How The Atkinson Cycle Works - Car Engines
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- Опубліковано 6 вер 2024
- How does a hybrid car engine work? The modern Atkinson cycle is used by cars such as the Toyota Prius, Ford C-max and Fusion Hybrids, Lexus CT200h, and Mazda SkyActive engines. The basic difference between the Atkinson cycle and the Otto cycle, is that during the compression stroke, the intake valve is left open for a slight duration, effectively decreasing the compression stroke. This in turn means the expansion ratio is greater than the compression ratio, and results in a greater efficiency of the engine.
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I never knew why turbos were more efficient than superchargers, strangely enough this video helped me understand that.
It's because usually the excess expansion forces just go out the exhaust and are wasted, but a turbocharger captures those forces as they're being pushed out and uses it to supply air. Turbos capture energy that would be otherwise wasted.
Also, the larger a supercharger is the more power it takes to work. If you make one too big it would eventually take more power to run it than would be gained by using it.
This was one of the main reasons why Jet engines were developed towards the end of the Second World War. The propeller driven aircraft were fast, they could reach a little over 500 miles per hour but they couldn't go any faster than that due to propeller efficiency losses as the tips of the blades reached supersonic speeds. Supercharged, high compression engines that could overcome the loss of propeller efficiency would be too heavy to fly.
But superchargers give better response. Efficiency isn't everything. Turbos are great for diesels and aircraft engines.
@@michaelbenardo5695 and even better on gasoline engines when more than one turbo is used.
In extreme cases when I worked on river boat engines I saw Detroit diesels with the blower that is needed for it with turbos on top of the blower. The blower of course is gear driven from the engine on those but I thought wow that's got everything I saw some of that it set up on some four stroke diesels also
Turbochargers mounted directly on top of a blower..
@@michaelbenardo5695 exactly I have a diagram of a WWII plane that has a 2-speed supercharger
It told about when to use it and the horsepower grass it would put out in low vs. High versus off
It seems like you missed possibly the largest benefit of the Atkinson Cycle. With Intake valve overlap you are "preheating" and mixing the intake charge that will be taken advantage of by the next cylinder or intake cycle. You are absorbing heat (a.k.a. ENERGY) into the intake charge, allowing better vaporization of the fuel/air mixture.
I guess that is why you don't see any DI applied to Atkinson cycle engines. Except for combo units like the the toytota D4S.
Doesn't he say this at 5:40?
I don't believe so.
@5:40 @Engineering Explained does mention the fuel rich air being moved to another cylinder's intake cycle once being exhausted from the intake valve (thus the fuel is not wasted) and you can deduct that the air was preheated (and the net benefits associated with this) if you're already familiar with thermodynamics, but that's an engineering topic most people don't know about.
Most people aren't familiar with thermodynamics and this youtube channel is called engineering explained, so I have to agree with @trat50. I think the video provides a good mechanical explanation of Atkinson cycle engines, but does not touch on the thermodynamic aspect.
Also, in the Atkinson Cycle there is less resistance to turning of the engine because it's not squeezing as much volume on the compression stroke, and it's not having to push out as much volume on the exhaust stroke. The Atkinson Cycle engine and the electric motor are really a good marriage. It allows the electric motor to be used both where it is needed as well as where it shines.
Yup thats what engineering explained said on this video
I’ve been trying to understand the purpose of this cycle, thank you Jason for explaining how the expansion cycle is larger than the compression.That’s what’s been missing from all the other videos. You be all smart and stuff 😁
Bingo
Thank you for making it so easy to understand the difference between the engine cycles in plain speak. Mazda did use the Miller cycle engine in its Eunos 500 (a Mazda 626, aka Mazda 6 now) back in the 1990's. Now I know what it did. Apparently, the Eunos 500 had pretty good economy and not bad power for its time. However, it was costly and came out at time when the world's economy was not ready for it; post 1987 mini GFC.
Basically a two-stroke.
Correct me if I am wrong. Atkinson cycle can be achieved using a variable valve timing CAM ? shift back to OTTO when required in that case ?
