Oil temperature and other things that might kill your engine.

[Viper2000]

Originally Posted by reflected

Viper: OK, thanks, I'll give it a try. Also, would using too much boost kill the engine on its own? Without exceeding the temperatures?

IRL yes, but not very quickly unless you really cane the poor thing.

Even using combat boost for too long could cause failure, but it's not really deterministic; working the engine harder increases the probability that something will break.

If you had access to 150 grade fuel in 1940 then a new Merlin III would be capable of +25 psi at sea level for a safe life of about 15 minutes; this was used with the Speed Spitfire, N17. The 150 grade fuel in question was very different from the late war production stuff; it was one of Rod Banks' special concoctions of alcohol and benzol etc. with vast quantities of TEL. Totally uneconomic, and suitable only for breaking records. But probably quite influential in the Merlin's development programme because it showed what the engine was capable of given sufficient supercharge; the development programme therefore basically consisted of improving the supercharger and strengthening the engine to survive high power running for an economically viable useful life.

In the sim you can't really use too much boost because Spitfire I seems to only give +6¼ psi with the cutout activated.

Spitfire II gives +8ish; some say that this is just because full scale deflection of the cockpit instrument is +8, but I don't think so because the no-cockpit view instruments go up to +12 but still show +8ish with the cutout activated.

You can break the engine with too much boost at low rpm, which is why it's important to throttle back before changing to coarse pitch.

You can also get "exhaust header" failures if you run at high boost & high rpm for very extended periods, which is fair enough, albeit perhaps somewhat over-done for a new engine, as failure usually took a few hours of abuse unless there was a bad weld or something.