2 stroke oil in a 4stroke engine's fuel

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You seem to be confusing volatility with susceptibility to detonation. These are two different things. Diesel fuel is relatively non-volatile, so it doesn't vapourise easily and thus is hard to ignite, but it has a low octane rating, and will suffer badly from detonation in a petrol engine. Butane illustrates the opposite case. Its highly volatile, so its easy to ignite, but it has a fairly high octane rating, so it won't suffer badly from detonation in a petrol engine. The people in this thread (apart from me, of course, but my query is ignored smile ) seem to be suffering from the same confusion, so don't feel bad. http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3964478/HerrStig#Post3964478 Re the valve sealing, you might be right, dunno. Some 2-stroke oils (notably castor, as an extreme "classic" example) polymerise on hot surfaces. This is discussed in the Forumosa thread I linked to above. I suppose this could have some cushioning effect, but I'd think it'd burn off the exhaust valves very quickly. It might accumulate on the intake valves, but I dunno whether I'd expect such deposits to seal better than the ground-in valve seats. They might actually be worse, creating high spots, for example.
 
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Originally Posted By: Surestick
Originally Posted By: MeeLee
Hi, and thank you for the response. Your questions challenge me to read up on topics I haven't studied closely yet, but so far I've found that in diesel, Octane rating isn't what causes slow burn, but 'cetane'. So in a way we both are correct, although I was wrong to assume it was Octane that was the cause of the slow burning fuel. That's why Diesel can have low octane ratings, yet burn a lot slower than gasoline. All I know is from playing with fire when I was a youngster, that igniting Diesel is a lot harder than igniting regular fuel; and less explosive when it does.
Not sure if you are trolling or not here... Cetane if sort of the opposite of octane. A higher Cetane fuel will ignite faster than a lower Cetane fuel. In a gasoline engine the fuel is in the cylinder and mixed with air before it's supposed to ignite. If ignites too soon (before the sparkplug fires) or too easily (before the flame front from the spark can reach it) damage can be done to the engine. This is why a gasoline engine is called a spark ignition engine. In a diesel engine fuel is injected directly into the cylinder at the time it's supposed to ignite. As the spray of fuel enters the cylinder the leading edge of the spray comes in contact with the air in the cylinder and ignites due to the high temperature and pressure present. Any delay in ignition will will cause a loss of power among other issues. This is why a Diesel is called a compression ignition engine. Basically the factors that are used to ignite the fuel in a diesel (high pressure and temperature air) are also present in a gasoline engine. In a diesel engine you want the fuel to ignite because of these factors so the fuel needs to be sensitive to them and ignite easily as soon as it meets them. In a gas engine the fuel has to resist igniting from these factors until the sparkplug fires (and even then, resist igniting all at once and instead burn steadily). Neither liquid diesel fuel or liquid gasoline burn, their vapours burn. Gasoline evaporates much more easily than diesel so it's easier to ignite a puddle of it (or at least the vapors above a puddle of it). In an engine both fuels are atomized so conditions are different.
diesel engines are compression ignition because the total heat (btu) in the cylinder at the start of the compression stroke is raised to the point of combustion through compressing the heat into a smaller space. Not all diesels are direct injection and the fuel isn't injected at the time of combustion
 
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Originally Posted By: Superflop
diesel engines are compression ignition because the total heat (btu) in the cylinder at the start of the compression stroke is raised to the point of combustion through compressing the heat into a smaller space. Not all diesels are direct injection and the fuel isn't injected at the time of combustion
You're compressing heat?
 
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Two stroke oil has been around forever. I think if adding it to 4 stroke engines was really beneficial everyone would be all over it. Word gets around fast.
 
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down in the park
Originally Posted By: Superflop
diesel engines are compression ignition because the total heat (btu) in the cylinder at the start of the compression stroke is raised to the point of combustion through compressing the heat into a smaller space. Not all diesels are direct injection and the fuel isn't injected at the time of combustion
yes, they all inject at the time of combustion. for direct injection diesels, this combustion chamber is insidethe piston, but for indirect injection diesels this is in the head and it's a swirl chamber.
 