That is what Toyota does.
Thanks for the explanation. I just bought a new Toyota Corolla Cross Hybrid, with the 2ZR-FXE engine also used in the Prius, that uses this Atkinson cycle, which I had never heard of before. This is my first hybrid car, and so far I'm impressed with it's fuel economy
If the Engine is Turbo\super charged, then will the opening of the inlet value at compression stroke force the air to flow outside via the Inlet value against the compressed air flowing into the cylinder (Driven by the turbo\super changer compressor). Will this in turn affect the upward movement of the cylinder and again affect the torque output of the engine ?
At first the Atkinson Cycle engine sounds like a horrible idea, but after you explained it, its quite ingenious!
it is a horrible idea after 8 years.
Brilliant. Well done. I didn’t fully understand any of it, but full credit for trying. Splendid.
The new 2.5 used in 2020 (and later) Hyundai vehicles uses both high compression 14:1 and Atkinson cycle by implementing CVVT. This engine also has GDI and MPI.
I've driven several of the new Sonatas with this engine and it has a very interesting, dare I say aggressive, exhaust sound when accelerating at low speeds. Cruising on the highway the engine is super quiet. It's mated to a traditional 8 spd transmission.
I was very impressed overall.
Ive only stumbled upon this method of combustion cycle recently. Im amazed at how things have changed. I guess another main advantage is with mordern variable valve timing the you can effectively still maintain the otto cycle or change to varying degree of the Atkinson cycle effectively exploiting the best of both technologies.
I just picked up a brand new 2020 Toyota Tacoma and was wondering what the deal with the Atkinson cycle was. Always awesome content to go back and reference!
New York taxi cab s utilized Toyota Camry hybrids..Generally good for 400,000 miles.. I own a 2017 camry hybrid, ..Generally get 40 mpg combined
Everything about the advantages in compression and combustion can be achieved on an Otto Cycle engine through restricting the throttle. Intake vacuum reduces the volume of intake gasses the same as holding the intake valve open longer. The only place I see where the Atkinson Cycle produces better efficiency is in the engine not having to pull against the intake vacuum. It's basically accepting a restricted throttle engine in exchange for optimum manifold pressure at an specific engine speed.
Wonderful Video... I'm curious about longevity of the Atkinson motor, with regard to "regular wear" on moving parts like the piston rings when compared to other engines. My prius has 292,000 miles and I'm astonished at how well it has performed.
they're more expensive to rebuild this way, taking care of the one with fresh oil will help them last they seem to be pretty good engines on Prius😢
How many subs did you have at the time of this video ?. I see your silver play button there...
Jason, it's 2021 and I'm buying a Maverick hybrid. Went back to look at your explanation of the Atkinson cycle and, holy moly, you've come a long way.
Race cams have lots of valve overlap, and the intake valve doesn't fully close until the piston is 1/2 way up the cylinder. But we know its not being "pushed out" back into the intake, because the column of rushing intake air precludes this. I'm sure it works, but I don't understand it. A properly cammed and intake runner tuned normally aspirated race engine can achieve better than 100% fill efficiency due to this "inertial supercharging" effect. I would like to see what the port design and intake runner length is, on these Atkinson engines.
Well explained. I have just bought a Toyota Corolla hybrid with an Atkinson cycle engine and wanted to understand the principle. Thanks for the video.
One question - where can I get a supercharger for my Atkinson??? That would be amazing! Miller Cycle HERE WE GOOOOOO! Words fail at how excellent this video is. I have learned so much from you sir. Thank you.
I drove a Lexus NX today with the Atkinson cycle and turbo and I was delighted by the smooth torque that it delivers.
+serge vivier This is actually deceiving; the 8AR-FTS Lexus uses on their 200t cars are actually BOTH; the engine can operate on either the Otto cycle or the Atkinson cycle depending on load, speed and throttle application. Toyota/Lexus calls it VVT-iW, or Variable Valve Timing intelligence "Wide".
