Proper octane level for lo206?
- Thread starter Double E Ranch
- Start date
like i said methanol is a pain it washes down the cylinder and makes rings wear and we were always having to change the oil. this will never be all agreed on some racers like gas and somelike methonal i guess they both work but i fell gas is just easier to deal with and everyone i have talked to told me the rings last way longer
Octane does NOT have any relationship to burn rate. You cannot test for OCTANE numbers at the track.
The best system so far is for the Track to specify the closest station to the track AND the pump number you use. THEN they buy a sample for the Tech man to compare to at trackside. END of story, easy peasy. Cannot argue with that. Well you can but you will not win that argument. Fair to all concerns.
Everyone ends up with the same % ethanol in the fuel.
Just a thought, (;-) TP
The best system so far is for the Track to specify the closest station to the track AND the pump number you use. THEN they buy a sample for the Tech man to compare to at trackside. END of story, easy peasy. Cannot argue with that. Well you can but you will not win that argument. Fair to all concerns.
Everyone ends up with the same % ethanol in the fuel.
Just a thought, (;-) TP
Double E Ranch
New member
We must run no ethanol and can not run methanol or alky in our division. We are required to run gas with no additives. They do test for this. In our clone program we did run a 87 octane. With the LO206 we have a compression ration of 8.5 to 1. I was curious if anyone had success with running a different level of octane. I have read VP provides a higher octane and seems to hold a better shelf life than standard pump gas. We are currently running 87 octane with no ethanol(or so the pump says). We too are running into issues of finding stations that truly have no ethanol in them. According to the blenders that I work with for my job, almost all pump fuels now contain so level of ethanol. I appreciate the feedback everyone has provided me. Doesn't seem to be any real consensus one way or the other in regards to a higher or lower octane. Kinda seems like personal preference more than anything. I have to say I enjoy the open dialogue my question prompted.
Don Westlie
New member
Jimbo
You can fool some of the people some of the time
Why Gas??
It's easier for the average guy to get. Therefore it brings more people into the sport.
Methanol scares some people away because they have never dealt with it and don't know where to get it.
Rumors abound about the dangers of methanol when in reality it's not any more dangerous than gasoline.
I wouldn't drink, take a bath or sniff any more of the fumes of either one of them than absolutely necessary.
Gas is here to stay for at least for a while.
It's easier for the average guy to get. Therefore it brings more people into the sport.
Methanol scares some people away because they have never dealt with it and don't know where to get it.
Rumors abound about the dangers of methanol when in reality it's not any more dangerous than gasoline.
I wouldn't drink, take a bath or sniff any more of the fumes of either one of them than absolutely necessary.
Gas is here to stay for at least for a while.
Unless they have repealed the law of physic's while I was asleep, octane does have an afect on the burn rate. Other wise there would be no reason for differant octanes for hi or low compressions.
I would prefer to have fuel at the track sold by a karting vendor that I don't have drive around looking for a pump....and pump number and worry if they got a new load of fuel that day. Simple specific gravity test for checking alky or a kart shop that has alky fuel as the only sorce for all to run. Easier peasy-er.
It has nothing to do with physics I have tested fuels with high octane AND slow and fast burn rates. The Octane level is HOW detonation resistant the fuel mixture is NOT its burns rate. Octane is TESTED using a KNOCK engine.
Most tracks we go to do NOT have a vendor present that WILL sell gasoline. It is just another level of responcibilities that a vendor does not want or need. If you cannot stop on the way into the track to get the spec gas ???? I dought that most gas stations will get a new load of fuel in the middle of race day (weekends).
You forgot to test for % of ethanol. It seriously effects OTHER things as well as HP.
Just a thought, (;-) TP
Most tracks we go to do NOT have a vendor present that WILL sell gasoline. It is just another level of responcibilities that a vendor does not want or need. If you cannot stop on the way into the track to get the spec gas ???? I dought that most gas stations will get a new load of fuel in the middle of race day (weekends).
You forgot to test for % of ethanol. It seriously effects OTHER things as well as HP.
Just a thought, (;-) TP
rainman
Member
Ethanol and methano are not the same. Anyway might also be related to quality. I am just stating what happened, not the resons. With appropiate jet results might have been different. My rotary valve Italsistem flies on 110 VP. Though I use it on my Unlimited for dirt I personally hate having to flush my engine when I run it on methanol.
alvin l nunley
Site Supporter
Just wondering, what test do you use to test for burn rate?
