You'll understand everything about Atkinson, Miller and Otto cycle engines after watching this video

[@d4a]

100 cars that changed the world: amzn.to/3DGXDf6 Stem engine model: amzn.to/3Y5iZLv 1-2-3 count with Car parts: amzn.to/3jxP7Z6 Patreon: www.patreon.com/d4a Become a Tuning Pro: hpcdmy.co/dr4a Support the channel by shopping through this link: amzn.to/3RIqU0u

[@jububoobaroo67]

Thank you for explaining how single attribution neglects credit to what is often a long collaborative effort. Michelson, Lorentz and Poincare should always be mentioned when Einstein is for example. He gave them no credit and stole their works as his own.

[@NickShl]

You look on Atkinson engine only from one point of view. Thinking that it reduces intake stoke is wrong. Have you touched exhaust pipe? Hot, right? That is because there some energy left. What if we will be able to catch this energy somehow... may be we can make power stroke longer, give exhaust gases more space to expand? But wait! That exactly what Atkinson engine does!

[@Danger_mouse]

Thanks for another great video 👌 19:15 I was lucky enough to be working for a Mazda dealer in Australia where we were Eunos agents. We had several Eunos 800Ms that we serviced and they were amazing cars to drive, and also for the owners. They were beautifully made, nothing went wrong, ever... We just serviced them as per the service schedule and sent them back out on the road. Mazda claimed of them back in the day, more power and torque than the 3.0 JE V6, better fuel economy than the KF 2.0lt. Our owners certainly reported they were good on fuel. I actually loved the Eunos range, the little 30X hatch with the 1.8 V6 was great fun, and the 500 hardtop was a nice looking contemporary car for the time, very unique. Maybe you could do a video on the Japanese luxury era with the RISE of Lexus, Eunos, Acura and Infinity... 🤔

[@Danger_mouse]

@@NickShl He mentioned that, however the fact remains that part of the compression stroke is lost and power is reduced.

[@Tetraden-a]

Wait a second... Why do you look almost like Nicolaus Otto? O_O

[@ozfugs]

This probably won't mean much to anyone else but I remember finding a Japanese guys personal university webpage back in the mid 1990's. I'm not sure if he was a professor or a student but it was like an encyclopedia for Japanese car technology of the time. He had excellent technical explanations and diagrams for all kinds of things. You could tell the guy loved the topic and loved sharing how it worked. That was part of my introduction to the Internet and even though the site is long gone I still have fond memories. And this channel reminds me of that. It's the same kind of intelligent and passionate effort. The same kind of enthusiasm. And it's cool to see how the delivery format has evolved from basic text to full on edited videos with 3d animations. I really enjoy this channel and appreciate the work that goes into it.

[@d4a]

Believe me, it means a lot to me. Btw I have very fond memories of the early days of the internet too

[@demef758]

AND, he can pronounce all of the funny foreign names that none of us can!

[@robertgift]

Why is the site gone?

[@Thinkle911]

@@demef758 He is indeed doing it very well! It's not the ususal "wet" and "sloppy" American/english interpreatiation of letters, but pretty much to the point normal german or french, only "Yougene Langen" was a bit off, it should have been Oigen Langen, Like in oil and a G like in graphics.

[@Videoswithsoarin]

have you tried finding it on the way back machine???

[@hoganfan924]

Good video. Ralph Miller’s original idea was to close the intake valve well before BDC to increase efficiency. He wrote about this (as I recall) in a 1948 ASME paper. I read his paper 25 years ago while working on VVL/VVT concepts for Chrysler. This works very well for low load efficiency (up to about 8% improvement), due to virtual elimination of the pumping loop by running unthrottled, and is what BMW Valvetronic and Fiat does Multi-air to run “unthrottled.” A guy at GM named Don Stivender did research on extremely low lift cams in the 60’s, and another GM guy named Tuttle made very short duration cams (with more normal lifts) in the early ‘80’s, testing Miller’s original concept. Tuttle also ran very long duration cams to control load (testing the later miller approach) Stivender claimed a 5% improvement in efficiency, and Tuttle around 8%. Stivender called his very low lift the STIVE cycle (Sonic Throttling Intake Valve Engine). Very clever! I built some very short duration cams with moderately low lifts to verify the blended “Stivender & Tuttle/Miller” with the very early intake valve closing concept in our 1.6l “Tritec” engine in 1999/2000 and verified the concept could deliver about 6-8% lower BSFC unthrottled. Most folks (even engine guys) didn’t understand how this works, but the evidence is right in the P-V diagram, and the virtual elimination of the pumping loop. Here’s are links to Tuttle’s 1980 & ‘82 SAE papers(I couldn’t find Miller’s): www.sae.org/publications/technical-papers/content/800794/ www.sae.org/publications/technical-papers/content/820408/ Here’s Stivender’s paper: www.sae.org/publications/technical-papers/content/680399/

[@jackreacher7183]

Great message and refences.

[@tomconner5067]

Let me begin by stating that your comment obviously indicates an impressive understanding of the compound processes and coordinated functions of internal combustion engines and the incentives behind the R&D by engine manufacturers. There are other viewers that demonstrate an understanding of the mechanical action, and some guys are on point, but this is the first time someone commented and there was no tunnel vision, or inaccuracy, without an air of bias or disapproval.

