@Rod Knox Two strokes don’t allow a full stroke of power during combustion. Stroke one combines power and exhaust strokes from a 4 stroke. The Bang-Blow of the Suck-Squeeze-Baqng-Blow of the 4 stroke cycle.
Part of the stroke is the exhaust event so complete combustion and the complete power stroke can’t occur. Intake and compression (Suck-Squeeze) are combined in the up-stroke. That is not such a big loss with direct injection. 2 stokes are very weight and power efficient but emissions are the issue.
The oil in the fuel thing can be fixed with full pressure oiling systems.
There’s really nothing new about homogenous charge compression ignition engines. This is a compression ignition model airplane engine. It has no glow plug, the screw on top of the cylinder head adjusts the compression ratio for smoothest running. These engines burn a special fuel consisting of kerosene, ether, a small amount of amyl nitrate, and lube oil.
@Rod Knox Two strokes don’t allow a full stroke of power during combustion. Stroke one combines power and exhaust strokes from a 4 stroke. The Bang-Blow of the Suck-Squeeze-Baqng-Blow of the 4 stroke cycle.
Part of the stroke is the exhaust event so complete combustion and the complete power stroke can’t occur. Intake and compression (Suck-Squeeze) are combined in the up-stroke. That is not such a big loss with direct injection. 2 stokes are very weight and power efficient but emissions are the issue.
What makes you think four stroke engines use the entire stroke for power production?
Let me share the valve timing numbers for my four stroke Kawasaki Ninja 300 motorcycle with you.
Intake open 36 degrees before top dead center
Intake close 56 degrees after bottom dead center
Intake duration 272 degrees
Exhaust open 61 degrees before bottom dead center.
Exhaust close 31 degrees after top dead center
Exhaust duration 272 degrees.
@BLE.
Your comparative temperatures that gas ignites relative oil in liquid form is totally inconsequential as it’s the fumes of gasoline that ignite, and they will ignite at ANY temperature. That is what makes low temperature starting much easier for gasoline. I stand by my statement. This property makes diesel a much safer fuel for marine use and gasoline a much better fuel for cold weather use in all autos, with or without typical spark plugs.
The spark of a spark plug is very hot.
Don’t confuse flash point with ignition point.
For Diesel or Jet A the auto ignition temperature is about 410 degrees F
Gasoline is around 477-536 degrees F depending on octane
Butane is 761 degrees F.
Natural gas is around 1100-1200 degrees F
Some diesels are modified to burn natural gas, a homogenous mixture of air and natural gas enters the cylinder just like a gasoline engine. The injectors inject a small amount of diesel which auto ignites and sets the natural gas on fire.
The flash point is lowest temperature where there are enough vapors above a pool of fuel to ignite. Gasoline’s flash point is about minus 45 degrees F.
You get ignitable vapors at any temperature, buy they don’t ignite at any temperature, otherwise the fumes coming out of your gas tank would spontaneously combust when you opened the gas tank.
It practically takes an open flame to ignite gasoline vapors and it’s actually very difficult to ignite gasoline with a lit cigarette.
I remember a guy throwing a lit match into a bucket of gasoline when I was a teenager. it did not burn or explode. he was making a point about it not catching fire as easily as people think, but I was not happy about it
@B.L.E., I’ve studied IC engine theory in college. There I learned of a term called volumetric efficiency (VE). That is the actual volume of air passed through the engine divided by the theoretical value. I’ve also built a bunch of race engines using these theories to make lots of HP and torque. A limited explanation of VE can be found here;
The volumetric efficiency is a measured value that determines the effectiveness of the engine’s intake system. When engines were first designed, the effect of the mass of the air was not well understood and valve timing was Intake open at TDC and Intake closed at BDC, reverse for the exhaust. When the weight of the air/fuel mixture was included, the valve open-valve-closed pulse-pulse-pulse inertia of the airflow into each cylinder could effectively be used to force more air into the cylinder. So the intake valve was opened sooner and closed later making more power. Same for the exhaust. Good race engines can exceed 100% VE without supercharging, good street engines can approach 90%.
That is why cam timing, intake pipes, intake plenums, air-boxes and exhaust manifolds on street and race engines are sized they way they are; to increase VE.
Now the inertial effect depends on RPM, so this doesn’t work all across the rpm band but this is why you can feel a high strung engine “get up on the cam” as it approaches the rpm where all this comes together.
From the link, an estimated VE of a 2 stroke is much less at 55% even considering tuned intakes and expansion chamber exhaust systems. Since 2 strokes fire every rotation and 4 strokes fire every second rotation, theoretically 2 strokes should produce twice the HP for the same displacement and rpm. They don’t, and VE is primarily why.
I remember a guy throwing a lit match into a bucket of gasoline when I was a teenager. it did not burn or explode. he was making a point about it not catching fire as easily as people think, but I was not happy about it
Today, I attempted to ignite a paper towel wet with gasoline using a shower of sparks from a grinding wheel. I couldn’t get it to ignite.
The octane rating of gasoline is sort of the opposite of diesel fuel cetane rating. High octane gas resists auto-ignition due to high temperatures in high compression engines, that’s the whole point of octane rating.
High cetane rating diesel resists ignition delay. You want diesel to come out of the injector burning. Mix diesel with your gas and your gas engine will detonate like you filled up with white gas. So will oil mixed with gas, that’s why two stroke engines often call for premium even though they don’t have real high compression ratios, to offset the lowering of octane by the oil mixed with the gas.
Those old John Deere tractors designed to run on kerosene had compression ratios on the order of 4 to one because of kerosene’s ultra low octane rating.
@B.L.E.
