How 2-stroke exhaust pipes work | Offroad Engineered
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- เผยแพร่เมื่อ 26 พ.ย. 2019
- If you ride a dirt bike, you most likely have a 2-stroke, especially if you do Enduro. However, it is also likely that you don't fully understand how your bike works or why it has certain parts. For example, have you ever wondered why the exhaust pipe, one of the most important parts of the 2-stroke bike, is shaped the way it is?
If you haven't, here's your chance! After this video, you'll understand perfectly how it works, the reasons behind its shape, and how it affects the performance of your bike.
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#ExpansionChamber #2Stroke #ExhaustPipe - กีฬา
Thank you all for the love you have shown, I really appreciate it! 😊Note: No, I did not mention the first back pressure generated when the pressure wave reaches the divergent, which is responsible for creating some suction on the crankcase. I left that info out to make the video clean and simple (so everyone can understand it without being intimidating) and focus on the main pressure wave generated on the pipe!
Nah man you cool
Wtf
@@Mr.WellingtonVonDukeIII I'm busting my ass out laughing with your comments, you're a legend! xD
Good explanation, people always wonder about 2 stroke pipe shapes. It must have been a freaky idea , whomever first considered it back in the day
@@richardkey4289 Agree! 😂
I didn’t know Zlatan Ibrahimovic knows 2 stroke engines. 😜
Zlatan knows everything 😎
Lol
At first glance i thought he looks like zalatan
Clearly he doesn't
@@StepstoPodium no no... Zlatan is knowledge
“It’s all about the length of the pipe”
Facts
There is no such thing as the legend of the pipe ..you have no facts at all and no concept of what an expansion chamber actually does as it it was explained to me by the team Honda Elsinore research and development program located in Milwaukee Wisconsin at American Honda training facility.. this was required by all Honda dealerships back in the seventies when Honda brought out the first of their two cycle Elsinore racing motorcycles as I was sent there by my dealership to learn all the technical aspects of 2 cycle Racing Engines
Sure it isn't! 😂
Thanks for the comment though, I appreciate you letting us know your experience on the matter! It must have been a great experience that seminar Honda USA did! Great to see that even back then companies invested in those kinds of events for their employees 😊
donnie baker who are you taking to?
In short: “According to some asians, it is not about the length of the pipe“
“It’s actually the technique” lmao
team 2 stroke for life honestly
👌😂😂💪😊
Im team both 2 stroke for wood and 4 stroke for track!!! If it’s got two wheels and knobs it’s a win for me ✊🏻
That seems backwards lol
Chris Webb idk 2 strokes a much easier to ride through tight tracks and hills, just abit more clutch work, but that’s quite easy, on track 4 strokes rip
@@huskyluva2180 four strokes rip because two strokes where ban from racing on tracks ...since the night at the indy mile when kenny roberts won the indy on a TZ750 two stroke inline four cylinder yamaha that in stock tune made well over 150 horsepower compared to all the four strokes barley make 100 horsepower ..it is impossible for the same size four stroke naturally aspirated engine you ever make more horsepower than a same size naturally aspirated 2 stroke that's why they were banned from MotoGP and the dirt track if you can't beat the competition get rid of it that is how we do it today
In early days the exhaust pipe was also referred to as an “ extractor” and the smaller pipe at the end was the “stinger”. M/Cs sometimes came with narrow stinger openings to get more horsepower but it caused the power to fall off at low rpm so commonly the stinger was widened in diameter to get power at lower rpm and prevent a bike from ‘falling off the pipe” or losing power. There were no silencers when I stated racing.
I ice raced Mercury sno twisters in the mid seventies and the pipes on those machines where never duplicated. Mercury even had Tipsters as modifications to enhance rpm. How to cut and shorten for a given rpm. Very high tech at the time. I believe it was Les Cahoun that developed those pipes. A talented 2 stroke engineer that ended up at OMC in their engineering room. A book called 2 stroke tunrs handbook was our bible in the racing days of design and mods. Cool stuff !
Excellent clear and detailed explanation!!
I’ve been wondering how this worked for decades!!
Thankyou👍🏻
Science 🤘
Biatche lol
Fuck yeahh
@@radowane101 ahhh you said it for me
I’ve been wanting to know this for the longest time
A good explanation to the black art of two stroke exhaust pipes.
Thank you for watching! 😊🙌
Thank you for the good learn on 2 stroke exhaust systems!🙂
thank you for watching and giving feedback! I appreciate it 😊
Thank you as a daughter who always annoyed her dad and brother with these questions this helped me understand why my kx 85 exhaust is shaped different from my klx 140
Just subscribed and I am looking forward to digging into more of your videos!