[@tomconner5067]

I see that some information sources shoot the concepts in the foot from the sidelines and do not back up their claims with any evidence, but rather stand behind the concept that they are correct if they can not be proven to be incorrect, or the opposite of what they state can not be proven ( it’s a form of industrial censorship backed by astrophysicists to make outrageous claims that make you either wonder if they’re jerking your chain or need a vacation at an inpatient behavioral research facility yet you must accept their subjective input if there’s no sound evidence against it, or no accepted standard or understanding exists to debunk the authenticity of their nonsense. It appears to be a blackloophole. A system of abstract speculative skepticism, used as a snubber by sandbaggers.

[@hoganfan924]

@@tomconner5067 Thank you for the kind comment. The engine development work I did at Chrysler from ‘97-2000 was the most technically challenging, mentally stimulating and rewarding work of my 35 year career in the auto industry, and I had a lot of tough, innovative and interesting projects. I loved doing advanced side projects like the VVT/VVL studies. I authored a white paper on that work, that I hope had an impact and laid the groundwork for future development.

[@DC-rn1fc]

Wait a second ... what sort of engine guy doesn't understand dethrottling? The highload-benefits are a tad harder to grasp, and only work really well with boosted engines. There, one could see the concept outsource a part of compression without impacting expansion. Outsourced to the compressor (be it attached to a turbine or driven by the crankshaft), cooled inbetween, thereby lowering p and T, yet having the same amount of charfe inside. That way, knock is countered, and that allows to either collect an improved efficiency at high load, or to increase the geometric compression ratio, thereby expansion ratio, thereby efficiency. But, as stated, this only applies to boosted engines - naturally aspirated ones, would lose a great deal of torque and power, if run on that mode, ... fits some applications, like Toyota's hybrids, but, there, these engines only are so successful because nobody really took them on - a similar drivetrain with a higher-tech ICE would outperform a prius in any regard. Anyway, the mid-load region is the only one where you won't benefit much from a variable valvetrain, be it two or three steps with a lobe each, or continuously like BMW made it ... the nicest VVT I found so far is Nissan's - I've had the very same idea, but came across it in a book that sums up a converence on VVTs (there were annualy ones when this was considered one of the three major promising paths - Downsizing, Stratified load and dethrottling by variable valvetrain), and thought ... cool, some dude in Japan had the same idea and actually made it happen. Nice! Got a more complex, but still better one up my sleeve any day, that could even spare an intake cam phaser, if some parameters match up. Anyway, I get that understanding the concept of outsourced compression and inbetween cooling may be a bit un-intuitive, but dethrottling, while sometimes hard to apply in reality, the basic principle is fairly easy to grasp...

[@jimosborn390]

Excellent explanation. When I was learning I was taught efficiency is related to compression ratio. Later I discovered it is really a matter of expansion ratio. Atkinson/Miller cycles let you have an expansion ratio much larger than an Otto cycle.

[@makantahi3731]

it can be monitored on 2 ways: 1. burning efficiency-higher pressure, higher efficiency, and 2. expansion efficiency: as nearer to atmospheric pressure/temperature as more efficient, so max eff will be if both are high: high pressure on the end of compression(start of combustion) and longest/expansion to the lowest temp/press on the end of expansion stroke

[@ahobimo732]

Thank you! I finished the video, and for the life of me, 8 couldn't figure out why a supercharger wouldn't just cancel out the increased efficiency of a Miller cycle engine. Your comment finally cleared it up for me. 👍

[@keithyinger3326]

@@ahobimo732 that's what I couldn't wrap my head around either. Sure the Atkinson cycle is sucking in air and then expelling some of it, but if you add in a supercharger and crammed even more air in there, then wouldn't that higher pressure charge of air be harder to compress than the usual charge of air? I would think that extra force it takes to compress the tire pressure charge of air would cancel out the benefits of having a shorter compression stroke.

[@ahobimo732]

@@keithyinger3326 I think the key is what Jim already said: it's not reduced compression that matters, it's increased expansion. The supercharger can raise the compression and the engine will still acheive improved efficiency, IF it has a longer expansion stroke.

[@ferrumignis]

Both things are true, thermal efficiency is linked directly to compression ratio, but having an expansion ratio greater than the compression ratio also benefits efficiency.

[@nathanaelvetters2684]

This is exactly what I needed. When I got my Prius, all I knew was "atkinson cycle more efficient less powerful" but was having trouble figuring out why or what the actual difference was. This explained everything and more. I think teaching engineering history is enormously helpful to explaining the concepts themselves.

[@Piracanto]

Same here, I was wondering why my Prius has an Atkinson

[@chiefdenis]

I dont think I've ever seen a bad video from this guy, been here almost/roughly 3 years, and this guy is the GOAT of mechanical KZbin school, no one explains things quite like him, and I've seen everything.

[@sallehsallehnewton3258]

The naked engine is a bad video

[@chiefdenis]

@@sallehsallehnewton3258 eh, i beg to differ

[@ishtiaquehussain2265]

Thanks a lot, man! You are unbelievably good at explaining complex engineering topics. Please know that we really really appreciate your channel, your videos and everything that you do for us. Wish you all the best for the future!

[@_monti142]

i needed this video so much, nobody explains engines better than you on youtube, many thanks :D

[@ddegn]

I'm not a "motor head" myself but I love the videos on this channel.

[@IllusionSector]

@@ddegn I'm gonna close my eyes and picture the words coming out of Christoff Walz's mouth.

