Go easy on me but I have a stupid porting question.....

[cmarti]

Yes I have searched, I have been stuck at work for 10 hours and had to do something.....
I enjoy restoring oldies more, but have widened ports, milled bases, cleaned transfers... all mild stuff.
.....But I got the urge to play with a spare cylinder. Are ports always wider at the Carb and muffler than they are at the piston? I have always given a slight taper/megaphone , but it has me wondering if folks play with shape and
degree of angle from inside to outside.

I will ask why not wider exhaust in the middle instead of always wider on the bottom in my next stupid thread....

 

[Chris-PA]

I've not ported enough engines to be able to test different tapers out. I would think that the main issue is just that there is a limit as to how big the actual port can be at the edge of the cylinder, but outside of that there are fewer limitations. So in the interest of reducing restriction, one would want to make it a bit larger if possible. To work out actual gas flow patterns and try to direct that flow would take a lot of iterations and testing, and perhaps some sophisticated equipment - or these days some good software modelling.

 

[old-cat]

If you think your question is stupid, how about some of my stupid ideas? I have spent many hours studying air flow in 4 cycle engines but that's only reading what the real researchers have learned.
For these impossible 2 stroke things, you'd want the exhaust to get out QUICKLY so the pressure is minimal when the transfer ports open. Air likes a nice big radius at port entry points, so that's what I do with the exhaust port, then I make the out end of the port as big as I can because I figure that helps it flow out faster.