Timing for SI 2-stroke?
I've decided that I want my first project to be a basic 2-stroke. Nothing fancy, just a single cylinder spark-ignition 2-stroke. I'd be elated just to get it to run.
So I'm currently deciding on placement of the transfer and exhaust ports. I know there's a lot left (head, entire carburetor, rings, clearances, etc.) but I want to make sure I have the size and placement of the ports correct, at least enough for it to run. Attached are pictures of the piston in the cylinder at different positions.
The bore is 1", the exhaust port is 0.175"x0.75". The transfer port in the crankcase is the same size but splits into two 0.15"x0.4" slots that angle upwards. Stroke is 0.4" The lines radiating out from the crankshaft are at 30 degree intervals. There's also a simple flow simulation with the piston at just below the transfer ports opening. It looks to me like the gas would hang around in the cylinder enough for most of it to get compressed and ignited. I'm thinking I'll make the exhaust port smaller to help keep the rings from bulging into it, maybe 0.60".
What do you think?