I think I can leave it here, but this IMO is the first time I heard of such technology of running both Otto and Atkinson on a single engine. Enough to warrant a separate video on? What says you, Jason +Engineering Explained?
Great explanation! I've been curious about this since I got my hybrid.
Still one of the best explanations 6 years later.
Still one of the best explanations 8 years later.
i tuned my VVT to create an atkinson effect on highway cruising. works well.
I would love to see a video that dives into the Toyota/Lexus 2gr-fks engine. I am fascinated on how they have used the Direct Injection in conjunction w/port injection as well as the Atkinson cycle, cooled exhaust gas recirculation & VVT-iW intake camshafts. I have a 2015 Lexus GS350 F-Sport. I can not find much out there on the engineering side of this engine. Thank you ahead of time if you can put something together about this!
I would love to see you do a video on the topic of cam-less technology (such as Koenigsegg's "Freevalve" system). Obviously an explanation of how it works, but also the possibility to incorporate variable combustion ratios, Atkinson Cycle and other benefits to greatly increase power and efficiency. I have always been in love with the next level valve systems, from V-tec, to Valvetronic and now Freevalve!!!!
Great channel, thanks for all your great content.
And don't get me wrong, your reviews are definitely top notch as far as car reviews go. You have a very unique way of showing the viewer a very personal view point. I do like your engineering vids better, but the reviews are very good for what they are.
After viewing countless animations and other videos, your whiteboard lesson clicked with my brain. Thanks!
Amazing that this design is so old, but in the last few years has started to get very popular in vehicles with ICE's. As of this date (11/28/22), Wiki lists over 50 vehicles built since 2018 with Atkinson cycle engines...and this video is from 2014...with a list of 5 vehicles.
Also note that by allowing the combustion charge to expand to greater than the initial compression charge, there is a reduction in temperature (expansion of a gas being generally endothermic) so the engine "runs cooler" by converting more energy into torque instead of heat.
Good point.
Some smart guy now needs to figure out how to do this with less moving parts. It will be the next flathead V8
How does air-fuel mixture, being pushed out of the intake valve, travel into another cylinder ? What is the path and conduit for that movement ? Is it to just one specific cylinder ? Which one ?
Thanks for making such an amazing video. I always love to watch the whiteboard work hehe♥️
Thanks for da clear explanation of da two
Tämähän se osasi selittää sen asian niinkuin pitikin. Just said that after watching. Kiitos juippi.
The only advantage I can see here is the piston pressure delta during the strokes. Of course it would need to have direct cyl injection to work right (pass emissions). It seems to me that a regular otto eng that simply has a crankcase pressure that closely matches intake pressure would be even better. Then you net all the bennies the Atkinson has, but fewer drawbacks, like pumping heavier air around the intake. You also net reduced crank/rod/piston air friction in the crankcase. You would not need direct cyl inj either. Seems like a win win?
Basically picture a PCV system with a much larger passage between the crankcase and intake to balance pressure very quickly. Of course it would need to filter out the oil, which I'm sure can be done. The only down side I see is a little more ring blow-by, but I'm guessing that would be very small and not much of an issue until the rings are nearing end of life?
Ideally it would use a small throttle valve to control flow through the crankcase. Meaning it would let some air in for pcv needs, but when you give it gas it would open with the throttle to flow air into the case so the intake isn't having to do both. If sized and actuated correctly, the throttle response should be normal and piston delta maintained. It would only notice when when letting off the gas, at which point it must suck down the crankcase, but I see no drawback.
If coupled with a turbo I'd assume venting positive crankcase pressure (above ambient) back into the intake before the throttle blade would be best?
So am I missing something or does this seem like a better plan?
This is amazing. Does they can actually do that to the engine. Have to know a low compression engine will last a lot longer than a high compression engine. So therefore you're able to use the low compression when you're idling. But when you going slow. Or cookies you just put a low compression engine in there. With very little power.
Very good video. I noticed a few comments confusing overlap scavenging and the Atkinson Cycle.
