Fuel/Oil mix

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Fuel/Oil Mix.

Well, there's been a lot discussion on this subject. I think Max2cam has finally summed it up. I don't pretend to be a Mechanical, chemical or a thermodynamic type of engineer, but believe there's alot of things going on inside a 2 stroke engine at the same time as discussed by this thread. This discussion could go on forever, with a lot of good points and opinions brought up in this thread, but believe it's finally come down to the summary Max2cam has stated. JMO. Lewis.
 
The man with the tallest boots wins here.

We yet need to discuss the venturi effect, pressure drops, cooling effects
of evaporation, and then reblend the variables of octane, temperature,
and/or synthetics, before this thread can achieve Walt Galer status.
Splitfire plugs burn more efficiently, thus cooler, so a well respected
chainsaw friend has told me.
In the past though, when ever I would encounter people watching
flames from their cigarrettes or lighter, indicated to me that they were
dropping acid.
One fun thing though, I freaked out a bunch of people once by getting
them to bet what would happen when I set a styrofoam cup full of water
on a glowing log in a campfire. Everyone bet that the cup would immediately
either melt or burn, and the water would splash out. They were wrong.

But Lewis has declared that this issue is settled, so that should end it all.
 
Fish said:
The man with the tallest boots wins here.

We yet need to discuss the venturi effect, pressure drops, cooling effects
of evaporation, and then reblend the variables of octane, temperature,
and/or synthetics, before this thread can achieve Walt Galer status..


Shoot, Fish, we're just getting warmed up. So far, we've been stuck in the combustion chamber (cooling effects of evaporization was just a red herring...pun intended). We really need to get into the crankcase and see the effects of oil ratio on it's intended purpose...lubricating. I'd dare say that most cylinder wall lubrication comes from beneath the piston. Then, there's the bearings etc. Clearances need to be defined. Oil films and adhesion properties need to be looked at. This thread could rival the "Official Joke Thread" for content.

Uh, that's not sour mash in your tumbler, is it?
 
Gasoline offers roughly 17,500 kj/liter of energy going into the saw, from that take:
40% away for the heat energy that goes out with the exaust
25% away for the energy that is harnessed by the crank
10% that is lost as unburnt charge or burn up in the exaust

that leaves only about 4375 kj/liter of heat energy that must be disipated by the saw, the total energy needed or absorbed to vaporize 1 liter of gas is about 200 kj. This said the cooling effect of the gas amounts to only about 5% of the heat the saw must disipate. Take into account a change between a 50:1 and a 40:1 mix and an approximation that oil is half as efficient a gas by weight for removing heat and the difference is.

about 0.2% or about 80 jouls of heat energy.
 
This is a good discussion about what goes on in the process of putting the fuel to work in our saws. Some of it is perhaps conjecture, but we are proof checking the points against known physical properties; whole lot better passtime than calling each other names. The fellow suggesting tall boots might see more on the inside than the out of his own! LOL!
 
Couple of points. yes, I did say that the gasoline must vaporise prior to to entering the combustion chamber. I never discounted the cooling effect gasoline has on the motor or doubted that gasoline accounts for the majority of the cooling in an air cooled motor. I did say oil has no effect on the amount of gasoline going through the motor, that more oiol in the mix doesnt effect vaposrisation of the fuel and I did bring up the point that oil must be vaporised prior to burning so it also in effect cools the motor as gasoline does.
No back to the question a previous poster had in regards to when the fuel vaporises. For sake of clarity it should be known that when I use the word vaporise, I am refering to the phase change from a liquid mist into a vapor or gas. As I am sure you all know fuel/premix leaves the carb in mist form. The first thing it encounters on its journey into the engine is a hot piston and con rod. This vaporises much of the mix. Whats left in liquid form enters the crankcase and encounters a hot crank flailing around at a speed that is hard to comprehend. Next it is forced up into the transfers buy a decending piston the under side of which is very hot. By now if the motor is tuned right and the fuel distallation curve is close the bulk of the fuel has undergone phase change and is headed to the combustion chamber where it is ready to be burnt. What little fuel that hasnt been vaporised and which has the ability to vaporise by this time is quickly phase changed inside the combustion chamber during the compression stroke.
I know there will be naysayers that discount what I have said, but it is scientific fact. I must also make the point that the process I described above is a ideal situation. Overly rich mixtures, fuel contaminants and the nasty high end components that are found in some of todays pump fuel allow some fuel to pass through the entire motor as a liquid and go out the tail pipe with out combusting( I am not refering to scavengeing loses).
Now for a simple real world things that prove my point. How many of you have torn down a two cycle and found oil everywhere in the crankcase, but little or no fuel? I have done many and they where all like this. Also take some mix oil and put it on your fingers and feel how slippery it is. Now do the same with premixed gasoline. Which has the ability to lubricate? This last little excercise is of vital importance to your engine, because without the fuel evaporating the oil would not drop out of suspension to lubricate your motor.
Another thing to consider is the effect carb tuning has on vaporisation and combustion. The carbs on chainsaws are very crude in nature and do not offer the tuning ability that a carb from a two cycle dirtbike does so I am going to use the bike as a example. When I raced moto-x typicly I set my pilot and needle taper so that the low end jetting was really lean while the mid and top where on the fat side. This provided for crisp transitional response while having max torque to pull out of corners. Now, many bikers dont have the knowledge or feel like messing with their bike to achieve this level of performance and typicaly they are easy to spot. They will go into a corner and let off the gas. after apexing the corner they will crack the throttle and you will see a puff of blue smoke and if you are close enough you will hear the motor bog/burble slightly(how much depends on how rich) and then rev out like normal. What is hapening here is that the motor at low throttle setting(after corner) is getting to much fuel to burn(vaporise) and as a result the combustion chamber temp is lowered to the point that alot of unburnt and partially burnt fuel is being blown out the exhaust(smoke).
I hope this clears up this subject alittle more for most of you. I have been snowmobiling since 8 in the morning and am a little tired. I will fix the spelling tommorow. :eek:
BTW to the poster that asked why do 4 cycles not smoke upon cold start. They most certainly do. Especially ones with crude carbs. Sometimes its less apparent because they dont have oil in the fuel to cause the blue haze, but non the less its quit apparent as you can smell the unburnt HC even if you cant see the smoke.
 
