I'm confused. I own a book called 'Modellmotoren" by Peter Demuth (1989) in which is stated that you have to calculate the compression from the point where the exhaust port is closed:




Another question: when designing a diesel-head, do you take into consideration the clearance between the piston at TDC and the head? (squish band) In my case this is 0.5mm (0.02 inch), which in my opinion, should have a considerable effect on compression ratio.