LO206 and ProGas Octane?

ClarkSr

ClarkSr

Member
My son and I are REAL new to the whole 4 stroke thing. Ran shifters and Tags for years, mainly road racing, and still do.

We recently got a ProGas Sportsman (WKA) for my 8 year old grandson to start sprint racing. So we figured we're get a 206 for his dad and I to race at our local sprint track too. For what it's worth, we're getting another one this winter---they are SOOOOO easy to take care of!!!!!!!!! WOW!!!

My question is, for both the ProGas and 206, have you engine guys seem any difference in performance between say, 87 octane pump gas and 93 Octane? I suppose you engine gurus at Carlsons, Fastermotors, BRE, etc, etc. would be a good source of info on this stuff. Or am I just overthinking it??!!:confused:

Thanks for your input folks,
Clark Gaynor Sr.
 
The low compression of the LO doesn't need or benefit from high octane fuel, but I would suggest meth free fuel for sure.
 
mopdog said:
The low compression of the LO doesn't need or benefit from high octane fuel, but I would suggest meth free fuel for sure.
Click to expand...

I would think that adding Alky would enhance the performance. If you would adjust the jetting to compensate for the alcohol, why wouldn't it? Why else would they have rules against it, and tests to detect it, if it wasn't something that would enhance performance?

The term, "octane" is so misunderstood. "Octane", is a measure of the fuel's ability to resist detonation. It is not a measure of performance. If you don't have a high compression engine, high octane will do you no good. It will, in all likelihood, actually hurt your engines performance.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
OK, so as not to make this too complicated, let's pretend I stop at the local Sunoco or Shell station on the way to the track Sunday. And I happen to need fuel for our ProGas and 206. Should I buy a gallon of 87 octane or 93?

Yes Al, I understand what octane is. I did mention we ran shifters, where with the mods you need at least 105-110, due to the high compression and larger ignition lead. Or with Stock Honda, you need in the neighborhood of 98 octane to keep det in check. I get it. And I understand a stock Briggs Animal is a low compression, low advance motor---I just don't know how low. 87 octane low, or 89, or 91 or 93? AND, all else being equal, would we see it on the watch?

Or as I asked before, am I over thinking the whole thing?
Thanks,
Clark Sr.
 
Lower grade is just fine.....No performance advantage with your engines (for reasons you are already aware of.)
Now, with that said -- check with your track to see what spec fuel they are using as a test standard. It should be specified by the track and usually the closest station to the track and a readily available grade (even specific pump number) so that competitors can purchase "legal" fuel.

--
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Thank you Brian, that is exactly the information I was looking for!!

At this time, our local track is just getting the 206 and ProGas classes going, so they haven't gone so far as to spec a station or pump. However, with any luck in a year or two, we'll have enough in each class to warrant specing the fuel supply. We're keeping our fingers crossed.

What a great motor package! Sooo user friendly. I just don't understand why the 206's haven't taken off everywhere. Watching that Canadian 206 Sr race was a hoot. We can only hope it gets that big around here.

Thanks again for the info,
Clark Sr.
 
One more point on the meth free fuel. Methanol is corrosive to aluminum parts. Meth free fuel is easier for maintenance. (In our Modifieds we run Methanol, but we flush them out with gas and oil after each race day and leave the gas/oil mixture in the fuel system during the week to prevent corrosion.)
 
CarlsonMotorsports said:
Lower grade is just fine.....No performance advantage with your engines (for reasons you are already aware of.)
Now, with that said -- check with your track to see what spec fuel they are using as a test standard. It should be specified by the track and usually the closest station to the track and a readily available grade (even specific pump number) so that competitors can purchase "legal" fuel.

Well said Brian........................we agree with you also.

Steve
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I saw mention of "methanol" but I think the concern is "ethanol". I would think avoid stations that blend ethanol with their gasoline if possible. "Ethanol-free" gasoline is available at a few stations in most areas, sometimes near lakes.
 