Last edited:
bwalker said:
BTW to the poster that asked why do 4 cycles not smoke upon cold start. They most certainly do. Especially ones with crude carbs.

Especially ones with 50:1 premix. ;)
 
Dan, you would be suprised how little that thing smokes. A puff at start up and thats about it in the next few years we are going toi go to e-tech outboards so the pre mix will be a thing of the past. Wonder of that old beast will run right on straight gas?
 
I hope you guys don't mind me jumping in here with this post.

I would like to say thank-you to all who have taken the time and effort to contribute to this thread and others on similar topics.

For someone like me who is basically a self taught, hobbyist parts changer with no formal training in engines. Being able to read the info that is being shared here is a godsend to those of us that are on the outside looking in. I'm sure I speak for a few others by saying that your efforts are not going unnoticed and are appreciated by many like myself.

Larry
 
The Long Mingling or Ripening Spark

I agree. This is a good thread.

The notion of a cooling effect within the gasoline engine by a "change-of-state" of the fuel charge inside the cylinder is a very old one. The controversy that goes with it is nearly as old as the gasoline engine itself.

The following comes from an old manuscript of mine about E.J. Pennington's supposed breakthrough 1895 discovery: "the long ripening or mingling spark."

It's given here purely for your entertainment in this mind-numbing quest to understand the infernal alchemy and hellish physics within the hydrocarbon engine. Bear in mind that the historical events described here took place in the late 19th century when people didn't yet knew the proper ratio between high-octane science and snake-oil. Maybe we still don't know. Nor what height boots to wear...

Max2Cam (Herb)

====================

From: "Airship Pennington and the Motor Cycle"

On the publicity of his demonstration of the Motor Cycle in Milwaukee, Pennington returned to Racine like a conquering hero. Over 200 orders for his engine poured in. New sizes of two to ten horsepower were promised in various layouts including a V-four. Stories about the Motor Cycle were widely circulated in the press and reporters thronged to Racine for interviews, but few were admitted into the great inventor's presence or allowed to see the Pennington engine up close. One visitor not turned away, however, was a reporter for the American Machinist, a young man named John Randol.

Sceptical at first, Randol soon fell under the influence of the "Elixir Hypnotique a Pennington." Mere days before the Chicago Times-Herald motor-vehicle contest took place, Randol's article hit the street. He wrote, "I saw...a heat engine of such exquisite simplicity that...a child might use [the pieces] for play-things; a machine...that...should not be able to even move itself; yet this incredible machine not only did move itself, but moved with such vigor of action as to drive loads far beyond its apparent possibilites."

Randol's article was the first detailed account of the Pennington engine and was simultaneously sceptical and yet fawning. Although Randol called Pennington's explanation for the engine's apparent super-efficiency at first glance "a ridiculously impossible theory," like so many others he was (in his own words), "first incredulous and then amazed, and finally enthusiastic."

