Alex Milenkovic

In a former life (read: past car) I had a turbo monkey as well, a '97 Ecilpse GS-T.

The eclipse comes with a 2.0l 4 cyl, that has a single turbo. Out of the factory it comes with a Garett T25 turbo.

Many DSM enthusiasts rename this turbo the "T 2 Small" because it is precisely that. The stock Eclipse gets something like 10 psi of boost, but the turbo cannot produce the necessary volume of airflow past 5000 or so RPM.

Now, from what I understand of the S4, the upgrade path for the turbos is to dump the KKK 03s and put in Garett T25s. The upgrade path for the eclipse, however, is to dump the T25 and put in a Mitsubishi 16g. One of the biggest things that was explained to me is that turbos have two characteristics: Pressure and Flow. And that even though a larger turbo may be run at the same pressure (10 lbs or whatever) by virtue of the higher flow it will be better, and it will be able to keep up with the engine.

My question is, if the T25 is too small for a 2l 4cyl, how on earth can the significantly-smaller-than-the-T25 KKK03s be even adequate? Yeah, each one only has to run half a bank (which is 3 cyl and 1.35l of displacement) but I still find it hard to believe that the stock turbos can keep up enough flow at high RPMs.

I'm pretty sure I've never seen anyone on here talk about putting T25s in their 2000 S4. But for all the tuning shops, and all the people that know the tuning shops, has this come up as an issue? Does the Audi engine have issues with high amounts of flow, but is okay with pressure?

Thanks.

Alex.

ErikR

2l for a T25. Turbo selection, as you know, is a compromise based on efficiency maps. The eclipse also had a low compression motor (at least in the gen.1), this means the engine can take the volume. With the S4, at the stock compression, you really just want a bit better top end flow with little lower end loss (make 1 bar over the whole rpm range).

George @ BostonAudi

I was under the impression the S4 upgrade path (Stage 3+) was KKK04 turbos?

I think one of the tuner shops has information about that on their website, but off the top of my head I can't think which one...

quikslvrS4

name looks familiar

Alex Milenkovic

No.. it really wasn't anything that special.. I took it up from 210 crank hp (170 wheel) to about 270-320 crank hp (225-270 wheel) depending on weather etc. I did suspension work, race tires, etc, and found out something profound..

No matter how much you mod a semi cheapie car, it's still a semi cheapie car

I got the s4 and I absolutely love it. The only reason I use the eclipse as an example is because it's the only other turbo car I've looked at modding. And I'm aware of the issues people had modding it, since it's a fairly inexpensive car, it had a HUGE aftermarket following. Some funny pics sometimes too.. one guy showed his 16G (what I have) compared to his new Ball Bearing turbo... it is literally 2x-3x larger.. quite the funny "compare and contrast".

Anyway, with the S4, I've discovered how wonderful a well engineered and awesome car can feel. Quite frankly, unless the Evo VI comes over, I will only own german cars from now on.

Btw:
I have now seen at least 3+ mags with a Left Hand Drive EVO VI. Yet Mitsu is staunch in their claims that they won't bring it over. I doubt that highly. My hopes are up.

Alex.

jmirandes

The car was imported to Puerto Rico and raced and the international speedway this past weekend. They say it was $60K+. Looks mean but kind of cheap-hey, it is nothing more than a mitsu mirange with regards to finishes and materials. It seems that it moves as well as claimed. The one I saw sits pretty high (looks like a Rallye car) and when breaking on the long it dipped down like crazy-needs some suspension mods in that department. I do not know where was it imported from but, it is here (Puerto Rico IS part of the US in case the question comes up..) it is left hand drive and I would not mind having one. Nevertheless, although different, I 'll keep the S4, the Evo is still a cheapie. If I had the money, would love to have it for track events.

Mike O.

Having been down too many roads to recall with the KKK03/04, here is the real deal when it comes to upgrade paths.
1. KKK03
2. KKK03 with an IHI or Mitsubishi compressor wheel in original housing and stock exhaust turbine
3. Same as 2 but extrude honed
4. KKK04
5. KKK04 with a Mitsubishi compressor wheel and a clipped turbine to match compressor flow rate
6. Same as 5 but extrude honed.

I am here to tell you that a single #5 can turn 20 psi all day at redline on the 1.8T.

You really don't want to get away from the KKK03/04 housing and cartridge because of the compact size and interated wastegate that is designed to work with the ECU.

Start with a chip and exhaust. Then work on fuel delivery and lastly work on the turbos. Everyone automatically thinks that pumping more air = more power. It usually just means more problems.

Mike O.

RS4.org - DaveH

The S4 has a problem getting enough air for cooling etc, this has been holding up some tuning mods

DK

Two K04 would certainly be easier as they bolt right into the stock manifold. From my experiences with the 1.8t, I feel that they do not provide enough of a performance gain worth the trouble of pulling out the engine.

The Garrett Ballistic Series T25 turbo is optimally rated for 280 hp (as published on the Honeywell website). For an S4, having one turbo for each bank of cylinders, two of these turbos seem to be ideal in order to maintain good throttle response and minimal lag. Ideally, better designed manifolds would be used.

If that is not enough, the Garrett GT25 is rated at 400 hp, and the GT30 is rated at 500 hp.

DK

matthewk

APR's upgrade for the turbos will have two GT25's