steved

According to sources in Germany, the S4 uses a pair of small turbos already running at 95% of their capacity. With the extra boost from a chip, the turbos are being pushed too hard and are failing. Problem seems to be more prevalent with the right side, perhaps due to greater backpressure and temperatures on this side. SD<p>Steve D'Gerolamo

LCP

...how can this be so? Sounds like something where you couldn't exceed 100%.<p><img src="http://pictureposter.audiworld.com/AudiWorldPics/2000/LCPawsig1.jpg">
- Lance (corporate lawyer type turned track time junkie)
"I can't stop apexing"

NASA racer

something running 90% would be recall bait.

The turbo failures don’t necessarily discriminate between chipped and un-chipped cars. I think it is just a system design flaw.<p><img src="http://pictureposter.audiworld.com/AudiWorldPics/2000/carssmall4.jpg">
00 S4 tip
Silver/Onyx
GIAC ECU/tip “race” chip (14.4 in 100 degrees)
V1

Sander

I've had turbo charged cars (XR4Ti and Eclipse GSX) for the last 7 1/2 years now. Not that that makes me an expert but I have a little experience with them and have a read a lot on their respective forums.

There are always horror stories about failing turbos. In some cases there is a design flaw like on the XR4Ti (oil supply line overheated causing oil blockage). In other cases there is misdiagnosis or simply an ingested part of some sort. Typically though good turbos don't just fall apart when they are properly lubed and cooled.

I'm sure turbos will fail at some speed/pressure because of physical limitations. More likely though though you'll hit a different wall first. Turbos have a map that shows their efficiency and pressure ratios. It also shows that when you get to a certain pressure the temperatures go up steeply. Essentially the turbo is raising the pressure by heating the air rather then compressing it. We all know that hot air is bad for an engine (ping etc.).

So, my point (and I do have one), is that before a turbo overspins and breaks it will limit itself by limiting the output the engine can generate. I therefore suspect that the turbo failures we're seeing are caused by faulty parts or faulty design. _Not_ because we're squeezing a little more boost out of them.

I don't believe (but this is just an opinion of course) that the stock turbos run at 95% (of what anyway?) at stock pressure. Not even the T-25 on a 2G Eclipse is that undersized. It would require large intercoolers to get any power increase at that point. We all know how a slight boost increase increases engine output. That would not be possible if the turbos were overworked.

Anyway, way long and rambling.

Let 'er rip,

Sander<p>--
2000 S4 Silver/Silver Tip/Conv/Cold/Bose
SF-Bay Area

Sander

<p>--
2000 S4 Silver/Silver Tip/Conv/Cold/Bose
SF-Bay Area

winder

he said, and demonstrated (with my car & other chipped cars) that stock chips manages turbos to about 78 to 80% of capacity, and most chips, including v1 MTMs were running turbos to 95+% of capacity. he said that was too high. we dicussed that this level would cause poor turbo response and could over-pressure the turbos and intake tracts.
w/o knowing all the details of what he found.... i DID get the chance to offer my S4 for "experiments" with the subsequent v2 MTM chip.
i was first car here to try it for a day (in the "chipped for a day" program!) we ran several tests for boost, turbo %'s and other params (like intake temp.. where i took out the fogs and got 12'C lower intake temps w/OEM. 10'C lower w/v2MTM!)
v2 MTM runs turbos at 78 to 82% and response was MUCH better than the v1MTM car that i drove. v1MTM was NEVER in my car. my car ran stronger with same or better throttle response and NO surge or lag.
i didn't want to give it back.

triada

Well, santorin did better than me on the dyno........MUST HAVE v2MTM......... =)<p>-Cheng
<a href="http://registry.audiworld.com/audi/registry/details.asp?car=5226"><img src="http://www.musicsend.com/myS4.jpg" border= "0"></a>

tompa

use a component at 95% of its rated capacity.

winder

Santorin!!!!
3rd... i think the v2 MTM is out. i was told that the fisrt of these was going to all MTM customers w/v1 chips. if you have an MTM, i'ld contact them, or where you got yours.
i'm not a rep, just a lowly winder trying to figure out all this jumble of data in a complex world of S4 performance.

Richard Solomon

<p>Richard
'00 A6 2.7TQM
"Turbos make torque, and torque makes fun." -Corky Bell