Question for the Motor Heads

[Seeker]

Originally Posted by ARM505

Funny that A2A is mentioned, because I seem to remember that LOWERING RPM in the A2A Spit LOWERS boost (ie, lowering prop RPM's via the prop control lever at a constant throttle setting results in less boost indicated). This is explained in the A2A docs - the supercharger, being directly linked to the engine, is now being turned at a lower RPM, hence a lower manifold pressure - the opposite to unforced induction, where lowering RPM at a constant throttle setting will result in higher manifold pressure, the 'car going up a hill in a high gear' analogy.

Yup, just checked the A2A Spit, and that's what happens. COD seems to behave in the opposite way - lowering RPM's lowers manifold pressure. One is right, the other wrong I suppose. Funnily enough, once again we seem to have a multitude of inputs explaining why COD is correct. Oh well. I'll just go and fly my Spit IIa IRL to check it out quick

To be honest, my vote goes to the A2A Spit, which is frankly awesome, even though the engines tend to wear too fast!

There's a thread about the Spít I and II in the FM forum where people are beating each other over the head with docs and charts as usual.

In the thread there's a comparative test between 109 and Spit, and the RAF docs clearly state that the Spit pilot reduced revs to 2600 which raised the boost...