[@ralphwarom2514]

This video reminds me to not take forbgranted what we have now. Its crazy how gold stuff I today compared to the early days of the ice

[@tarstarkusz]

What is in this video is wrong and right, but more wrong. You absolutely need compression to get high thermal efficiency. Compression is why diesel engines are so much more efficient than gasoline engines. Large expensive diesel engines powering things like container ships or desiel locomotives can reach 50% thermal efficiency Compression does not merely improve power, it improves efficiency.

[@ddegn]

@@tarstarkusz "You absolutely need compression to get high thermal efficiency." I thought the need for compression was stated in the video? The question is how this compression is achieved. The compression can be achieved using a supercharger rather than using the entire compression stroke. I don't know why compressing using a supercharger has advantages but I doubt Mazda would add this complication without having a good reason.

[@kristianhermann5971]

On efficiency, it's worth mentioning the added power with Otto allowed for engine downsizing too - so on a HP-to-HP basis, added efficiency with an Atkinson required a larger engine - awesome history lesson!

[@zazugee]

efficiency is thermodynamic efficiency and it's related to the type of cycle, it have nothing to do with the downsizing the generan efficiency is real world one and you can impact it by reducing weight ...etc

[@seanlovi8798]

I can't believe am getting this education for free, it's almost illegal.

[@makantahi3731]

then donate some money to be legal

[@jcorkable]

Please, don’t give the government any ideas.

[@orangejjay]

@@jcorkable lol big bad "the government" better watch out! They'll get ya!

[@litutheking6646]

Illegal😂

[@pickipanfil6042]

Selling education should be illegal...

[@jasperrodrigues7026]

Goodness GRAVY! You are unbelievably good at explaining and illustrating things. I can only imagine how much time and work you put into honing your skills and knowledge. Thank you so much for posting your videos and sharing your knowledge with the rest of us. - Jasper

[@that1guyonpoint213]

Another great video. As a mechanical engineering student you've taught me way more than any class ever could!

[@DuaneKerzic]

You really need to pay attention in thermodynamics as this guy got it all wrong.

[@eli6394]

@@DuaneKerzic What did he get wrong? In my thermodynamics class we analyzed the Otto and Diesel cycles within a control volume and neglected energy loss, energy in and out, and mass in and mass out . We solely focused on the changes in temperature and pressure within the control volumes to keep things simple. The video doesn’t go into depth about the chemistry and thermodynamics but his approach is realistic and applicable. I didn’t notice anything wrong about the information in this video but I could have missed something. 🤷🏽‍♂️

[@DuaneKerzic]

@@eli6394 In my thermodynamics classes, we learned how to analyze the Carnot, Otto, Diesel, Stirling, Ericsson, Atkinson, Miller, Brayton, Rankin, 2 cycle internal combustion engines, along with the effects of turbo and super charging (with and without intercooling), economizers, super heat, reheating, and much more. He got the linkages correct. But the linkages aren't why an engine makes power. They make power by extracting heat from a gas due to the expansion of those gasses. As we know efficiency of an otto cycle is proportional to the compression ratio of the engine, the compression stroke doesn't rob power from the engine. In the case of the Atkinson and Miller cycles the efficiency closer to the expansion ratio of the engine. The reason these cycles were developed was to allow greater expansion ratios while still using externally mixed low octane fuels to control knocking and preignition which is limited by the compression ratio. The 'super charger' in the Miller cycle wasn't replaced by an electric motor. There were naturally aspirated Miller engines in constant speed use before Toyota and Mazda. Which is basically how they are used in hybrids with generators and CV transmissions. The reason for the electric motor is to allow for a lower power, lighter, smaller displacement, high efficacy engine that runs at a constant speed and constant power most of the time. An auto only needs full power for very short periods of the drive cycle such as starting from a stop, climbing steep hills. I could go on.

[@magnusgustavsson6475]

@@DuaneKerzic I agree with you point on thermodynamics, It is the longer expansion cycle that gives a more complete combustion. About Toyotas hybrids, I think he meant that the supercharging is replaced by the electric drive at low rpms of the engine.Basically, the engine i an hybrid can work on a single rpm so there is no need for a responsive and low torque engine there.

[@DuaneKerzic]

It has nothing to do with how complete the combustion is. In our regular gas engines we aren't allowing unburned fuel to be exhausted. We just aren't expanding the gas after heating it as much.

[@eTiMaGo]

I guess Toyota didn't want people to think "It's Miller time!" about their engines :D Seriosuly though, thanks again, I knew the basic conceptual differences between these engine types, but you have brought me a new level of understanding :)

[@bravo_cj]

ngl I’m totally impressed by the Miller cycle. Such a genius, simple yet effective idea! It’s absolutely beautiful!

[@jhaluska80]

I have been enjoying the history and engineering lessons you provide on engines. It really helps me understand and appreciate them more.

[@deano3580]

Tried a couple of videos looking for this explanation. This guy has thoroughly nailed it and was by far the best. Clear, to the point, no waffle, good, appropriate graphics

[@-Jethro-]

I’ve always thought of this more as increasing the power stroke length to extract more usable energy, rather than decreasing the compression stroke. It’s really the same thing, but I believe it better expresses the intent of increasing efficiency. Thanks for the video! Good stuff.

