VP110 Octane Fuel

I'm new to the LO206 motor and it looks like most tracks are running 93 octane fuel here in Indiana, except for SIRA. They are running 110 octane VP race fuel. Is there anything I should change in the carb settings to run this higher octane fuel?
 
Octane is a measure of the fuel's ability to resist detonation, nothing more. In a low compression engine, you'll probably go slower using it. If you have a high com, ((pression engine, depending on how High,(110 is for the highest compression) it would be better. And
 
To answer your question. the carb will handle each one efficiently.
As in any question about adjusting carb. There is little you can do to the 206 carb other than adjust the air bleed on the low speed circuit.
But that is the beauty of the Lo206. Everyone has to run the same gas, same jet, same spark plug, same everything. So there is little to gain by the engine. If everything is set perfectly to specs.
There are a couple of little thing that can be done that are technically legal That will very slightly!! increase the flow of air to the engine. Does not include any grinding, polishing, or altering of any part. But I will not discuss those thing. Most engine builders know them.

Al is correct. The higher octane rating does not in any way increase horsepower or torque of an engine.
All it does is prevent premature detonation of the fuel in the cylinder under pressure , Before the spark plug fires.
The LO206 has compression ratio of 8.5 to 1 which is well within the specs to burn 87 Octane fuel. And produce maximum hp and torque.
Any higher and you will gain nothing. Except higher fuel cost.
 
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Thanks for the responses. I didn't figure it would gain any power since the motor is low compression, was just curious if the carb would need to be adjusted for the higher octane. I've been running clones on dirt for several years, so I found it odd that the 206 spec fuels are higher octane for no apparent advantage...
 
There is more different about race gas than simply the octane. The substance(s) used to increase the octane may be the reason that we see differences in both EGT and Lambda when running 110 race gas compared to 89 pump gas.
How much does this contribute to different carb tune? That depends even more on the air density (& density altitude) when it is used.
110 race gas seems to be less forgiving to me, even in a low compression engine like the L206. It is more sensitive to small carb adjustments and fine tuning. On the surface, this seems like a good thing to the tuner. For the beginner, although this doesn't appear to be the cause of any sort of real damage to their engine, it certainly creates different performance levels from their engine. Without a solid knowledge (and data to go by) a beginner will often tune the wrong direction on their engine rather than correctly. Other times, I've seen/heard of guys "accidentally" tuning the correct direction.
For this reason, and many others, when we dyno a customer's engine in our shop, we use the specific fuel (and oil) that the customer will be running.
It may not be the perfect tune all season, but it's a lot closer (and more reliable) than guessing. :)

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That seems a little rough to me. It's fine for the two strokes, but 206's...wow! Even for the greater majority for 2 cycles (Eg: Yamaha's, Tags, etc), 110 is NOT needed. Only the shifters and Superkarts realistically need that level of octane.

We road race, so our fuel supply is generally available on site in the paddock area. For all 2 cycle classes, we spec Sunoco 110 Leaded Race Fuel. For the 206's we spec. Sunoco Ultra 93 unleaded, the same stuff you can get at your local gas station. But again these fuels are available at the track in regular credit card gas pumps. For events where the fuel supply must be brought in, a local gas station is usually pick from the surrounding area, and a specific pump and octane level is picked, and that's where all the 206 folks MUST get their fuel. The Charlotte event is a good example.

I suspect you also pay a premium for VP 110. Like maybe $9-10 per gallon? Not really a big deal since you likely burn less then a gallon per event, but still!

Brian, you guys would know better the I, but in a 206, would the slower burning 110 end up spending most of it's energy in the pipe and not in the engine. I'd be curious to see the drop in HP using 110 octane vs. 93 (or 87). And also the increase in pipe temp vs. HP loss. Interesting, but pretty useless information :> Maybe sometime when you don't have anything better to do!!!!:cool:

And really, per the Briggs 206 rules, they "recommend" 94 octane max, available at standard service stations. VP110 doesn't really fit that.

SIRA should really consider changing their 206 fuel requirements to a local gas station and get away from the 110 leaded race fuel stuff.
Just my $0.02. Have a good day, stay safe.
Clark Gaynor Sr.
 
In the 206 classes Al, you really can't change anything, or VERY little. Sealed short block, fixed timing, spec main and pilot jets and jet needle.
You can adjust float height and needle clip position, but little else. We're not even allowed to put a EGT thermocouple in the pipe. And even if we could, we can't adjust anything anyway.
I was just curious about how much HP is lost using 110 octane fuel vs. 87, which the engine is designed for.
 
-There’s plenty of adjustment to make the carb too rich or too lean within the rules with an gas I've tested on the dyno.

-The benefit of race gas over pump gas is not dealing with ethanol corroding the carb and plugging your jets. The performance increase is measurable with pump gas but if everyone is using the same gas it doesn’t matter. Gas prices for a 206 should not even be a concern because we don’t use enough to even make a dent in your wallet.
 
For some background, that series is a street racing series that brings their fuel with them. The whole point is just to only have to bring 1 fuel (logistically easier) and be able to tech everything from shifters to 206. Agreed, not ideal, but it is an even playing field.

OP, no need to change anything. Street races are not won or lost on carb tune. Keep it out of the barriers ;)
 
I'm totally fine with using 110 octane for simplicity sake, just wanted a bit of advice on things I might want to change when running it to avoid damaging the engine and to optimize performance. Thanks for all of the responses!

I've raced SIRA for many years and love street racing!
 
-There’s plenty of adjustment to make the carb too rich or too lean within the rules with an gas I've tested on the dyno.

-The benefit of race gas over pump gas is not dealing with ethanol corroding the carb and plugging your jets. The performance increase is measurable with pump gas but if everyone is using the same gas it doesn’t matter. Gas prices for a 206 should not even be a concern because we don’t use enough to even make a dent in your wallet.
Excellent post Gary !
 
"Tune for the difference"? How do you do that? The difference in area between a .039" jet and a .038" jet is over 5%. I doubt there's a 5% difference in the flow requirements between 89 octane and 110 octane.

Maybe someone could confirm that on a dyno?
 
I'm totally fine with using 110 octane for simplicity sake, just wanted a bit of advice on things I might want to change when running it to avoid damaging the engine and to optimize performance.
Engine damage won't be a problem, so you're good there. Brain damage from leaded fuel, that's probably for another topic.

You could consider experimenting with float height if you really feel you're down on power due to jetting on the 110. Chances are you'll be fine as is.
 
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