Talk:Atkinson cycle

Animation

An illustration would make this page a lot clearer. (anon user, Aug 23 2005)

Sorry, Carlton Bale! Your edit was not in keeping with the Atkinson cycle heading. The rotary engine has been placed before the four strokes as it more closely conforms to the true Atkinson cycle (one power phase per revolution and different intake/expansion volumes). The original Atkinson engine completed its cycle in one revolution not two revolutions as in a four stroke engine. The different Intake/expansion volumes are achieved by late valve closing in the four stroke engine. This is not really comparable with the original Atkinson design which was based on geometric principles, as is the rotary engine. Regards, Sowilo 19:30, 2 November 2006 (UTC)

Fluzwup; Your previous edit removed a working animation. This has now been reinstated. I have been for many years researching new applications of the Atkinson cycle. The rotary Atkinson cycle engine is currently undergoing computer simulations. This engine represents a major step forward in the use of this thermodynamic cycle. Therefore I would suggest that the entry should remain unaltered unless you have some valid reason why it should not. Regards, Sowilo 11:35, 3 November 2006 (UTC)

Text and diagram don't agree

The text of the "Ideal thermodynamic cycle" section and the PV diagram in figure 1 don't agree. The diagram shows an addition of heat at constant pressure (3-4) that follows the step 2 addition of heat at constant volume (step 2a?). Step 4, the rejection of heat at constant pressure is clearly a rejection of heat at constant volume (5-6) in the diagram. Lastly, there's a reduction of volume at constant pressure (6-1) in the diagram that's not reflected in the text.

Unfortunately, I don't know how an Atkinson engine works (that's why I was looking here!), so I don't know whether it's the text or the diagram that's in error.

ExDonH (talk) 16:21, 18 September 2008 (UTC)

I believe the diagram is wrong. However, it is possible that two different cycles might be called "Atkinson" or possibly the diagram is of what is called the "Atkinson-Diesel" cycle. I am looking into this but am rather on the boundary of my knowledge. Expert advice very much appreciated! Thincat (talk) 13:50, 9 January 2009 (UTC)

alexander.mitsos I am looking at one of the references (Heywood's ICE book) and the cycle is given in four steps isentropic compression, isochoric heating, isentropic expansion, isobaric cooling. This matches several documents online. There may be two versions of the cycle? However the article needs thorough change.

Production year

Clarified to model year, production year can be the same leading to confusion. —Preceding unsigned comment added by Jappahut (talk • contribs) 18:52, 29 October 2009 (UTC)

Since we have the standard dilemma of US vs the rest of the world and the years are not particularly important in this article, I figure it's easier to simply delete the years. All these particular models are current models anyway. Cheers.  Stepho  (talk) 22:23, 29 October 2009 (UTC)

Hmmm... according to this CNet article, the 2019 Honda Insight hybrid will use an Atkinson engine to run its generator (to charge the Li-Ion battery pack and power the front drive motors) AND have the ability to latch up directly to the front drive axles, but the previous version[s] of the Insight did not use an Atkinson engine. I don't see how dropping the model year/s is going to continue working in that section. Darr247 (talk) 19:37, 21 June 2018 (UTC)

You do realise you are responding to a thread 9 years old? Also, the 2019 model year Insight has not been released yet, so it cannot go in a list of production cars. When it is released we can add it and update the 'as of' date.  Stepho  talk  22:00, 21 June 2018 (UTC)

Could be better

Both this one and the article about the Miller cycle are filled with assumptions, spin-off examples, an half-trues.

Miller cycle/engine: It should be possible to find proper references (patent by Ralph Miller?). To my knewledge, this uses altered valve timing to achive a difference between compression and expansion ratio of a 4-stroke engine. This type/technical solution is the one several engine manufacturers use today (the listed examples) to get either reduced compression ratio (knock preventing, boosted engines), or increased expansion ratio (efficiency, naturally aspirated engines e.g. the engine used in later Toyota Prius cars ).