[@crezychameau]

I also like this way of explaining the concept better :) It is litteraly the concept behind 5 strokes engines

[@kilura1]

Yeah, this is quite important. See, If you have less mass of air + fuel mixture in the end of compression stroke, the pressure and temperature of gasses will be smaller in the end of combustion stroke (compared to OTTO cycle). This can be also achieved by throttling air intake during suction stroke (basically, this is what happens when you release gas pedal, gasses outlet temperature drops down). But this will strongly increase intake manifold resistance => efficiency will be less. Also Mazda's Skyactiv engines are designed to have very big Compression ratio. This allows you to maintain Pc (compression pressure) same as in OTTO engine. (In general, increasing Compression and Combustion pressure leads to increasing of efficiency). Marine Diesel Engines now have gigantic stroke of up to 3.5 meters(!). In order to expand gasses as much as possible thus utilizing as much of energy as possible.

[@allanallansson9532]

Agree! This increase power extraction even overcomes some of the thermodynamically unavoidable losses due to lower compression. Part of the efficiency of diesel engines is their high compression ratio and ethanol mix in in gasoline makes for higher efficiency due to higher octane value which allows higher compression ratio without knock.

[@chrissmith2114]

Pumping losses are the problem with petrol engines, diesel does not suffer from them.

[@ferrumignis]

@@chrissmith2114 Even diesel engines suffer pumping losses,they are just lower because they are not usually throttled (though some diesel engines are). The additional pumping losses on a petrol engine occur when the engine is throttled upstream of the intake valves, so the piston is expending energy working against the partial vacuum in the intake manifold/plenum. This can be eliminated by not throttling in this way, instead using adjustable valve duration like the BMW Valvetronic system or Fiats Multiair.

[@KO-pk7df]

I have known of these engines for a long time but now I actually understand the difference between them! Thanks.

[@PaulThomas-qo9vy]

Thank you for the BEST comparative explanation of these 3 piston engine cycle types! Very clear & precise!

[@Raj-nh3fc]

Wow, once again thanks. You are raising our knowledge and understanding of IC engines almost vertically. We want more!

[@reneneron2971]

Great video. Not all Toyota hybrids use the Atkinson cycle engine in their hybrids; the 3MZ hybrid engine does not. Further, Toyota will often increase the base compression ratio on an engine used in the Atkinson cycle model so that the effective compression ratio is similar to the Otto cycle version (an example being the hybrid 2AR-FXE versus the standard 2AR-FE). The camshaft profiles and valve timing are different as well. With proper engine management, the 2AR-FXE can be operated as an Otto cycle engine to gain power with a loss of efficiency with higher octane fuel. There is still a loss of power with the Atkinson cycle compensated for by the electric motor, but improved efficiency. Detonation (and octane) limits the practical compression ratio of any gasoline ICE engine.

[@chicken29843]

It should also be noted that these engines are not actually driving the wheels in the hybrids.

[@AndreiGrozea]

The 2ZRs in the prius and corolla seem to be very good engines despite the shortcomings of the Atkinson engine, but it's still not recommended to run them at speeds over 140km/h as far as I understand.

[@djhrjeiwhri]

All toyota vvt-i, vvti-ie is atkinson cycle

[@reneneron2971]

@@chicken29843 yes, they are, though coupled to the drive wheels through a CVT. The motor generator can operate in 4 modes: engine only, electric drive only (engine off) , engine and electric drive operating together, or regenerative (charging battery). On AWD variants, a separate electric traction motor drives the rear wheels directly. A Highlander relies more on the I/C engine than, say, a Prius.

[@reneneron2971]

@@djhrjeiwhri incorrect. VVT-I is Toyota’s name for variable valve timing on the intake valves, which has been used for decades to improve performance and/or fuel economy on IC engines. Independent of Atkinson cycle, and certainly not limited to the hybrid engines…nor do all Toyota hybrids use Atkinson cycle IC engines.

[@AGC-f8g]

Just wow. Been watching videos for an hour trying to understand what this guy does so clearly. Thanks a lot. Glad I found this video.

[@ISHQEAMEEN381]

This type of video i was waiting for Thank you so much bro Keep it up

[@Max-mz5ls]

I swear i've watched like 50 of your videos and they never leave me confused, you explain everything so well, so much better than anyone on youtube or even college

[@AnthonyCelata]

This is legit the best and most educational youtube channel on the interwebs

[@olavl8827]

Great video as always. Personally I'm not much of a car person and I drive just a cheap old boring car, which serves my needs. But I love learning about technology and engineering in general and this explanation was just fantastic.

[@jackrichards1863]

This is the most revealing story of engine types I never heard before. Thanks Mr.

[@SONO4B11T]

I never bothered to learn these different cycles, cause where i'd read about them, they just made it sound complicated. This video on the other hand, was fun and informative. And who doesn't like a bit of history!

[@MrMarty77]

That was the best explanation of these 3 different cycles that I've heard so far.

[@jakemartin4305]

This is amazing ive always believed that knowing how something has evolved over time helps you understand the current technologies and even helps is repairs of those technologies as well love this channel 👏👏👍

[@maccaberry1041]

Awesome homage to the internal combustion engine. It's not dead yet and we owe our modern quality of life to this ingenious invention. Thankyou.

[@kevinpulver4027]

You taught me something! I have castings for a model Atkinson Cycle engine. But I didn't realize that the compression and power stroke lengths differed. I know some guys in Nebraska who have working examples of Otto's "Schumm" engine referenced in your video. For those who want to read more about the history of engines, "Internal Fire" by Clessie Cummins has a lot to say.

