Hawk21

My Feedback: (7)

I have some question and hope that someone have the answer;
is there any noticiable differance running an engine on higher octane?
also if I increase the compresion of the engine could it be better to run on higher octane?

krayzc-RCU

My Feedback: (31)

87 burns quicker higher octane burns slower run 87 on most rc motors

Tired Old Man

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Higher compression ratios better utilize higher octane fuels. Most of our engines will not benefit under most conditions from anything higher than 87. There are some caveats that apply to hot weather conditions but for the most part 87 works just fine.

KI8FR

Im glad to see this post.. I will be bringing mine down to 87 I was trying 93 just cuz I thought it was beter.. never thought to ask.. good quetion.

nonstoprc

My Feedback: (90)

ZDZ engines require higher octane gas. 87 does not work.

Tired Old Man

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I've heard that about the ZDZ and 3w's. Run a whole lot of 3W's with 87, don't really know the ZDZ all that well.

Antique

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What happens ? Does not work as in does not run at all ? Maybe they need the 93 octane because they don't have much fin area ?
I ran a ZDZ80 inline twin last week, I had already set the timing to 28 BTDC using an aftermarket ignition and CM6 spark plugs, ran fine...
I ran some 100LL from the airport for a while, couldn't tell any difference in my overweight underpowered G62 lite
The exhaust smelled better though..
What does Dick run in his ZDZs ?

rc bugman

My Feedback: (30)

Silversurfer,

3ws will run on 87 octane. If you are trying for max rpms to pull things that drag a lot, higher octane will give 300 or so more rpms. The book says 88 is minimum. I always run at least 89 to get max rpms.

In your application where engines are loafing for most of the run, the octane makes little difference.

Elson

Zippi

My Feedback: (10)

So what about heat? Will the 87 octane let the engine run cooler in the hot summer months vs the 93 octane?

Tired Old Man

My Feedback: (1)

No, it will not, but until the ambient temps are above 95 it's not worth the extra expense or hassle. The vast majority of the people running a gasser would not note the differnce in any case. Nothing sarcastic there, just the way it would be. About a 10-20 degree CHT diff.

AndresAM

Wouldn´t this mean also an small power gain?. (in hot ambient temps this is)

Tired Old Man

My Feedback: (1)

Yes

KenLambert

My Feedback: (107)

I run the 93 octane in all my gas engines just because that is my preference, and probly couldn't tell the difference but mixing a gallon or two at a time doesn't really cost a lot more.

My opinion is that the higher octain burns cleaner , just my opinion.

AndresAM

OK, I will give the higher octane gas a try. We have very high temperatures all year around where I fly, so if it makes the engine run cooler, and might get some power increase why not.... The cost difference is not that much anyway.

RTK

My Feedback: (1)

Elson-- Is that RON or ROM or RON/ROM

Rcpilot

My Feedback: (78)

Who flies when it's 95 degrees anyhow? Not this lazy kid. I'm long gone and sitting home in the AC by the time it gets to about 90F at our field.

I'd rather fly in the snow in 35F weather than sweat my butt off in the sweltering summer heat up here at 6000' elevation. It don't take long to catch a ripe sunburn at 6000' elevation. Even with sunscreen, I still get to looking a bit like a lobster if I'm out too long.

We can't even get 93 octane in Colorado. Best thing you'll find is 91. It's full of ethanol too. Someone told me to try the higher octane because ethanol takes power from the fuel. Any truth to that?

KenLambert

My Feedback: (107)

on ethenol you may get 1-2 miles per gallon less but its the injecters that take the biggest loss they seem to clog more often especaily the earlier versions

BTerry

My Feedback: (8)

Also the ethanol wreaks havoc on the diaphragm in the carburetor. Hopefully we won't have problems very often, but the diaphragm will definitely degrade.

Tired Old Man

My Feedback: (1)

The gain in power using higher octane fuels is often extremely minor. The largest benefit for our uses is in preventing pre-ignition, or pinging. There just ain' no way to compensate for too small of an engine or high density altitudes without either a larger engine or turbo/supercharging. Unless you have a means of monotoring real time rpm and cht via a telemetry system and can go back to view what went before when it was cooler you prolly won't notice much. In most cases, a more likely candidate for developing more power and lower cht's would be better engine tuning by the owner.

rc bugman

My Feedback: (30)

RTK


The US way to calculate it.

Elson

larry@coyotenet

My Feedback: (21)

I have a question. I have seen many posts and heard from other flyers who use Coleman Fuel instead of gas to get rid of the gas smell.
All I have seen suggests that it works just fine if a little expensive. From what I remember Coleman fuel is basically naptha. Naptha is a petroleum distilate with an octane rating of 50 to 55. I also remember reading that the smaller the engine the less the importance of the octane rating of the gas. This was from a book about the history of automotive research and Charles Kettering ( the man who developed the use of lead as an octane booster). What I would like to know is if our gas engines run just fine on Coleman Fuel why waste the money using anything above 85 octane gas? I have always used 85 octane in my gas engines and my performance is as good as anyone using 87 or higher octane gas. Are the superior results reported for higher octane gas real results or wishful thinking? As an aside, after reading about the benifits of using gas and oil in a 32 to 1 mix I tried that with my last 2 gallons of fuel. Using Castrol petroleum based 2 stroke oil mixed 32 to 1
my G-62 powered P-47 ran and flew the best it ever has. It was noticeably more powerful than when I ran a 50 to 1 mix of synthetic. Don't have scientific results to prove it but I plan on using the 32 to 1 mix from now on. Also ran same mix in a Fuji 32 powered Fiat CR-32 biplane with even better results. As they say "what's so conventional about conventional wisdom?"

Larry

Hawk21

My Feedback: (7)

I am going to try 93 octane and look for any difference
in power and temp
My engine has a slightly increase in compresion so I will let you guys know
Thanks all for sharing your knowledge this is a great topic to know about

Where do you find coleman fuel?

Tired Old Man

My Feedback: (1)

Increasing the oil content of the fuel, up to a point, also increases available btu's. However, you must keep leaning the mixture as the oil content increases.

For SOME, and that's a select few, engines an increase in performance is real using a higher octane gas. That's generally to be obtained under specific atmospheric conditions, though. How much is argueable and often simply a matter of perception. As for using Coleman fuel, if I had that much of an aversion to the odor of gasoline I'd fly electric.

Antique

My Feedback: (4)

Been arguing against "conventional wisdom " and oil mixture for years...Those of us who use it know...It's hard to compete with "conventional wisdom"..As in all the flyers who won't touch the "factory" carb needle settings

Tired Old Man

My Feedback: (1)

Ahhh yes, "factory" settings. The demise of so many good engines and planes, and the conundrum faced by so many engine manufacturers.[X(]