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CheYuen

Octane!

22 posts in this topic

I understand that here in the states octane is calculated using a different method than what they use in the owner's manual and that 91 octane should be sufficient to run in an '05 wr 450. What I'm not sure of is if there is a danger (other than loss of power) of running too high or too low of an octane. I found 100 octane from a gas station near my house - is this too high to use?? Do I risk damage to my engine? :D

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No risk of damage, but you may not get as much power out of it. Forgot the theory behind it but something to do with combustibility and oxygenation??? Plus that 100 is very expensive.

On the other hand too low octane can cause detonation a/k/a knocking. A very bad thing. I always run 93. :D

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Damn,,, I wish I could get 100''' Your not going to hurt it at all.. The thing has 12 ta 1 compression..

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The way I understand it, if your bike is not experiencing detonation (pinging) you do not need to move up in octane. Higher octane gas burns slower and produces fewer BTUs of energy than a lower grade. You may end up with incomplete combustion and less power.

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The way I understand it, if your bike is not experiencing detonation (pinging) you do not need to move up in octane. Higher octane gas burns slower and produces fewer BTUs of energy than a lower grade. You may end up with incomplete combustion and less power.

:D:D:D

The other thing to consider is the higher you are in altitude, the lower octane fuel you require for normally aspirated engines. Here, our Regular fuel is 85 octane, premium is typically 89.

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The owners manual suggests running 95 octane or higher, If I were you I would mix a gallon of that 100 octane with 5 gallons of 92 and you should see around 94 - 95 octane gas and should be sufficient.

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as long as it is under 104 you are ok

under 91 octane with 12:1 compression will cause detonating

to high and you can burn a hole in piston

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Compression is actually 12.5:1. A minimum of 95 RON is recommended, which is equal to a 91 pump octane number (RON+MON/2).

At 750' asl, my 2002 actually needs 95+ to run good and stong without pinging so I mix with 30% 100LL Av gas which has a 105 MON, compared to 91's 86 MON. RON stands for a fuel's Research Octane Number. This value is measured under fairly easy test conditions. The MON, or Motor Octane Number, is a tougher test measured at higher engine speed and temperature.

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I reckon go with the 100, even if it does nothing, big deal i usally only pay less than $8 fuel for a trip whats an extra dollar or two?

Cheers!

Felix

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Compression is actually 12.5:1. A minimum of 95 RON is recommended, which is equal to a 91 pump octane number (RON+MON/2).

At 750' asl, my 2002 actually needs 95+ to run good and stong without pinging so I mix with 30% 100LL Av gas which has a 105 MON, compared to 91's 86 MON. RON stands for a fuel's Research Octane Number. This value is measured under fairly easy test conditions. The MON, or Motor Octane Number, is a tougher test measured at higher engine speed and temperature.

does that LL fuel create some exhaust fume smell due to the lead?

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I just had this talk with my parts and service folks at Yamaha - I have been running 89 in my 04- I did all of the mods, I run it pretty hard, and have no detonation- I even took out the core of the pipe, and it runs great. They were surprised. But the bike starts right up every time, and the plug looks perfect and the pipe has no soot on the exhaust. This is my 1st dirt bike, but, I have always been under the thought, as long as it does not ping, you are OK. I have not touched the jet, or the mixture screw. Am I heading for disaster?

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I have a Honda 450x and I run half avgas 100LL and 92 pump gas and I like it alot. Seems to have evened out the power.

Yes it smells kinda like race gas. We will see if the lead helps the valves.

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" minimum of 95 RON is recommended, which is equal to a 91 pump octane number (RON+MON/2)."

what he said :D

i run 94 pump or 91 if that is all they have. never had any detonation. just make sure the station has new tanks so there is no water in there. you don't need anything higher then 94 pump. don't fool your self. :D

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Doesnt VP racing fuels make a gas specificly for thumpers?

U4

Used in stock and modified 4-stroke applications, as well as stock 2-strokes. Makes up to 6% more power than pump gas and any basic nonoxygenated racing fuel. Passes fuel rules for AMA amateur racing and is also perfect for club level racing, CCS, WERA and AFM.

• Color: Clear

• Motor Octane: 92

• Specific Gravity: .718 at 60° F

:D got it straight from http://www.vpracingfuels.com/vp_01_fuels.html?mgiToken=0C15B7C812685993C8

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Compression is actually 12.5:1.

If you are going to get picky,,, Compression is actually 12.3:1... O5 WR450 USA version...

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There's so much mythology here....

read up on the subject:

http://www.faqs.org/faqs/autos/gasoline-faq/part3/

In short, Octane is a measure of the fuel's resistance to pressure induced detonation, nothing more. It has nothing to do with energy content, ignitability, flash point, vaporization rate, burn rate, burn temperature, or anything else whatsoever.

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does that LL fuel create some exhaust fume smell due to the lead?

It smells good. The peculiar airplane exhaust flavour is slightly perceptible.

As stated in owner's service manual, more than 95 RON is recommended if pinging or knocking occurs...

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