Everything You Don't Know About 2 Stroke Engines 🤯 

Where?

For sure, and people still wanna argue that 4 strokes are better 😂than

Outboards are absolutely awesome in 2 stroke configuration as well.

@@awesomeproducts1582 It's the noise and oil/fuel mixing that people don't like - plus smoke.

@@paulsawczyc5019 Just the commie EPA son,--who duped those people. Properly jetted for the most power, and they actually make very little smoke. Only on start up. What I don't like is the EPA force, that drives up the cost of everything,---which is why you won't be able to afford much.

2 stroke go braaaap

Dang I hope they get better

I bet neither mode works as well as they do in separate engines.

Why do we give praise and agree with people when they really don't know exactly what they are talking about? Because we don't know the difference. I do. :) Sue your schools son. They do the same thing today.

I do know, what this vid and you don't. When you don't know much, any information can be seen as correct information. That is why we graduate form our schools today,----------------------stupid.

How do you know? I do. :)

Thank you!

Fr

I build 2-stroke engines for a living, racing applications and recreation. If you have "seen" a lot of other explanation,---they were all probably just a bit worse than this one. I give this a B- for technical information, and a F for the EPA propaganda.

How do you know?

How do you know? You don't.

Yeah - it's almost kinda like a pump.

Nope, the bot did not explain the pipe well. It may be the most naive explanation I ever heard. I have made a living modifying 2-stroke engines for the last 2 decades. I see a brain dead bot here reading from a ill educated HS research paper. :)

Yeah not too shabby !. Where in Au are you ?

Hi. Tell me those points so I add them in other video. Thank you!

@@pauloconnor7951 In Melbourne, Sthn Burbs, grew up here.

@@repairman22 A bit too lengthy for the comment section. I do 2T vids that go down the rabbit hole on each topic so maybe look over those if you like. I sent some via your email. But as mentioned your vid covers the basics fairly well.

Sure. No problem.

That's not a liquid cooled engine so yes that is 2 stroke smoke.

can be bluish, depending on mix ratio...

not loop charged you mean cross flow. yes they had heavy pistons and less potential as in a looper outboard, but they idled like a sewing machine and most where very quite.

@@ct1762 "Loop scavenging" replaced "cross scavenging",---a long time ago. 70 years maybe?

Finally, a guy who knows what he is talking about. Kudos. Doug @ ESP (Earth Surfer Performance).

They are the same thing. Schnuerle (sp?), developed "loop scavenging". You are right though, the programmed bot missed that,--and the fact that a sound wave in the pipe, that the bot confused with only pressure.

what are you talking about? im an outboard mechanic and have only seen 2 crank seal leaks in motors from the late 1970's on through the early 2000's have a crank seal leak. o rings and oil seals. extremely effective!

@@ct1762 He is talking about the normal maintenance that he is too lazy to do. Factories usually don't sell new engines in those worn out conditions. :) Pretty sure this guy hates shoe laces. Too complex, and he does not have time.

Really ?. Who does that please ?

​@@pauloconnor7951That's irrelevant. The only things that matter, are power, reliability, and light weight.

@@Bill-sp8kb i agree with that but for boats, having a DFI 2 stroke that gets 35% better fuel economy at cruise is huge! some are even better than that like an OptiMax

When I first read it I thought the same as you. Then I understood the formula that I put on the screen. 150/100= 1.5 so, if i have 1atm, then i will have 1.5atm.

But, the back pressure will help hold in the fresh gasses from leaving the ex. port at lower rpm's, before the sound wave is in effect. We use the calculations of "sound speed" to created a proper length and geometry tuned pipe. If you build too much pressure, (a small diameter exhaust end bleed, the end of the exhaust), then the engine will get hotter at higher rpm, like the close cats on your car overheating your engine in an effort to burn every hydrocarbon. Nope, the EPA does not care how long your gas engine lasts, unless it is a shortened live span. I don't see Toyota ads today, like we did 40 years ago, bragging about 300,000 miles.

