Thank you, Keith et al. As you might guess, this is coming from a weird ATPL exam question. I have a supplementary: Surely (don't call me Shirley) the volume of gas pasing through a piston engine is constant at constant RPM. Or does the fact that there is a time when both inlet and exhaust valves are open (valve overlap) mean that volume flow is susceptible to change of MP or exhaust back presure?
Dick
Edit: Bookworm posted while I was writing this. I think the engine is a fixed displacement pump.