Octane question

[LohringMiller]

We ran VP's UL-1 in our Quickdraws. It's advertised as 101 octane. What is the BZM combustion chamber volume? If I remember correctly our 26 cc Quickdraws had around 1.2 cc. Premium pump gas uses ethanol to boost octane rating. The 92 octaine fuel we tested was 8% ethanol. The power issue with ethanol in our engines is that we usually can't change the combustion chamber volume, ignition timing, or pipe design to take advantage of alcohol's potential power boost. Theoretically you could do that with a BZM, but you would need a careful test program.

Octane rating is a measure of detonation resistance. You only need enough to prevent detonation. If you want to run a smaller head button volume you will need higher octane fuel. You could also derate the engine with more combustion chamber volume to take lower octane fuel. In any case you need to check exhaust gas temperature. That determines pipe length. There is a trend in some two strokes to run lower compression to get more energy for the pipe. Again, this would take a test program that's beyond my abilities these days.

Lohring Miller

 

[John Beardslee]

I’ve always used 100 LL aviation gas and mixed Redline or Stihl Ultra. Other than no smell with av gas is the stability, it lasts 10 years and won’t varnish up the carbs. The octane rating is also held to a finer tolerance. If your engine is built with higher compression and requires higher octane don’t run lower octane gas, I’ve seen it blow the lugs off the jug when it detonated. $$$$$.

 

[ACTION JACKSON]

We ran VP's UL-1 in our Quickdraws. It's advertised as 101 octane. What is the BZM combustion chamber volume? If I remember correctly our 26 cc Quickdraws had around 1.2 cc. Premium pump gas uses ethanol to boost octane rating. The 92 octaine fuel we tested was 8% ethanol. The power issue with ethanol in our engines is that we usually can't change the combustion chamber volume, ignition timing, or pipe design to take advantage of alcohol's potential power boost. Theoretically you could do that with a BZM, but you would need a careful test program.

Octane rating is a measure of detonation resistance. You only need enough to prevent detonation. If you want to run a smaller head button volume you will need higher octane fuel. You could also derate the engine with more combustion chamber volume to take lower octane fuel. In any case you need to check exhaust gas temperature. That determines pipe length. There is a trend in some two strokes to run lower compression to get more energy for the pipe. Again, this would take a test program that's beyond my abilities these days.

Lohring Miller

Guess I should have mentioned I'm running the 29.5 bzm size motor that would have helped. At this point I'm going to run the motul brand of oil at 10 Oz for break in. I will do the glass visual to make sure there's no separation of fule & oil. That was a big help that I never would have thought to do. You all have helped with great information that will keep me from destroying my motor. Can't wait to burn some water this year.

 

[NAMBA860]

Really can’t take advantage of high octane fuels with a fixed timing engine

 

[David Bryant]

The only motor I know of that require anything over 100 is the CMB 27. According to Stu, he had to run that high to get the engine to run correctly in his rigger

yes, that's what I plan on running (110 octane) in my CMB 27cc Alpha-EVO engines

 

[RobertDoak]

So straight up Coleman lantern fuel/white gas?

So...don't add oil or nothing....just pour in bag and run?

 

[John Beardslee]

So...don't add oil or nothing....just pour in bag and run?

No no no, you must add oil!!!

 

[RobertDoak]

Thank you John...I'm glad you straightened me out on that....that would have hurt the ol wallet...

 

[LohringMiller]

We did run an engine without oil by mistake. It lasted a few seconds on our dyno and completely destroyed itself.

Lohring Miller

 

[ChrisHerzog]

I have basically only run C-12 in my gas boats for years but I want to switch to
C-9. Does anyone have any experience with C-9?

 

[DON MAHER]

Dumb question of the day! What the heck is C-9?

 

[FloridaScaleBoater]

Dumb question of the day! What the heck is C-9?

Zactly??
And C-12?

 

[Mark Anderson]

They are expensive racing gasoline.

 

[ChrisHerzog]

VP race gas. They make C-12, C14, C-16 and recently started making C-9.

Most drag cars (the serious ones) that run on gas run C-16. C-12 is for 2-stroke engines so your dirt bikes and snowmobiles & jet ski engines run on C-12. It runs great in out boats but it does run hotter then gas station fuel. C-9 solves the heat issue from what I’m told.

 

[LohringMiller]

There are two main factors in race fuels that matter; octane rating and oxygenation. Both require an engine that;s tuned to fit the fuel. High compression requires high octane. Oxygenation adds power by adding oxygen to the fuel. Nitro is an oxyginating agent in nitro fuels. Most RC gas boat engines aren't going to benefit from either. Quickdraw says either C10 or 100LL runs well in their engines. Our tests show higher octane is a waste in modified Zenoahs. Exhaust temperature really effects pipe design. I'm sure you can get a few more hp out of a head button engine with an extensive test program. Otherwise, save your money and run an inexpensive gasoline.

 

[DON MAHER]

What Lohring said is what I have experienced!