Question about the KI43

[Vudu15]

Most a/c as you climb will of course lose some power but I'm curious why the KI takes such a hit in Manifold pressure but only from 13-14K then from 21-22K while once exiting these sections of air returning to what would seem a normal loss in manifold pressure.

Thanks Vudu15

[Big Rat]

SBD does a similiar certain alt range big performance hit.  My guess would be it would have something to do with the superchargers at certain alts, but hopefully someone will chime in that knows.

 
BigRat

[Wmaker]

It is due to the fact that Ki-43 like many other planes in AH has a two-speed supercharger. At mil power the first gear reaches its critical altitude (altitude above which the supercharger gear can no longer maintain manifold pressure for the particular power setting due to the thinner air) at ~10k. At ~14k the second supercharger gear (which spins the supercharger impeller faster) can be switched on without feeding too much air into the cylinders and the power is maintained to ~19k which is the critical altitude of the second gear.

[Big Rat]

Thanks Wmaker, figured it was something like that

 
BigRat

[Vudu15]

Yea thanks sir.

[FLOOB]

at 14k in level flight map decreases as you gain speed. why?

[FLOOB]

I said why damn it!

[Vudu15]

thinner air offering less resistance but critical alt on the super charger at the same time maybe.... Im not sure just learning myself.