Atkinson (much older) used a special crank mechanism that also gave such difference. Side effect of this mechanism: 1 cycle <=> 1 crankshaft revolution <=> 4 piston strokes. To my knewledge, no mfg use this one, despite that they say that they do (Toyota?).

Is'nt there some student, or anyone else, that have time and can gain some credit for it, to do some research and rewrite these articles? — Preceding unsigned comment added by 193.12.111.194 (talk) 14:10, 10 October 2011 (UTC)

Rotary Atkinson cycle engine: Expand as a main article

The Rotary Atkinson cycle engine is a very interesting topic in its own right. Its also complex; what is described and explained here appears to be just the tip of an iceberg. It should be expanded into its own article, Rotary Atkinson cycle engine. I've temporarily redirected that page to Atkinson cycle#Rotary Atkinson cycle engine. —James Haigh (talk) 2013-03-13T02:23:17Z —Preceding undated comment added 02:23, 13 March 2013 (UTC)

If you have information then please do add it. You can add it to this article for the moment. If it gets to be more than a handful of paragraphs, then we can split it into its own article. But beware not to just duplicate large bits of the Otto cycle rotary article - ie we only need the bits that are different to the Otto cycle rotary. Cheers.  Stepho  talk  08:19, 13 March 2013 (UTC)

Atkinson differential engine - diagram request

I've put in a new section on this, and I've described its operation with a word picture, also giving a book reference. However, the section should really have a proper diagram showing the Atkinson differential engine's internal workings, but the only images I've found so far have been for the engine's external appearance, e.g. at http://www.pbase.com/captain_carl/image/86215717 and http://www.pbase.com/captain_carl/image/86215675, and I don't know their copyright status anyway. Can someone who knows how to do it work up my description, those images, and maybe material from the book reference I gave into proper graphics for this section, ideally an animated gif? Thanks in advance. PMLawrence (talk) 11:18, 30 May 2014 (UTC)

Change needed in'Modern Atkinson Engine Cycle, section.

About mid away through the first paragraph in thE section on the modern Atkinson, the following sentence appears (w/ no reference provided); .

'...when this occurs, all the available energy has been obtained from the combustion process...' . This statement suggests naive ignorance of the laws of thermodynamics and their strict enforcement, or a calous wanton defiance. Either way, suggesting all the available energy has been removed mean the exhaust was no warmer than ambient, and that a pump would need to add energy back to enable flow out the tailpipe. 166.173.248.167 (talk) 10:20, 15 October 2015 (UTC) BGriffin

Modern Atkinson Engine

So it's just a regular Otto cycle engine with slightly different valve timing? It sounds like engines with variable valve timing could operate somewhere between Atkinson and Otto cycles. 24.85.213.54 (talk) 16:36, 17 October 2015 (UTC)

The complicated linkage that has been done away with is 'the Atkinson cycle" part! this is by definition an Otto cycle engine with variable valve timing! It is dishonest marketing by the likes of Toyota. They have a good product, why must they be dishonest about it. — Preceding unsigned comment added by 58.96.55.7 (talk) 04:06, 10 July 2016 (UTC)

Not quite. VVT is mostly about advancing or retarding one or more cams but generally the duration of each cam remains the same. However, variable valve lift often has a side effect of changing the duration.

The defining characteristic of the Atkinson cycle in terms of how the fuel burns is the expansion ratio can be different (usually longer) than the compression ratio. This gives the power stroke more chance to burn 100% so that there is no excess pressure left to derive power from - ie 100% power recovered. Of course, we will never get 100% but that's still the goal we aim for. Note also that VVT has the same duration for both the compression stroke and power/expansion stroke regardless of how advanced or retarded each cam is.

The other characteristic is more to do with the linkage avoiding Otto's patents.

Modern so-called Atkinson engines have the first characteristic by leaving the valve open during the compression stroke, effective cancelling part of the compression stroke and therefore altering the compression ratio. Whereas power/expansion stroke is left unaltered and gets the entire duration. Thus the compression and expansion ratios can be quite different according to the duration the inlet valve remains open during the compression stroke.

