What fuel to run?

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Moev

Moev

Well-Known Member
Messages
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HI there! Whatched some Horizon videos on Losi 5T. It is suggested to use "high" octane fuel and the guy in the video was pumping 91 gas. Here in Europe almost everywhere 98 is the lowest you can find. So I will be running mostly with it. But what will happen if I put 100+? Will it get more power or will it destroy the 2st. engine?
 
You don't need anything over 91 octane fuel unless you have the compression to support it. 99% of the small engine stuff is nowhere close compression wise to being able to benefit from higher octane. Higher octane without the compression to support actually makes less power.

I have done this engine stuff for 40 years for a living and a ton of dyno testing and the numbers don't lie.
Back when we're running karts, and I had an engine dyno there was a boatload of testing going on here. The high-octane fuel made less power than the 87-lemonade pump gas.
Why?
Not enough compression.


91 non ethanol and your favorite flavor of oil and send it!
 
i red some other forum the other day that 2 strokes lose power higher you go. i also came across this on google: High performance 2 cycle engines love the octane they were designed for. Any higher octane rating over that will contribute to overheating and lower power. Higher octane fuel does one thing. It burns slower.
 
Moev said:
HI there! Whatched some Horizon videos on Losi 5T. It is suggested to use "high" octane fuel and the guy in the video was pumping 91 gas. Here in Europe almost everywhere 98 is the lowest you can find. So I will be running mostly with it. But what will happen if I put 100+? Will it get more power or will it destroy the 2st. engine?
Click to expand...
It won't hurt to run higher octane but, unless you have really high compression, you won't gain anything. In fact, you often loose power going to high octane unless your engine needs it. One of the well known chainsaw porters over here in the US did a bunch of testing on octane ratings doing timed cuts using a computer contolled Stihl professional saw. 87 efree pump gas was consistently the fastest of all the pump gas. VP racing 94 octane engineered small engine fuel was just as fast. It's designed for small engines so that makes sense. I believe he went as high as 100 leaded aviation fuel. Its not all about the octane. A fuel's vapor pressure and other factors as well as octane dictate its performance in certain engine designs. I ran Coleman lantern fuel for years in these cars. It's 50-55 octane.
 
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