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Discussion Starter · #1 ·
I have a 98 XCR 440 Sp. and I'm wondering if there is a minimum octaine that you have to run in the sled?[?]
 

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I wouldn say 87 is probely the lowest, and the most optimal. Someone will most likely correct me if I'm wrong, but 87 is most likely the octane your sled was designed to operate with...
 

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I agree with AlaskanGold, most sleds are set for either 87 or 89 octance. Running anythng higher, you would lose performance on your sled and wasting money.
 

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Originally posted by crimsonride
[br]Lose performance, really? I didn't know higher octane would cause it to lose performance.
Yeah, a higher octane will have a higher flash point for combustion, which your sled is not set up for, so the fuel is not being used properly.

Anybody can correct me on this, but I have heard and read this multiple times from good sources.
 

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Yeah that is why I said most, some sleds are set up for higher or can do both. I beileve the 98 would be set up for 87 or 89. Owners manual is the way to go, but going over the suggested octane is going to be a waste.

Just the other week we picked up my friends new F6 and my friend noticed the 89 octane suggestion on the sled. The dealer told him to make sure that is all he runs in it for the same reasons I stated before.

It does have an ethanol and regular switch, which has nothing to do with octane. Like I said, owners manual is the best bet.
 

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Discussion Starter · #9 ·
polaris-man where are you when i need you?
 

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Their right, 90 octane or higher is a waste. Unless you have the timing advanced far enough. Then you will gain performance. I though, would always run the highest octane you can afford, just in case. You never know how accurate the station in the middle of nowhere's octane count is. But I suppose if your timing is stock then it doesn't matter. Now I am just babbling...lol
 

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For my 1998 XCR 440 SP, it said in the manual

440 XCR MODELS MUST RUN MINIMUM 91 OCTANE FUEL

It also said under the hood on a sticker I should run 91 octane.
 

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okay, so for my old exciter sleds I should probably run something lower than premium. I guess I could turn up the timing, I've got a light but I've never done it on a sled and I don't want to risk burning my pistons. Hmmmmm....that's nice to know then.
 

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I don't have a 440XCR but a 96 XLT SP. Under my hood it says minimum 91 octane. The dealer I bought it from told me to run 87 in it. Who's right[?][?][?] All I ran last year as 87 octane. Seemed OK but if I need to be running premium since it is better for the motor then I'd like to know.
 

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I was under the impression that higher octane fuels had a lower flash point, not higher. Thus being able to run a higher compression engine.
 

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we wnet over this the other day in automotive class..... lower octane # the quicker the gas burns, the quicker the gas burns then less continious force is pushing the piston down, so if you change from 87 to a 93 the 93 will burn longer cuasing there to be more force on the piston the entire time the piston is traveling down to BDC. i ran 87 in my XLT last year and im not gonna run anything less than 93 in my vmax this year... the polaris is my dads so he pays the gas. this year it will still be doggin it with 87...[xx(]
 

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You wont gain anything by running the higher octane in your vmax unless it calls for it....
 

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Darkstar is right you won't gain any improvement if your sled is not designed for extra octane. The only thing it will do is give you an extra margin of error for preventing a piston burndown in a lean condition.
The flash point of gasoline increases as octane increases. That is why higher octane fuel can withstand higher heat of higher compression without preigniting [that rattling noise you hear just before your piston melts].
You do lose power with excess octane, but it isn't usually noticeable except maybe on the dyno. Maximum power comes from using the lowest possible octane that eliminates preignition, because the lower the octane, the higher the BTU's of heat energy per unit of gasoline. The only problem is that temperature, or elevation, or low snow conditions overheating engine can lead to going past the safe point, and ruining a motor.
As for myself, I always run 91+ octane just to be safe. The extra little bit of power just isn't worth it. Also I have found that higher octane fuel seems to make an engine a lot easier to get the carbs set-up properly. I'm not sure why, but I'm not going to question the fact
 

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Discussion Starter · #19 ·
is this bad if i didnt run 91 octaine in my sled last year polarisman?
 
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