So typically an atkinson cycle engine has a lower compression ratio vs a normal otto cycle engine? These engines also produce less tq...The mazda skyactiv engine seems to have eliminated atkins drawbacks...its running a 13:1 compression ratio and is fairly torquey. Mazda's piston design and GDI allow for great efficiency and performance!
You explaned the the Atkinson Cycle very well thank you from Australia.
Been watching your videos since I saw one of your first ones. With plug ins and hybrids growing in popularity would I’d love to see a redo to how you do it today. Just bought a fusion energi and want to understand it more.
How is the gas system different? For instance in the Ford Maverick, Apparently there is 2.7 gallons worth of equipment inside of the gas tank to work with the Atkinson motor. What would that equipment be? Apparently the EcoBoost and Hybrid vehicles have the same gas tank but the Ecoboost is 16.5 gallons and the hybrid has 13.8 gallons. So what does the Atkinson motor need in the fuel system to run and how complicated is the fuel system? Thanks
Can you explain the difference between this and the one that is on the Tacoma which don't have aether electric engine nor super charger.
My understanding is that, while modern Atkinson engines do close the intake valves with less volume, they also raise the piston further to create a *_higher_* compression ratio. I'm choosing these cars because they use essentially the same engine, so all other factors are the same. And I'm getting this data from Wikipedia:
Toyota Camry, Engine model A25A-FKS, compression ratio 13.0:1
Toyota Camry Hybrid, Engine model A25A-FXS, compression ratio 14.0:1
Toyota Corolla, Engine model 2ZR-FAE, compression ratio 10.5:1 or 10.7:1 (conflicting data)
Toyota Corolla Hybrid, Engine model 2ZR-FXE, compression ratio 13.0:1
Also, it seems to me that, while efficiency is increased, it comes with both lower power *_and_* a narrower range of rpm where efficiency is at least good. Neither is a disadvantage for a hybrid, where the motor(s) help(s) to keep the engine in the narrow range where efficiency is very good.
They can't raise the piston any further than the top of the stroke, but they can increase the compression ratio by making the combustion chamber smaller.
@@rbez1984 "They can't raise the piston any further than the top of the stroke."
The "top of the stroke" is determined by the crankshaft. Which is different,explaining the published difference in the compression ratio.
I wish your videos had more views. Very informative. Your videos make things easy to understand for us non engineers :)
Wish granted!
So after watching the RC-F video I had to check this out, ....so for Atkinson cycle does the mixture lean out as well? I would assume not due to the fact that Nox would increase right? or am I wrong Jason?
I believe NOx would not increase, since in an Atkinson cycle the temperature developed within the cyclinder would be lower than Otto cycle... ( Lower compression ratio = less NOx )
so are we pushing the air fuel mixture out? (1:38) is it true only for port injection engines? what happens in compression stroke in direct injection engines? like toyota M15A-FKS?
very educative. thank you regards
And in non hybrid vehicles Toyota combustion engines can switch between Otto and Atkinson cycles using variable valve timing technology? In Toyota VVTi system valves operates by electronic systems? Do I understand it right?
Very well explained
you mention thermodynamic efficency of a higher compression ratio.
compression ratio is a factor of the fuel octane number and is limited by preignition and detonation, the higher tie octane number the higher the allowable compression ratio and therefore the higher the efficency of the engine.
the lowering of the compression ratio from 12 to 10 to 1 negates any savings and advantages made by going to atkinson cycle, however... by using atkinson cycle and ensuring the compression ratio stays at 12 to 1 by reducing combustion chamber volume accordingly will give all the adavntages the atkinson cycle engine can offer and by having a variable timed intake valve in tandem with a knock sensor the compression ratio can be varied to maximum efficency to suit what ever octane fuel is being used at the time.
It was my understanding that a miller cycle engine has longer exhaust valve duration open into the intake stroke to help equalize cylinder charge, and aid exhaust scavenging, this equalization helps forced induction multi cylinder applications have equal forces on the crankshaft and allow smooth power delivery and improve reliability! Please let me know if I am incorrect!
