14:1 compression 2 strokes

[Blownsilver]

Anyone else running this compression? What fuel do you run, told pump gas at elevation and 110 down low. Whats your experience, 110 is so bloody expensive the way my cat goes thru fuel

 

[Luke The Drifter]

I had an RKT 14:1 head on my 06 M7, it was setup for 91 octane and ran fine on pump premium. Every engine is different but what sled are you running this on?

 

[Blownsilver]

Im running the speedwerx 925 on a 2012 m8 (I know theres all kinds of wrong going on here lol) but it is what it is

 

[cnelson6]

Ran one on my 860 skidoo and never had a issue on pump. But always kept it easy going up the trail to elevation.

 

[Blownsilver]

I want to run the Athabasca rally next weekend I did whitecourt this weekend but ran the 110 for both days. I can get the different domes for the head but there another $400 to get the 13:1 domes plus the time to install. I want to know if anyone has run around 3000ft elevation on av gas, 100, or 105 without any problems as I do most of my riding at elevation but don't really want to switch just for the weekend

 

[adamg]

There was a thread a few months ago about a guy in I think Edmonton selling av gas by the barrel for what I thought was pretty damn cheap, practically 91 pump price.

 

[0neoldfart]

You have effectively changed the engine compression ratio to make up for some power loss (less atmospheric pressure) at altitude. 14:1 domes (unless your squish is huge) will not live at lower elevation without race fuel to combat detonation. Not the answer you wanted to hear, but you can't have both. You need 13:1 or 13.5:1 domes (even the 13.5:1 will need a blend of better fuel for the engine to live), or run the octane requirements as stated by the builder.

 

[HotShotHarry]

So in your opinion,would a 13.1 head run safely at sea level on 91 gas?

 

[0neoldfart]

So in your opinion,would a 13.1 head run safely at sea level on 91 gas?

Depends on the flame front relief area cut (squish), deck height, and actual engine model. Too often a head is cut, but the squish isn't machined back into it. Most any head builder will know their product - best to check with them. Example: I ran 13.5:1 @ 3500' on pump, but had .060" squish on a 05 Doo 800 HO. If I had only .040", I would have needed better fuel to sustain a decent WOT pull. Plug color and piston wash will tell you if you are lean, as well as the exhaust note. BTW, too "tight" of a pipe will also back up heat to the exhaust port and necessitate better fuel to survive.

 

[HotShotHarry]

Thank-you for the reply. The reason I'm asking is because I have a 13.1 PAR head on my 11 pro 800 and am taking it to Ontario next week. I wont be able to mix any higher octane race gas other than the 1st tank of fuel when we leave on our sled trip. I am hoping to just be able to add octane boost to eliminate the potential DET issues. To the O.P. I hope you are not offended with this somewhat hi-jack of your thread.

 

[j335]

Thank-you for the reply. The reason I'm asking is because I have a 13.1 PAR head on my 11 pro 800 and am taking it to Ontario next week. I wont be able to mix any higher octane race gas other than the 1st tank of fuel when we leave on our sled trip. I am hoping to just be able to add octane boost to eliminate the potential DET issues. To the O.P. I hope you are not offended with this somewhat hi-jack of your thread.

Email power addiction. I ran the 13-1 on my pro, def would have needed to mix av/race gas had I ran low elevation.

 

[HotShotHarry]

For anyone interested. I contacted Brad at PAR. He said if mixing race/av gas is not available,then use a 2-stroke oil compatable octane booster and try to achieve a 94 octane rating. Thanks Blownsilver for starting this thread.

 

[imdoo'n]

you could get a couple 32 oz cans of torco accelerator, which will raise your octaine a full 8 points. from 91 to 99 octane. easy to carry, you mix 8 ozs to 5gals of primium gas to get 95-96 octain rating. about the same cost as mixing av gas, less mess and better mixing,

 

[HotShotHarry]

Thank-you for the reply. Now where to find Torco Accelerator?

 

[imdoo'n]

Try the auto speed shops or call ahead to ontario, if you can't find pm me , i have at least 2 cans

 

[chemmod]

If your running an 11 pro make sure you run it on ethanol used fuel setting at lower elevation. That will help you from detonating a little, also if your running a fuel controller you could beef up your numbers.


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[DRD]

14.5 with .057 squish, run straight 100LL with no worries.