Magic_Man
Oh Yea !
- Local time
- 11:24 PM
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- 9
- Joined
- Dec 4, 2015
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- SE Ohio
I would like to discuss compression in 2 stroke engines without insulting anyone or anybody getting red-assed(my word for butt hurt) . My background is mostly in 4 stroke engines. As I am learning more about 2 strokes and how they work I find it interesting that so many put so much value in cranking compression test pressure readings. It seems there are so many variables in a 2 stroke that would contribute to cranking pressure variables.
Things like ring and cylinder condition, port timings, and even case compression all come into play. Am I also right in thinking that with the case pressures and scavenging effect that the cranking pressures would actually increase with rpm ?
What made me thing about this is that when we used to build v8 engines we would calculate the static compression at let's say 10:1. Once a cam was installed actual cranking compression would be less depending on intake and exhaust openings. In actuality the higher the performance cam(more agressive intake and exhaust timing), the lower cranking compression would be. It seems this would be the same in the 2 stroke, more agressive timings would lead to lower cranking pressure numbers.
Things like ring and cylinder condition, port timings, and even case compression all come into play. Am I also right in thinking that with the case pressures and scavenging effect that the cranking pressures would actually increase with rpm ?
What made me thing about this is that when we used to build v8 engines we would calculate the static compression at let's say 10:1. Once a cam was installed actual cranking compression would be less depending on intake and exhaust openings. In actuality the higher the performance cam(more agressive intake and exhaust timing), the lower cranking compression would be. It seems this would be the same in the 2 stroke, more agressive timings would lead to lower cranking pressure numbers.