trapp350 Posted April 4, 2008 Report Posted April 4, 2008 This might sound like a dumb question but what is it about the shee engine that you cant run very high compression before detonation on pump gas? Is it the timing? the way the cylinder is layed out? 2 cylinders have something to do with it? What I get is from the site is that 150psi or so is the limit for most people running pump gas but other 2 stroke engines 150psi is low compression on my 250r I run 178 psi in the cylinder with pump gas. I need some educating lol Thanks Quote
fastrthnu Posted April 4, 2008 Report Posted April 4, 2008 This might sound like a dumb question but what is it about the shee engine that you cant run very high compression before detonation on pump gas? Is it the timing? the way the cylinder is layed out? 2 cylinders have something to do with it? What I get is from the site is that 150psi or so is the limit for most people running pump gas but other 2 stroke engines 150psi is low compression on my 250r I run 178 psi in the cylinder with pump gas. I need some educating lol Thanks Ive aways been under the impression that you could run 93 up to around 10.5:1 cr which is abouts 160psi safely. 178psi is around 11.5:1 and should be run about a 100. Quote
Bansh-eman Posted April 4, 2008 Report Posted April 4, 2008 (edited) it isnt just a banshee engine thing,its all motors. its the fact that the lower octane fuels will experiance pre-ignition (detonation) with the higher compression. The fuel just cant take that much pressure and will ignite before the motor is ready for it to. There is no 100% you must run this fuel at this compression its more or less a saftey thing. some guys will run pump all the way to 160 psi and be fine, how ever people like myself would rather spend a few extra bucks and get a better fuel and have the peace of mine that my motor isnt going to go pop in the middle of the dunes. Edited April 4, 2008 by Bansh-eman Quote
trapp350 Posted April 4, 2008 Author Report Posted April 4, 2008 I did some research and I guess it has something to do with the motors exhaust duration on a two stroke as what PSI in the cylinder is made according to there compression ratio with the exhaust duration and what octane fuel you need to run in a engine. A 250 single cylinder 2 stoke comes stock from the factory with 160 psi on pump gas so running pump at 175psi on pump gas dont sound to far fetched but a banshee comes stock with I think 6.5 to 1 ratio with in turn with the stock exhaust duration equals 125 psi stock on pump gas and 150 on pump gas dont sound to far fetched. So I guess I answered my own question but I still would like to now more about this exhaust duration thing in relationship to psi and octane requirements if anyone has any insight. thanks Quote
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