam....  The OBVIOUS cummulative effect of ALL these issues, is the
RS2 can't keep the performance level at the EXPECTED/CHARTED 300rpm torque
peak differential.">>

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:

1)	the same flywheels
2)	the same clutch assembly
3)	the same gearbox
4)	the same axles and hub assemblies

re-read that scott.  i am not an apologist for the dual mass flywheel but it
is *not* a factor here.

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.

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?

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

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?

dave
'95 rs2
'90 ur-q
		-----Original Message-----
		From: QSHIPQ at aol.com
		Date: Wed, 12 Jun 2002 09:11:58 EDT
		Subject: Re: [urq] RE: RS2 turbocharger
		To: quattro at audifans.com
		Cc: urq at audifans.com, torsen at audifans.com

		--
		[ Picked text/plain from multipart/alternative ]
		Dave
		Comments inserted
		In a message dated 6/11/02 6:08:20 PM Central Daylight Time,
		deaton at tranzrail.co.nz writes:


		>you mention "maths" but you haven't posted any.  this isn't
rocket science,
		>and it isn't hard, so i cannot understand your difficulty
in coming to ter=
		ms
		>with this.

		Thanks for bearing with me.  What I have a really hard time
understanding
		Dave, is a motor that has specifications indicating that
torque is equal at
		2300rpm, and torque is 40lb/ft higher only 500rpm later
(2500).  In my simp=
		le
		world, I equate more torque with a cars "ability" to
outperform another.  Is
		this not correct?  When I see the type of lag you are
posting vs an
		engine/turbo published output, I'm looking at everything BUT
the turbo.


		>Mph     rs2    s2     rpm range        outcome
		>20-40  14.8  11.1  (813 to 1626)    rs2 33% slower
		>30-50  12.5    8.9  (1220 to 2033)  rs2 40% slower
		>40-60  10.2    7.0  (1626 to 2439)  rs2 46% slower
		>50-70   7.7     6.1  (2033 to 2846)  rs2 26% slower
		>60-80   6.0     6.4  (2439 to 3252)  rs2   6% faster
		>70-90   6.1     6.8  (2846 to 3659)  rs2 10% faster

		>it is quite clear from this table that the rs2 is not
providing useful boo=
		st
		>(and acceleration) to the car until the turbo is spinning
over 2,500 rpm.
		>you can also see that the k24 is spooling up more rapidly
(30-60mph
		>numbers).  the rs2 turbo is only providing better
acceleration to the avant
		>when operating over 3,000 rpms.  a close look at the
numbers (particularly
		>the 50-70 vs the 60-80) also indicates the steep ramp-up in
the rs2 turbo
		>performance.  this again is what your butt tells you when
you are driving
		>the car.  it is the classic definition of "turbo lag".

		A different summation:  RS2 cars have classic turbo car lag
symptoms.  The
		question?  How do we reduce that?  Reduce rotating inertia
(Ok Bernie?).
		That would include, those big heavy wheels/tires/brakes the
RS2 sports, the
		clutch assembly mass.  You might also consider looking at
the OTHER known
		differences:  the intercooler efficiency (larger IC's tend
to be less
		efficient at lower PR), even the intake manifold is
different, exhaust
		manifold is different, so is the exhaust cam....  The
OBVIOUS cummulative
		effect of ALL these issues, is the RS2 can't keep the
performance level at
		the EXPECTED/CHARTED 300rpm torque peak differential.
		



More information about the Torsen mailing list