macgillivary Posted October 26, 2005 Report Share Posted October 26, 2005 hey im at sea level, i have 21cc domes with 145psi, gonna get some port work done so im guessing i will get a lower compression number, currently running +4 timing with a 70%pump and 30%AV gas anyways can i run av100ll straight with 21cc domes and a +7 instead of +4 after the port work????? orrrrrr i highly doubt i can do this think i need something like a 110 fuel but i do have a set of 17cc domes dont have a compression spec though at sea level it would be like 200+ probably, is it possible to run those with like a +2 or +4 on AV100LL????? now heres the dumb question, is AV100 actually 100 octane or what? im assuming it is but i really wasnt sure shit i probably just shoulda pm'ed dlnoss hes the man for this thanks Quote Link to comment Share on other sites More sharing options...
dawarriorman Posted October 26, 2005 Report Share Posted October 26, 2005 Well it depends on the type of porting you're looking at. If you're looking at more of a top end port or drag port, then the exhaust port will be raised, which will lower your compression. If you're getting a woods or mx port, then the exhaust port more than likely won't be raised, so your compression won't be changed. If your running AV gas you can switch to +7 now, and you'll be fine. Im pretty sure the 100 AV gas is 100 motor octane. Motor octane numbers are generally lower than your traditional r+m/2 numbers that are used at the pumps. So your 100 motor octane would be higher if it was rated like pump gas. 17cc domes are going to be more compression than you'll probably want at sea level. Quote Link to comment Share on other sites More sharing options...
Ducman Posted October 26, 2005 Report Share Posted October 26, 2005 100LL is aroound 101 octane by (R+M)/2 method. You could use straight premium pump fuel 91 or 93 octane the way you are set up now. If you go to +7 timing you probably need to use the pump/ av fuel mix you are currently using. If you go to 17cc domes you will definitly need a welded crank and 110 octane and it wouldn't have any benifits on top end power, probably hurt top end power in fact on a typical moderatley ported cylinder motor, same goes for too much timing. It would give a lot of low end/ mid range torque but not top end. You will need to replace the piston rings much more freequently to maintain that high compression. I would recommed just getting it ported, keep +4 timing w/ 21cc domes and run straight premium pump fuel. If you want to run straight 100ll then get some 19cc domes and +4 timing. Quote Link to comment Share on other sites More sharing options...
dawarriorman Posted October 26, 2005 Report Share Posted October 26, 2005 100LL is aroound 101 octane by (R+M)/2 method. 429905[/snapback] 100LL is 99.5 motor octane. http://www.chevron.com/products/prodserv/f...ecsandtest.shtm Quote Link to comment Share on other sites More sharing options...
PassionRE Posted October 26, 2005 Report Share Posted October 26, 2005 (edited) If you'll look closer tat that chart you''notice it says "lean mixture rating" , 99.5 octane. That is at stoichometric ratio...approx 12-1. 100LL jetted richer than stoicho is higher than 99.5...chart says like 130 or so on rich jetting, but that for aviation 4 strokes...you would lose alot of power running that rich on Banshee motor...Jim Edited October 26, 2005 by PassionRE Quote Link to comment Share on other sites More sharing options...
macgillivary Posted October 27, 2005 Author Report Share Posted October 27, 2005 thanks guys i was hoping i could run the +7 but didnt expect the 17cc domes to work, im setting my bike up for mx, i thought all porting lowered your compression but i guess not woah i dont understand aviation fuel i guess it can range from 99.5 to 130 depending on how lean/rich you are? Quote Link to comment Share on other sites More sharing options...
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