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Post by ruppluver on Oct 10, 2008 11:31:10 GMT -6
What octane fuel do you use in your Rupps? 87? 90 w/ethenol? Premium 93? Or higher? In my area,regular unleaded sells for 10 cents higher a gallon than the 10% ethenol. Can 10% be used in Rupps? Or any vintage sled?  |
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Post by wigman25 on Oct 10, 2008 15:40:07 GMT -6
With a 14:1 compression ratio stock, the liquids need at least 100 octane or they will get real bad detonation and break piston skirts. The last we ran it, I used 93 octane unleaded with octane booster, seemed to work pretty good. That was several years ago, tho, I don't know the quality of the gas nowadays for them. My Nitro hasn't been run since about 2000. Too bad old Sunoco 260 wasn't still available. Wig
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Post by ruppluver on Oct 10, 2008 16:33:55 GMT -6
The higher the octane the better,but what about unleaded w/10% ethenol=90%.Just curious,as I rode my 440 40hp all last winter with 87% and 90% w/ethenol. It still seems to run ok.
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Post by bankRUPPt on Oct 10, 2008 19:34:08 GMT -6
The higher the octane the better Why is higher octane better? There's really no reason to run anything but pump gas in about any Rupp snowmobile unless it has been modified. It's hard to get into compression ratios in two strokes because there's different ways to figure it. You can't just divide uncompressed volume by compressed volume because the exhaust port is open for a certain duration in between. Modifications to the exhaust can change the compression the engine runs at. Too much octane and you're just wasting money and you won't gain any performance. High octane gas isn't more volatile, but there are some gasolines for racing that are... The oxygenated fuels (10-15% ethanol, or other oxygenate) can be used in sleds. An engine that's jetted for for regular gasoline may need bigger main jets. But with the added fuel, you probably won't have a power increase, just a mileage decrease! But to the main question, I usually mix half 89 half 110 in the sleds. This gives plenty of detonation protection to sleds that were made to run on pump gas, and it smells cool! |
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Post by onlyhere4themoney on Oct 10, 2008 19:59:23 GMT -6
pump 91 92 octane is all you need to run any stock Rupp. If you want it to smell cool use klotz oil.
by the way the 440 is 13.4:1 and the 340 250 are 12.2:1
This is not the same as a ratio that is use for you car engine either.
Like Eddie says they are using the full stroke and you do not start to make comprission untill you get above your ports.
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Post by Ruppsforever on Oct 10, 2008 21:42:19 GMT -6
I use 110 Turbo Blue. Its maybe a little more than I need but I want to have a little security blanket. But I'm not running stock motors either though. Also theres a thing about ethanol in 92 Octane that kind of scares me. When you get into higher octane you really don't need to worry about ethanol wrecking all the rubber seals and running a motor lean. And whats up with the terrible exhaust fumes ? My eyes burn right out of my skull when I'm standing by a sled thats running 92.
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Post by alaskaruppguy on Oct 18, 2008 13:38:16 GMT -6
You guys are making me want to go start my sled and get my fix. ;D ;D ;D
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Post by Ruppsforever on Oct 18, 2008 19:26:47 GMT -6
One step ahead of you buddy !!!!!!!!! I just got done firing one just to smell the race gas and hear some pipes bark !!!!!!!! GOD I LOVE IT !!!!
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Post by scotth on Oct 20, 2008 8:13:50 GMT -6
I usually use up the leftover Turbo Blue race gas I use in my race car the first part of the winter in the sleds. There is nothing better than the smell of Turbo Blue + Klotz.
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Post by klong on Nov 3, 2008 3:57:05 GMT -6
where are you guys getting race gas in the winter? most places i know switch those pumps over to karosine
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