Then I would not buy a modified engine from the bot. :)

You are talking about supercharging the intake. But on the 2-stroke, when the transfer ports are open, filling the cylinder, so is the exhaust port. So it all blows out the exhaust. I am sure the flowing action would clear out the burnt exhaust gasses better in the head and cylinder area, and maybe find a bit more power because of that purity of fresh fuel/air. But you will be blowing a huge amount of fresh gas/air out of the exhaust port at the same time. Until communism in china has to deal with an EPA,---I have to consider their arguments against gas engines, coal electric generation, etc., a load of crap.

sure. can be done but it's very hard to force-induct a 2 stroke. so much boost is lost to the exhaust port, but proper port timing can minimize this.

The vid is wrong with compression ratios. it compares the 2-stroke method (about 8:1), to a full stroke 4-stroke engine (12:1). 10:1 with the 2-stroke method (only the area above the ex. port is calculated), and you probably could not run gasoline.

@@EarthSurferUSA My Jawa has a 10:1 compression ratio. I have a compression tester and that is correct and have to run it on 98 octane gasoline. As you say only the area above the exhaust port when it is sealed by the f irst piston ring is calculated as swept volume for compression ratio calculations.

Rotax 2 stroke engines used in microlights (jet-skis too?) have rotary intake valves. Also, model airplane engines typically have hollow crankshafts that incorporate rotary valves

Traditional 2 stroke Vespa motor scooter engines use a rotary valve intake.

"The transfer port and the exhaust ports are the ones open at the same time." Nope. The exhaust opens much earlier then the transfers. The cylinder pressure has to "blow down" to about zero pressure, so the transfers can flow into the cylinder. The measured number of degrees of crank rotation between the exhaust opening up, and the transfers opening up, is called "The blow down phase". It would not run if they opened at the same time. "Loop Scavenging" is the correct term. I would like to build a rotary valve engine from scratch. I think I can get the most power form them.

@@EarthSurferUSA I didn’t mean to imply that they both open at the same time, you are correct, the top of the exhaust port is higher in the cylinder than the top of the transfer port so that the high pressure in the cylinder can blow out before the transfer port opens. They are both fully open though at bottom dead center. The intake port is never open when either the exhaust or the transfer ports are open.

No bot vid in the world----knows that. :)

Excluding the force of the EPA, probably the longevity of the engine. A tame 4-stroke ( not a racing engine), will go a lot longer than a 2-stroke with out a top end rebuild, but costs much more to rebuild it.

Must have been faster, with less friction. Older road racing bikes had 1 ring, eg Yamaha TZ 125, 250, 350, 750cc

@@liloldsnoopy4279 Less friction, but more blow by. Racing engines still use both.

many many outboards used DFI/Ficht/HPDI/TLDI direct injection with no problems in crankcase heat! most used a vapor tank that recirculated warm fuel by cooling it down and putting it through the crankcase. oil had a seperate pump directly to cylinder walls and crankcase, which is what really helped combined with raw water cooling

Nope, (to the best of my knowledge). KTM is using "transfer port injection", (because of EPA force). What they dropped is the direct injection into the cylinder during the compression stroke, (like this vid shows), because it requires much more pressure, probably making metering and reliability not as sound. The bottom end temps will be the same. But, there is the cooling factor you mention, so maybe I am wrong, and the bottom end just gets warmer with only oil injection on the bearings.

In any part of the video, the piston goes under the intake port.

@@repairman22 Yes, & it's wrong. The piston top never goes low enough to open the intake, it would defeat the scavenging if it did. Look at any 2 stroke, Your video is wrong!

​@@Not1Editsorry, if the piston doesn't open the fresh air intake port, nothing will happened.

@@franckn8338 YOU HAVE NO CLUE HOW A 2 STROKE SINGLE CYCLE ENGINE WORKS, & IT SHOWS. INTAKE VACUUM IS CAUSED BY THE PISTON GOING UP & AWAY FROM THE INTAKE PORT WHILE COMPRESSION OF THE CHARGE THAT CAME THRU THE TRANSFERS IS ON IT'S WAY TO COMBUSTION. AS THE PISTON GOES DOWN ON THE POWER STROKE IT IS OPENING THE EXHAUST TO LET SPENT GASSES OUT. WHEN THE EXHAUST IS ALMOST GONE THE TRANFERS BEGIN TO OPEN, & SCAVENGING TAKES PLACE DUE TO THE DECENDING PISTON PRESSURIZING THE LAST INTAKE CHARGE & BLOWING IT OUT THE TRANSFERS, SWIRLING AROUND THE COMBUSTION CHAMBER & OUT THE EXHAUST BEFORE THE SOUND PULSE FROM THE EXPANSION CHAMBER HOLDS IT THERE & THE PISTON RISES & CLOSES TRANSFERS & EXHAUST PORTS AS THE PISTON COMES UP ON THE NEXT STROKE DRAWING IN THE NEXT INTAKE CHARGE FROM UNDER THE PISTON, NOT ABOVE IT. THE INTAKE IS NEVER ABOVE THE RINGS IN A 2 STROKE.