I’m familiar with the knock engine, and the procedure used to test for octane, but that test does not check for burn rate.
Can you give me a reference, or source, for your information on burn rate. I don’t remember where I heard it, but I have always been under the impression that high octane fuel burns slower. Now I could be wrong about that, and my mind could be change with solid engineering information.
Comments compliments criticisms and questions always welcome.
hiya Al, here is some sound info on fuels . also look at the download info. One simply test is to optimize the engine for max HP. Then look at the comparison of Low end HP vs top end HP. Now change the fuels and retest. slow fuels tend to make more HP at low rpm where it takes longer to cycle throught the ignition stage of combustion. The fuel burns at a constant rate BUT the combustion time does NOT the high the rpm the less time you have to get it all burnt. Faster burn fuel do better at high rpm slower burn fuels do better at lower rpm as a general rule.
What an engine likes is tied to the effeciancy of the combustion chamber. The idea is to get all the fuel burnt before the push cycle is over. at low speeds an engine has TIME to get it done at HIGH speeds not so much. So IF you over time to compensate for the top end you loose on the low end.
NOTE SINGLE cylinder 4 cycle engines are very SENSITIVE to counter torque produced by the ignition process and where you have to lead the timing a lot to get it all done. unlike 2 strokes and multi cylinder where they are not as sensitive as they have HELP to get it all done and in the case of 2 cycles they tend to have very efficient combustion chambers by design.
2nd test is to jockey the ignition timing while changing fuels. Fast burn fuel normally require LESS timing than slower fuels at a givin RPM.
Most fuel companies will NOT give out the specific burn rate data it is mostly secret data held close.
A general rule but not always is tied to the specific gravity of the fuel. Most fast burn chemicals come from the high end of the stack (lighter in specific gravity) . HINT HINT
The specific gravity also effects the Fuel air ratio as the F/A is calculated as WEIGHT not volume. Here is where people get it wrong in testing. They change fuels but do NOT rejet OR retime to correct the F/A ratio or burntime component, so they may or may not see a gain and pass right by a faster fuel.
% ethanol, there are gains to HP be had here IF you understand the features of Ethan and non ethan fuels . Rejetting and timing IS required to see the benifits. Hint, ethanol brings its own Oxygen to the party(;-) BUT it behaves differently from straight gas.
NOW add all that up with atmospheric changes and a sharp crew chief can bring SPEED to the table for his driver. In road racing there can be large differences in speed from the basic engine design especially with a Spec engine like the LO206 where you CANNOT change the low speed or main jet size to correct for conditions.
NOW that is just a nutshell version, do your OWN testing and research. The Chemist at fuel company's will talk with you most of the time. You just have to NOT be afraid to ask questions and when you do PAY attention.
Just a thought, (;-) TP
What an engine likes is tied to the effeciancy of the combustion chamber. The idea is to get all the fuel burnt before the push cycle is over. at low speeds an engine has TIME to get it done at HIGH speeds not so much. So IF you over time to compensate for the top end you loose on the low end.
NOTE SINGLE cylinder 4 cycle engines are very SENSITIVE to counter torque produced by the ignition process and where you have to lead the timing a lot to get it all done. unlike 2 strokes and multi cylinder where they are not as sensitive as they have HELP to get it all done and in the case of 2 cycles they tend to have very efficient combustion chambers by design.
2nd test is to jockey the ignition timing while changing fuels. Fast burn fuel normally require LESS timing than slower fuels at a givin RPM.
Most fuel companies will NOT give out the specific burn rate data it is mostly secret data held close.
A general rule but not always is tied to the specific gravity of the fuel. Most fast burn chemicals come from the high end of the stack (lighter in specific gravity) . HINT HINT
The specific gravity also effects the Fuel air ratio as the F/A is calculated as WEIGHT not volume. Here is where people get it wrong in testing. They change fuels but do NOT rejet OR retime to correct the F/A ratio or burntime component, so they may or may not see a gain and pass right by a faster fuel.
% ethanol, there are gains to HP be had here IF you understand the features of Ethan and non ethan fuels . Rejetting and timing IS required to see the benifits. Hint, ethanol brings its own Oxygen to the party(;-) BUT it behaves differently from straight gas.
NOW add all that up with atmospheric changes and a sharp crew chief can bring SPEED to the table for his driver. In road racing there can be large differences in speed from the basic engine design especially with a Spec engine like the LO206 where you CANNOT change the low speed or main jet size to correct for conditions.