Pennington's explanation was elegant in its simplicity. His gasoline engine needed no fins or water-jacket due to his unique discovery that waste heat from a typical internal combustion engine could be converted into useful work upon the piston. This discovery was Pennington's "long mingling (or ripening) spark," a patent application for which he had applied for that May. As experience is the best teacher, Pennington first took Randol for a fast ride on the tandem Motor Cycle over Racine's brick paved streets and across some railroad tracks near the factory. The experience appears to have satisfied Randol's lust for speed as a motorcycle passenger and he called Pennington's gasoline-powered bicycle "a demonical and demon driven" machine.

Afterwards at the factory Pennington cooled Randol's frayed nerves with French champagne, and sometime later permitted the reporter to feel the Motor Cycle's cylinders who found them "surprisingly cool" to the touch.

In fact this machine had the newly water-jacketed engine with just enough cruising range to scare the bejesus out of Randol, but the great inventor shamelessly pronounced that his engine actually ran better with "naked" cylinders. Then Pennington launced into an explanation of his greatest breakthough to date: the long mingling or ripening spark.

However many drinks Randol may have consumed by this time, he was now all ears. What he heard amounted to a mechanical revelation. Because the inventor now revealed to Randol that the spark of ignition during the power-stroke in the Pennington engine did not take place until the crank was 45 degrees past top-dead-center. Previous to this 45-degree ignition spark, however, another critical event took place within the cylinder. This was the addition of another spark in\0troduced earlier in the cylinder and that Pennington dubbed the "mingling spark."

According to Pennington this early spark did not ignite the fuel charge, but instead transformed the liquid hydrocarbon fuel into a vapor. Not only did this vaporization spark insure more perfect combustion that greatly increased engine power, but Pennington also proclaimed that according to the immutable natural laws of physics that during a change-of-state when a fluid is converted into a vapor vast amounts of heat are taken up by that process. This was the well-understood principle upon which refrigeration is based. Thus, with his premature non-igniting spark, Pennington claimed to have achieved an internal refrigeration effect inside the engine that was so effective that the cylinder and piston temperatures were kept at wonderfully safe levels.

Whether Randol totally believed Pennington's explanation remains an open question. But the reporter was clearly convinced that amazing results had been achieved. Randol stated that, "nothing approaching the weight and power given has ever been shown by any motor within the general knowledge of the public...No fire, no water, no boiler, no carburetor; only a few pieces of steel with a few brass-bushed joints, a battery weighing one pound, and a gallon of kerosene, put these with a bicycle, bringing the weight of the whole piece of wizardry up to 58 pounds, and a man may be carried by it on a smooth road a mile in 58 seconds, as a man was carried...in the city of Milwaukee a few days since."

Indeed smitten, Randol then gave his opinion of Pennington's breakthrough discovery. "The efficiency of the Pennington motor," wrote Randol, "lies in the effect of the first spark. This statement is as incredible to my mind now as when I first heard it from the lips of Mr. Pennington [and] the only agency through which this motor achieves its miraculous results...and so opens a new round of dazzling possibilities to the engineer."

Well?

www.atthecreation.com
 
A non igniting spark eh? sounds a bit like cold fusion! There have been some interesting combination engines that used gasoline to vaporise kerosene and make it burnable in a spark ignition system. Wonder if it was some version of this.
 
The fellow suggesting tall boots might see more on the inside than the out of his own! LOL![/QUOTE]

The FELLOW? What kind of quasi-****-fraternitysexual term is that?
Are you an arborist?
At least Glen and Ben shovel their poop with a Man's shovel, not a girlie
gardening trowel!
I have been nicey-nice with these new posting guidelines, but by God I will not be called a "fellow"!
I expect to hear from your lawyers with an offer!
 
I wish to take this time to formally apologize to the forum, as I am running
dangerously low on beer at this time, and I live in hillbilly country, which
frowns on purchasing beverages on Sunday, unless it is from the local, rich
bootlegger family, which I will not pay their price, those scumbags.
But never has anyone of them called me a "fellow", except for the gay one
that wears turtlenecks. But since he is kinda cute, I let him get away with
it.
He wears fingernail polish to match his chainsaw, to keep on topic.
 
Fish said:
I just tried the teaspoon/torch test, but had some complications. I will try it again
for the site's sake, but next time I will go outside.

Also I will get my parts guy to do it, he is not married.

Just wondering if you were able to rerun the teaspoon/torch test? :) :) :)
 
FISH, was that indeed you who who suggested we be needing tall boots around here? You are then truly a fellow of a learned society; one of the cognoscenti! Obviously intimately familiar with BS. As to your sexual preferences, I cannot comment except that I seem to remember some past snickerings of misogynism with LLamas being the standin. I guess some lawyers do indeed get involved in breeding contracts, but since I have cows and chickens but no llamas, I have nothing to offer at the moment.
 

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