100+ Octane Racing Fuel Heaven

Jomo

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I noticed many years ago that despite running premium unleaded only in my saws, my carbs'd gum up and require a thorough cleaning to get back on the pipe n run right.

But about 3 years ago I switched to 100 plus octane racing fuel with extremely good results throughout my entire stable of saws. No more carb issues period.

At ten bucks a gallon it's expensive no doubt, but the results in both performance n reduced carb maintenance intervals make it well worth the price IMO.


Jomo
 
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  • #3
I believe it is leaded Jim, not positive though.

All the local racers who run extremely high compression ratio engines both 4 and 2 stroke use it exclusively in their expensive weekend play toys.

Works well for me too.

Jomo
 
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  • #7
I'm fairly certain lead in gas acts as a lubricant in high compression motors.

Jomo
 
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  • #9
Yup, without lead to boost the octane, pre ignition knocking caused big problems.

An F One engine has an ungodly 17:1 compression ratio and spins up to 18K RPM.

Their fuel additives are closely guarded secrets these days it seems.

I suspect our industry has a higher on the job fatality rate than formula one racing.

All the fun stuff's deadly in some form or another it seems!

Like Al Capone, dead from lead build up in the body!

Jomo
 
Real high octane in Jap gas with no ethanol, I suppose the power of the auto industry in the economy is a factor in that. Pump premium is 100 octane. Have used premium in my saws for years, particularly the modded ones, but I had to face the truth that they simply run better on regular, couldn't lie to myself any more. :)
Racing fuel must be something different.
 
Yeah, no problem.

I personally hate lead. Shell and others are working on a 100UL formula that would get the lead out so to speak, and be a direct replacement for 100LL (low lead). I dont believe it is healthy to breathe lead fumes in contained in exhaust gasses.

People who work at indoor gun ranges have at times tested startlingly high for lead, and of course we know that lead is removed from the body very slowly. Its about as good for you as mercury, but we dont mind breathing lead fumes, but would shit if we knew we were breathing in mercury. (dont go to China) Even you Comrade Gongfu.

Lead is a bitch to remove from spark plugs when you do your annual inspection on an aircraft engine. The little pneumatic cleaners will not touch it. You just have to scrape it off with a pick, off of each of the four straps on an aviation plug.

If they ever come out with 100UL it will be just as good Jomo, just no nasty lead in it. Av gas is great for some things, it does not gum or varnish, usually has no water in it, does not boil easily, lasts for ever and so on.

100UL is supposed to be cheaper too. Yeah right!

Typically your lower comp engine do run better on lower octane fuel Jay. High octane fuel is harder to ignite, and lower cylinder temps caused by lower compression ratios can cause an engine to loose economy and power on premium.

Sometimes the premium fuel has better additives in it, as well as not having ethanol, so people run it anyway. I do.

I dont see a problem with ethanol for newer stuff, I just dont have much new stuff. Ethanol is an oxygenate, which is an anti knock agent as well. Corn squeezings add octane!
 
I remember getting a metalic taste in my mouth from fumes years ago. Good stuff, that lead. When a car used to pass you when you were on foot or bicycle the fumes used to be thick years ago. Progress really has been made.
 
For what it's worth the original formula for gasoline was isooctane and heptane .100 octane would have been 100 percent isooctane.

Todays gasoline use "Octane" rating as additives and antiknock compounds are in the mix today .Tetraethyl lead was an additive to lubricate the exhaust valves .Modern 4 cycles don't even need it any more .

Another tid bit of info fwiw.During the 60's McCulloch racing engines recommended using white gas which had no lead at all in it .Of course remembering all alone even that far back they knew what nitromethane was --and used it .
 
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  • #17
A fascinating insight on high octane racing fuel, from the folks at Sunoco, who sell a lot of it here locally.

Overheard at the local track:

“High octane fuels burn slower.”
“My motor doesn’t need all that octane so that fuel won’t do me any good.”
“I need the highest octane so I can max out my timing.”
Unfortunately, those statements are not always true. As a matter of fact, those statements only have some merit in the street gas world where 93 octane fuel is king and 87 is used by most. In the world of racing gasolines where higher octane choices abound, sharp engine builders and racers know they need to look beyond octane to find the right fuel.

But before we ignore octane, it’s important to look at how octane is measured in the first place.

Octane numbers are measured using single cylinder engines that look more like something out of a Model T than any modern engine. These so-called “knock” engines are operated by trained technicians in labs under controlled conditions. Two tests are used – one for Research Octane Number (RON) and another for Motor Octane Number (MON). The RON test results in a higher octane value than the MON test.

If you average RON and MON, you get an octane value called AKI, short for Anti-Knock Index. It's often labeled (R+M)/2, reflecting the fact that it is the average, or midpoint, between RON and MON. AKI is used to rate retail pump fuels, and it is the most commonly used octane value for race fuels as well.

