RK Tek Posted December 25, 2003 Report Share Posted December 25, 2003 There seems to be many misconceptions regarding what higher octane fuel will do and NOT do..... 1st major myth is that higher octane fuels burn at a slower rate.. This is entirely false!! 89 octane and 110 octane will burn at the same rate once ignited.. What the 110 octane will do that the 89 octane will not ...is resist combustion longer given the same internal engine conditions. In other words... the 110 will be able to withstand rising cylinder/head pressures longer before combusting than the 89 octane. Once combusted... ALL is equal between the 2 (well ... anything measureable). Running a higher octane fuel than needed in an engine will not add power. Will it lose power??? Yes, sometimes... but only because the engine will have been running in an "un-tuned" state and that is what is causing the performance loss. The un-tuned staed could be remedied by different jetting or timing or both but it is not the fuel causing the performance loss.. it is the fact that you have place the engine in an un-tuned state because of feeding it an octane that is not needed. Once you tune the engine for the new fuel's octane.. it will run as it did before. not any better and not any less. YEARS ago I aided Martin Saint and Dan Wade in writing an article that addresses these very issues. It is located here: RACE FUEL MYTHS. It may be a good read for some of you. Kelsey Quote Link to comment Share on other sites More sharing options...
Big Mike NY Posted December 26, 2003 Report Share Posted December 26, 2003 1st major myth is that higher octane fuels burn at a slower rate.. This is entirely false!! 89 octane and 110 octane will burn at the same rate once ignited.. What the 110 octane will do that the 89 octane will not ...is resist combustion longer given the same internal engine conditions. If the 110 resists combustion longer, that's the same as "burning slower". Quote Link to comment Share on other sites More sharing options...
boonman Posted December 26, 2003 Report Share Posted December 26, 2003 I disagree with that Mike. It doesn't burn slower. It resists compression ignition (the high octane I am speaking of here) so that you don't get pre-ignition. However, 89 octane and 110 octane will burn at the same rate ONCE IGNITED Once ignited. That is what we're speaking about here. It is not a matter of how long it takes to burn, they will both do the same thing, provided you set the motor up to run that specific fuel... Quote Link to comment Share on other sites More sharing options...
boonman Posted December 26, 2003 Report Share Posted December 26, 2003 I just poked through that link that RKTek put out. Here is an excerpt from it for those who do not wish to read it all. It IS a good read however..... Race Fuel Myth's Race fuel burns slower than pump gas:- NOT TRUE, the burning speed of all gasoline's are fairly constant, the burn rate has more to do with the distillation curve and the turbulence in the combustion chamber. So its not a generalisation you can make. Race fuel is expensive so I'll just add octane booster to pump gas:- BIG MISTAKE, first pump fuel is notoriously inconsistent in its blend, often changing weekly if not daily. Different manufacturer's mix fuel in different ways. If you travel across the country to ride then fuel can and does change between area's. therefore you have no baseline to work from. How much octane booster will you need? You will never know. Add to this the fact that octane booster's will only increase the octane by small amounts, no matter how much you add, you will get problems. OK I'll use avgas:- On your head be it, Avgas is designed for high altitude constant running engines as found in aircraft. The distillation curve is all wrong for a two-stroke and can give rise to poor throttle response and bad starting. This does not mean you can not use it, but its not the best bet for two-strokes. Note It does have some good characteristics for keeping engines alive at high rpms, more to come soon. Race fuel is more dangerous:- All gasoline based fuels are dangerous, highly volatile and poisonous. Treat all fuel's with the respect they deserve. Handle carefully, avoid spills and minimise you exposure to the vapours. Race fuel will make me quicker:- NOT TRUE, just adding high octane fuel to your stock engine will not make more power, an engine need's to be set up to gain the benefits and it will just hurt your pockets Here is Sainty's site, http://www.stealthengineering.com/ and here is the old one as the new one still under construction. http://www.stealth.fsnet.co.uk/index.html Quote Link to comment Share on other sites More sharing options...
Banchetta Posted December 27, 2003 Report Share Posted December 27, 2003 hmmm.......If the burning rate is the same, then why do you have to run a more advanced timing for higher octane???? Quote Link to comment Share on other sites More sharing options...
shellbyzfan33 Posted December 30, 2003 Report Share Posted December 30, 2003 u guys sure know what ur talking about!!!.. well my only question is that i just bought a 2001 shee and it came with a cool head but i have not put it on yet until i know for sure what type of fuel to run? the guy told me that they were 17cc domes. so what should i do when i put these on? Quote Link to comment Share on other sites More sharing options...
Blue Duece Posted December 30, 2003 Report Share Posted December 30, 2003 u guys sure know what ur talking about!!!.. well my only question is that i just bought a 2001 shee and it came with a cool head but i have not put it on yet until i know for sure what type of fuel to run? the guy told me that they were 17cc domes. so what should i do when i put these on? hold on tight?....no get a compression gage check your compression if its below 160psi run pump premium if its over mix 50/50 with at least 110......unless your up high you'll be somewhere around 170 psi?....id get my crank welded just for shits and grins..... Quote Link to comment Share on other sites More sharing options...
boonman Posted December 30, 2003 Report Share Posted December 30, 2003 hmmm.......If the burning rate is the same, then why do you have to run a more advanced timing for higher octane???? You don't necessarily have to run more advanced timing, it's just that with high octane fuels, you can get away with running more advance and not detonate. That's all.. Quote Link to comment Share on other sites More sharing options...
shellbyzfan33 Posted December 30, 2003 Report Share Posted December 30, 2003 50% gas and 50% mix ? wow thats a lot of mix! Quote Link to comment Share on other sites More sharing options...
Blue Duece Posted December 30, 2003 Report Share Posted December 30, 2003 50% gas and 50% mix ? wow thats a lot of mix! you mix pump fuel with race fuel......then add your 2 cycle oil...... Quote Link to comment Share on other sites More sharing options...
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