I didn't forget.Just to refresh you, remember that the speed of sound depends on the exhaust gas temperature.
But thanks for pointing that out. I probably should of been clearer on why I came up those figures. Which I grabbed from here. http://www.engineeringtoolbox.com/air-s ... d_603.htmlThe speed of sound in an exhaust system would have to be at it's slowest point probably 350 M sec to over 550 M sec in the manifold
An interesting link, I think I'll stay with 4 stroke for a while longer. Long way from a rocket scientist.