How Two Stroke Engines Work (How It Works - 2 Stroke)
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- čas přidán 24. 07. 2024
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Learn how a two stroke engine works! We look at the two stroke engine’s main components, how it works, its applications, advantages and disadvantages. The animation clearly shows the cycle of the engine as it moves though the induction, compression, power and exhaust strokes. Coloured arrows are used to show the movement of the gasses through the engine.
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▶️Introduction
Two stroke engines are of a simple and robust design. They are almost always petrol/gasoline fired engines. Two stroke engines are spark ignition type engines and are used primarily for small or very large applications.
The two stroke engine has found widespread use as it is relatively cheap and has a high power to weight ration compared to other prime movers.
Components shown in this video include the crankcase, crank webs, piston, con rod, injector, cylinder liner and spark plug.
Advantages
Simple design.
Robust and reliable.
Few components.
High power to weight ratio.
Disadvantages
Not very efficient compared to other prime movers.
Noisy/loud compared to four stroke engines.
You can read more about two stroke engine in our technical encyclopaedia:
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The more I look at stuff like this the more I'm in awe at human ingenuity.
For many years I never fully understood how a two stroke worked. This video is outstanding.
This is a great explanation of 2 stroke engines. Thank you I understand this much better now.
One of the best videos ever seen about the 2 stroke......
So glad you covered the inefficiency-- key to understanding, especially the loss of air-fuel during the intake stroke.
Doing our best!
Thank you so much for this! I just have an individual project starting at uni involving improving a two stroke engine, and this really helps! TYSM!!
Glad it helped!
Great video - thanks! May be worth mentioning that the fuel is pre-mixed with lubrication oil which means the lubrication is done within the mixture and thus no need for all the complicated lubrication systems the 4-strokes need :-)
It made me understand the workings of the engine far better than the other videos.
One of the best videos ever seen about the 2 stroke. PS your cylinder is worn ;p
How automatic transmission works like scooters .
Nice video but I don’t think you are explaining it fully. What causes the exhaust gas to exit the cylinder? Does it exit before the piston reaches the transfer port or does the incoming gasses push the exhaust out.
Yeah the best explanation ever
@@smithfam90 suck
your*
Super detail and easy to understand! Thanks so much
Thank you very much. for a novicel ike me, this is practical and easy to understand. Keep progressing.
What an explanation man!!! Just superb✨
To the guy that replied to my comment. I teach at a technical high school and the program is called "Outdoor Powersports" . We learn about and work on motorcycles, ATV's & snowmobiles and it was one of my students that noticed the piston! I will let my students know of the kind words of encouragement you sent our way, thanks so much
Excelent video and excelent explanation. PERFECT!
This is such a helpful explanation. I am currently studying to take my EETC Technician Exam and this is the perfect supplemental material. Thank you so much!
saVRee 3D I definitely will. You rock
excellent explanation, well done!
It's nice to understand basic concepts 👍
Good vid. I would like to see additional discussion about how the exhaust (expansion) pipe shape creates a shock wave that helps to prevent unburned fuel and air from escaping. This is why two-stroke motorcycles have the fat exhaust pipe whereas four stroke engines have a pipe with consistent diameter.
I was waiting for an explanation on why the air fuel mixture doesn't all just go out the exhaust pipe, i assumed there was some sort of clever valve that would be controlled by the direction of travel of the piston, but this sounds way more interesting
Fantastically clear explanation.Thanks.
I learned in trade school suck-push-bang-blow and still remember 40+ years later! Great explanation!
The best video I have seen . Very well explained. Well done.
The best video about engines that I have ever seen.
Great explanation on the 2 stroke engine!
nice explanation thank you this helped me a lot
Very well explained. Thanks.
Very informative video and well explained. First time I have understood a 2 stroke
Glad it helped
Great Video, bro... I' really touched from the human & intellligent touch of your explanation
Best regards from Naples, Italy
Very detailed and complete. Excellent work. Liked and subbed
Awesome animation and explanation!
