Me too! I had a 1970 Kawasaki 3cyl 500cc Mach III 2 stroke. Went up a freeway on ramp smoking like a Phantom fighter on takeoff, and wailing like a banshee.
Epic ride!
Two-cycle oil Formulations
- Thread starter MolaKule
- Start date
Epic ride!
MolaKule
Staff member
The average cooling numbers I have seen bantered about is 25% to 30%. I have never seen a published document supporting these figures, nor how this relates to an actual measured temperature reduction. There may be an SAE paper or a text out there that shows measured temp reduction but I have never seen it.
Last edited by a moderator:
I had one of these when I was in high school... and am still alive! O.M.G.
- Joined
- May 31, 2024
- Messages
- 744
Thanks, I have not read anything regarding the cooling effects of fuel evaporation.
I have read about the overheating of parts due to a lean mixture, but for other reasons.
MolaKule
Staff member
Well, it would be similar to sweat cooling a body,
If one could nail down the material values for a 2-cycle engine, these equations could used to determine the actual temperature decrease due to vaporization. While the example below is for a temperature change due to a melting phase change, the same principles apply.
https://openstax.org/books/physics/pages/11-3-phase-change-and-latent-heat
- Joined
- May 31, 2024
- Messages
- 744
I am well aware of cooling from evaporation. Sweat cooling, swamp cooler, refrigerant in an evaporator etc..
I'm am having a hard time grasping the volume of fuel being evaporated, and the volume of resultant cooling vs the total heat generated in a running engine. As reported to be a large part of the total.
I know there is math to answer this, I thought maybe the presenter could elaborate on this. Crickets so far.
Is this kind of like a fella walking on hot coles in Hawaii, and not feeling much? Water evap? Is it a part of the process, or the result in line with this principle?
or like using exhaust gas to lower combustion temps.....the phasing of the exhaust gas absorbs more juice?
MolaKule
Staff member
Agreed. The volume of the mixture entering verses the actual temperature drop is the big question that Mr. Walker and others have yet to answer.
Right now I don't have the time to program the equations in MatLab.
Last edited:
MolaKule
Staff member
Kinda.
None. That does not change a thing. At least I understand the simple mechanics of a two cycle and how's its lubricated. Hint..its not lubricated by liquid gasoline with a smattering of oil in it. Its lubricated by oil deposited when the fuel entering the crankcase changes phase from a liquid to a gas.
Last edited:
If the fuel does not change phase from a liquid to a gas it will not ignite, which is why engines use chokes. This applies to any IC engine. The idea of a choke is to provide so much liquid fuel to the combustion chamber that enough gas is created to light off the extremely lean mixture. Lean in that the air to gaseous fuel ratio is lean, not the amount of liquid fuel in the motor, which can not light off.
Last edited:
Pre mix enters the crank case as liquid droplets. It changes phase inside the crankcase to a gas and deposits oil in the process. Liquid premix has no lubricating ability, but the oil deposited by the evaporation I mentioned does.
What I am telling you is, air is not a lubricator so the base oil and additives from the fuel mix is the only thing left to lubricate.
The fuel/air mix enters the bottom part of the crankcase as a vapor (see my comprehensive explanation above). As this point the fuel-oil droplets deposits on the various components, lubricating them. A short time later, the piston moves down to compress the vapor below it; the combination of compression and residual crankcase heat results in a phase change converting most, but not all, of the residual vapor to a gas. As the piston moves up the gas below the piston is allowed to enter the "combustion chamber" for ignition, the power stroke.
Now you're discussing the thermodynamics of the 2-stroke engine. Heat is removed from the head by air passing over the cooling fins. Thermal energy (heat) is conducted to the fins and air removes heat by convection.
Another measure of cooling is accomplished by what is called the, "Latent Heat of Vaporization" to which you may be referring, but you never identified the cooling process.
The amount of energy absorbed or released during a phase change is called, "Latent Heat." The
"Latent Heat of Vaporization" is highly dependent on the temperature and pressure at which the phase change occurs.
See for example, Fundamentals of Thermal-Fluid Science, by Yunus Cengel, et. al.,, page 71.
I didnt feel the need to wax on about the thermodynamics involved because it really does not matter to this discussion. That and I am not trying to baffle with BS.
