Ive driven formula reiza at montreal in the rain ,monaco and barcelone and each time at aome point ill have to pit to fix my engine because it will start getting damaged and eventually blow during normal racing, happens with authentic max and authentic low damage (iirc authentic is the full damage setting). It will impact my race as i have to pit midway through to fix the engine, can also easily be observed by revving at the start line the damage will go up quickly
Have you tried to change the radiator opening setting in the setup screen? IIRC default was 80 or 90, try a lower value and monitor the temp in the car. Perhaps you are burning the engine. If this is the case, and you are using default setup, this is still a good report since I guess default setup should be enough to do a race in every reasonable scenario.
I had a lapsus writing that, I tried to suggest higher. I'm away from my sim to give it a go to confirm the issue.
The engine is sensitive to high redline RPM, i've forwarded that (it might be a tad overdone) but i recommend slightly earlier up-shifting and slightly later downshifting in races and maybe even avoiding absolute redline too often.
Had it on automatic gearing when the issues occurred, havent tested it with manual yet as ive only started using manual like 3 days ago.