Turning 60 this year means nothing to me, I have four 2 strokes, two enduros and two trials, and I feel like I'm 40!
But I have no problem learning from younger people and you clearly know what you are talking about! Thank you for your commitment to providing such good information!
Blessings from Colorado!🙏
Thank you so much for your comment and nice words!! I really appreciate it and I hope to see you around in thr comment section! 😃 Let me hear more about what you think about the videos 💪
I’m turning 61, have multiple bikes including my new Beta 300 rr, from Colorado and feel 45 when I’m riding. Greetings from Buena Vista!
When I was a young bloke I rode in a club, one day this old guy turned up on a WR Husky. I thought "were gonna a be hanging around waiting for this guy to catch up", well stuff me, he rode the ass off me and most of the other guys.
It’s curved bc it can’t go straight. Got it bro.
Thank you! That was really clear and made it simple to understand.
I once built an exhaust pipe for my 2 stroke and it wasn't easy!
There was a very good book on improving 2 stroke performance and the exhaust pipe was a huge part of that. Sadly, I lost that book somewhere along life. :(
Im happy to hear that!
I bet it wasn't but it sure was a good challenge, I imagine 💪
Likely " the 2 stroke tuners handbook by Gordon Jennings"
Another factor is the length of the divergent and convergent sections help broaden the usable rev range. as the convergent gradually contracts it is sending a positive sound wave back the whole time, weaker, but broader. This means it will reach the exhaust port over a wider rpm range, but it's peak wave pressure, and thus the engines comp ratio will be less than a more aggressive angled convergent section, same goes for the divergent section except reflecting a negative pulse for scavenging.
Great to see you explain it so clearly.
There is a mathematical formula for calculating length and shape of the pipe. I bought a book called The 2 Stroke Tuners Handbook 40 years ago and still use it. It has all the info for building pipes in it. I have built 3 and they all worked great. I checked Amazon that book is still available.
thank you, I appreciate it 😊
maybe I'll get it! it's such a complex subject, it's never too much knowledge lying around 😆😂
I use to race shifter karts and jet skis in my younger days. Temperature also affects the speed of the sonic wave. A rich or lean mixture will change the exhaust gas temperature and the tuning within the pipe. On our jet skis we would inject water into the pipe at various places and this would change the powerband due to the temperature change. We also used what were called center bleed pipes were the exhaust would exit out of the side of the cone. Didn’t affect power but made packaging easier. Lots of interesting theories on expansion chambers.
Nice! Thanks for the info! It's amazing how specific the technologies can get in the various motorsports!
Yep, the difference in the sound wave speed is because of differing exhaust gas temps, as the sound wave does travel a bit faster through hotter gasses. If your pipe and porting are tuned fairly well together, on normal pipes to me (not water injected), you can wrap the pipe with some pipe wrap insulation, for hotter gasses in the pipe and usually gain some top rpm.
My Dad mentioned this to me back in the 1970's, but now I understand the dynamics. Thank you!
I'm glad I could help! thank you for watching! 😊
This is incredible info. I've been riding for 30 years, and just now learned why the power band comes on at a tight RPM range. Thank you!
I'm glad I could help! I appreciate it 😁
When the 2 stroke is running, after the exhaust gas is pushed out, some of the fresh fuel air mixture gets into the exhaust pipe and that is what is pushed back into the motor to charge the cylinder with more pressure.
exactly :)
@Nimbus Nimbus Not really, the video kinda implied that the gas beeing pushed back is already combusted gas, there wasnt a mention of fresh mixture escaping the cylinder and that beeing pushed back. It might just be a language barrier thing :P
@Nimbus Nimbus No he didnt? He didnt say it was fresh mixture that escaped the cylinder, he used the exact same icon for them as the icons for the exhaust. Implying its combusted gases that get pushed back in. Not my fault if you are not mechanically inclined
@Nimbus Nimbus Its a smoke icon, explain why unburnt air and fuel would represented with a smoke icon? U are dense mate.
@Nimbus Nimbus Also give me the timestamp where it says new air fuel mixture escapes the cylinder.
It's really crazy to think, how just change the exhaust system can completely change both the power and the torque in the 2 stroke engine
I figured the bulb part of the pipe would be closer to the exhaust port , instead of 1/2 way down the pipe.
Not only 2 strokes and not only bikes
My gosh! how simple you make it!
Congrats!
Thank you so much! 💪💪💪
Very comprehensive video my guy. It's rare to find such high quality info, and graphics from such a small channel. Keep it up!
