Effect of boost control cutout prior to +12 psi boost modifications

[TomcatViP]

Originally Posted by Viper2000

Because operation of the boost control cutout with 100 octane fuel should allow +12 psi boost at 3000 rpm, which should give about 1100 bhp at sea level, rising to 1310 bhp at 9000'.

At present, the Spitfire I can only achieve the 87 octane rating of +6¼ psi boost at 3000 rpm which should give 880 bhp at sea level, rising to 1000 bhp at 15500'.

As I explain in this thread, operating the cutout should produce roughly +17 psi boost with 87 octane if the power lever is fully advanced, leading to rapid engine failure. At present, operating the cutout doesn't do much unless you're flying a Spitfire II.

The Spitfire II can get about +8 psi with the cutout operated, which would give 1000 bhp at sea level. However, it gets the sort of performance I would expect from a Merlin XII at +12 psi boost.

It's been a while since I tested the Hurricane. However, since it also has the Merlin III, logically the Hurricane I and Spitfire I should exhibit identical engine behaviour in all respects other than coolant temperatures (since they have different radiators).

Ok I dig out part of my database (in fact I took a short cut).

Merlin XX !!

ALT(ft) SHP BHP (diff correspond to the power used to drive the supercharger)
15K 1267 1048
20K 1298 1073
20K+ 1362 1126
25K 1162 960
30K 945 778
35K 700 568

What is funny is that I made this exat assumption based on value long stacked in my memory and was told I was wrong.
Same As the exhaust gaz power (remind that conv some years ago on WC forum ?)

I do repeat thus are Merlin XX -20 data 1941/RR !!

Max power boost is at 21k is 9lb and then decrease steeply at a 7lb/10Kft ratio.

As I made the assumption max boost (the famous 12lb is only for Take off - supposedly 1min max emergency power at low alt too)

I do repeat : I am not trying to be the guy with the right info or data but only want to help (if I ever could ?!!) this sim to be better to her ancestry, path that I am certain is off all the Ninja FMed planes.

Typical 1940 RAF pilot had guts, faith and anger against the Nazi war machine. Those are the only WunderWaffen they had in hands.

I'll stay tunned in case some needs more of this.... but I hve to say that I am a bit angry

~S!