However, modern, so-called Atkinson engines do not follow the linkage of the original engine.

The article did point out that the modern version follows the burn characteristics but not the linkage design. Therefore, I think your wide-sweeping changes to the article to say that these modern engines are just Otto engines with VVT was not quite accurate. To a reader it sounds more like you have an axe to grind than an informative article.  Stepho  talk  15:00, 11 July 2016 (UTC)

I agree the vvt stuff was misleading and wrong and soapbox. Greglocock (talk) 17:29, 11 July 2016 (UTC)

Face-palm - So what you guys are saying is that my old 1970's ford Cleveland is now a Atkinson engine due to its Hot cam and resulting increased intake valve duration? Because your Otto cycle engine has revised valve timing that may more efficiently extract energy from a given charge, does not make it any variation of an Atkinson cycle engine. Note: It cannot be both an Otto cycle and an Atkinson cycle.

"The other characteristic is more to do with the linkage avoiding Otto's patents." Just think about that for a moment! without the linkage this engine is infact an Otto cycle engine! Atkinson did not patent Boyles law, he patented an engine, one with very defined features. — Preceding unsigned comment added by 59.100.214.26 (talk) 03:38, 12 July 2016 (UTC)

Wow, your 1970 Ford 351 had a different compression ration compared to its own expansion ration? Ford engineers were more advanced than I thought. I wonder why my 1975 Cleveland didn't have that feature? Of course, we're both being facetious and we both know it.

As I mentioned above, there are 2 features of the Atkinson cycle - the difference between compression and expansion ratios within the same engine that affects how the fuel is burnt and the particular system of linkages. I believe that the way the fuel is burnt is the primary consideration and that the linkage system is not particular important. A similar situation exists with the Otto cycle - it can be used in a conventional crank engine or in a Wankel rotary engine. The conventional and Wankel engine are about as different as you can get internally but both implement the Otto cycle and the fuel burns in the same way. Which implies that the system of linkages is not actually a defining criteria of the cycle but is only one way of implementing it.

Also, VVT does not normally change the effective compression ratio. Only by radically changing the timing so that the inlet valve remains open during the early part of the piston up stroke (what would normally be part of the compression stroke) would this happen. So, it is possible that a particular VVT configuration could be made to awkwardly simulate an Atkinson cycle by effectively cancelling part of the compression but we can not say that all VVT engines can do this because most VVT engines have limits to how far they can alter the timing. Or to put it another way - a horse has four legs, my dog has four legs, therefore my dog is a horse. A better way to simulate an Atkinson cycle is to alter the duration of the inlet valve so that it extends into the compression stroke - something VVT does not do.

And with a bit of design work, it is possible to make an engine that can change from Otto cycle to Atkinson cycle while running by changing the timing and duration of the inlet valve.

I'm not saying that you don't have a point. The article can be cleaned up a bit but your changes went too far in the other direction and introduced errors concerning what VVT can do.  Stepho  talk  06:09, 12 July 2016 (UTC)

"I'm not saying that you don't have a point. The article can be cleaned up a bit but your changes went too far in the other direction and introduced errors concerning what VVT can do." - you are absolutely talking about what VVT does do, this is VVT! - I cannot believe you are sticking to your guns on this! — Preceding unsigned comment added by 59.100.214.26 (talk) 07:05, 12 July 2016 (UTC)

"And with a bit of design work, it is possible to make an engine that can change from Otto cycle to Atkinson cycle while running by changing the timing and duration of the inlet valve." - Garbage, you are wrong. you are calling a horse a dog in your words. — Preceding unsigned comment added by 59.100.214.26 (talk) 06:58, 12 July 2016 (UTC)

CHANGING THE VALVE TIMING DOES NOT CHANGE THE FUNDAMENTAL 'CYCLE' OF AN ENGINE — Preceding unsigned comment added by 59.100.214.26 (talk) 07:07, 12 July 2016 (UTC)

We seem to be stuck on what VVT can and can not do. I will explain what I think it does and you can tell me where we differ.