[@francoistombe]

Clessie was the founder of Cummins ( and has his own autobiography ( pun unintentional)). His son wrote Internal Fire. He used the name Lyle Cummins, but as C Lyle Cummins so I guess he is Clessie junior.

[@mikejohnson4617]

Wow, I learned something today! Thanks. Spent 30 plus yrs in engine engineering labs as a technician on Otto engines. As a retiree, have been curious about these other cycles and have never grasped the differences until now.👍 Subscribed.

[@scampilover00]

Would be good to hear more about the sky active technology from this channel, your explanations are unmatched

[@gregroles69]

Considering buying a Skyactiv CX-5 turbo for the missus, and had my head around Miller cycle a bit, but wow, this has to be the best and most visually perfect description I've yet seen. Kudos!!

[@CheeseFriesAndCoffee]

I'm so happy I found this channel. Your explanations are both easy to follow and interesting.

[@manojvishwakarma9954]

I just can't believe this man explained so many concepts in such a brief and effective way... Hats off to you man.keep it up!

[@BB-lm7cs]

Fun fact: Some of Cat's ACERT diesel engines (BXS and MXS for example) also used a miller cycle. Boost close to 60psi was provided by series turbos. I think there was a variant of Cummins' big cam engines using the miller cycle too.

[@Ceedub3406]

ACERT is Miller cycle. Helped meet EPA07 by reducing NOx production in cylinder. Pretty cool stuff. Basically reverse Jake brakes

[@bradferguson4943]

You're right. And it's switchable. There's a brake-like device on the intake rocker called an IVA that can hold it open longer. It can be turned on as needed.

[@mrpetit2]

​@@bradferguson4943 If it didn't have that it probably would be impossible to start.

[@omniphoriusvcf907]

Love how there's no yelling on this channel, just great explanations.

[@pontifier]

In high school I independently came up with the miller valve timing idea for increasing efficiency of four stroke engines. My reasoning was not to reduce the energy of the compression cycle, but realizing that a combusted fuel takes up much more space than it did before, the power stroke should be longer to allow the piston to reach atmospheric pressure before the exhaust stroke starts.

[@hitanshupatel2519]

This is exactly what I was thinking as I watched the video. It is impressive that you thought of that in high school. Did you have formal thermodynamics education?

[@pontifier]

@@hitanshupatel2519 No, but I'm fairly good at making accurate mental models of things and seeing how they behave as parts move and interact. That includes pressures and forces, and I sometimes I can see how and where fluids will flow and things will break. My dreams are accurate enough that I had a dream about driving backward and had to learn how to drive quickly by looking in the rear view mirror. When I woke up, I found that I was able to use what I learned to drive very quickly backward in a real car.

[@zazugee]

yes, i had the same thought when i heard of Atkinson cycle, i never thought it was about reducing compression.

[@zazugee]

thought for natural aspirated it's straight forward, but when you're using a supercharger, it's like you're combining a renkin cycle on top of oto/atkinson-cycle

[@vmkkdt1729]

While browsing\watching automotive and car engineering videos and not looking for any otto, atkinson or miller proces details, I more or less came across this video by chance. Amazed! A very well made (entertaining) video explaining the principles, differences and last but not least the history of the otto, atkinson and miller processes and applications. A million thanks and thumbs up for driving4answers!

[@tunebyaotphilippines2546]

Learning at its best! 👌🏻

[@rocka07]

one of the best and most underrated channels on YT

[@phatwayne]

Thanks for yet another topic brilliantly explained.

[@blairkinsman3477]

Great video identifying the Otto and Atkinson/Miller I was taught that the Atkinson/Miller benefit was two-fold: one was the reduction of waste in compression, but the other was the extension of the expansion stroke which allows more of the pressure created by combustion to be converted to work. 17:02 you draw a horizontal line as the cylinder moves upward and point out the reduction of compression waste by ~20% .. and we have that .. but if we reference the datum at start of compression instead of start of upward motion, what we also have is ~ 20% greater extension of the power stroke allowing the pressure in the chamber to work longer. At 8:55 the diagram showing Atkinson having shorter intake stroke and same length power stroke is actually Miller. Atkinson would have both blue squares the same size and a resulting longer red square, illustrating the extension of the power stroke. Traditional kpi such as power per cubic inch displaced (the same size red square) show Atkinson as lower, but power per cubic inch compressed (and therefore power per amount of fuel consumed - the same sized blue square) show Atkinson higher. As you said, with car engines being mobile, weight matters and pure Atkinson requires a larger chamber. As engine material technology improves, that gap in weight becomes less. As you said, the addition of the electric supplementary motor corrects the “low responsiveness” feeling - lower power per cubic inch displaced - of the Miller. New engine designs are looking to alternate mechanisms besides reciprocating pistons to obtain the benefit of Atkinson expansion. In the big picture, the 150 years of reciprocating pistons is a short time in human history.

[@ericsalmazo481]

Unbelievably good content. Thank you for your work.

[@karlplasser1314]

Thank you very much! I finally understand how my Ford Galaxy Hybrid can have an Attkinson motor without having funny rods. Your lesson was extremly revealing.

[@zaidkidwai7831]

Fantastic work my man. Love your videos, explained clearly and concisely.