Just what i wanted. thank you or the best explanation
Very good two stroke video.. 👍
I am from Kerala, India
Very well done video. Thank u
Thank you and Well done............Any plans to entend to the carb and reed valves ?
Thanks for this video... We want more free videos to learn
Very good explanation!
really helpful, thank you
the upward motion of the piston also creates a vacuum to bring in the mixture.
Impressionante a tecnologia de um motor à pistão e seu mecanismo. E lá se vai quase um século e meio de sua invenção.
Best video on 2 stroke engine
Awesome way to explain it man. I got my first bike and i was curious about the difference between 4 and 2 strokes. But i still can get what makes the piston go up.
Inertia of the crankshaft ?
And the flywheel
Great video, thank you!
4 stroke makes more power per stroke (efficient)
2 stroke fires twice as often, that equates to 25-40 percent more hp per cc
Two strokes are self supercharging engine. As you have been shown in this video fa showing the air/fuel mixture being compressed in the crankcase 1st above atmospheric pressure ..then it is compressed again in the combustion Chamber becoming supercharged
Best explanation !Thanks
So useful!!!
Great Video...Just to reinforce my understanding, if I have an engine that idles at 2,500 RPM is it safe to say that the piston completes 1 up/down stroke (crankshaft revolution) 2,500 times within a minute?
Do you lose some air/fuel mixture in the upwards compression stroke? I'd say if you compress it but for a moment the exhaust port is opened you lose some compression and mixture.
good work
Very well explained. How come the crankcase can keep lubrication if gasoline is a solvent ?
I know two cycles engines uses lubricant and gasoline mixed on the tank but will t keep the crankcase still lubricated under these conditions?
I love the thumbail zundapps are the best 2 strokes out there
Very nice ! Thank's
¡Excellent! I remember an Auto Union ( the brand that eventually became Audi) when I was a child had a two-stroke engine (motor de dos tiempos) and there were many on the streets. It uses a mixture of petrol and oil so its combustion should be carefully controlled to meet today's enviromental standards. I don't know if TS bikes are still manufactured
great commentary!
Thanks!
When the piston comes back up are you losing some of the air/fuel mixture out of the exhaust port before compression above the exhaust port?
Thanks😊
The 2 stroke engine was patented by a Mr. Alexander in the 1860's as an improvement over the Otto 4 stroke engine.. Like most things in the world, the 2 stroke engine was yet another British invention. The Alexander 2 stroke features a charging piston and chamber. Crank case induction (British again) didn't appear until the 1890's
Ships use the Webb 2 stroke engine, which has a wet crank (like a 4 stroke) and an inlet valve in the cylinder head. The Webb 2 stroke engine predates the crank case induction 2 stroke by over a decade, originating in the late 1870's.
On a ship's Webb 2 stroke engine the cycle is as follows (starting at BDC):
The piston closes the exhaust port (which opens as the piston nears BDC).
The inlet port in the cylinder head opens and pressurised fuel oil is injected.
The inlet valve closes.
The upward travelling piston compresses the fuel oil.
At TDC the compresses & hot fuel oil spontaneously combusts.
The piston travels downwards on the power stroke.
The exhaust port is opened near BDC.
The piston reaches BDC and the cycle is repeated.
The earliest Alexander and Webb 2 stroke engines of the 1860's were fuelled by coal oil. They were used by generators and pumps. 4 stroke generators and pumps used domestic gas supplies (coal gas). Liquid fuelled engines didn't appear until 1885 when Gotlieb and Daimler invented the world's first motorcycle running on kerosene (petrol didn't appear until the early 1900's).
In 1886 they invented the motorcar. The modern safety bicycle was also invented in 1886.
@10:55 the motorbike and the mower are 4-strokes. I don't like water, so IDK what the boat motor is.
You should have said something about tuned exhaust pipes (ie: what they are/how they work).
keep the good job up.