VVT advances or retards the cam(s). It can do this to one or both cams. On some implementations it changes both cams the same amount and on other implementations it changes them separately. The amount of time the valve stays open does not change.  Stepho  talk  07:34, 12 July 2016 (UTC)

The point on which we differ: The fact that these engines can alter their duration or timing having an impact on their cycle type. I do not want to get into a 'over simplified' exchange of ideas and some resulting compromise...but here we go (FML), If I took a conventional Otto cycle engine, ground a cam up for increased intake duration, such that the intake valves close when the piston is half way up the cylinder, it is still an Otto cycle engine and still not an Atkinson cycle engine (albeit a low performance Otto cycle engine). The Valve timing/duration altering technology does not change the engines cycle type. N.B. if I have a wild cam in my vehicle, and it does increase the duration significantly enough to bump the compression cycle, then the effective compression ratio is different from the measured compression ratio...So...you were also wrong about me being facetious, I am more frustrated. A little about me: I am a Mechanical Engineer with a strong background in Automotive. — Preceding unsigned comment added by 59.100.214.26 (talk) 07:57, 12 July 2016 (UTC)

I am a mechanical engineer with 35 years in the automotive product development game. I suggest you go and read Heywood on the topic of over expanded engines as he calls them . Greglocock (talk) 08:36, 12 July 2016 (UTC)

Greglocock, I have to say that I am surprised that you would take the position that you have with those credentials, or perhaps not after further thought pertaining to my experience with career academics and shiny bum engineers! The text speaks of 'complete expansion within the cylinder to exhaust pressure' and that effect can be achieved in 'conventional four cycle engines', Even if it did go on to call those four cycle engines the 'A' word, I could point you to many, many poor decisions made by note-worthy people. Firstly, the text differentiates between the two, secondly, you are making a very loose connection, I am not sure the author expected manufacturers to con certain demographics by calling their engines something they are not. I will never agree that valve timing changes the stroke type. How engaged in this marketing are you exactly? — Preceding unsigned comment added by 59.100.214.26 (talk) 09:02, 12 July 2016 (UTC)

Guys, I am sorry if I have come off a little harsh, but from where I am standing, it is just silly beyond words. You really need to fix this page! It is misleading. — Preceding unsigned comment added by 59.100.214.26 (talk) 09:02, 12 July 2016 (UTC)

I suggest that there is a difference between harsh and hypocritical idiocy, and to me the second seems a better description of your posts. Why is it OK for you to quote your qualifications but not me to quote mine?Greglocock (talk) 13:29, 12 July 2016 (UTC)

For the record, I am a software engineer of 30 years experience who writes software for ECU's on CNG vehicles. Recent projects include the Volvo V60 and V70 Bi-Fuel vehicles. But my technical qualifications are in mathematics and software rather than the mechanical engineering field, so I'm prepared to be taught when needed.

A cycle is defined by its PV diagram. If different implementations follow the same PV diagram then they are the same cycle. I was trying to say this above when I compared the Otto cycle in conventional crank engines and Wankel engines - same cycle, different implementations. The internal details of linkages is relevant to stress analysis of the linkages and bearings and highly relevant to patent lawyers but irrelevant to thermodynamic analysis of the cycle itself.

If we compare PV diagrams of the Otto and Atkinson cycles we can see that they are identical except for the tail at the right covering the end of the expansion process and the beginning of the compression process. Heywood has diagrams 5-6 and 5-11 on pages 174 and 184. For those who don't have Heywood, http://www.mikalsen.eu/papers/natGasMiller.pdf by Mikalsen has PV diagrams in Figure 2 (although technically figure 2b is a Miller cycle but it is close enough for our purposes).

