turbo comparison...

Q Q at IntendedAcceleration.com
Mon Aug 5 14:25:13 EDT 2002

The K numbers refer to the turbine side
The RS2 turbo IS a K24 with special K26 compressor housing. . .

How is the RS2 turbo different from the "stock" K24?

     Larger shaft for greater high rpm stability
     Larger bearings
     Larger compressor
        Same exducer diameter as "stock" K26
        Inducer is larger than both "stock" K24 & K26
           So "stock" K26 has its own built in restrictor
           "Stock" K24 does not have enough metal to bore out.
        Before the RS2 turbo tuners would sleeve a K26 compressor
        and then machine it larger
     Larger exducer from the turbine
        More lag
           That is why we offer a special model
           with an exducer between the two.


-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com] On
Behalf Of Jim Green
Sent: Monday, August 05, 2002 11:59 AM
To: Lewis, Gary M
Cc: Quattro list
Subject: Re: K24 vs RS2 Spool-up. RS2 Results is now turbo comparison...

> 2.  Above 5,000 feet I never pushed (right foot
> application) my K24 above
> 1.6 bar.  Casually speaking with no expertise or
> hard data, I'd say if your
> live above 5000 feet, stick with the K26, or get an
> RS2 or K24/K26 hybrid.
> Audi put an altitude checking thingy in the 1991 TQ
> to keep the K24 from
> over spinning at altitude, as the 20V T's ran 1.8
> bar factory.  If Audi was
> worried about it, the issue probably has merit.
> Also, Scott Mockry ran some
> turbo coldside exit temps while going through
> Colorado's Eisenhower(is that
> what it is called??) Tunnel, and was getting HOT
> temps, like 440F.  Woah...
> You really need to ask an expert (Scott *QSHIPQ*
> Justenson (sp?) is one) on
> the pressure ratio's of the turbo's in question.
> Check the archives, we've
> been talking (and fighting) over this one for at
> least 5 years.
> Bang for the buck the K24 is a GREAT mod.  If you
> have altitude concerns,
> I'd investigate a K24/K26 hybrid, K24 coldside, K26
> hotside.  The RS2
> hotside exit opening is 55mm, a lot bigger than the
> K24.  Break out the
> grinder, get the K26 to that spec.  Also, the K24
> cold side intake is 43mm
> vs the RS2's 48mm, which appears to me was achieved
> by grinding.  Again,
> lotsa btdt on the list and in the archive...
> Gary Lewis
> 1990 200TQW, RS2 Turbo, 1991 TQ Intercooler, 1.8
> bar, Bypass Valve, Euro's,
> Bilsteins, Redline in tranny and diffs

I thought I'd suggest a few things.  It's interesting
that you get a little pinging at 1.8 bar.  I would
think that it should be rock steady at that level with
your turbo and intercooler.  I'm sure you've already
messed with base timing, but you might want to
re-check it.   Also, from tuning my Haltech ignition
system, I can't stress how important intake temps are.
 They are very picky at high boost.  Say I have
everything tuned in for 95 deg. outside temps.
Without any air temp adjustments (advance), my mixture
will barely fire at 15 psi in the morning when it's 60
degrees outside.  All I get is some nice chugging.
I've also been looking into making an enclosed airbox
that is well insulated, and has a cool air intake, vs
the K&N with metal heatshield I have now.  It looks
like you already have a single pass IC?  Even if you
do, you might want to consilder something else when at
2.2 bar.  You might be able to eliminate the need for
water injection.  To me, it's one of those things you
use for drag racing, not everyday driving, if that's
your goal.


Jim Green
'89 90tq 034EFI, Haltech IG5

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