In a move which I should have done much earlier on, I installed a digital EGT at the inlet to the turbocharger turbine to take a look at how hot the combustion process was getting deep in the heart of the beast.
Based on my measurements, my "265HP stage 1" tune was ~1650f EGT up to 4500rpm and then long stretches of 3rd-to-4th gear peddle mashing would see peaks to 1780f (!!) Looking at the tuning maps, the injector duty cycle was maxed at 100% after about 4500rpm. Perhaps not.enough.fuel.
So, I decided to open up the exhaust even more...which is mentioned in a different post. But then I decided to try to get a bit more fuel into the engine. A simple experiment was upping to the 3.5bar fuel pressure regulator with matching T7Suite tuning. But that only got peak EGTs down to 1720f.
I then read about the wonky 'air flushed' injectors used in 1999 B235Rs and jumped into the deeper end with changing to the "late B235R" cast single-piece intake manifold and conventional fuel injectors. I sprang for a new set of Bosch green injectors (after looking past the disgust of these being Volvo parts). The change of the manifold also needed a solution for the threaded-type 1999 MAP sensor. Conveniently, the hole in the later manifolds is the perfect 12.3mm diameter for an M12 x 1.5 thread insert, done and done.
More tuning is needed and perhaps I'll eventually learn that the tiny 5 cm^2 turbo turbine inlet is too small, but for now, hopefully I can get EGTs and the combustion temperatures down to something in the 1600f range to make sure things have a longer life.
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