RS2 ?'s

Mihnea Cotet mik at
Tue Dec 16 14:24:03 EST 2003

Hi all,

Just my 2 euro cents of 20vt engines tuning:

The K24 on a 20vt starts boosting around 2.1k RPM, full boost is achieved 
at 2500 or thereabouts (depends on the exhaust system and if it has cats or 
not) but boost has to start dropping at around 4k RPM because of the high 
potential of overspinning the turbo.

Maximum HP on a stock turbo is around 280-285 HP at about 6000 RPM 
(sometimes lower too), torque can go as high as 310 lb/ft.

The RS2 turbo, if the ECU is programmed properly and when testing in the 3 
highest gears (either 3rd 4th 5th or 4th 5th and 6th on euro UrS4s and 
RS2s), makes reasonable boost at 2.6k RPM (2.5 Bar absolute), goes up to 
2.7 Bar at 3k until 4.5k, drops to 2.55 at 5.5k and 2.1 at 7k RPMs. This is 
sufficient to give 440 lb/ft (no typo, I've BTDT on the dyno in real time 
and I have the graphs to prove it) at around 3.3k RPMs and 365-370 HP (at 
the crank as all figures quoted here) between 5.5 and 6k RPMs.

Lag isn't a big problem either, with proper "tweaking" of the fuel/timing 
maps, as well as the WGFV map, the RS2 turbo ends up having very little 
lag, possibly as little as a stock turbo being run by a stock ECU.

WRT RS2 EM, it doesn't really bring much HP, but instead it brings torque, 
because of the fact that it flows more gasses at peak torque RPMs, which in 
turn allows one to push the knock limits a lot further, thus increasing 
torque, without getting any knocking/pinging/whatever and with keeping EGTs 
at much more reasonable levels. I used too to think the RS2 turbo didn't 
bring much, but ever since I've BTDT on the dyno with 2 cars running the 
same setup minus the RS2 EM and finding out that the one with the RS2 EM 
could run very easily at least 10 more degrees of advance at WOT and peak 
torque RPM, I'll never say again that it's useless.

WRT efficiency (for Brett), it is not all a matter of boost levels or 
intake air temperatures but rather a matter of air flow supplied by the 
turbo. Let's say we want to run a stock turbo with 2.3 Bar absolute boost 
at 6k RPM in order to get close to 300 HP, just because 2 Bar makes between 
270 and 280, the result, even with extra intercooler sprayers or whatever 
to keep the intake temps low, will only be overspinning the turbo and 
possibly ripping the shaft apart.


Mihnea, tired of tuning for the whole weekend  (6 cars in 3 days)

At 17:20 15/12/2003 -0500, Ingo D. Rautenberg wrote:
>I think the lag issue is WRT the K24 -- so instead of getting boost around
>2400/2500 rpm you'll get it closer to 3k/3200 rpm -- still better than the
>K26 at 3500 rpm, plus as Brett said, a lot more boost up top -- all the way
>to redline.
>Brandon, just ask one of your fellow UrS listers who hasn't yet HaperSized
>his turbo to go for a ride in an RS2-equiped UrS4/S6 :-)
>'91 200q20v...Slightly modified (soon F/S)
>'84 Tornado Red Urquattro
>'91 v8 quattro 5-Speed (not exactly stock) :-)
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