I don’t really know where you are going with this. When you say mixing gasoline with diesel some how stops a Diesel engine, it has as much to do with the engine as the fuel. Diesel engines are made to run on diesel fuel, not gasoline. Gasoline is more volatile then diesel and that alone would affect how "mismanaged " excessive concentrations of gasoline would affect the Diesel engine. This increased volitility can destroy a diesel motor easily where the opposite is not necessarily true at all.
As far as this increased volatility of gasoline over diesel, it makes it more dangerous to work with in environments where the fumes don’t disperse well. “Flash points”, aside, that has nothing to do with this fact and is just a reassurance that some of us can google as well as the next guy,
It sounds like some others too are making a case that gasoline somehow won’t burn easily. We are saying nothing about spontaneous combustion; obviously you need a source. But to keep implying that gasoline is difficult to ignite when that is NOT the source of the debate. Gasoline is easier to ignite then diesel and if you want to run around thinking that it’s safe flipping lit cigarets around gasoline vapors, you go right ahead. Just do it somewhere else. The fact remains that gasoline is more volatile then diesel which makes it easier to ignite in colder weather and, under any conditions, except under water, you need to be careful about supplying any ignition source. That includes lit cigarettes. Fortunately there are fewer people who smoke.
You can never be sure of how concentrated the fumes are and how much oxygen is present to support the combustion out side the environment of the combustion chamber of an automobile engine. Don’t go flipping lit cigarettes around gasoline ! A gasoline dampened rag may not generate enough fumes to ignite by a spark. An electrostatic spark which you may have less control over in a semi enclosed environment with exposed gasoline and not a dampened rag can be disastrous. .
The point is just because gasoline vapors burn explosively when ignited and gasoline can provide explosive vapors at very low temperatures, it does not necessarily mean it’s easy to ignite. However, if there is an open flame anywhere in the room, the vapors will find it. So yes, gasoline is more dangerous to handle than diesel.
When one of our salesmen filled up one of our diesel pickup trucks with gasoline, the engine did not detonate or blow, it just stopped running, as if it ran out of fuel. There’s a reason compression ignition engines burn oil and spark ignition engines burn gasoline.
The temperature of an electric spark can reach nearly 10,000 degrees and it only has to ignite one molecule of gas for the chain reaction to spread.
On the other hand, just because something doesn’t burn explosively doesn’t mean it’s hard to ignite. I have seen someone light a cigarette with a soldering gun, in fact he borrowed my soldering gun just so he could light his cigarette with it. You can spend all day trying to light a propane stove with a soldering gun and not be successful.
In the old days, because fuel oil was so cheap, there were a lot of farm tractors with spark ignition fuel oil engines. These had the intake manifold inside the exhaust manifold to vaporize the fuel oil so the spark plugs could ignite it and had to be started and run on gasoline until the engine was hot before switching over to fuel oil. Because kerosene and diesel have octane ratings somewhere between 15 and 25, these engines had very low compression ratios. Usually less than 4 to 1.
Not only will a Diesel engine stop because of too high a concentration of gasoline, but it can very well be severely damaged. That gasoline is harder to ignite in many cases then other fuels, does give a distinct advantage in safety over those, but that is not to be construed that it is safe and it’s OK to be smoking with gas fumes abundantly present. For that reason, gasoline powered close quarter boats have long given way to diesel for that and economic reasons. Fires on boats are not to be trifled with by lit cigarettes and gasoline fumes. Personally, static electricity sparks can be quite powerful enough to ignite gasoline fumes vs diesel oil.
This motor concept is interesting enough to follow but more interesting is that it’s promoted by the competition with hybrids and the EV. Mileage mandates keep pushing ICE technology but to what end ? Burning fossil fuels more efficiently is a noble effort and worth it if it can’t be replaced. Though everyone would love to see that happen, my diesel powered tractors will still have the best power plant for the job for decades. There are some things that in our short life times at least, fossil fuels will have no replacement .
That, and gasoline is now in abundance domestically and we need to promote it’s further use to keep our economy growing and trade deficit under control by exporting gasoline. All in all, worthy of consideration if you aren’t concerned only with the environment but local economies as well. Maybe, these motors could find their way into industrial use and generators. Gasoline engines that ran like diesels have a definite set of advantages. I think you might see them in lawn and garden tractors before cars…I digress.
With compression ignition, the trick will be controlling detonation…Also, will there be an air throttle as in spark ignition engines or will power and RPM be controlled entirely with fuel metering and timing as in a diesel engine…The engineers have lots of variables to play with…
My curiosity over the efficiency of 2 stroke engines was based on those using blower forced induction such as the Detroit Diesels. I have for years wondered why no one had experimented with a gasoline 2 stroke engine using a blower and direct injection. As for wasted power in the 2 stroke process there is little power transmitted from the connecting rod to the crankshaft in the final 30* before bottom dead center. As the crank approaches BDC the continued pressure on the crank throw seems detrimental in fact.
Turns out that lots of experimentation has gone on (google ‘advanced two stroke engines’ for more links), but that the benefits weren’t big enough, it seems.
I clicked the cycleworld link and what comes up but a picture of a Kawasaki triple two stroke. What a beast! I had the 500 cc version and I’m not sure how many miles I put on it…the odometer only records the number of miles that the front wheel is on the ground.
One interesting approach to the over scavenging problem inherent in two stroke engines was the “split single”, basically a folded opposed piston engine with one piston uncovering the exhaust ports and the other uncovering the transfer ports. Puch, who’s bikes were sold by Sears under the Allstate brand was most well known for using this technology. The two cylinders were parallel but they shared a common cylinder head and combustion chamber.
I actually took a Puch/Allstate 250 for a short spin many years ago, not the most powerful 250 in the world but it was said to get excellent gas mileage.