Well done, I 'scribed and Liked to help the channel although honestly I'm just seeking some quick remedial-overview, am familiar with/use timing wheels and port my engines well most of them, anyways they're all chainsaws and I found something fascinating / confusing / conflicting in your presentation here (not saying you're wrong, you're certainly *not*, just saying it makes me unable to understand something chainsaw-porters do), you conceptualize the '4 phases' so well and I knew/understood the powerstroke (downstroke of piston) however, in chainsaw-porting, one of the most-common tricks/moves people do is to literally go and raise the exhaust roof with a dremel to 'decrease its timing' (ie if OEM spec had the exhaust port cracking at 110* ATDC, someone grinds/dremels their exhaust roof higher so that now it's cracking open at like 105* atdc, 98* atdc etc.) Would love to know your thoughts on this - I have engines ported this way - it does seem to work but I just don't get *how*, I mean I can understand the old thinking of "higher exhaust roofs mean higher RPM but *some* drop in torque", that's how chainsaw guys talk about it, but in understanding the 2-stroke better I can't help but think that it's not "a fair trade" IE the increased RPM is accompanied by a proportionately-larger *loss* of torque in the engine. Would love your thoughts on this!!
The other main approach is to CNC the cylinder base, and the squish band, to effectively drop all the ports' heights (and increase compression, or 'dial it in' since the #'s cut are chosen by "squish" or the amount a piece of solder gets squished in-between the piston & the squish-band, in chainsaws people just jam solder in 1 side and test that way....I know it doesn't account for piston-rock, I also do measurements from base-to-band now to accompany my squish #'s -- surprise, surprise, there is less variance reflected in "squish #'s" than in true measurements of base-to-band, obviously because piston-rock is "smoothing out" things a bit!)
Thanks a ton for such a great presentation here, have watched several of these hoping for "aha's", lol, and the way you put "the 4 phases" (intake/compress/power/exhaust, repeat!) totally helps me with putting things in perspective!!
Best job of all
Nice explain tq sir
Wow. You have explained it so clear. Nice video🤙
God bless you Sir thank you
Is there lubrication in crank shaft chamber? It will mixed with fuel and air
During the compression, is the mixture not going to enter the exhaust port?
excuse me, just think what the application render to make that animation, thanks for the response.
This is the most learneable video i hawe ever seen of a 2stroke engines funcktion, Thenk you :)
What if you intentionally dumped a lot of air-fuel mixture into the exhaust in the suck-phase and had a 2nd spark (or just having high exhaust temp) and a turbo to extract the energy?
Great video and explanation. could you please explain why we need to mix oil with gas (petrol) in two stroke engines?
Because of the design of the cylinders with the ports in the sides, oil can not lubricate the entire cylinder. Adding oil to the fuel allows lubrication from both sides of the piston.
In this explanation, at some point both the transfer port and exhaust are open. So the doubt here is, does the air+fuel from transfer port not ooze out from exhaust, as the piston moves up compressing the mixture?
Question. When the air mixture is going in, it goes to the bottom but is the transport port open when the air mixture is going in? Because if it is wouldn't the air mixture being wasted?
Nice video 👍🙏
Great thanks.
Been maintaining my 4-stroke engines for years, but have never touched or even ridden one of these.
Seems these would be lower maintenance than a 4-stroke.
Cheaper to rebuild for sure, not cheaper to run considering all the oil you have to buy to go in the gas and they can drink the gas pretty fast. The noise like a 2 stroke dirtbike makes make neighbors really hate you also lol, but you can get almost the same amount of power from an engine half the size like a 125 2 stroke can out run alot of the basic 250 4 stroke trail bikes.
Will not fuel mix with lubricating oil?
While moving from suction port to transfer port...
What keeps the fuel air mixture from escaping through the exhaust port during the compression stroke?
Is there engine oil in the crankcase?
For one thing here, the exhaust port is WAY too high, releasing hot gases to exhaust avoiding doing much possible work, besides enabling much "short-circuiting"- having incoming charge from transfer port go right out the exhaust. Can you spot the other ways the port timings (because of location) are seriously sub-optimum? The tuning of a 2-stroke also depends very much on area and shape of the ports.
As I was alluding to, the phenomenon of "short-circuiting" is some air/fuel charge going from transfer port(s) right out the exhaust. Exhaust path must flow very freely in a 2-stroke or NO power. Short-circuiting in common crankcase-scavenged 2-strokes is so bad for emissions that Zenoah/Komatsu developed stratified scavenging to greatly reduce it for Redmax. Husqvarna bought Redmax. Many references available- Google is your friend.