Another home work assignment. Why do purpose built two cycle racing gasolines have a distillation curve with the lower portion( 10-50% boiling points) having lower temps than say a pro stock drag fuel? Ill give you a hint. It has to do with relative intake runner length.
Last edited:
RE: Two Stroke cooling.
https://www.cycleworld.com/another-...=So we have to cool,or left in unheated sheds.
"When production DFI two-strokes were built, it was found that without the evaporative cooling of fuel passing through the crankcase, the case and all the rolling bearings in it ran a lot hotter than before. Well, OK, we’ll core coolant passages in the cases to pull that heat out. And now the engineers are talking about two-loop cooling systems – a low temp loop for cylinder walls and crankcase, and a hot loop for the head and exhaust-port region."
https://www.cycleworld.com/another-...=So we have to cool,or left in unheated sheds.
"When production DFI two-strokes were built, it was found that without the evaporative cooling of fuel passing through the crankcase, the case and all the rolling bearings in it ran a lot hotter than before. Well, OK, we’ll core coolant passages in the cases to pull that heat out. And now the engineers are talking about two-loop cooling systems – a low temp loop for cylinder walls and crankcase, and a hot loop for the head and exhaust-port region."
MolaKule
Staff member
You're confused in your understanding of material phases. Oil is not a gas, it is a liquid.
Thermodynamics and material phases is definitely important. Why not discuss the thermodynamics? It was you who introduced evaporation and cooling,
We thought you might have some quantitative answers to how much cooling is done by this process, but you continue to ignore the details and we wonder why?
"The fuel/air mix enters the bottom part of the crankcase as a vapor (see my comprehensive explanation above). As this point the fuel-oil droplets deposits on the various components, lubricating them. A short time later, the piston moves down to compress the vapor below it; the combination of compression and residual crankcase heat results in a phase change converting most, but not all, of the residual vapor to a gas. As the piston moves up the gas below the piston is allowed to enter the "combustion chamber" for ignition, the power stroke."
Last edited:
Never said that the oil portion was a gas and you know that. In fact for lubrication to take place at all it depends on the oil not changing phase. The gasoline portion of the pre mixed fuel changes phase to a gas and the oil portion does not. Are we clear?
For the umpteenth time. Premix enters the motor in liquid droplet form. The gasoline portion changes phase to a gas and deposits the oil on the rotating assembly.
I dont feel the need to quantify the cooling effect from the gasoline changing phase because it really does not matter at this point. It happens and it is significant. If you do the research you will not be able to refute this or anything else I said.
Last edited:
MolaKule
Staff member
Q
When this mixture is combusted, both oil and fuel are combusted. Before the phase transition of the fuel-oil mixture droplets into a gas, those vapor droplets lubricate the lower rotating components and the rings as the piston moves down past the input port.
Furthermore, since the gas phase contains components of both fuel and oil, it lubricates the upper cylinder walls as the piston moves up for its combustion phase. Fuel alone cannot lubricate the upper cylinder walls which is why a two-cycle oil is mixed with fuel.
How you can magically separate chemical components of the lubricating oil from the fuel in the premix denies reality.
Here we go agaiin with your circular explanations. So you are saying we have some kind of magical distillation/seperation process going on within the crankcase?
By this statement you still do not understand that the premix is a low viscosity mixture of lubricating oil mixed with fuel and that it is the oil, with its oil film and additives, that actually provides lubrication.
When this mixture is combusted, both oil and fuel are combusted. Before the phase transition of the fuel-oil mixture droplets into a gas, those vapor droplets lubricate the lower rotating components and the rings as the piston moves down past the input port.
Furthermore, since the gas phase contains components of both fuel and oil, it lubricates the upper cylinder walls as the piston moves up for its combustion phase. Fuel alone cannot lubricate the upper cylinder walls which is why a two-cycle oil is mixed with fuel.
How you can magically separate chemical components of the lubricating oil from the fuel in the premix denies reality.
- Joined
- May 31, 2024
- Messages
- 744
Rudimentary stuff for sure. I still see no answer to how "large" of a portion of the cooling evaporation of fuel accounts for.
If it interests you that much do some digging.
What I described is exactly what happens. That you don't know that is telling.
A guy that allegedly developed a two stroke oil should at least know how one is lubricated. So you can wax on all you want about chemistry if that horns you up, but you clearly dont know what your talking about.
Last edited:
Similar threads
- Locked
- Sticky