Is E10 fuel making your YZ run different?

4 replies to this topic
  • KAS

Posted October 20, 2008 - 09:54 AM


I can swear that ever since all the gas stations have gone to E10 fuel, my bike pings a little bit.

Is it all in my head? Or is anybody else noticing this?

I thought of maybe mixing a little race fuel with premium from now on.

  • grayracer513

Posted October 20, 2008 - 11:03 AM


Ethanol should not cause pinging directly, that is, it should not lower the octane number of the fuel. It may cause a reduction in fuel energy output that will cause you to use more throttle than you used to, and that might cause the pinging. You could consider adding 10-15% toluene to see if that fixes the pinging.

Something to remember is that Ethanol is an oxygenating agent. That is, it releases additional oxygen into the combustion process. Because of this, you may need to go up one size on the main jet, and possibly the pilot also, to get it to perform properly.

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  • MicahAdams

Posted October 21, 2008 - 08:54 PM


Ethonal and methonal requires a richer fuel mixture that gasoline. So anytime any alcohol is added to gas you will have to compensate.
It just sucks having to tune for gas and E10

  • RJB

Posted October 23, 2008 - 07:04 AM


Ethanol should not be dropping the octane of the gas, as its use is generally as a replacement for MTBE. Downside is as Gray points out that it produces less combustion heat (26945kJ/kg as opposed to 38220kJ/kg for MTBE). The RON of ethanol is slightly higher than that for MTBE. A downside to ethanol, is that it plays real nice with water mixes a little too well. Could this be a factor? Might try a different brand of gas to start with

  • grayracer513

Posted October 23, 2008 - 08:22 AM


The hygroscopic nature of alcohols is a two edged characteristic. The fact that it will absorb water is an advantage in that it prevents water from plugging up jetting and such, because once absorbed, the water no longer has any surface tension, which is why it blocks jets to begin with.

But alcohols tend to be so hygroscopic that they will absorb water from the air in the tank, too, which would not ordinarily happen with gasoline. That ends up "watering down" the fuel, so to speak.

It usually isn't a big problem at 10%, though, and the truth is probably either that the gas is an inferior blend in other ways, or is stale (EPA friendly gas can be remarkably unstable), so the suggestion to try another brand is a good one.

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