I was wondering if yall could give me some specs for your china girls including
port diameter
port length
port flange diameter
also looking for your port timings and if you have the time the average exhaust temperature your exhaust is at on a ride
why do I need all this? I'm making custom expansion chamber tuned pipes and need some specs to have a good formula for a "universal" exhaust
thanks
Edit: if you could give me your stroke lengths that would be appreciated
This will be quite the task, the china girls stock porting vary quite a bit, has two different strokes with different rod lengths used in both which alters timings.
Those whom do port work generally do their own thing making no two the same and having an effect on the over all length needed, then there is fitting it to different style frames.
Port length/depth is easy at 28mm (center) however the windows can vary greatly with the average being 23-24mm across and 11-12mm in height which gives an equivalent dia of 17.83mm - 19.03mm, big difference there and that's just stock as most prefer to widen everything when porting as well as change the timing, my ports are all matched at 23mm and that's not very aggressive compared to some as I prefer to retain torque as much as possible with improved flow/cylinder fill and keep rpm at or below 11k.
Port timing is critical in determining pipe length and stock timings can be between 140-150 depending on stroke and rod length and most tuners/builders prefer 170 or more with 20+ degrees of blow down when going for high rpm or if torque is the goal staying just under that with slightly less blow down, ether way it's a huge difference again.
Port flange dia can be anywhere from 19 -23mm depending on model, and that is stock untouched if ported ??? depends on the builder/tuners choice.
Exhaust temps also will vary greatly with so many factors contributing to it, I can tell you that an engine with good flowing characteristics and an average running temp of 220-240f will have around 1300f into the pipe for about the first 4" or so.
Stroke lengths are 38mm and 40mm but there are also 41-44mm stroker cranks that many use.