ClarkSr said:
OK, so as not to make this too complicated, let's pretend I stop at the local Sunoco or Shell station on the way to the track Sunday. And I happen to need fuel for our ProGas and 206. Should I buy a gallon of 87 octane or 93?
Click to expand...
the right octane is a moving target. If the compression ratio is low, 8 – 1, in most cases, 87 octane is good. Good if you have the right jet in the engine. A lean engine, under load, can start detonating. Have you ever been driving up a steep hill in the hot summer and started hearing a knock out of the engine? An engine that will run just fine in moderate weather, with low octane fuel, may start detonating with a significant increase in air density, temperature or load. If the air density goes up, more air gets pushed into the engine, and it takes no genius to understand that more air needs more fuel.

With a 2 cycle, the carbs are fairly easy to adjust to match the conditions. A good driver will be constantly adjusting the mixture to match the conditions during a race. If necessary of course, it's not always necessary.

It's harder with a 4 cycle that has a fixed jet carb. I don't know where you live, but in California where I used to race, there are tracks where the air density can vary significantly from the early morning to the late afternoon. Or from the late afternoon to the early evening. I would think it anywhere, if they race into the early evening, there has to be significant changes in air density. I'm told I'm wrong, but I'm told that by people who don't have air density gauges, in most cases, who don't really know if I'm right or wrong.

Here's a test you might try. Pull the head after every race. An engine that is detonating will have some clean areas around the edge of the piston, it looks like sandblasting. This can appear on the head also. Don't fool yourself, if these sandblasted areas appear, you're getting detonation. It could be caused by insufficient fuel octane, but can also be caused by a lean condition.

If you already know all this, good, so disregard these instructions, just realize that a lot of other people are reading it that may not know about it.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
This air density changing from time to time is very real. I used to race gas powered R/C cars on a Saturday we'd start at 6pm and race until 10pm. If you weren't watching your temp and dialing out the fuel needles as it cooled down at night you'd have a stuck piston in very short order. A lot of the 2-cycle guys will have an adjuster right on the steering pedestal, watch their temps on the mychron, and adjust accordingly.
Btw 10% ethanol fuel has 3% less fuel value by volume, I don't see it being a bad thing as long as you are jetted a little richer for it. I took the main jets in my little 4-cylinder Volvo in the boat from 110's to 115's so I could run E-10 and it's fine.
 
Compression ratio VS Octane
5:1 =72
6:1 =81
7:1=87
8:1=92
9:1=96
10:1=100
11:1=104
12:1=108
 
Jimbo said:
Compression ratio VS Octane
5:1 =72
6:1 =81
7:1=87
8:1=92
9:1=96
10:1=100
11:1=104
12:1=108
Click to expand...
I don't know, I think the compression ratio in my V6 Taurus was 8.0 – 1 and it ran fine on 10% alky unleaded regular 89 octane. On the highway I was getting 28 miles to the gallon. And that was on California gasoline.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
All interesting data, another consideration when choosing what octane rating to use is related to volumetric efficiency and ignition timing. Compression ratios are a static calculation that are not the only controlling factor in cylinder pressure during the firing stroke. Most if not all kart engines are operating considerably below 100% volumetric efficiency. I,m sure Steve V. can weigh in on this, he is an expert in this field!
At least for the Animal Pro Gas engine, we have not seen a power difference between 87 and 89 octane fuels. I am not sure what the ethanol % was since we purchased this test fuel at local gas station and pump says up to 10% ethanol may be present. We have tested a lot of the Ignite Green fuels and find variation in power based on level of ethanol presents.

Steve
 
steve baker said:
We have tested a lot of the Ignite Green fuels and find variation in power based on level of ethanol presents.

Steve
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have you ever read the story of how the motor octane rating is arrived at?

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Clark, what did you / do you run your TaG on? We ran TaG a few years ago, along with Alky Animal, F200 Briggs, and Stock Honda Shifter. There were times I wore a white Lab coat and looked like Dr. Zorba! One year, we took the TaG ( Leopard ) to Rock Island to race there. The Spec Fuel was VP98 Octane Unleaded with ( I think this is correct ) 8oz per gallon of Red Line Oil. That thing ran like a champ! I was mixing 110 VP and 89 Unleaded for the TaG at the Road Race tracks, and the same with the F200. That was a pain. Pretty sure the VP98 does not contain ethanol. FWIW.

Dave E.
 
alvin l nunley said:
have you ever read the story of how the motor octane rating is arrived at?

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
Click to expand...

Al, I might have years ago but I forget a lot these days. Love to hear the story however...............thanks!

Steve
 
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