Chris-PA
Where the Wild Things Are
I was curious if others had measured the stock port timing on various strato engines. I measured a GZ4000 and got:
E = 132
I = 137
I(S) = 165
T = 103
So it looks like they used a short exhaust duration short to keep combustion pressure up, run a very small angle between exhaust opening and transfers opening ("blowdown" = 15deg) because it's mostly just air lost to scavenging, and a long combined intake duration. The strato intake ports open quite a bit before the main intake, but it is pulling air down through them and into the case, so it would seem they should count as intake duration.
The strategy seems to work very well, producing quite a lot of power for a 40cc saw. I'm wondering if other strato saws use the same approach?
E = 132
I = 137
I(S) = 165
T = 103
So it looks like they used a short exhaust duration short to keep combustion pressure up, run a very small angle between exhaust opening and transfers opening ("blowdown" = 15deg) because it's mostly just air lost to scavenging, and a long combined intake duration. The strato intake ports open quite a bit before the main intake, but it is pulling air down through them and into the case, so it would seem they should count as intake duration.
The strategy seems to work very well, producing quite a lot of power for a 40cc saw. I'm wondering if other strato saws use the same approach?