calm down gents, its an interesting discussion, no need to rush, and i must say when it comes to
( automotive?) pistons i thought about it and must admit i am not pretty sure here.
due to my knowledge hot exhaust gases are a "waste" not being able to convert into useful output. it is also a common knowledge that rising the compression rises thermal efficiency- so a higher compressed piston engine , a more efficient engine will give less "waste" hot exhaust gases and so the exhaust temperature will be lower. but i googled it and found this pdf.
http://rescomp.stanford.edu/~efroeh/...erformance.pdf
when you search for the "exhaust" or "temperature" you will find statements and graphs showing that indeed the EGT is lower at a higher compression and as well it is lower when spark timing is advanced.
so slippery truly seems to be right here when we discuss the theoretical coupling of EGT and compression.
but ots not thats not that simple- fuel mixture, piston design, cylinderhead design and much more seem to have an influence on it. and oggers gave also a lot of useful information. and all this seem to be valid on piston engines.
cheers.