I'm just trying to put together a very basic engine model with extremely limited combustion. Basically, I am modeling isentropic compression, combustion (using LHV to calculate the delta T), and isentropic expansion. At the moment, I am calculating a peak cylinder temperature under motoring of ~400 C and a peak cylinder temperature under firing (5 deg BTDC) of ~2800 C. This puts my exhaust gas temperature around ~1200 C, which all seems to make sense. I am using a compression ratio of 8:1 and air standard conditions. However, when I try to convert these numbers to a cylinder pressure, my ~2800 C point is exploding to ~3700 bar! Obviously, this is not correct. I am using an isentropic expansion equation (P2/P1 = (T2/T1)^(g/g-1)). Any ideas? Can anyone double check my reasoning and let me know what you get?