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Author Topic: 100LL Avgas?  (Read 738 times)

Offline Knock10090

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100LL Avgas?
« on: June 23, 2014, 05:53:23 am »
I have a question for running 100LL avgas

What jetting do you recommend for it.  I have a Paul Turner Pipe and Fat Boy 2 silencer.  A set of Boyseen Reeds and a aftermarket foam air filter in the stock airbox.  I was thinking about running it with the airbox lid off.

For the price of 94 at the local sunoco.. For an additional $1 per gallon more I could run the 100LL.  My premix will be 32:1 Klotz.

Is the extra work for the 100LL worth it over 94 at the Sunoco?

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Offline Motoman991

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Re: 100LL Avgas?
« Reply #1 on: June 23, 2014, 06:52:13 am »
If your engine isn't set up for high octane, you're just wasting money.

Offline MotorGeek - Jerry Hall

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Re: 100LL Avgas?
« Reply #2 on: June 23, 2014, 07:53:24 am »
I have a question for running 100LL avgas

What jetting do you recommend for it.  I have a Paul Turner Pipe and Fat Boy 2 silencer.  A set of Boyseen Reeds and a aftermarket foam air filter in the stock airbox.  I was thinking about running it with the airbox lid off.

For the price of 94 at the local sunoco.. For an additional $1 per gallon more I could run the 100LL.  My premix will be 32:1 Klotz.

Is the extra work for the 100LL worth it over 94 at the Sunoco?



You will NEVER hurt an engine by running fuel with a higher octane fuel than what the engine requires.  Fuel with a higher octane than what your engines build requires is often cheap insurance against detonation if atmospheric conditions change a little or your speed drops to a crawl for a few minutes that cause the engine temperatures to go extremely high.

Most pistons will not usually have a heat related failure if you can prevent the engine from experiencing detonation and keep the coolant in the engine.

Offline Knock10090

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Re: 100LL Avgas?
« Reply #3 on: June 23, 2014, 09:13:22 am »
Didnt know that.. I am for sure going to run it then.. For that extra $1 per gallon.. its worth it.

What jets should I run with the airbox lid off and an aftermarket pipe/silencer? 

Offline Glamisrider

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Re: 100LL Avgas?
« Reply #4 on: June 23, 2014, 09:35:04 am »
What jets should I run with the airbox lid off and an aftermarket pipe/silencer? 

If you want better answers, you need to ask better questions

You're missing a ton of information to even start to think about answering your question.

Porting?
Elevation?
Weather/conditions?
Bore diameter?
What carb are you running?
Type of riding you're doing?
Has the head been modified?
Compression is ??

Does it run now; iIf so what type of gas and what jets are you running?

  Is it acting up; if so what's it doing?, what's it sound like?


Offline Knock10090

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Re: 100LL Avgas?
« Reply #5 on: June 23, 2014, 09:58:16 am »
All good questions..  Let me work on those and re-post my question.  Haha..  Didnt even to think to consider most of those.. Some are going to be big unknowns.

Offline QuadMan8

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Re: 100LL Avgas?
« Reply #6 on: June 23, 2014, 09:56:58 pm »
Is the mentioned avgas perfetly save to run in a modified 2 stroke that only needs 100 octane. right now I mix 1/2 110 octane race fuel with 88 non ethanol pump gas and at my 5000 foot on ported motor it runs great----running straight avgas would be easier than mixing,,forget cost as a factor.....is av any better or worse than what I am doing
If they can't kick start it--THEY CAN'T RIDE IT

Offline El Diablo

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Re: 100LL Avgas?
« Reply #7 on: June 23, 2014, 10:28:31 pm »
This is where I really wish WestTexasKing would chime in & answer. But he's been MIA for a good minute now. Anyhow, you will not have any issues running AV in your bike. The only real major difference between 100LL AV & 110 Race gas (besides 10 points of detonation protection) is that the race gas usually has additives to speed up the propagation of the flame front in your combustion chamber. This may help your high rpm power. Remember that AV is designed for piston aircraft engined that redline in the area of 3200 rpm. Your 2 stroke 250 probably sees 8000 rpm a few times every ride.
Brian
1988 Suzuki LT-250R (The HPR test mule)
1987 Suzuki LT-500R
1990 Suzuki LT-500R
1982 Honda ATC-185S
1982 Honda ATC-250R

Offline Motoman991

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Re: 100LL Avgas?
« Reply #8 on: June 24, 2014, 04:54:49 am »
Almost all low compression motors will lose power by using high octane fuel.  This has been proven time and time again on the dyno.

http://www.rc51.org/fuel.htm

Offline Q2W

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Re: 100LL Avgas?
« Reply #9 on: June 24, 2014, 06:19:33 am »
you'd have to have pretty low compression to lose power with 100LL.

It's true that just because it's higher octane doesn't mean it will run better but 100LL will never be an issue for these bikes.

Offline MotorGeek - Jerry Hall

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Re: 100LL Avgas?
« Reply #10 on: June 24, 2014, 08:49:16 am »
Almost all low compression motors will lose power by using high octane fuel.  This has been proven time and time again on the dyno.

http://www.rc51.org/fuel.htm

I read the link.  The information in this link was testing on four strokes and mostly low compression street bike engines that were designed to run on pump gas

I agree that if your engine does not need high octane fuel....do not use it.

I have made about 200,000 dyno runs in my 40 year career working on four and two stroke engines.  My dyno test results on four strokes agrees with the link provided but test result on two strokes does not agree  with the above link when it comes to testing fuels on two strokes.


Any large displacement single cylinder engine especially 500 cc two strokes, will have or is on the verge of having detonation problems  regardless of the compression ratio, at partial throttle and higher RPMs due to the scavenging problems that is inherent in all two strokes.   The four strokes scavenging process is totally different than what occurs in a two stroke.  Detonation is directly related to cylinder pressure, mixture temperature, mixture purity, and the distribution of the fuel within the combustion chamber during the combustion process.

Putting high octane fuel in a low compression ratio two stroke engine will usually lower the power if the ignition timing, the exhaust system and the jetting is not optimized for the fuel being used.

 The design and operating principles of Two strokes and four strokes are so different, one has to be very careful using testing result from one type of engine design to try to sell ideas or products that do not share similar principles or apply to engines that operate on completely different principles.

Offline Glamisrider

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Re: 100LL Avgas?
« Reply #11 on: June 24, 2014, 02:56:49 pm »
Is the mentioned avgas perfetly save to run in a modified 2 stroke that only needs 100 octane. is av any better or worse than what I am doing

Quadman, there are actually a few threads on this topic, here is one that might help:
http://www.suzukiquadracerhq.com/engine-13/avgas-or-mix-of-race-gas-and-premium/msg21629/#msg21629

Offline Nekrofilliak

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Re: 100LL Avgas?
« Reply #12 on: June 24, 2014, 05:29:17 pm »
2 year ago i used avgas 100ll then pump 91, then avgas 100ll,  with the same  mix and oil , the jetting is identical.  smell better.

The answer to your question is : jet it well ( rich side )
88 Lt250r.
79 Lawnboy 21" ;-P

Offline Knock10090

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Re: 100LL Avgas?
« Reply #13 on: June 24, 2014, 05:33:59 pm »
Im going to give it a try...   If the airport is a hassle. (dont know the situation there) I will mix 110 race gas with 93 (50/50).  It will be a few dollars more but might be worth it if they are a pain in the rear at the airport.

 

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