metrogdor22
Member
- Joined
- Jan 8, 2017
- Messages
- 14
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Hi all,
I posted here a few weeks back on how the port timing on my (future) 2-stroke SI engine should look. I took some advice from the comments and switched to closer to a loop scavenging approach, and also simplified the machining.
My main question is still how my port timing looks. The exhaust ports open 97.5 degrees before BDC, and the transfer ports open 52.5 degrees before BDC. Both are symmetric about BDC. Exhaust ports are 2x5/16". Transfer ports are 1x7/8" that separates into 3x5/16". I may decide to start with only 2 transfer ports and see how that goes. If I need to add more transfer or more exhaust, I can later. Intake port is 3/4".
Bore is 1.25", stroke is 0.96". 0.08" gap between the head and piston @ TDC. I figure it'll be easier to add spacers and make that gap larger if I need lower compression. 13.02:1 uncorrected compression, 6.89:1 only counting after the exhaust ports close. Crankcase CR is 1.34:1.
Attached are pictures of the piston at TDC, Exhaust Opening, Transfer Opening, BDC, cylinder from the top, and cylinder from the bottom.
Should I move the transfer ports closer to the sides of the cylinder? Do you think this would run as is? Around what size carburetor should I need? I plan to have a reed valve on the intake port, what about the exhaust port?
Thank you for all the help this forum has given me!
I posted here a few weeks back on how the port timing on my (future) 2-stroke SI engine should look. I took some advice from the comments and switched to closer to a loop scavenging approach, and also simplified the machining.
My main question is still how my port timing looks. The exhaust ports open 97.5 degrees before BDC, and the transfer ports open 52.5 degrees before BDC. Both are symmetric about BDC. Exhaust ports are 2x5/16". Transfer ports are 1x7/8" that separates into 3x5/16". I may decide to start with only 2 transfer ports and see how that goes. If I need to add more transfer or more exhaust, I can later. Intake port is 3/4".
Bore is 1.25", stroke is 0.96". 0.08" gap between the head and piston @ TDC. I figure it'll be easier to add spacers and make that gap larger if I need lower compression. 13.02:1 uncorrected compression, 6.89:1 only counting after the exhaust ports close. Crankcase CR is 1.34:1.
Attached are pictures of the piston at TDC, Exhaust Opening, Transfer Opening, BDC, cylinder from the top, and cylinder from the bottom.
Should I move the transfer ports closer to the sides of the cylinder? Do you think this would run as is? Around what size carburetor should I need? I plan to have a reed valve on the intake port, what about the exhaust port?
Thank you for all the help this forum has given me!
