- Location
- Ontario, Canada
Hey peeps, I figured I would put out a little bit of info. Perhaps some of you will find this useful, but essentially I wanted to get a little bit of knowledge out there regarding fuel. Make no mistake, the prefix to the thread is Octane but I thought it just worked with the subject at hand 
To get onto this useful base knowledge I thought it be important to mention that as of lately I have noticed what seems to be a lot of fuel delivery system related issues popping up, but never thought to bring forward the question of the fuel its self. This is just a rhetorical question and asked as a general thing, it's not meant to sound ignorant or implied to be so, so in general the question begs to be asked do you really know what is in your fuel? When I researched this a long time ago I found that it helped me with having a better awareness of how my ski was responding to various carb settings and hardware changes such as jets or flame arrestors.
This I am going to assume is basic knowledge to those in the know, but for those having a hard time tuning it is a good thing to remember a few details that could very well be why you are having a hard time tuning your ski. Since the late 90's, the EPA implemented a policy that all fuel be oxygenated. What this means is that they chemically bind additional oxygen atoms to the chain of carbon molecules meant to formulate the fuel at the pumps. How does this affect us? When the fuel has additional oxygen bound into the mix, the fuel will actually be about 20% leaner than the pre-oxygen rich fuel. This is where the need for over-jetting can become useful. As the manufacturers became aware of the transition they compensated for the most part after about '98 and began to use slightly larger jets in certain applications, most commonly in the 4-stroke market. But it still holds value to us 2-stroke lovers. How often have we noticed that after a full rebuild or complete carb overhaul, or any additional mods added on that tuning is usually quite on the money at first, but after a short period of time the tuning becomes a little more tricky and weird fuel-like symptoms turn up. Well, it could just be that jetting is holding you back. But there is a little more behind the scenes that could be creating gremlins and would never been seen.
This gremlin mentioned could have something to do with the blend of fuel you have encountered. Since the earlier part of the year 2000, new regulations required that all fuel blends be mixed with ethanol. I am quite sure everyone here is no stranger to it. But another rhetorical question...do you really know what it does? Ethanol is a bio-fuel, it is just a fermented batch of raw materials (mainly corn) and turned into high proof alcohol. What is not abundantly known is that in it's non-fuel mixed state, it is used in areas requiring mildly corrosive properties such as paint strippers, it is used to chemically mix with, trap and retain water molecules, and it is a particularly slow and cold burning substance. Where does it affect us? Directly in the tank both on the skis and at the pumps. When the ethanol absorbs the water in the tanks at the pumps, it becomes heavy and settles to the bottom. While it is settling, it is also losing it's octane rating because the volume is changing with the introduction of the moisture or direct water contact. When enough water is absorbed, the fuel mix will settle in a layer called phase separation. This is a layer of fuel volume that has such poor combustible properties that even a 4-stroke all terrain vehicle can only barely idle on it. It is so reduced in combustible properties that it has no ability to burn quickly enough to generate power beyond the most minimal fuel air ratio...this would be the idle only mixture of about 15:1 (or 15 parts air to 1 part fuel). When you open the throttle you increase the air flow but with such heavily water diluted fuel, the weight is too heavy to cycle through quickly enough and lacking the properties needed to achieve any performance above idle. In the two stroke engine, this can be noticed if when you have the flame arrestors off and open the throttle, you might see a large amount of "fuel" being sprayed through the bomb site and landing on the throttle butterflies but leaving a fluid film on the butterflies, not evaporating quickly like true fuel should.
