bansheeqc Posted September 28, 2008 Report Posted September 28, 2008 I want to know how to convert mm to degree and degree to mm for a stock stroke crank and a 4mm crank... Quote
Snopczynski Posted September 29, 2008 Report Posted September 29, 2008 banshee 54mm stroke stock, piston travels 180 degrees top to bottom. Im not so sure you should be doing porting if you need to ask this question. I read a bunch of books and used some formulas to figure out all this stuff for port durations. Theres alot more to it than just someone telling you here on the forum. Thats about all I am willing to tell unless you educate yourself by reading further into it. Or you could buy some race logic port templates and carve it out to a standard like all the other guys who just want some more power. Quote
deckheight Posted September 30, 2008 Report Posted September 30, 2008 It is doable mathemaically, not sure how though since I flunked rocket surgery 101 in school. Thus I have to let a computer program crunch the numbers... I do know it involves the rod length (on centers) and stroke and that it is not a constant due to the lower end rod pin being off center of the crank axis so each degree (or fraction) would need to be calculated individually. Easiest way without computer help would probably be the old fashioned way with a degree wheel mounted to the end of the crank. If you have something specific you want to do e-mail me private and I'll do a sweep on the computer. Quote
RadarRacing Posted October 3, 2008 Report Posted October 3, 2008 Roughly heres maybe what will help you. A degree wheel wheel gives you the actual real readings because a port is not "open" till the piston is slightly below the port and the port is open. The deck hieght is not the top of the cylinder, it would be TDC of the piston travel. Each degree compared to mms will change as a port is higher or lower. In the middle of the pistons travel 1mm might be 5-8 degrees for example but close to the top or bottom of the piston travel 1mm might be 20 or 40 degrees. I didnt double check the math or #'s to be correct so if you cut yer crap up it's on you. I only gave you the #'s to help you. A good builder does much more on a cylinder than raise ports. Radar Exh 185 degrees stock is 29.1809 mm from deck 190 deg is 27.9859 mm from deck. 195 deg is 26.7828 mm transfers 115 deg stock 43.8899 mms 120 deg 43.014 mms 128 deg 41.5463 mms Quote
Rune Posted October 3, 2008 Report Posted October 3, 2008 here are some port timing in mm http://home.mchsi.com/~xen-uno/2-stroke-timing-xen.xls Quote
bansheeqc Posted October 5, 2008 Author Report Posted October 5, 2008 Thank for every reply... It's for a friend. He don't have degree wheel, and he want to know what it's his actual port timming. bansheeqc Quote
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