Your brother-in-law, Justin Time, stopped by to say he wasn't going to be late after all. Thought you should know.
This is quite the nerdy question, but how does the efficiency of the Atkinson cycle compare to that of the Otto cycle when both are compared to the Carnot cycle? e.g. Atkinsons is X percent of Carnot efficiency and Otto is Y percent of Carnot efficiency?
Smaller volume fuel charge relative to the power stroke volume means more complete combustion and thus more energy extracted. The real magic is in the fact this can be controlled in real time by variable valve timing. There are lots of ways to restrict the the air fuel intake but if you physically restrict the air intake flow it makes the engine less efficient. This method restricts the air fuel charge by timing the valve closure and not by restricting air/fuel delivery.
Basically an turbo otto uses the leftover pressure to push the turbine, an Atkinson engine avoids that leftover pressure and thus avoids waste energy.
You don’t explain that a major reason to use Atkinson is to avoid pre-ignition (as well as to improve fuel economy) when you want full power. Only the electric motor of a hybrid, PLUS Atkinson, can give the equivalent (and more) power of the Otto cycle (assuming no change in valve timing). Please confirm.
Well, obviously it works, since you've not only done the maths but also seen the dyno results. But back to the theory: I always learnt that the ram effect in the induction gas column was greater than the initial backpressure of the rising piston, thus continuing to fill the cylinder during the upstroke. Now you're saying that at the point where filling is achieved (inlet pressure < cylinder pressure), the inlet valve remains open, raising the pressure in the inlet tract. Thus, the inlet tract is continuously at higher pressure than on an equivalent Otto-engine and becomes something of a pressure vessel, held steady within a sinus-wave by the turbocharger. So the turbocharger has more work to do on an Atkinson-engine, but that on a weaker input-force, since the exhaust-pulses contain less expansion-gas-moment. I'm assuming standard turbocharger technology.
Hi dude, say you hi from Ecuador..! Explain me, How can have the crankshaft a longer career than the intake? it´s just a timing synchro with the valves?
I think a longer duration cam( different grind all together)
If some of the mixture flows back to the intake manifold during the compression cycle in an Atkinson engine, does it actually solve the common problem of carbon buildup on the intake valves in GDI engines? I'm driving a 2018 Hyundai Ioniq Hybrid and it has an Atkinson variant of Hyundai's GDI kappa engine.
I suspect the fuel is injected after the intake valve closes, but good question. Would like to confirm this as well. I have a KIA Tellaride which is using the Atkinson variant of Hyundai's GDI kappa engine.
Same question.
*Hmmmm well it seems to me the Atkinson cycle is the same 4 stroke but basically a long duration cam in a sense with short lsa timing (like a atmospheric race engine) .. instead of the overlap of valves for scavenging of poor flow heads etc.. the scavenge of the exhaust pulls the intake air in the combustion chamber.. but with this they don't scavenge as much as they close the exhaust abruptly to keep some of the exhaust and to push some of the intake air back out.. plus using some of the exhaust keep nox down and deleting the egr valve, and pre heat the gas/air mixture.. interesting.. this was obviously adopted from race technology and came useful for the generator hybrid generator system. For one this technology sux for a vehicle that needs torque and throttle as the hybrid usually runs at one speed to charge the batteries and run the motor aka "hybrid" lets just say interesting. I like it for what it is..
perfectly explained! thank you
Will the efficiency of Atkinson remain same if we use Turbo Charger with it? Turbo charger will push more air into cylinder increasing the pressure. Does it mean cancelling out the positive aspect of Atkinson by having turbo charger?
I'm not an engineer but I'm pretty sure, that there will be some difference because the engine will still push some of the air out.Maybe it might create some extra "air friction" for the turbo, resulting it to slow down, but nothing crazy.
I take it you could not use this on a 1 cylinder engine. Might it be that you could use it only on 4 cylinder, or multiple of 4 cylinder engines since the gas is needing a place to expel into another intake?