[@liorm2877]

Guys totally love watching your reviews. Bought a car (unrevoewed) a few months back, still watching with joy, but this was so super brilliant and I am so happy to see it. Loved it all, but Jim's bit had me in stitches!

[@loganpe427]

Very, very interesting video! I was retiring as a mechanic at the time Mazda announced it's SkyActive engine, I heard about it but didn't pursue any research, I had no idea it was based on the Miller cycle! Thank you, great information as always!

[@rkc62]

This is amazing - thanks for posting! The explanation graphics are excellent as always, but the Otto history graphics are exceptionally entertaining.

[@jozsefizsak]

Thank you so much! This was interesting and informative but also uplifting, due to how wonderfully well you explain things.

[@jacobski5726]

Never ever start do a lame intro/ad stuff. Straight to the point good work man!

[@patrickfargie1146]

My dude, it's 7am here in Tennessee. You can't be posting videos this late 😂 Nevertheless, I'm always here for it.

[@tdsdl1]

This is one of the best series on You Tube. Wonderfully presented and understandable. Thank you.

[@georges3799]

Very well presented. I especially enjoyed the historical aspects of engine designs. Would you please, explain how these engines are lubricated? What is happening to the oil in the engine?

[@abba_ra]

Also to add to your plea, how the engines are cooled too with liquid cooling

[@JPMotorhead1993]

Hey man, really enjoy your videos. Just a small detail I wanted to mention about the Otto and Langen engine operation: The top of the cylinder is actually open and does not build pressure on the other side of the piston (beyond atmospheric). Once the intake charge is drawn in by a short upward stroke of the piston, the chamber is sealed and the mixture ignited via flame ignition, sending the piston/rack upward (clutch freewheeling). The momentum of the piston/rack causes the piston to travel beyond full expansion, pulling a vacuum inside the cylinder which is compounded by the rapidly cooling combustion gases. With a strong vacuum in the cylinder, atmospheric pressure acts on the top side of the piston causing it to travel downward (clutch engaged) and transfers power to the shaft until pressure equalizes in the cylinder. Quite a unique but fascinating engine!

[@Appletank8]

How does the piston go up for intake after it falls down after combustion stroke?

[@TarenGarond]

@@Appletank8 Search on "Startup & Instructional explaination of 1867 Otto Langen engine operation" on KZbin, about 15 and a half mins in it is shown and discussed what is happening.

[@Appletank8]

@@TarenGarond aight, thanks

[@JPMotorhead1993]

@@Appletank8 There’s a clutch that engages after it drops past a certain point which turns an eccentric attached to an arm that lifts the piston/rod up a couple inches for the intake stroke.

[@Appletank8]

@@JPMotorhead1993 I see. Now that I'm squinting at it, it's like the world's most inefficient two-stroke engine.

[@Trendyflute]

Good video, I enjoy when you look at the different types of one thing and explain the similarities, differences, and history! I thought the Miller Cycle Mazda Millenia S was so cool back in the day (as a comfy sedan goes). A video like this on the history and variety of variable valve timing systems would be neat. Or even maybe before that, just valvetrains in general?? I feel like I know most of this stuff but you always manage to slip in a few new bits of info.!!

[@kerrylewis2581]

I may still be seated, but I'm giving your explanation a standing ovation. Fantastic video

[@johngray5360]

I had to do head gaskets on a Mazda millenia s about 10yrs ago and what a nightmare! There are sooo many vacuum lines, plastic tees and check valves under and around the supercharger that break just looking at them!🤯🤬 Great video and can't wait for an update on the MR-2

[@Moshe_Dayan44]

Thank you very much for this video. Very well-explained and illustrated, and giving a great balance of design and industrial history with sufficient technical detail to leave the viewer with a good understanding of how to explain these different engine models to another person. As the owner of two Toyota Prius cars (a 2nd gen 2008 and a 3rd gen Prius V), I can attest to the excellent fuel economy of these vehicles in both highway and city driving. I willingly accept the tradeoff of somewhat less acceleration power off the line and for passing on the highway as more than worth the consistent 50 mpg for the 2008 Prius, and 40+mpg for the 2012 Prius V. The fact that these Priuses also don't have an alternator or starter motor to wear out is really great. Starting these cars in -25 degree weather is also a zero-stress operation; you just have to make sure you never leave the interior light on, as the 12 volt battery in them is absolutely tiny.

[@BlackStar250874]

As usual, a very impressive educational demonstration, or could you say a broadside. Five stars! ***** Greetings from Finland from one hybrid user with an Atkinson-cycle ;)

[@Tom-Lahaye]

Excellent explanation! Essentially the development of the ICE followed the same route as that of the steam engine. First steam engines as developed by Thomas Newcomen in 1712 were atmospheric, the engine would suck steam at atmospheric pressure into the cylinder at the downward stroke of the piston, the valve would close and the steam allowed to condense as the cylinder wall was cooled by water. The condensation of the steam would create an under pressure wich sucked the piston back upwards. These engines also had poor efficiency and low power output, 5hp for an engine that filled a building, they were used to drive pumps at coal pits. Then someone got the idea of using steam created in a boiler under higher than atmospheric pressure, and using the expansion of the steam trying to equalize it's pressure to atmospheric pressure, and not to condense. Power output and efficiency raised dramatically, steam engine became small enough to power vehicles on rails and road. So a very similar story thus, and I think the development was a continuation of the development made in steam technology, and the idea after the ICE at that time was to drop the steam generating boiler with its thermal losses and space requirements.

