PV/T=C and Pressure x Volume to the power n (the Adiabatic index) is still a constant too!. They purely relate to the mechanical work done on the gases compressing them and the work taken out of them when they expand, not affected by the combustion process.
It is always better to ask a stupid question than to do a stupid thing.
Blimey BP, as this Robert Boyles law goes back to 1662 I never thought you would remember it. Long long time since I had to do all that Thermodynamics stuff. Live heat engines at the technical college trying to wrench themselves out of the floor and all that stuff. Bet Robert Boyle never dreamt that this law would still apply today even with the invention of CR. Quite an achievement that it still holds true today. Wonder if it's part still of getting tickets in Canada?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.