Great explanstion but what bugs my mind is the oxygen/mixture sensor and the intake manifold operation, sounds a lot more complex in this type of engine
Is it more energy efficient or fuel efficient? If you wanted fuel efficient would you just put less fuel in and more air, and keep the compression
This is the one topic that always escapes me. I follow you through nearly all of it except for the Atkinson being more efficient. I think what I'm missing is the exhaust stroke, because there is less pressure due to the lower compression, the piston is used more to push out the exhaust gases? As opposed to the otto cycle with higher compression equalling higher pressure that is pushing the air out without the assistance of the piston?
+JHMBB2 Yes. It's a bit odd to think about, but you have it right.
JHMBB2 Yeap You're not alone buddy, This explanation did not make a bit if a sense to Me.
Ok so since the stroke of the engine is the same between atkin and otto you pull in the same volume of air. The intake valve in the atkn cycle closes after bdc letting some of the intake out. So you end up with less volume in the cylinder when the compression stroke starts. After the combustion stroke the exhaust gasses form from combustion. Since the intake valves let out some intake air the volume of the cylinder is more than the air fuel mix that was inside it, so the exhaust is less volume than the cylinder. Meaning there inst as much force pushing against the piston (by the exhaust gas) when forcing out the exhaust gases and as much exhaust gas to push out
JHMBB2
You are saying that in an Otto engine there is extra pressure in the exhaust cycle so when the exhaust valve opens, the gas escapes quickly on its own without the help of the piston. When that excess pressure escapes on its own it is inefficient and wasteful. That was pressure that could’ve been used to further move the piston in the power cycle. That is the main advantage of the Atkinson cycle, less waste.
to understand that you have to understand how the original atkinson cycle engine worked
it was called differential engines
which means it used 2 pistons to change the chamber volume between compression and decompression phases
those cycles are all based around the thermodynamic of gases
a gase at constant pressure will expand to generate work
so gas before combusion have a lower pressure than gas after combustion
hence, oto cycle waste energy, while atkinson cycle match better how a gas expand after combustion
Curious when do you think you will cover Adiabatic Engines? (Like the Smokey Yunick hot vapor engine? )
Do you think a split cycle engine be better performing as far as different intake and compression stroke volumes are concerned?
Hi, I have a question to this topic. Is it possible that turbo/supercharging does exactly the opposite to the Atkinson Cycle? And therefore getting higher possible output power but less fuel efficiency?
I was just reading about the atkinson cycle engine and it can change its compression stroke size, what if we used this method instead of a restricting air flow using a throttle valve?! you could have a clear intake and adjust the intake timing to produce the power you demand (controlled by the throttle position).
surely if the cylinder has the same amount of air inside it doesn't matter if that air was controlled by the intake valves letting air back out before it closed or the throttle valve restricting the flow, it should produce the same power. The only difference is that you don't suffer from pumping losses.
when a traditional cylinder closes its intake valve it actually has a lower pressure in the cylinder then atmosphere so you're actually getting a lower compression ratio (like you would with an atkinsons cycle) when you're not pressing the throttle down hard.
Am I missing something or does it mean that you'll push out 0.2l of air-fuel-mixture back trough the intake valve? What happens to the fuel?
bro, I believe u get confused the Atkinson cycle with the miller cycle, Atkinson cycle is using group of linkages which are driven by the crankshaft to achieve shorter intake and compress stroke, therefore to make the compression ratio smaller than the expansion ratio, miller cycle is the one u're talking about which short the compression ratio by adjusting the intake valve timing. even they both make the similar out come, but they still using different way.
+Tommy Jiang I agree. This is not the Atkinson cycle.
Does the pressure increase in the intake manifold? Does this cause a problem with leaks from the intake gaskets?
Thank you for the great explanation. Very helpful information.
This would be a good use for that new free valve engine. You could run your traditional otto cycle when you need more power, and then run the Atkinson cycle while cruising.
Honda does exactly that with VTEC on their Atkinson cycle engines
Pressure has units of energy per volume -- essentially energy density. This fact is very useful for thermodynamic analysis and is commonly forgotten.