This is why the fuel stations are required to test their tanks for phase separation on a weekly basis, once the levels get too high they have to have the bottom of the tanks siphoned and send the diluted fuel back for disposal. When does this affect us? Whenever the tanker trucks fill up the stations. As they load up the new supply of fuel, they stir up the phase separated layer at the bottom, the new fuel supply absorbs the stirred bottom layer and the new supply begins to lose octane numbers immediately. This is why it is absolutely critical that when you buy your fuel, get it from a station that sees a lot of traffic. This is the only real management for keeping the bad fuel levels low as the bottom of the tanks are frequently being cycled. Additionally so, since the year 2009, most pumps have stopped labeling the different fuel grades as being just that, different. What I mean by that is, they used to only label the 87 and 89 octanes as having ethanol blends. Now they are utilizing higher ethanol contents, here in the north land we see blends as high as 15% and premium 91 octanes and higher are no longer on a class of their own. All fuel grades can now potentially be ethanol blends. The only safeguard against that now that I have found, is this nifty little website I stumbled across. This will help us locate the fuel stations that still promote the higher quality old school blends of true MTBE...or methyl tertiary butyl ether...which has no ethanol in it and is the original blend that all the older skis were built to burn. Have a look and see where in your state or province is a registered supplier of good fuel, it just may solve a lot of your carburetion nightmares. I hope this was helpful, if nothing else, the link at least should be. Thanks for reading y'all
http://pure-gas.org/
To get onto this useful base knowledge I thought it be important to mention that as of lately I have noticed what seems to be a lot of fuel delivery system related issues popping up, but never thought to bring forward the question of the fuel its self. This is just a rhetorical question and asked as a general thing, it's not meant to sound ignorant or implied to be so, so in general the question begs to be asked do you really know what is in your fuel? When I researched this a long time ago I found that it helped me with having a better awareness of how my ski was responding to various carb settings and hardware changes such as jets or flame arrestors.This I am going to assume is basic knowledge to those in the know, but for those having a hard time tuning it is a good thing to remember a few details that could very well be why you are having a hard time tuning your ski. Since the late 90's, the EPA implemented a policy that all fuel be oxygenated. What this means is that they chemically bind additional oxygen atoms to the chain of carbon molecules meant to formulate the fuel at the pumps. How does this affect us? When the fuel has additional oxygen bound into the mix, the fuel will actually be about 20% leaner than the pre-oxygen rich fuel. This is where the need for over-jetting can become useful. As the manufacturers became aware of the transition they compensated for the most part after about '98 and began to use slightly larger jets in certain applications, most commonly in the 4-stroke market. But it still holds value to us 2-stroke lovers. How often have we noticed that after a full rebuild or complete carb overhaul, or any additional mods added on that tuning is usually quite on the money at first, but after a short period of time the tuning becomes a little more tricky and weird fuel-like symptoms turn up. Well, it could just be that jetting is holding you back. But there is a little more behind the scenes that could be creating gremlins and would never been seen.
This gremlin mentioned could have something to do with the blend of fuel you have encountered. Since the earlier part of the year 2000, new regulations required that all fuel blends be mixed with ethanol. I am quite sure everyone here is no stranger to it. But another rhetorical question...do you really know what it does? Ethanol is a bio-fuel, it is just a fermented batch of raw materials (mainly corn) and turned into high proof alcohol. What is not abundantly known is that in it's non-fuel mixed state, it is used in areas requiring mildly corrosive properties such as paint strippers, it is used to chemically mix with, trap and retain water molecules, and it is a particularly slow and cold burning substance. Where does it affect us? Directly in the tank both on the skis and at the pumps. When the ethanol absorbs the water in the tanks at the pumps, it becomes heavy and settles to the bottom. While it is settling, it is also losing it's octane rating because the volume is changing with the introduction of the moisture or direct water contact. When enough water is absorbed, the fuel mix will settle in a layer called phase separation. This is a layer of fuel volume that has such poor combustible properties that even a 4-stroke all terrain vehicle can only barely idle on it. It is so reduced in combustible properties that it has no ability to burn quickly enough to generate power beyond the most minimal fuel air ratio...this would be the idle only mixture of about 15:1 (or 15 parts air to 1 part fuel). When you open the throttle you increase the air flow but with such heavily water diluted fuel, the weight is too heavy to cycle through quickly enough and lacking the properties needed to achieve any performance above idle. In the two stroke engine, this can be noticed if when you have the flame arrestors off and open the throttle, you might see a large amount of "fuel" being sprayed through the bomb site and landing on the throttle butterflies but leaving a fluid film on the butterflies, not evaporating quickly like true fuel should.
This is why the fuel stations are required to test their tanks for phase separation on a weekly basis, once the levels get too high they have to have the bottom of the tanks siphoned and send the diluted fuel back for disposal. When does this affect us? Whenever the tanker trucks fill up the stations. As they load up the new supply of fuel, they stir up the phase separated layer at the bottom, the new fuel supply absorbs the stirred bottom layer and the new supply begins to lose octane numbers immediately. This is why it is absolutely critical that when you buy your fuel, get it from a station that sees a lot of traffic. This is the only real management for keeping the bad fuel levels low as the bottom of the tanks are frequently being cycled. Additionally so, since the year 2009, most pumps have stopped labeling the different fuel grades as being just that, different. What I mean by that is, they used to only label the 87 and 89 octanes as having ethanol blends. Now they are utilizing higher ethanol contents, here in the north land we see blends as high as 15% and premium 91 octanes and higher are no longer on a class of their own. All fuel grades can now potentially be ethanol blends. The only safeguard against that now that I have found, is this nifty little website I stumbled across. This will help us locate the fuel stations that still promote the higher quality old school blends of true MTBE...or methyl tertiary butyl ether...which has no ethanol in it and is the original blend that all the older skis were built to burn. Have a look and see where in your state or province is a registered supplier of good fuel, it just may solve a lot of your carburetion nightmares. I hope this was helpful, if nothing else, the link at least should be. Thanks for reading y'all
http://pure-gas.org/
