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Fuel Questions

"Dear Ralph" November 28, 1999 0
Dear Ralph: I have a ’99 ZL 600 EFI along with an extended (non-manufacturer) warranty that expires in 2004. Neither the Arctic cat warranty...

Dear Ralph:
I have a ’99 ZL 600 EFI along with an extended (non-manufacturer) warranty that expires in 2004. Neither the Arctic cat warranty nor the DFS extended warranty cover “pre-ignition” nor “detonation”. My manual says to use a minimum fuel octane rating od 88.
My objective is to maximize engine life/reliability and I don’t give a ____ ___ about a loss (or gain) of a two-three horsepower. If my manual recomends a “minimum” octane of 88, does this imply that a high octane is better? I’m told higher octanes contain more alcohol and that alcohol burns hotter (which is bad)? What are the trade-offs in using higher or lower octane fuel? (A/C dealers tell me one thing, experienced mechanics tell me another).
Neither warranty covers damage resulting from air or water in the fuel, so which method is best for insuring any and all water is removed from the fuel, the “bag” or Isopropyl alcohol? Or both?
My A/C dealer tells me air cannot get into the fuel line because my EFI “automatically pressurizes the system”. How do I prevent air from getting into the fuel line; how do I check for air in the fuel line; how do I remove air from the fuel line?
Your input would be great,

Chris Kinson
Fon du Lac, WI

One at a time Chris, we’ll take care of your concerns. Your warranties specify they do not cover pre-ignition or detonation as an “out” if something really weird happens. The intent of a warranty is to protect you from defects in components or workmanship, not to provide you with “free service”. Engine failures on a snowmobile are far too often caused by things like improper jetting, fuel quality, fuel system icing, things that are more environmental and not the result or fault of the manufacturer. A good relationship with a servicing dealer is far more important than a piuece of paper in my opinion.
On fuel octane, lower octane fuel burns hotter, higher octane fuel burns cooler. Higher octane is generally considered “better” because it a) keeps the engine running cooler, hopfully avoiding reaching the melting temperature of aluminum in whatever condition you may encounter, b)if you start out with higher octane fuel, despite aging or whatever condition the fuel may be in, by the time it runs through your engine it hopefully will be volatile enough to still be the minimum 88 octane. Fuel that was 91 octane in November when it was dumped into the tank at the filling station may not be 91 in Janruary by the time it is burned in your sled!
Higher octane fuel MAY contain alcohol, it may not. Alcohol does raise the octane of any fuel it is added to, but you can get 91-92 octane with or without alcohol. Buy high octane fuel from a busy station and you should be OK. Alcohol actually burns cooler, not hotter. The confusion with this is that alcohol increases the oxygen in the fuel/air ratio, so a sled may display hotter combustion temperatures, thus the logic in running larger main jets or using your EFI jumper to increase the fuel delivery.
Trade-offs in octane? I don’t want to get into a detonation vs. pre-ignition article here, but lLower octane makes slightly more power, higher octane makes slightly less power. More important is the flame speed and ability to resist detonation. Higher octane resists detonation, and whatever power loss (if even detectable) isn’t worth worrying about. Your sled asks for 88, run fresh 89 and don’t worry. If you add pipes or higher compression heads, run 91-92. Octane is very motor (and elevation) dependent. You can get away with lower octane fuel at higher altitudes due to the reduced cranking compression. Ever wonder why you can buy 85 octane out West? An engine that is happy running 87 back East at low altitude is happy running 85 out West at higher altitudes.
Removing water from fuel; the in-tank absorbers, or “bags” as you refer to, work fine at removing fuel from the tank. They do absolutely nothing to remove water thas has been sucked in through the air intake. For this reason, although more inconvenient I prefer Isopropyl, as it will remove water from both the tank and the engine.
Yes, you can get air into your EFI system. If your fuel level gets low enough and your fuel pump starts sucking air, you have a problem. If you ever suspect you’re running put of gas on an EFI, you want to shut it down. This holds true for most all injection systems, autos too. How do you prevent air from getting into your fuel line? Keep enough gas in the tank! How do you check for air? By looking at the fuel line for air pockets. How do you get it out? Get some fuel in the tank and run the sled at idle until all air is purged from the line. Hope it works, or you do have a problem!

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