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Hi peeps

I am form South Africa and only recently found your site and I must say found a lot of info on issues I had. Especially with the limiter in reverse.

Now we have 93 and 95 unleaded at the pumps at R7.00/l = that would be like $1.00/l :crazy:

what would you say I use then??? :3question:

Keep up the good work!!! :thumbsup:
 

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US gasoline octane numbers are reached by the (R+M)/2 formula while much of the rest of the world uses RON (Research Octane Numbers) alone meaning that a gasoline in a pump in the US would have a lower number on the sticker than identical fuel in a pump outside North America.

The vast majority of discussion you see on here about octane and compression will be using the US equation for octane ratings so just remember that our 93 octane may not behave the same as your 93 octane.
 

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Mad Dog said:
US gasoline octane numbers are reached by the (R+M)/2 formula while much of the rest of the world uses RON (Research Octane Numbers) alone meaning that a gasoline in a pump in the US would have a lower number on the sticker than identical fuel in a pump outside North America.

The vast majority of discussion you see on here about octane and compression will be using the US equation for octane ratings so just remember that our 93 octane may not behave the same as your 93 octane.
Mad dog, do you know the comparison between AV gas Octane and Octane ratings for land vehicles
 

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Yes Av gas is more consistent but it is formulated to burn longer. This could cause serious heat problems in some engines. Lead may also be a problem. 100LL (Low lead) has more than twice the lead automotive fuel has and could cause buildup problems. Aviation have different timing and clearance specifications and compression ratios than quad engines. In most cases Av gas is not a good idea for small engines. Aviation fuel is designed for aviation engines.
(Got this of the previous posts email)
 

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pewterpecker said:
Anyone here tried running e85 in their rappy? It's cheaper than race gas and has plenty of knock-resistance to boot. All you would need to do is increase the fuel flow a bit to make up for the lower BTU's.
I am sure you could run it but your raptor booklet says not to run the "gasohol" it if it is more than 10%.
 

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Discussion Starter #27
If you really have a full concept of how the fuel, ignition timing, compression, valve overlap...and know your static to dynamic compression, you'll be good... a few riders in here really know there $hit, especially dealing with heptane, toulene, xylene,..ect...not to foget av gas. a good steady mix prepared just for your engine will work. The problem we face is to do it as efficiently, and cost efective as possible, without sacrficing engine power or integrity.
 

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Am i able to run 93 octane in a fully stock engine with no jetting or other mods?
you do not need to run 93 in a stock bike, 87 or 89 is perfectly good, there is NO power gain from higher octance
 

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I have 720 stroker with 11:1 compr. and i was using 93 oct. pump gas, but I'm thinking to go with 12:1 compr., so, 93 octane would be fine or I have to go with higher oct? Thanks.
 

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I have 720 stroker with 11:1 compr. and i was using 93 oct. pump gas, but I'm thinking to go with 12:1 compr., so, 93 octane would be fine or I have to go with higher oct? Thanks.
a 12:1 will require race gas so over 100 octane
 

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Cam profile and cam timing will also play a role in octane requirements of an engine. I have ran my 14.5:1 812 on regular unleaded, only to get some heay cyles on it, then it was converted to straight methanol. My 690 12.5:1 duner has spent many weekends at the coast running on premium pump gas which is 93 octane in Oregon. I was careful to listen for any detonation and it ran very well without pinging. Elevation also plays a role in octane requirement so it is imposible to make a blanket statement that at X compression you need to run X octane. As was stated earlier, you need to run only enough octane to prevent the engine from dtonating under load. If you ride at 5000' and have 15:1 compression, you can probably get away with a lower octane than you would think. It is worth mentioning that as the compression gets higher, the higher octane fuels are worth some power because of usually having a slower burn rate which translates into longer "burn" time and usually more torque and HP.
 

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Cam profile and cam timing will also play a role in octane requirements of an engine. I have ran my 14.5:1 812 on regular unleaded, only to get some heay cyles on it, then it was converted to straight methanol. My 690 12.5:1 duner has spent many weekends at the coast running on premium pump gas which is 93 octane in Oregon. I was careful to listen for any detonation and it ran very well without pinging. Elevation also plays a role in octane requirement so it is imposible to make a blanket statement that at X compression you need to run X octane. As was stated earlier, you need to run only enough octane to prevent the engine from dtonating under load. If you ride at 5000' and have 15:1 compression, you can probably get away with a lower octane than you would think. It is worth mentioning that as the compression gets higher, the higher octane fuels are worth some power because of usually having a slower burn rate which translates into longer "burn" time and usually more torque and HP.
I live in Vancouver WA, and I ride on Oregon coast sand dunes... Currently I have 720 stroker, stage 2 HC, P&P head, 11:1 piston and duals. Sounds like pump gas (93) will probably be OK if I go with 12:1 CP piston...
But would I be safer if I mix race gas with pump gas? If I mix 50/50 would I get just about right octane for 12:1? And how much gallon of race gas cost? Thanks
 

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I have no idea what race fuel costs. I have one bike on alky at about 240 for 55 gallons and the 12.5:1 I run 100ll in at about 4.50 a gallon. If it was my bike I would try it on 93 and listen very carefully for "pinging" under load. If it detonates you need more octane. You might try to locate some 96 or 97 octane fuel. I would look for your local oil supplier they usually can get fuels also. Or if you have any dragstrip or circle track friends they may know a place to get race fuels
 

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Your atv will be most reliable and perform best when it gets just enough octane to keep it from pre-detonating/pinging, no more and no less. If your bike runs right on 89 you're not going to gain any benefit by using a similar fuel with higher octane.
best statement in the entire writeup. My car for example is 12:1 28* of timing and runs great on 93, and if I ran race gas I would lose power unless another factor is changed ie timing. Just run what is right for your setup if you know damn well you should only run on 104 then run on 104 etc.
 

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Ok call me stupid but some of that is a little confusing. Let's break it down and just let me ask everyone what they run in their Raptor's (no major engine work). I typically run 90+ in mine, but am I wasting my money?
i run 93 most of the time.shell is the best.
 

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Just reading and thinking (never at the same time, that's dangerous).

"Octane number is the number which gives the percentage, by volume, of iso-octane in a mixture of iso-octane and normal heptane, that would have the same anti-knocking capacity as the fuel which is under consideration. For example, gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90. [1]"

What about avgas that is over 100, like 110LL?
WELL if by av gas you mean aviation yes it does have a higher octane BUT it also contains things that help it burn at high altitudes and keep it from freezing being so high in the sky the air is thin and can get very cold so its a common misconseption that aviation gas is a good performance gas stick to klotz and vp for your race gas
 
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