Originally Posted By: Superflop
Originally Posted By: Surestick
Originally Posted By: MeeLee
Hi, and thank you for the response. Your questions challenge me to read up on topics I haven't studied closely yet, but so far I've found that in diesel, Octane rating isn't what causes slow burn, but 'cetane'. So in a way we both are correct, although I was wrong to assume it was Octane that was the cause of the slow burning fuel. That's why Diesel can have low octane ratings, yet burn a lot slower than gasoline. All I know is from playing with fire when I was a youngster, that igniting Diesel is a lot harder than igniting regular fuel; and less explosive when it does.
Not sure if you are trolling or not here... Cetane if sort of the opposite of octane. A higher Cetane fuel will ignite faster than a lower Cetane fuel. In a gasoline engine the fuel is in the cylinder and mixed with air before it's supposed to ignite. If ignites too soon (before the sparkplug fires) or too easily (before the flame front from the spark can reach it) damage can be done to the engine. This is why a gasoline engine is called a spark ignition engine. In a diesel engine fuel is injected directly into the cylinder at the time it's supposed to ignite. As the spray of fuel enters the cylinder the leading edge of the spray comes in contact with the air in the cylinder and ignites due to the high temperature and pressure present. Any delay in ignition will will cause a loss of power among other issues. This is why a Diesel is called a compression ignition engine. Basically the factors that are used to ignite the fuel in a diesel (high pressure and temperature air) are also present in a gasoline engine. In a diesel engine you want the fuel to ignite because of these factors so the fuel needs to be sensitive to them and ignite easily as soon as it meets them. In a gas engine the fuel has to resist igniting from these factors until the sparkplug fires (and even then, resist igniting all at once and instead burn steadily). Neither liquid diesel fuel or liquid gasoline burn, their vapours burn. Gasoline evaporates much more easily than diesel so it's easier to ignite a puddle of it (or at least the vapors above a puddle of it). In an engine both fuels are atomized so conditions are different.
diesel engines are compression ignition because the total heat (btu) in the cylinder at the start of the compression stroke is raised to the point of combustion through compressing the heat into a smaller space. Not all diesels are direct injection and the fuel isn't injected at the time of combustion
I was trying to keep it simple for the OP who is obviously learning (or trolling!).
 
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Originally Posted By: greasegunn
Two stroke oil has been around forever. I think if adding it to 4 stroke engines was really beneficial everyone would be all over it. Word gets around fast.
Phooey. In cars this is going to be a marginal effect which is unlikely to be detectable without a serious investigation, which no one is likely to fund. So no one knows, or is ever likely to, but that doesn't prove theres no benefit. In modern cars the downside is likely to be slightly faster catalyst poisoning, which would put me off trying it. In vehicles in general, the downside is likely to be slightly raised emissions, and maybe a slightly higher risk of coking up the piston rings. Might be worth trying in a carbed motorcycle, especially if (as the OP claims) there's a detectable subjective difference. The higher revs/power output is more likely to show benefit, and it'd be easier to decoke.
 
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Originally Posted By: Superflop
Yeah lol looks like that. Compressing whatever is in the cylinder that contains the heat
The air is heating up from being compressed, compressing any gas heats it up. I ran 2-stroke oil in an old lawnmower that refused to run without it. Limped it along on 50:1 for several years, drastically helped the ring and valve seal.
 
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I’m stuck on the part where you mentioned gearing your motorcycle 50 percent higher from the extra boost in power. I do agree these little bikes seem to be geared very tight but 50 percent is a lot. And I would think any power gained from adding 2 stroke oil to your 4 stroke engine would be very minimal and not even able to be noticed. Let alone noticed enough to make any type of gearing change. I do agree though on these small cc bikes it is good to gear them up a bit so your not running such high rpms on the highway. I’ve found for my wife’s ninja 250 1 tooth larger on the front sprocket helped quiet a bit. I did the same to her Yamaha R3 when she graduated from the 250. I tend to use a dose of 2 stroke oil or marvel mystery oil for winter storage to help lubricate the inside of the tank,lines, and everything else sitting through the cold winter. Mine are currently all tucked away for the year in my workshop.
 
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