Awesome
nice video
Loved the vid, then used a 4 stroke bike pic! Please swap for a 2 stroke dirt bike.
that is why we have to put lubrification oil mixtured with the gasoline.Because the fuel go in the crankcase and it needs oil to reduce friction.
I need to know how to make the mixture. I got the1 litre but need to know how to make the mixture?
Best of all
Pleas sir, Do the all videos automobile in 3D animation upload
Best video
During the upward journey of the piston ( before the spark happens) , will not some air-fuel mixture pass through that exhaust pipe and be wasted ?
12:23
just a quick question do you guys call it only the power stroke because in canada we say combustion stroke
Thanks
Welcome
Explain what a reed valve is please. What a a pulse port for on atwo stroke? What is a rotary reed valve used for? How does a Rotary reed work and why do two stroke engines such as Snowmobiles and motorcycles use them if the use a carburetor?
When the AF mixture is in the crank case, is it primarily liquid or gas?
Gas
at the moment of combustion chamber compression... the outlet point is opened... why not some air fual mixture escaped that way when piston is returning to top end??
when the piston is at BDC both the scavenge port and exhaust port are open. Can anyone explain how unburned air fuel mixture which is coming from the scavenge port into the combustion chamber is prevented to escape out from the exhaust port??
it doesn't get prevented to escape. part of it escapes.
You need to ad the flapper and the way of the sound wave coming back to the combustionchamber
how to modify the rinse hole to increase power
I'm sure i missed something, but when the piston moves up again to compress the fuel air mixture, the exhaust canal is open for a small time until the piston closes that opening. Will you not lose a great deal of fuel and compression that way?
@@savree-3d thank you for your prompt reply! I bought an old rusty 50's lawn mower engine recently to try and repair as a project with my dad and my neighbour. I have very little knowledge about engines, that's why I looked up your video. It was very informative, thank you for a great video!
He completely left out the reed valve system ALL two stroke engines use EXACTLY for that reason alone. The reed valve is a box with a flexable thin metal reed that flexes under pressure during compression preventing lost compression and only allows the exaust reed to open at a certain time PREVENTING what you stated. Some engines use a round reed valve that operates on a timing wheel with an opening that come into alignment at exactly the right time . It usually works off a cam shaft the is set to operate off the flywheel or crankshaft. He never mentioned a pulse line eather. This line utilizes some of the back pressure in the bottom of the engine to operate the fuel pump.
Yes, unburned fuel mixture is released into the atmosphere, thus why the EPA no likely the 2 stroke.
do intaked mixtures of engine and fuel doesnt goes out to exhaust valve when they compressed? cause the exhaust valve is open before the piston goes up
@saVRee 3D
Is it used only in motorbikes?
Why do the engineers not design a 2 stroke with restriction on the exhaust port, so that the little amount of air fuel mixture is not wasted during the Piston downward movement or compression?
is it the same like 2 stroke engine 1 cyclinder motorcycle. like kawasaki k-1 115c?
and any oil filter to change for? or just topup with new M oil?
- Brunei ( Borneo )
@@savree-3d Honda MB5 and MT5 series mopeds have a separate oil tank with pump. You put normal "4-stroke" petrol in the tank and that oil pump mixes the petrol from the tank with the oil from the small separate oil tank. I suppose that setup has some sort of oil filter.
What causes the piston to move back up instead up remaining in the down position after explosion?
Inertia and the crank counter weights.
What is the problem if engine oil goes to exhaust ? Plz give me a advice tnx
You do know that a two stroke used a gas oil mixture? Some engines use an oil injection system so you do not have to mix the oil with the PETROL. Those type of engines use a metering system using a system that delivers more oil to the cylinder the more the throttle is given. These engine use a carefully calibrated syatem that makes it more efficient and less oil is used than a straight gas oil mix. An oil leak on this type of system could indicate a bad oil seal or bad oil line.