Thank you so much! I really appreciate it! 😊💪 Next week I'm uploading a mega video about suspensions so don't forget to subscribe 😆😉
That is more commonly called an expansion chamber, but it also causes the power to have a narrower band. My friends used to say it was like a turbo charger coming on suddenly. For the average rider this can be very unnerving. For the others it gives a thrill to hold on tight and keep the front end down. My dirt bike had it, and my Yamaha RD400 had two, with the effect almost better than sex.
"with the effect almost better than sex." - best way to finish any positive opinion about anything xD
Think i missed something in this video haha, ended up asking my self more questions. I learned something new today doe so tyvm for the video.
more knowledge always leads to more questions, so you're on the right path 😉
thank you! 😊
@@StepstoPodium almost cause you are close but not on the right path of the purpose for an expansion chamber ....its not about exhaust "back pressure" its all about the reflecting of sound waves traveling back to the exhaust port to seal in the boost pressure created in the crankcase ..the amount of fuel/air mixture you claim is being pushed back into the combustion chamber and to create higher compression has every little effect at all ...the higher compression was already created in the crankcase from naturally aspirated atmospheric pressure draft in the crankcase and then compressed by the Piston to higher than atmospheric pressure then transferred by the Boost Ports into the combustion chamber where it is compressed again before it is fired off
Dude...... A sound wave IS a pressure wave.
and no, the amount of boost that comes in through the reed valves isn't only from the crankcase, but also from suction created by a negative relative pressure created by the pipe (I explained on the pinned comment with I didn't include that part on the video). Look it up please.
Thanks for answering the question of why that shape.
it's a pleasure! Thank you for the comment, I appreciate it 😊
i was always very confused and curious how this pipe works and why it looks like this, thank you for explaining so simply!
I really appreciate it! thank you for leaving a comment 😊
Parabéns pelo excelente trabalho que tens feito... Espero e desejo que o crescimento do canal seja proporcional à tua dedicação.... Um grande abraço...
Um enorme obrigado Vítor 👐 é bom saber que quem vê os vídeos tem a noção do trabalho e dedicação por detrás dos vídeos 💪💪 grande abraço!
And that "perfect" comp & rpm range is what we old guys refer to as "getting on the pipe". Nothing else like it. From 50cc to 500cc, 2 strokes can be a blast.
amen to that!👌
HAHA!! I've nearly gotten friends in trouble in front of their parents for saying that. "oh yeah, we came around the corner and got on the pipe" or hit the pipe, and they thought we were smoking something. Just tires on the street, or roostin!
Having watched several longer vids that left me none the wiser, finly crackled it. Thanks .. muito obrigadu!
thank you for watching! I'm glad I could help! 😊😊
Zappa goes technical! Well done, thanks for sharing.
Thank you for watching! 💪
Ah...a bela pronúncia portuguesa sobre o inglês :D
Não engana!
Não conhecia o canal, muito interessante.
Obrigado! 😉
Muito bom!!
Muito obrigado Rui! 😊
@@StepstoPodium Bem me parecia que eras tuga XD XD XD assim como o M Cunha não conhecia o canal... Big Props
@@ChocoFreak66600 o que vem de Portugal tbm é muito bom 😆😂
grande abraço e muito obrigado! 😊
quick and interesting, thumbs up! i had a gasgas 250 enduro, and made dent, so... you answered a question that was in my mind almost 10 years XD
thank you! I appreciate it! 😊
well, better late than never 😂
Dude thank you. I couldn’t this anywhere. Thanks for the great work and animation was super helpful!!!
I'm really glad I could help! Thank you so much for the comment and for the good words 😀👌💪
Fantastic video! Definitely a must see for any two stroke enthusiast.
Thank you so much! 😀 take a look at the suspension videos if you are interested in that topic as well 😁🙌
Esse sotaque portugues nao engana ninguem ahahah. Subscrito! Adorei o conteúdo e a explicação direta ao assunto.
💪💪💪
It's not to increase the compression. It's to reclaim some of the raw fuel that escapes the cylinder during scavaging.
CORRECTION. ... What I should have said was you can stuff " force " more air and fuel into the cylinder which can result in higher pressures and possibly more horsepower. However the compression ratio never changes.
I understand what you mean by that, but it's a matter of perspective. If there was no expansion chamber, there would be no fuel escaping the cylinder due to scavenging (partly created by the expansion chamber) :)
Which adds compression...
Steps to Podium I’m pretty sure a considerable portion of inlet charge (fresh fuel and air) would still be wasted out the exhaust port(s), even if there was no pipe.
