Hello everyone,

I have an S3 8L with an ME7.5 ECU and a big turbo setup. Since day one after the big rebuild, I’ve been struggling with very high EGTs. During normal driving at around ~130 km/h on the highway, I’m always seeing 800–840°C. Under full load, the EGT rises sharply even further.

With my first turbo setup (G25-550), we sometimes had to run as rich as lambda 0.76 under full load just to keep EGTs from exceeding 950°C. Despite solid hardware and a perfect tune on 102 octane, we had to stop at around 400 hp because EGTs would climb even higher with more boost.

Now I’ve upgraded to a G25-660, and the problem still persists. I sold my old turbo (+ manifold) to a friend, and with the same LAMFA tuning, he’s only seeing around ~850°Cat full load — even at higher boost levels.

I’ve been to two different tuners, and both had the exact same issue. Ignition timing is also already at the limit, so that can be ruled out as well.

What has been done / checked so far:

- Exhaust backpressure: I’m running a 3" catless downpipe with a 3" Bull-X exhaust system. I also installed a pressure sensor to check for any possible backpressure → everything looks fine
- Injectors checked and replaced with others
- Fuel pump checked and replaced
- Different spark plugs (previously PFRQ7 → now BKR8EIX)
- Lambda sensor replaced and cross-checked with an external AEM 30 0300 gauge → the measured lambda value from the car is definitely correct
- TDC marks rechecked and verified, everything is 100% correct (cams are stock BAM)

At this point, I’ve run out of ideas and honestly don’t know what could be causing this anymore… It’s not just that the EGT is reading high — you can clearly feel it. After every normal drive, my turbo and manifold are glowing, and bolts in the exhaust system keep coming loose due to the extreme temperatures.

On top of that, I can’t really get the car properly tuned like this.

In the attachment you can see a log with a 2-3-4th gear pull. Boost ist 2,2 bar at ~ 5.000rpm and then strong reduced to only 1,4 bar at 6.500rpm (limited due to the EGT) and then const. 130 kph.

If anyone has any further ideas, I’d really appreciate any suggestions!

the EGT is measured. The sensor is also working 100% correctly (Was checked and compared with an external Typ K Element).
Cams are Stock like mentioned above.

I did a compression test a while ago, I had about ~ 11 bar on all cylinders. Valves, steam seals etc are all ok since I had the head down a few months ago (new headgasket for 8,5:1 CR). I havent really measured how high the oil consumption is since I dont drive the car a lot but I would guess it was about 0,5L on 1.000km (Had to refill only once).

Intercooler piping, FMIC etc are "dry". But I do have the feeling that something is not really fine with the pcv setup. I rund only a big hose from the engine block directly to my catchcan and then into my inlet (with the oem valve). So I dont have a hose which goes to the manifold with a check valve if that should play a role.