Spitfire & Hurricane flight model & engine performance thread. (1.09 patch)

[JtD]

Originally Posted by Kurfürst

So by all means model the boost cutout and enable pilots to obtain +17 lbs boost and blow their engines at free will...

You make it sound as if it was a useless option or a bad idea, but it is not. If it is combined with a decent overheat / engine damage model, it would imho be the best and most useful way of implementation in game. The engine could take 12lbs of boost, as we know from the take off setting, and disabling the automatic boost control would give the player a chance to manually set and maintain it. What it is not is a simple press a button solution. It is the minimum that was available historically, it's useful and interesting.

Thanks 41Sqn_Banks for the 17lb figure, I wasn't sure if other restrictions were in place before the 12lb modification was carried out. So I went with worst case.

[41Sqn_Banks]

Originally Posted by JtD

Thanks 41Sqn_Banks for the 17lb figure, I wasn't sure if other restrictions were in place before the 12lb modification was carried out. So I went with worst case.

About +17 is the amount of boost that the supercharger can produce at sea level, it's not restricted.

[JtD]

That I find highly unlikely, if it can produce +9 lb at 17000 feet, it should be able to produce about ((9+14)/527*1013)-14 lb at sea level, which is about +30 lb. The compression ratio should not change much. If it does happen, though, there's some sort of throttle in the way, and be it just too small cross sections somewhere between the intake and the supercharger.

(Note about the calculation: (9+14) - total pressure in the supercharger at full throttle altitude; 527 - outside pressure at full throttle altitude; 1013 - outside pressure at sea level; - 14 - to get from total pressure in the supercharger to overboost as used by the British)

[41Sqn_Banks]

Originally Posted by JtD

That I find highly unlikely, if it can produce +9 lb at 17000 feet, it should be able to produce about ((9+14)/527*1013)-14 lb at sea level, which is about +30 lb. The compression ratio should not change much. If it does happen, though, there's some sort of throttle in the way, and be it just too small cross sections somewhere between the intake and the supercharger.

(Note about the calculation: (9+14) - total pressure in the supercharger at full throttle altitude; 527 - outside pressure at full throttle altitude; 1013 - outside pressure at sea level; - 14 - to get from total pressure in the supercharger to overboost as used by the British)

You are of course correct. +17 boost is for Merlin III, but Merlin XII runs at much higher boost.

However I doubt that any Merlin XII had a unrestricted boost cut-out.