@@mareksumguy1887 Probably, yeah!
I left out the word "ratio" on my first post which is my mistake. What I should have said was you can stuff "force" more air and/or fuel into the cylinder which can result in higher pressures and possibly more horsepower. However the compression ratio never changes.
Bernoulli Principal is everywhere, great explanation! Thank you.
Great video! Super easy to understand
2 strokes get so much extra power from a performance exhaust compared to stock, its crazy :D
True indeed! 😁
Another reason: they look fricking cool!
Thank you for the edifying lesson.
🙌💪💪
Simple and clear explanation. Thanks.
Thank you Tommy! I appreciate it 👌🙌
gases when travel at speeds lower than sonic, their pressure increases when the cross section area of passway increases and their velocity decreases, and viceversa
Correct. A bit of fresh mixture will end up in the header pipe but the return wave shoves it back in just before the port closes. The sound wave helps the pressure wave.
It’s opposite. You’re referring to the Venturi effect, when the cross sectional area increases, the velocity increases and the pressure decreases.
saeed note ---- what? you got it wrong?
Walter Kaaden was responsible for the tech originally which came directly from the development of the V1 pulse jet flying bombs from WW2. Fascinating story
Great visual and explanation of the body of the expansion chamber exhaust. There is one more part that has a major effect on the performance of the engine and that is the Stinger, length and diameter.
I think this must be the best video ever made to explain how it works or how to escape from a 2-stroke bike. Thanks !
thank you so much for that! 😁😁💪
They're shaped that way so you have to buy a new pipe every time you smash a log.
👌😂😂😂
heat gun + air compressor 😏
But make sure to secure the plugs and be careful. Slow and steady.
Edit: Actually I might have used a torch. It was a long time ago!
They should use rave valves / power valves like jet skis. Then you wouldn't need the complex curves.
@@lalilulelo1989 yeah, I do that sometimes. I wear my full riding gear when I do, had a plug shoot out at mach 3 before, haha.
I actually learned something!! Like my taste in women, more compact and lots of curves. EXCELLENT
I'm glad I could help! 😊 and damn good comment! 😂😂😂😂
Nice. Clear and concise.
Thank you for watching!!
Excelente video!!!
Muy clara la explicacion.
Saludos desde Argentina 🇦🇷
Muchissimas gracias Martin! 😊 Saludos! 💪
I learn...
Walter Kaaden, the man that invented the expansion chamber, said that when you get the perfect shape for the expansion chamber, it will not fit on the bike.
😂😂😂😂
The YPVS really helped the RZ 350s get some low end torque, and with a set of good pipes and pistons and reed valves and head work you could fly.
The clever here is the way everything is explained.
(Without falling asleep) 👌
thank you soooo much! I really appreciate it 😀💪
It’s hard to beat a light two stroke in the tight woods
true that!! 👌
Unless you are built like scott sumer was when he won the GNCC on a 1996 Honda XR600R that weigh over 300 pounds wet and when you kill it and crash you will kick it till you see stars before it will ever restart ...but ok scott didnt crash much at all , until one day he tried to battle it out with my friend's son who ran scott sumer off a cliff life lining scott to a hospital and costing team honda the GNCC championship for the year...the boy who did in sumer was Samson team rider and importer for TM off road dirt bikes
donnie baker I used to watch him muscle that hog around
donnie baker The TM’s, that’s cool, never in my price range, but an EC300 with those gorgeous blue rims? Oh yeh, I’d love to give that a home.
@@deborahchesser7375 miss that *a lot...*
Read prof Blair two stroke book. You have it partly wrong, when the exhaust wave hits the end of the primary pipe or header and hits the first diffuser there is a wave that returns to the exhaust port with a negative sign and helps extract more incoming charge thru the engine, it will pull a negative wave all the way back to the inlet port of the engine. In a well tuned engine I have seen negative and positive pressures over 7lbs and higher, the header length, diffuser and baffle cones will change the character of the engine. The tuning of the “stinger” will effect the temperature at the piston and effective rpm.
I know I didnt explain every single detail about the difuser, it was meant to keep it simple and informative for about 90%. Sometimes if you go too much into detail, you loose the big picture, but I might do a video just for the 2 stroke!