[@nickrider5220]

Very well described sir ! and extremely fascinating 👍

[@samrodian919]

Fascinating video. Thank you that was so informative and I had no idea about Mr Millers engine design, and the VVT was the reason behind its introduction in so many manufacturers engines. I myself had a Toyota 1300 cc VVT engine in my Yaris from 2001.

[@pirat87pl]

I needed this explanation really badly ever since I was at a Lexus showroom and they boasted having 'Atkinson cycle' engines, but none of the salespeople could explain how it works. It was driving me nuts. Google only had general explanations that always felt incomplete.

[@mrpetit2]

Salespersons usually aren't techies. A good salesperson would get a mechanic from the shop to explain that for him.

[@pirat87pl]

@@mrpetit2 I don't care. If someones selling me something they don't understand - I'm not buying it. If they can't even explain things that are on the sticker then how am I supposed to believe anything they say?

[@catingloves]

Excellent. Now I know what it meant by Atkinson cycle in a Prius. Great education.

[@wadeepperson6906]

It was kinda cool to learn how vw’s new 1.5 was a Miller cycle combined with a turbocharger to reduce the power lost with the shorter compression stroke. I always thought they were supercharged but it’s the same approach with no parasitic loss.

[@xavierdesdoigts3507]

Once again, a delightfully clear presentation that makes me feel more intelligent at the end. You did it again.

[@charliefoxtrott1048]

Wow! Just wow! Thank you 4 this!

[@heinpereboom5521]

You are still my favorite technician! Wonderful explanation of the development of the engine with the important details!

[@NukeTshernobyl]

You can also supercharge Toyota's Atkinsion engines. It was totally interesting, when I saw a supercharged CT200h on a car show. This thing made just above 300hp, and was a menace on the track.

[@asharma9345]

Dude, This is Excellent Video. Full of Information.

[@fabiopereira9113]

The goal is not to reduce the amount of energy wasted during compression, but to increase the expansion stroke. Just look at a PV diagram.

[@arnabrazor1]

You are absolutely unbelievable! What a gem! 💯💯💯

[@guglegugle8075]

Bardzo dziękuję👋 W zaledwie 20 minut pozyskałem sporo wiedzy świetnie zobrazowanej i bardzo logicznie przedstawionej 👌👍

[@wernergamper6200]

Great explanation. And, the fact that there's no shitty background music is way underrated. Keep doin' it this way, please.

[@jgfjfgjfhjf]

I'm sure the title is correct

[@ifixem9585]

This channel is the definition of articulation. Spoon-fed knowledge bombs being dropped, well done Sir!

[@jpsother1183]

I get the feeling Toyota uses "Atkinson" instead of Miller for branding reasons. Their method is more Miller without the charger than Atkinson's differing length of piston movement. A true Atkinson would do best in a stationary and/or very low rpm situation and that is more what it was designed for, than use in a mobile situation.

[@RyanAumiller]

The electric motor functions as the "supercharger" in this case, it just makes up for volumetric efficiency by acting as a variable geometry flywheel. there's really nothing "atkinson" about the toyota version I call "miller cycle 2, electric boogaloo" because it does nothing to vary stroke geometry/displacement like say... the infiniti VC-Turbo engine that utilizes bellcranks similar to an actual atkinson engine to vary the stroke geometry and instead makes up for its lack of volumetric efficiency with a more direct power-adder. I see anything that utilizes changes in cam geometry to control volumetric efficiency for the cycle as "miller" and anything that utilizes changes in crank geometry to physically change the displacement as "atkinson" especially since examples of both exist... I don't agree at all with toyota calling their hybrid synergy drive an "atkinson" based cycle when it does nothing to make displacement a variable.

[@jpsother1183]

@@RyanAumiller "miller cycle 2, electric boogaloo" made me guffaw. Also it is very appropriate for the situation.

[@Verklunkenzwiebel]

great clip, you presented a lot of concepts I wasn't aware of. Biggest surprise is that hidden behind marketing mumbojumbo these basic concepts (Atkinson/Miller) have been taken into production. Thank you for compiling all this into a well produced video.

[@xXVintersorgXx]

My dad had one of those millennium's. It was a great car until the super charger self destructed. The major problem with it was actually that it required high octane gasoline

[@magnusgustavsson6475]

Would be perfect then on E85!

[@xXVintersorgXx]

@@magnusgustavsson6475 I think it needed 91 octane according to the manual

[@tomschmidt381]

Great explanation. I had heard of the Atkinson cycle used by Toyota in their hybrid cars but I have never heard of the Miller cycle. Thanks for the education.

[@waelal-zubieri5358]

I believe more modern engines can switch their VVT even at low RPM since they are electronically controlled rather than controlled by oil pressure like older Hondas. I believe pretty much any modern turbo charged today uses the miller cycle to save on gas. It's why these engines get excellent highway efficiency but the moment you are driving in the city in stop and go situations, efficiency drops significantly. In my car, I can easily get 30+ MPG even at relatively high speeds, but in the city can only achieve 16-20 MPG.

[@d4a]

Yes but there's still a catch. When you can switch to Miller at very low rpm the engine ends up being in Otto most of the time and the number of scenarios when you're actually running Miller is very much reduced. It's impossible to be responsive at low rpm and be in Miller at the same time, maybe that's how I should have phrased that part.