So during the compression cycle, the delay will allow the piston push some of the fuel out through intake valve, right? why not close the intake valve earlier before piston reach the bottom during intake? It can cause extra loss,maybe?
you are describing a normal otto cycle engine. the thing with an otto is that there is still power in the cylinder when it reaches the bottom of the power stroke. if you take less gasses in, there will be less power left over at the end of the power stroke. you take in 1.0l of gas, but it expands to 1.2l upon combustion, you are able to extract more power out of the gasses.
misclik Am I correct by saying that Atkinson cycle is the Otto cycle with less gas taken in? It seems that closing valve earlier during intake cycle has similar function as closing valve later during compression.
Are there any diesel engines that use atkinson like cycle ?
Also, would it make sense to use a small gasoline atkinson engine and a turbocharger ?
Diesel engines work on the Diesel cycle, which is altogether different from the Otto and Atkinson cycles.
Mr. EE said at the end of the video that some older supercharged engines used the Atkinson cycle.
What percentage increase in fuel efficiency comes from Atkinson vs Otto?
Could you use this when you have low load cruise?
Can I ask how the induction cycle differs from that of a hot race cam? In both instances the inlet valve is held open a long time after BDC... I'm confused?
I've got question: since the modern engines running on the Atkinson cycle effectively use variable valve timing to perform this concept. Do they classify as variable compression ratio engines? I mean if they do adjust the timing such that the intake can close earlier, they would essentially return to having a compression ratio equal to the expansion ratio, or am I missing something?
K Sadek Timing is different from duration. You can alter the timing, but if the duration is short it would mean the intake valve would be closed for part of the intake stroke, unlike on these engines.
So turbocharging an atkinson cycle engine is not a good idea because of the lower pressure exhaust gasses, right?
Also I think that an otto engine with lower displacement or less cylinder but turbocharged or supercharged would be as fuel efficent and, maybe, more powerful than an atkinson engine with bigger displacement and more cylinders.
Correct on your first point.
The thing is, with an atkinson, you get more energy out of each unit of gasoline. realistically, you could try to have the power stroke twice as long as the compression stroke and you might still make power. the only question is how little power can you get away with making? there is basically a trade off between power and efficiency, one goes up, the other goes down.
Hmmmm.. I just have a small question though.. if you are gonna burn only 1L of intake charge, but start compressing 1.2L of intake charge comes in, are you still gonna call it "a 1.2 L engine" or a 1L engine?
I'm confused. In this explanation, how does an Atkinson engine injecting 1.2L into the cylinder result any differently than if the Otto engine had just injected 1.0L into its cylinder?
I have the same doubt... This is not increase of fuel efficiency in Atkinson cycle... This is just reducing the capacity of Otto cycle engine
threej4pope - don't be confused, just accept that engineers wouldn't use the Atkinson cycle if it didn't bring better fuel efficiency.
The 1.2L Atkinson cycle in the example compresses the same amount of air and fuel mixture (namely 1.0L) into the same space (namely 0.1L) as a 1.0L Otto cycle. However, the Atkinson cycle then allows that 0.1L to expand to twelve times its volume, while the Otto cycle allows that same 0.1L to expand to only ten times its volume. The Atkinson cycle allows the high pressure gases to expand 20% farther than they would expand in the Otto cycle before discarding them through the exhaust port. This extracts more useful work from the same amount of air and fuel, thereby improving fuel efficiency.
Great video. I think you missed a point. You have explained how both engines run on full throttle. if you run the Otto on half throttle to produce the same power as the Atkinson on full throttle, the compression pressure at TDC with be similar. This is because the cylinder will be at a lower pressure at BTC, due to the part closed throttle. Is the better efficiency due to lower pumping losses in this case. Is more energy used as the piston has to pull a partial vacuum on the induction stroke in the Otto?
thanks great explanation!