For example - Sunoco Ultra 93 typically has a RON of 98 and a MON of 88, thus yielding an AKI of (98+88)/2 = 93. If you look closely at the yellow octane labels at gas stations, you'll see the (R+M)/2 description under the big octane numbers. We provide all the octane numbers for all our race fuels - RON, MON, and AKI. So while we may refer to fuels like SR18 as "118 octane" (that's the AKI value), we also show the RON and MON numbers under "Technical Details". For SR18, that would be 120 and 116 for RON and MON, respectively.

Many times you’ll hear that MON is more important than RON because the MON test is performed under higher temperature and engine speed conditions. While this may be true, the laboratory test conditions are not indicative of what real race engines – heck, even mild street/strip motors for that matter – see at the track. Also, some engines have shown a better correlation between horsepower and RON. So, a word to the wise: don’t get hung up on octane numbers.

For a great example of why octane is not the only fuel parameter to ponder, consider the engines used in Formula 1. These engines have compression ratios exceeding 18:1 and spin at RPMs pushing 20,000. Sounds like a candidate for 116 octane race gas, right? Nope - they use a 96 octane fuel!

It’s hard to find a wider variety of race cars than what shows up at your local drag strip. On any given weekend you can see all sizes and shapes of engines ranging from raspy 4-cylinder motors to booming big blocks, and with all kinds of power adders thrown in the mix. This is where looking beyond octane becomes real important. What works for your buddy’s Pro Stock car may not be the best choice for your other buddy’s turbocharged import.

Naturally aspirated race motors with large combustion chambers spinning at high RPMs really like high-octane, fast burning fuels. They need the octane to prevent uncontrolled combustion, and they need a fast-burning fuel so that the flame front can span the large bore of the combustion chamber quickly. If you’re not sure which fuel burns faster than others, one indicator is specific gravity. “Lighter” fuels – fuels with a lower specific gravity – tend to burn faster because fast burning hydrocarbons are themselves light. Look for a specific gravity close to 0.70 and you’ll likely find a fast burning fuel. Of course, consult with the fuel producer to verify your assumptions. You might be surprised to learn that some of the highest octane fuels may also be some of the fastest burning fuels!

You might also be surprised to know that fast burning fuels may not need as much timing as their slower burning counterparts. Many times we get calls from individuals who are dialing in new motors on a fast burning fuel but they’re using timing and jetting numbers from their old motor and fuel combo. “Retard the timing a couple degrees and see what happens” is not the suggestion they expect to hear! With high octane, fast burning fuels, it is easy to dial in too much timing. In such cases, the engine is not detonating, but it is past the point of optimum spark advance, so it’s just heating things up and making less power. A little less timing may really wake up the motor.

http://www.racegas.com/article/10

First time I tried it many years ago, I asked for the station's white sheet for the racing gas pump. It listed an octane rating of 115. There are racing fuels with an octane rating of 150 for exotic high performance piston engine aircraft.

Jomo
 
Thanks for that Jim, an education in a few simple sentences. Well done.

We have a lot of old stuff up here too. Every once in awhile I'll hear someone say "He should be running leaded gas in that", and I never knew why.

It takes a village.
 
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  • #19
Well my high octane racing fuel chainsaw gas seems to be a cure all for Harvey homeowners whose box store stihl 170 something's that won't rev up n run right!

Did a beetle kill stone pine removal, no haul, homeowner doing the clean up after I left with his own box store stihls. Getting nowhere cuz his saws were gutless pieces of crap that'd start but not cut.

So he gives me the oldest one for a tune up n carb adjustment. I simply cleaned it up, dumped out his gas, filled it with mine, sharpened it, no carb adjustment whatsoever, and presto! Ran like a bat out of hell, better than new according to him.

This of course led to him giving me his newest saw for the same tune up since it ran like a dog compared to the old one now. Same treatment, with the same results!

He now runs racing fuel mixed with stihl's silver bottled synthetic oil too.

Seein's believin I guess!

Jomo
 
Why is it that we have lower octane fuel at the pump here in the Rockies than in the Midwest? 84 is the common gas here.
 
I wouldn't have believed it until I read just 1 minute ago .Above 5000 feet elevation from what they say 84-85 octane rating works as well as the 87 we get at lower elevations .

Now what I do remember from years ago in the high mountains around Vail was needing to lean the chainsaw out for it to run right .The air gets real thin at 9,000 feet .
 
Octane is just interesting if you have issues with pre detonation.
If it is above 75 it is usually no problems.

As we older fellas know anything "pre" is usually not good...
 
Why is it that we have lower octane fuel at the pump here in the Rockies than in the Midwest? 84 is the common gas here.
Lower atmospheric pressure means lower pressure inside the cylinder and less chance of pre-ignition (knocking).
 
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  • #25
The high octane racing fuel's attributes include an extremely long shelf life compared to ethanol laced fuels.

Ideal for semi-retired blokes like me, as well as the Harvey homeowners that go months without running their chainsaw.

Jomo
 
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