[@ferrumignis]

The Honda VTEC is electronically controlled, but it electronically controlls the flow of oil to actuate the valve timing system. This is the same as the vast majority of other manufacturers VVT systems. The only examples I can immediately think of that don't use oil pressure are BMWs Valvetronic (electric motor directly drives a mechanical system to control valve lift) and the koenigsegg free valve system. There may be a few others but they are in the minority.

[@ThomasBarone]

Amazing video! I feel like bloated like after Thanksgiving dinner but it's my head, with information, instead of my stomach with food! I'm amazed how much of this I was unaware of but I understood every single word.

[@velvetsmack2645]

Great explanation and video. Learned quite a lot. I actually owned a Mazda Millenia with the miller. I truly miss it. What's interesting about this tech is that we're now looking at the new age of electric, which ultimately means (or will mean) times almost up on this piece of engineering. Hydrogen may save it for a while, but I see a driven world with less engineering complexity - which would maybe lead to its ultimate demise.

[@markedwards4879]

That’s the best and simplest explanation of the differences between engine types that I’ve ever seen. Well done. What is really amazing though is that all of these are going to be made useless with the even more rapid developments in battery and electric tech. I loved my V8s and manual transmissions but am addicted to the responsiveness and power of my EV. No more fuel burning.

[@OttoMatieque]

I am biased in favor of the Otto engine

[@timwintersoncntr]

Yet another example of excellent research and presentation from our favorite engine tech guy explains fully this oft misunderstood subject.

[@adityadiesel7668]

This is why I subscribe to this channel

[@Truetoself3838]

Your video is pretty amazing. So much history intertwined with the basic science of how the engines work... thank you...

[@paulklem9249]

Great job in distilling the information. The editing and visual graphics with the "beat of a drum" narrative. Really valuable for passing on the information.

[@laura-ann.0726]

We own two Toyota hybrids: a 2019 Prius Prime, and a 2020 Corolla Hybrid. They both get phenomenal fuel economy: 58 mpg in the Corolla, 65 in the Prius Prime. Both have the same 1.8l VVT Atkinson cycle engine. The Prius Prime has a larger 8 kw-hour lithium ion battery and this can store more recaptured energy from regen braking, than the small 1 kw-hr NIMH battery in the Corolla, so it's fuel economy is better. My personal opinion is that plug-in hybrids are the most versatile vehicles ever developed. Depending on battery size and weight limits, it should be possible to build a 5-passenger sedan or 7-passenger Mini-van that would have up to 100 mile EV range. Pair that with an Atkinson cycle engine (1.5 liter in a sedan, 2.5 liters for a Mini-van), and a 16 gallon fuel tank, and you would then have 600 mile range for those long road trips that Americans love to take. For people living in areas with very cold winter climate, having an ICE lets you run the heater full blast without significantly reducing driving range, and running the ICE for a few minutes can warm up the traction battery far more quickly, so that it can accept a faster charging rate if you do stop somewhere at a DC fast charging station. I Loved this video! It's the best explanation and best graphics I've ever seen to explain just how Atkinson's crank linkage and Miller's VVT valve timing concepts actually worked. The Atkinson engine with the complex linkages would probably have never worked well in a passenger car: too complex and too bulky. But the way Toyota uses a Miller/Atkinson hybrid cycle (VVT, naturally aspirated) works amazingly well in the Toyota Hybrid Synergy Drive. In the Prius Prime and Rav4 Prime, most of the propulsion power comes from the electric motor, unless you are climbing a steep hill, or the traction battery is depleted, in which case the ICE comes on-line. Thanks for the video!

[@brentlanyon4654]

Well done. I've googled Atkinson cycle a couple times because I know that is used in the Prius. This very clearly states the difference from Otto cycle (less compression stroke), the resulting efficiency gains, and the performance trade offs.

[@paleocon777]

Some Recent Hyundai & Kia’s too

[@CautelousOne]

First time ever seeing one of his videos. Instant Subscribe. Details without tedium. Perfection.

[@vanci161]

Wow.. Got this video as a recommendation from the KZbin and it amazed me. Wonderful explanation.

[@Chris-l9w9g]

Excellent video, thank you! He would (or maybe actually is) a great mechanics professor. I've learned that only if you really master a topic you can explain it in such a simple but yet rigorous way. Love this channel!

[@stephanwerner19]

What an amazing video! With regard to Atkinson/Miller differences: Atkinson has a very late intake close, past BDC, Miller has an early intake close, before BDC. In Miller cycles you actually shorten the intake, creating a partial vakuum before you compress. Atkinson pushes fresh intake air back out of the combustion chamber.

[@d4a]

I think you're mixing up Miller and Buddack

[@stephanwerner19]

@@d4a you can argue about that, VW/Audi started off calling it Miller when they introduced their EA211evo and only after some time switched to Budack. Nowadays in R&D it's mostly referred to as Miller by several OEMs worldwide. Probably because it's easier to say "we'll be millering" instead of "budacking".

[@viktorbalaz9848]

Absolutely perfect explanation. Learned something today and didnt have to force myself into it. This is why I love internet. Subscribed.

[@davidshort7978]

Thank you for such an informative article. Your explanation ot the Miller Cycle was far superior and easier to understand than that of a Mazda Dealership Service Manager gave to me in the 90s. Cheers.