Compression ratio x compression pressure 4

[rdd48856]

What is the reason why with a compression ratio of 1:8,5 you should get between 11 and 13 bar of compression pressure? You shouldn't only multiply compression ratio times the atmospheric pressure?

Thank you.

 

[ivymike]

...because the temperature rises during compression, further increasing pressure. Look up "polytropic compression" on the internet if you want more.

 

[rdd48856]

Thank you, I'll do that!

 

[kitabel]

Or read my comments here:

http://victorylibrary.com/mopar/cam-tech.htm

 

[turbomotor]

I use a polytropic exponent of between 1.3 ~ 1.35 when I begin to model an engine. However, to more accurately model the actual process, one would require a continuosly changing exponent as the thermal energy, volume, molecular species, and surface area (heat transfer in or out of the cylinder) change.