Alfa 147 JTDm 150hp - EGT problem (GTB project)
I'm new to the forum and I'm not a real alfa owner (hope I didn't break some rules).
I'm here to try to resolve a problem on a my friend car.
I'm a computer science student, I've a good experience on engine tuning (mechanical part) and I'm well prepared on the ecu tuning side.
Some months ago we planned a GT2056 turbo (Trim 55) upgrade due to original turbo failure (broken vnt actuator and noisy turbo), we built from scratch the exhaust manifold and adapted everything else.
Stock turbo back exhaust without cats and stock intercooler, upgrade of both were surely planned but not yet installed.
GT2056 was choosen only because I had one used unit available.
Started tuning the part-throttle and quickly realized EGTs were sky high, with almost stock injection and boost pressure of 1.5 bar 900°C were archived after no more than 15 sec at WOT.
Considering that installed turbo started making some very strange noise even at low boost (no surge) we planned to swap to a brand new GTB2056 (Brera 210hp) thinking that the high EGT problem was related to bad custom exhaust manifold design.
After that we finally installed the GTB on the stock exhaust manifold.
Started tuning the VNT maps and actually I was really surprised having better spool than stock with no sign of compressor surge.
MAF started giving error due to max flow reached so I planned to switch to speed-density (MAP).
Anyway the problem was that with completely stock injection and 1.4 bar boost (a bit more that stock) we still had EGT higher than 850° on a 20 sec. pull.
After that we double checked everything:
- IAT ~70° max after a very long pull and heatsoaked
- EMP ~1,3 bar
- changed the EGT sensor with different type and make
- no boost leaks
- EGR closed physically & on the ECU
- no sign of smoke from the exhaust
Having no idea of what the problem could be the stock turbo was reinstalled.
With stock turbo EGT went down a bit (780°C) on a 20 sec. pull.
Finally found a possible problem: timing belt slippage anyway EGT went down to 760-770°C.
Before adjusting the phasing with the dedicated tools we checked it with the old soldering tin method and we also found that the glow-plug was white coloured. (normally black)
Having no experience on JTDm engine (have worked a lot on TDIs) I'm really struggling to understand if those EGT figures could be normal or not.
Some time ago I've read somewhere that maximum EGT on factory cars (OEM recomended) must stay below 750° and every car I've seen until now stayed below that temp. even with FAP\DPF installed.
Considering that the car is running an empty turboback exhaust excl. final silencer I'm pretty sure the EGTs I'm seeing are very strange.
(I think I'll easily see more than 800° on a very long pull)
The car is the "no-DPF" version with the old injection system (1400bar).
Have anyone measured the EGTs on that car?? Maybe ori & mapped?
Thank you and sorry for such a long post, I've tried to write everthing useful!!