@@Not1Edit Well it happens in a 50cc engine called Huskvarna Flinta. The aftermarket crankshaft is wrong, they have increased the stroke by 2mm but only downwards, so the piston opens the intake port.

I found several technical mistakes in this vid., coupled with EPA propaganda.

It all depends on the size of the engine. little 2-stroke nitro engines rev to over 30,000 rpms, (and can not use a piston ring because of it). And I build 30cc gas 2-stroke engines for a living, that probably rev higher than anything with a ring, staying together at 21,000 rpm. How much rpm it can take, pretty much primarily depends on the size and weight of the parts. How would you like a screaming, 5lb little 21,000 two stroke engine for a noise maker at the bike races? They have a sound---all their own. :)

@@EarthSurferUSA what are these 30cc nitro engines fitted to? 🤔👍

As a 2-stroke engine builder myself, I would have to disagree with #3 a bit. I would say the rotary valve intake offers the best performance, then reeds, then piston port. The reason is the difference way they fill the crank cases. Reeds offer a wider power curve, (and usually more power, as piston ports rarely have a 5th transfer), over a piston port, and it flows based on different pressures and not piston location, and can have an open duration of the intake to a full 360 degrees, allowing fuel to flow when ever pressure differences let it happen. But, the reed valve is an obstruction. Rotary valve, similar to the piston port as the flow is controlled by mechanical means instead of different pressures, has the ability to tune the intake duration at closing, and opening, where the piston port is symmetrical, but is more expensive to build. Obviously, the MX factories went with reeds starting in the 70's, because they are out performing the piston ports. But I think the rotary valve has the best potential because of that intake control, and no obstruction like a reed valve. I will listen to this vid, (which is probably a bot vid, just repeating what it learned, correct or incorrect), and I bet I could find other discrepancies also. :)

But the reed valve is of little use, if there are no reed transfer ports to increase time area of the transfers, so we can increase the time area of the exhaust port to match. I have only seen one piston port MX bike engine (an old Montessa), that was able to use a 5th transfer. It was the only time I saw that unusual casting configuration, but there may be more.

@@EarthSurferUSA - finally, a RU-vid commenter that knows of what they write! I completely agree that rotary valve 2-strokes have the highest potential power output (I was simplifying my comment for the majority of the RU-vid audience). The title of my senior undergraduate thesis was, "Expansion chamber exhaust in loop-scavenged two-stoke engines". I did a lot of research and theoretical work, backed up by cutting, rolling, welding and testing several different exhaust systems (I even built a dynamometer from scratch for testing). My test "mule" was an old TZ-250 Yamaha. I ended up with a set of "top speed" pipes which sacrificed torque spread for top speed, and a set of "acceleration" pipes for tighter tracks with no significant straits. Those were the days (I still love the smell of burning castor-bean oil)!!

no?

@@MSKarting No what? Have a look

It depends on the size of the engine, and the tune (is it a race engine, and what kind of racing?). Typically, 2 stroke can be made to rev higher, because they have less reciprocating mass and no poppet valves. Now, if we go by rotations of the crank, I am seeing high revving 4-strokes. But if we go by the entire power cycle, (each spark, twice as may crank rotations for a 4-stroke to complete one cycle), than that would be half. But we measure crank rotation only. I build 30cc (approx) racing 2-strokes for a living. let me know if you can find a 30cc 4-stroke that will rev to 21,000 rpm with out breaking.

@@EarthSurferUSA agree, i race with a 100cc 2 stroke kart that revs up to 20,000 rpm

Nah

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