[torsen] Re: RS2 turbochargers

QSHIPQ at aol.com QSHIPQ at aol.com
Mon Jun 17 11:11:01 EDT 2002

Comments inserted
In a message dated 6/14/02 9:29:41 PM Central Daylight Time, 
Dave.Eaton at clear.net.nz writes:

>finally, you agree....
I missed where, but ok.  I thoroughly enjoy reading the logic, I just don't 
come to the same conclusions given the data Dave.  What we need IS the 
baseline of what the k24 does in the real world.  We know that peak torque in 
the RS2 (how audi tested it) is 40ft/lbs more 500rpm later (equal 300rpm 
later), and our "road data" *appears* to discredit that.  Then let's take a 
hard look at the k24 in terms of "claim".  I'm betting you won't see a peak 
torque at 1950 on a chassis dyno. 

>have to say i chuckle at the comments about the lack of "optimisation" of
>the rs2 turbo in the rs2, or that the "case" showing that the rs2 is very
>poor below 3,000rpm vs the k24 isn't proven yet.

A couple things to consider Dave, since very few have actually taken the RS2 
turbo apart and played with it.  First, in application designs of turbos, 
"acceptable whine" is a target.  As soon as you play with the RS2 
turbocharger unit, "acceptable whine" becomes an immediate factor.  BTDT.  
Very slight changes in blade pitch, cold side application, even closing turbo 
tolerances, results in the police siren near the motor, BTDT2.  Up to and 
including the passengers looking behind the car for the cop.  I know there is 
a lot more in the RS2 turbocharger unit to be had.  I doubt audi would EVER 
bolt it onto a flagship S car after doing so.

>last time i checked under the hood, there was a name cast into the inlet
>manifold.  wasn't "audi", iirc, it was "porsche".  and they sure as hell did
>a lot more to the car than just plumb a bigger turbo in.  fact is that they
>wanted more than 300hp, and in order to get it, without modifying
>displacement, they went for a bigger turbo.

No, they really needed more airflow, and didn't want to lose low end torque.  
Audi already delivered 300+HP with a bigger turbo 10 years prior to the RS2, 
it's in the SQ.  So they "went for a turbo" that gave k24 lowend MAP 
emulation, and highend flow.  This required that KKK develop a hot side turbo 
housing and wheel specifically for the I520vt.  It has NO other application.  
BIGGER?  No Dave, in fact, it's *smaller* than the 200/5000tq K26 
applications with <200hp.   

> that comes at a penalty of
>(comparatively) lethargic low-end response.  this is despite the changes
>over the s2 (with aby) which comprised the map, the boost, the exhaust, the
>inlet & exhaust manifolds, the exhaust cam and fuelling, the airbox and
>intercooler.  ipso facto.

Interesting comment.  In my 10vt application, the RS2 is SMALLER, and it 
outperforms the stock "bigger" k26 across the board.  

>the result is a very strong 315hp, a great top-end and a lot of smiles, and
>all cars quickly sold.  happy punters.

Those of us doing our homework realized exactly what the RS2 car was in 
comparo to the AAN.  EM, exhaust cam, fuel injectors, FPR, MAF, IC, and IM, 
19psi.  Oh, and the turbo itself.  

>interestingly there is always someone (funnily, most often someone with
>something to sell) thinking (or stating) that they can do a better job.
>claims are easy, and cheap.  happy to see a product, and get some experience
>of it.  any offers for an "optimised" rs2 turbo out there? ;-)

Dave, I share BTDT along with the next guy.  I'm *laughing* at your 
"discredit by selling" argument.  I understand what selling IS, I was a sales 
manager for 12 years.  I also might offer, that WRT the RS2 turbocharger, 
it's *just* BTDT.  I bought my first in Jan '95, and built higher performance 
RS2 turbochargers off it within a couple months.  Many steps backward, but 
quite a few forward.   I laugh, we *still* have vendors claiming it's a K24 
turbo. WRT "selling" and 'optimizing' them, I haven't *sold* an RS2 
(7200comp) since 1997.  The reason?  Well, to "optimize" one now requires the 
baseline investment of a complete turbocharger.  Up until 1997, you could buy 
7200 service parts (that's the hot side separately to you).  You can't do 
that anymore.

In my job, I tend to do more counseling than selling.  Big-*ss turbos make me 
chuckle.  IF you don't need it, or it can't meet it's own design parameter on 
the I520vt application, sub par comes to mind.  One can choose monster turbos 
from a variety of sources, most of them will bolt up to the I520vt.  Some can 
give gains on the high end, many can't.  I haven't seen any data logging or 
turbo/chassis dyno that would support many of the swaps folks have taken.  I 
see a lot of opinion, most of it based off absolutely no knowlege of turbo 
MAP or function.  Yours included Dave.  

>i'm happy with my rs2, happier with my k24 ur_quattro.  just don't tell me
>that lag doesn't spoil the rs2, because it does.

Well, I'm not sure why you went to lower comp pistons if "lag" was a concern. 
 I can share that IME, it isn't LAG that spoils the RS2 equipped cars.  
Without question, many on these lists need to get a better understanding of 
"how turbos and turbo sizing works".  Specifically, what *doesn't*.  After 
playing with modified turbos for over 10 years, I just come away with a lot 
more respect for that RS2 hot side wheel and housing than most.  It would 
appear that includes you, Dave.  

I'm quite comfortable with that.

>i stick with my stopwatch in the meantime.  there is no fooling that...

There's no fooling time, only your conclusions of it.  Appreciate your 
sharing of all the road test data, and your opinions of the RS2 turbo based 
on it.  I look back at your original line, and think, nope we don't agree.  
I'm happy to leave it at that.


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