Nonetheless I really appreciate leaving a comment with your feedback, and surely everyone reading the comments do as well 😊😉
I will read it! thanks for that info! 😊
Very complex subject, this explanation managed to at least touch on the major points. Most important being the fixed pipelength = fixed rpm peak or a trade off necessary - the graph showed it well. Well done! .
thank you very much! I'm really glad you could appreciate the time and knowledge put into the video to explain it in a simple way 😉😀
I was looking to solve this question for years! Awesome! Great video! ☺️
I'm glad I could help! Thank you for watching! 😀
Lets say i would ride a 2 stroke withouth a silencer would it lose lots of power
silencer or expansion chamber?
without the silencer it would do a loooot of noise.
without the expansion chamber, it would do a lot of noise and lose a lot of power 😂😂
@@StepstoPodium so I've been thinking about a aprilia rs 125 stunt bike and i thought i could take off the silencer and put a db killer at the end of the expansion chamber so it wouldn't be so loud and this is because the silencer gets destroyed every time I fall
@@vflinck1324 you will affect the performance of the pipe and the performance of the engine if you do that!
Depend, if the espansion chamber is designed to work whithout silencer, adding a silencer will reduce power
@@ginettaclark2387 all bikes have silencers after expansion chamber
Two strokes pips are called a tuned expansion chamber
Simple and to the point. Great explanation
thank you so much 😀
Very well put and easy to understand.
thank you very much! I really appreciate it 😊💪
Hense the name expansion chamber. 😉
Expansion=cooling=reduction in pressure=minimize back pressure
And I thought it was just to tell the difference between 2 and 4 strokes.
Awesome channel, Love the content!
Good explanation, thanks for posting
I appreciate it, thank you for leaving a comment 😊
You missed something. Gnarly vs fatty maybe in a new video :)?
in this video I didn't mean to compare specific brands/products, but yes, maybe for a next video! 😊
Yes that would be awesome
You look like Zlatan Ibrahimovic.
I've been told 😂😂
A vegan zlatan....
that, I haven't been told 😐😂
Don't feel bad... Zlatan is a big dude!
And I don't think there is such a thing as a two stroke lovning vegan.. 😀
Exactly the video/information I was looking for! Thanks
Glad I could help! 😊 thank you for watching 💪
Nice explanation
Very good information, I’m glad you included moped/scooter pipes.
thanks! 😊
Thanks for the simple explanation. Good video
Thank you do much! 😊
Great video! I learn something new everyday!
Great information, explained in a simple to understand manner. Thanks.
Glad to hear that! Thank you! 💪🙌
great video. This must have taken a LOT of work. Thank you for the detailed explanation
Thank you so much for that! it really took a lot of work but I'm quite proud of how it came out, I'm glad I could help so no many people understand this 😊
Such a great explanation, thanks a lot!
Thank you! I appreciate it and thanks for watching 😊
Well explained. Thank you.
Thank you for watching! 🙌
Thanks nice explanation. Being older I can relate. Everything was 2 stroke. Yes, I have mangled many pipes on the old saki lol.
Thank you! I appreciate it 😊
Wow, excellent video!! Thanks for making it!!
Thank you for watching!! 🙌💪
Great explanation, thank you!
I appreciate it and thank you for the comment! 😊
Very clear explanations ! Keep up ! Greetings here from Philippines! 😊
thank you so much! 😊
I was just wondering about this. Thanks!
I'm glad I could help! I appreciate for leaving a comment! 😊
brilliant lesson
Thank you for watching!
Back in the 60's my first bike was a 1957 Zudapp 250 Super Sabre.. It was a great machine. I sure wish I had it now.
Amazing video, what a knowledge.
Thank you, new day new thing learned!
I'm glad I could help! Thank you! 😊
That was a very good explanation thank you.
Thank you for watching 🙌💪
Great information bro! I just bought a used Goped gas scooter and it’s 2 stroke. I was thinking about making a rhino/snail shaped exhaust but didn’t know how it works. This helps!
Awesome. This is something I have always wondered and now I know great explanation much appreciated.
Thank you Sir! I'm glad I could help! 😊
Awesome video! I was always wondering how they worked.
Thank you! I really appreciate you leaving a comment 😊
Jeez, hours of watching "fuel, air, spark" when it's "fuel, air, compression, spark".
Never knew I needed a proper fit to get that back pressure, thank you!
Very informative and explained great. Thanks!
Thank you for watching! 💪💪
Excellent video. I'll subscribe. I owned the first Elsinore 125 back in the early seventies and now I know why it had such a beautiful big exhaust.
Thanks for the lesson 👍
I'm glad I could help! 😊
Finally... a gr8 explanation
thank you! ❤
I now fully understand what "on the pipe" means. Thank you!
I'm glad I could help! thanks for watching! 😊
Great explanation!
Thank you🙌💪
Great explanation
thank you!😊