NOW that is just a nutshell version, do your OWN testing and research. The Chemist at fuel company's will talk with you most of the time. You just have to NOT be afraid to ask questions and when you do PAY attention.
Just a thought, (;-) TP
alvin l nunley
Site Supporter
What information? I think you forgot the URL.
alvin l nunley
Site Supporter
My problem is I think I know everything and quite obviously that's not possible.
This article says at 3000 RPM you don't need fast burning fuel. Why is that? Wouldn't you want the most complete burn rate possible, at any RPM?
Comments compliments, criticisms and questions always welcome.
We have hundreds of dyno runs on LO 206 engines. We use shell 91 with good results. Any fresh clean gas in the 87 - 91 range will run fine. Jet or adjust float so plug reads correctly. We have done some tests with a couple of top brand fuel additives on red slide 206 and found engines lost power. Also an unleaded 110 racing gas {not VP} was tested no power gains on red slide motor.. So my 2 cents 91 will do the job........
Jimbo
You can fool some of the people some of the time
You can be pretty sure that the 87 octane fuel you buy at the local gas station is fresh since it is consumed at such a fast rate.
If you buy your fuel from a station in a metropolitan area you can be pretty sure that it is going to be less than a month old. I
If you buy it from a station on the sticks who knows how fresh it is.
Higher octane fuels that you buy at the local gas station or in the sticks may be much older depending on the consumption rate at that station and how long it has been in a storage tank somewhere else.
I have built some carbs for high school high mileage teams that use the LO 206 engine and burn E85.
I was surprised to find that they don't make any more HP than a LO 206 on normal 87 octane pump gas but they sure do use a lot more fuel.
If you buy your fuel from a station in a metropolitan area you can be pretty sure that it is going to be less than a month old. I
If you buy it from a station on the sticks who knows how fresh it is.
Higher octane fuels that you buy at the local gas station or in the sticks may be much older depending on the consumption rate at that station and how long it has been in a storage tank somewhere else.
I have built some carbs for high school high mileage teams that use the LO 206 engine and burn E85.
I was surprised to find that they don't make any more HP than a LO 206 on normal 87 octane pump gas but they sure do use a lot more fuel.
Octane Facts Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored since it can result in serious damage to the engine.• High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high.• If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in switching to higher octane gasoline.
there you go Al!
Octane rating does not determine fuel burn rate. It is a measure of the fuels ability to resist detonation.
Quote from a Sunoco Engineer:
The burn rate of a fuel is a measurement of the time required for complete combustion of the air/fuel mixture. The notion that octane ratings affect the burn rate of fuel is about 180-degrees from reality; burn rate is a function of several variables, and the two are completely independent, although there is generally a correlation between octane ratings and burn rates.
To give you a good example of this, we contacted Jim Wurth from Sunoco Race Fuels. He explains, "A perfect example is Sunoco Maximal, which is our fastest burning fuel, and coincidentally one of Sunoco's highest octane fuels at 116 (R+M) / 2. A lot of Pro Stock teams rely on Maximal for those sub-seven second runs. When they are turning 9,000 rpm or more, the fuel has to burn pretty quickly to achieve complete combustion".
Quote from a Sunoco Engineer:
The burn rate of a fuel is a measurement of the time required for complete combustion of the air/fuel mixture. The notion that octane ratings affect the burn rate of fuel is about 180-degrees from reality; burn rate is a function of several variables, and the two are completely independent, although there is generally a correlation between octane ratings and burn rates.
To give you a good example of this, we contacted Jim Wurth from Sunoco Race Fuels. He explains, "A perfect example is Sunoco Maximal, which is our fastest burning fuel, and coincidentally one of Sunoco's highest octane fuels at 116 (R+M) / 2. A lot of Pro Stock teams rely on Maximal for those sub-seven second runs. When they are turning 9,000 rpm or more, the fuel has to burn pretty quickly to achieve complete combustion".
Generally, the lowest octane you can get will be the way to go. Problem is that its very rare that octane is the only difference between fuels.
So, since you are stuck with a certain jet you will need to try different fuels and note findings including ignition advance.
When thinking about burn rate, remeber to consider bore size too!
So, since you are stuck with a certain jet you will need to try different fuels and note findings including ignition advance.
When thinking about burn rate, remeber to consider bore size too!