Need octane help??

[verticallydefiant]

I just got my computer back from being reprogrammed, the sled is now runing 19.5 lbs of boost, or 22 lbs at the flick of a switch. It now calls for 94 octane fuel.
If I'm running 91 octane premium, what is the amount of say 110 octane race gas I would need to mix in for every ten gallons of said 91 to achieve 94-95 octane??

Thanks

 

[Givemeaboost]

What kind of turbo are you running that only needs 94 octane at 22# of boost?

 

[verticallydefiant]

Stock Polaris KKK turbo in an 08 FST. It runs 14.5 lbs stock on 87 octane. It now runs the higher boost and only needs 94-95. All of the factory pre-sets are still programmed into the computer for reliability.
It is currently a stage 3 program at 19.5 lbs of boost. With a manual controller and a dash mounted switch it'll hit 22 lbs, of course higher octane will then be needed.

 

[constructionLake]

8 gal of 91
2 gal of 110

8x91=728
2x110=220 add them 948 and divide by 10 equals 94.8 octane.

 

[DWHalverson]

Figureing octane ratios isn't that simple. It needs to be checked on a certified octane test engine. The math calculation is roughly better than a guess.

 

[triple7]

Yep, pump gas kills race gas. Its not a 1:1 type mix scale. Probably more like 4 gallons of 110 to 6 gallons of pump for an actual 94-95. But, again that is a guess. Like Halverson said, you would need to check it out on an octane tester.

Unless someone on here has done the tests and knows the mix.

 

[SnowSnob]

Try Klotz Kl-602, 1oz per gallon raises 2.5 numbers. I run 2oz per gallon with high compression heads and nitrous without a problem.
Otherwise do a search for octane calculator, like said above it won't be 100% but it will get you close. A rule of thumb I go by with mod sleds is if it requires 94 then calculate for 96 minimum. Pump gas is always an uncertain which is ridiculous with the prices we pay....that chet should be spot on for making us bend over like they do.

 

[NoSecondChances]

A rule of thumb I go by with mod sleds is if it requires 94 then calculate for 96 minimum. Pump gas is always an uncertain which is ridiculous with the prices we pay....that chet should be spot on for making us bend over like they do.

Yep - add the 15% fudge factor in as well, whatever you mix. Too much typically hurts less than not enough.

 

[76FOMOCO]

Yep - add the 15% fudge factor in as well, whatever you mix. Too much typically hurts less than not enough.

I have a bench full of this to prove it, spend the money and go a little high and be safe.

 

[verticallydefiant]

AV gas?

Thanks for all of the advice, I was going to try to mix for about 96 octane to be on the safe side. I'm not too worried about engine damage; one of the nice things about this set up is, the computer although re-flashed, still has all of the factory preset warnings and shut down programs in it. It'll sense for detonation and either retard the timing until the det stops, or it will throw a code to the computer and shut it down to "Limp Mode". It'll still run enought to get you down the trail, but then you'll have to go to the dealer and have the code cleared. I'd rather not have to worry about that hassle and just run plenty of octane.

Has anyone used AV gas? What kind of an octane rating does it have? It might be simpler to just run that.

 

[FCR112]

Typical Avgas is 100LL Which means 100 octane with a Low Lead content.

If I remember right it's Blue in color

 

[SnowSnob]

Thanks for all of the advice, I was going to try to mix for about 96 octane to be on the safe side. I'm not too worried about engine damage; one of the nice things about this set up is, the computer although re-flashed, still has all of the factory preset warnings and shut down programs in it. It'll sense for detonation and either retard the timing until the det stops, or it will throw a code to the computer and shut it down to "Limp Mode". It'll still run enought to get you down the trail, but then you'll have to go to the dealer and have the code cleared. I'd rather not have to worry about that hassle and just run plenty of octane.

Has anyone used AV gas? What kind of an octane rating does it have? It might be simpler to just run that.

Have you seen Big Johns thread about the re-flash all xp's should get? Won't have to go to the dealer to get it out of limp mode.
http://snowest.com/forum/showthread.php?t=150928

Av Gas is fine to run, it's not quite 100 octane but it's close.

 

[DWHalverson]

The octane rating of AV gas is an aviation rating and not a pump/street rating. It is higher octane than pump and is fine to use. It has it's limits though and then you need race fuel.

 

[SNOW JW]

AV is a great turbo fuel and is has a 99 motor octane rating.

Also what are your charge temps at that boost level??

 

[FCR112]

I was wondering what the exact octane rating of 100LL is as it would seem difficult to reason why aviation octane ratings would differ significantly from "pump gas" ratings. It's all going into an internal combustion engine.

 

[SNOW JW]

http://purvisbros.com/afi/index.htm

 

[SNOW JW]

http://www.avweb.com/news/maint/187232-1.html

 

[FCR112]

Good links. Lots of information there.

Those tighter tolerances used in production of Avgas result in less chance of water contamination, the TEL makes it much more resistant to Pre-ignition and Detonation, along with less corrosion on rubber, and less build up. Wish all our fuel was that good and consistant.

But I'm sure that all adds to the cost, which makes sense to pay in an airplane as the engine it's running is supplying the thrust to help people escape gravity and all

Didn't see any difference in octane rating systems in there just a different way to achieve it; ie alchohol type additives versus TEL. Did I miss something?

Either way 100LL works real well with 4 stroke airplane turbos which I'm sure are a whole different ballgame (lower compression, and probabaly a million other differences) than the turbo snomobile engines, 2 or 4 stroke.

Didn't mean to derail the thread.

If it's as easy as "the higher the octane fuel you run the more boost you can produce in the same motor"
I guess everybody should be looking for some of that purple dyed stuff.
115-145 octane would surely RIP!