So, in line with 177SCamro's thoughts, if I put some high compression pistons in my engine and a longer intake duration camshaft (bump stick), I'll effectively make my engine an Atkinson cycle...
during this year's 24 hours of le mans, an audi official said they were running a hot-on-the-inside v motor for maximum turbo efficiency, yet they weren't harvesting electrical power (TERS/MGU-H) off the turbine like porsche, toyota and all of f1, preferring to extract maximum power from the crank. does this sound like the atkinson cycle taken to the extreme?
keep up the great videos!
TheBostonDangler I very much doubt the atkinson cycle would be used in racing. It requires a larger engine to make up for the specific power loss.
This is how modern Atkinson engines work. The old style changed the stroke by some complicated mechanism
Instead of intake valve timing. Wonder if in hybrid application the intake stay open and free wheel when coasting
So electric motor more efficiently switch to charging mode.
The ICE (Internal Combustion Engine) doesn't rotate during coasting, free wheel or regenerative braking. Watch a video on how the CVT works in a Toyota. No belts, clutches just two planetary gears and two motor/generators.
i gots to wonder.
efficiency vs power? seems like all the valve does by being left open longer is to push back the air/fuel mixture into the intake manifold so there is less fuel being used. kinda like vvt letting less in.
so if these two motors in identical cars going identical speeds for identical distances, the atkinson will use less fuel to get there? but dont all motors use less fuel if you use less of it its power? and if you need or just want to abuse the power available, the atkinson isnt going to have it, making it the only reason why its more efficient.
Very good explanation, but this topic is ripe for a redo considering how much more prevalent the Atkinson cycle is. Do you think the Miller cycle engibe will ever be added to hybrid sports cars?
Couldn’t you achieve an Otto AND Atkinson cycle motor with variable cam duration? Switch between which cycle is best for current driving conditions. Essentially just having a longer intake duration to achieve Atkinson cycle? Switching between Otto and Atkinson for power vs. efficiency. Just speaking out loud
Great video, thanks for explaining it. I own a Toyota Prius and was curious what ist type of engine is. It is not so bad in the end :)
Does the Atkinson cycle help clean intake valves on direct injection vehicles?
I have a very important question. Is it possible now or in the future to run in Atkinson cycle engine that is powered by compressed hydrogen? Is this even at all possible?
Thanks
Did not know that, cool, I've been upgrading my fuel to air ratio by supplementing the air with hydrogen/oxygen/brown's gas. My videos try to explain this "other hybrid" method to make every car a hybrid. Thoughts?
It's all very interesting, but if we compare the two cycles with the same displacement and the same combustion compression ratio, what is the difference in fuel economy? Is it worth it?
I came back to this video because of something interesting I experienced with my hybrid at high altitude. I was expecting the usual power loss, but was surprised that there was no noticable change. After my complete trip up and down the mountain, my efficiency went up by about half a MPG. I also have a "sport" mode which drops my MPG but is fun as heck to drive! I'd say that makes my hybrid worth it!
Bruce, my understanding is that Atkinson cycle is only "worth it" when used in conjunction with a second power source - which is why it is used with hybrids.
For a vehicle with only one power source (non-hybrids) Otto cycle is preferable, which is why it has been universal until the advent of hybrids.
I have read tonight that Toyota have a motor that switches between the two cycles. Didn't know about that, so haven't thought that through, but that may not "disprove" the original proposition, if one considers the Otto mode a second motor to the Atkinson mode.
Does Atkinson cycle increase the lifespan of the engine (pistons, rings) due to lower pressure and temperature?
Looking into this to understand my cars engine: 2.5L 2018 Mazda 3
If I'm trying to drive fuel efficiently, the engine feels weak, as if it was bogged down, unless I really hammer it. This must be due to the Atkinson cycle it uses at lower loads. If I switch the car to Sport Mode it really springs to life, but the Mazda folks told me not to use Sports Mode often.. odd because to me, Sport Mode merely acts like an exponential curve; it appears to just amplify my throttle inputs quicker without providing any more power than if I were to go 0-100% throttle really fast.
I can also feel when the ECU transitions out of the Atkinson Cycle because of a 'lurch' in power and sound, despite smooth throttle inputs. Anyone got thoughts on this? Cheers