From the PV diagram, it is obvious that the Atkinson cycle can be thought of as the same as an Otto cycle where the expansion continues a bit longer (the downward curve goes for longer), or equivalently where the compression cycle is delayed a bit (the return towards the left is constant pressure for a while before compression starts to raise the pressure).

Modern engines using the Atkinson name achieve that delayed compression by extending the open time of the inlet valve into that period, nullifying any possible compression, and therefore can be analysed thermodynamics as an Atkinson cycle.

Since this is implemented by merely extending the opening time of the inlet valve, it is possible to implement this using VVT (as suggested). In practice this is beyond the range that VVT normally operates (a not insurmountable objection). But since VVT advances/retards both the opening and closing times of the inlet valve, any extension into the compression stroke also means delaying the opening inlet valve time, which robs us of the incoming charge. We need to extend the duration of the inlet valve to make a practical engine and VVT does not do this.

But as I said above, I'm prepared to be shown where I'm wrong or misguided.  Stepho  talk  14:33, 12 July 2016 (UTC)

Stop confusing yourself with your views of VVT. I suspect you are set on some existing commercially available product. For this discussion it is not important, as above, think about a conventional engine with a different camshaft. — Preceding unsigned comment added by 59.100.214.26 (talk) 21:10, 12 July 2016 (UTC)

Guys, I do not accept or believe that you can define an engines 'Cycle' by its thermodynamics. To say that its thermodynamics behave like this other engine with this other 'Cycle' (which it doesn't btw, as the Atkinson cycle does it all in one turn of the crank instead of two) seems like some very strange perversion.

"A cycle is defined by its PV diagram." - A grade bolonium, you are confused, Atkinson cycle and Otto cycle describe physical mechanical properties of an engine, these may have characteristic 'thermodynamic cycles', but these do not define the fundamental mechanics of these engines. — Preceding unsigned comment added by 59.100.214.26 (talk) 22:25, 12 July 2016 (UTC)

"Stop confusing yourself with your views of VVT." I explained above what I thought VVT did and invited you to correct me. Instead you hand waved that away and jumped to a different topic. Now you want to chastise me on what you think is my incorrect understanding of VVT. I'm more than happy to be taught where I am wrong but hand waving followed by chastising is unhelpful and just plain rude on your part.

I have also pointed out that the Otto cycle can be implemented on both conventional crank engines and on Wankel rotary engines, yet have totally different internals. Do you agree or disagree with this statement?

Please sign your messages with four tildes (eg ~~~~ ) at the end instead of relying on SineBot.  Stepho  talk  01:10, 13 July 2016 (UTC)

Stepho - You are killing me. You keep saying that you are more than happy to be taught. Please walk your talk! This is a very simple matter that you are repeatedly over complicating, I am not going to engage you on the Wankels, because once again, you are asking me to accept conditions that will lead me to your conditional truth, I do not accept your conditions. Let me ask you two very simple questions: 1. Is a Toyota Prius engine covered by the Otto cycle engine patent? 2. Is a Toyota Prius engine covered by the Atkinson cycle engine patent? — Preceding unsigned comment added by 59.100.214.26 (talk) 03:08, 13 July 2016 (UTC)

Ah, so you refuse to engage in any topic of conversation that may not support your view.

Since both the Otto and Atkinson patents expired a century ago, then the Prius engine is covered by neither patent. However, if you can point to a patent that says the Prius is covered by the Otto or Atkinson cycle then I will be happy to read it.

Please sign your messages with four tildes (eg ~~~~ ) at the end instead of relying on SineBot.  Stepho  talk  04:01, 13 July 2016 (UTC)

Stepho - the Wankel thermodynamic cycle and what you think of it, the patent expiry dates and your interpretation of variable valve timing is immaterial with reference to the actual discussion which is "the inappropriate use of the term Atkinson cycle to describe Otto cycle engines". No amount of ducking and weaving will make you correct.59.100.214.26 (talk) 04:47, 13 July 2016 (UTC)

I see your debating technique is to hand wave your opponent's arguments as 'immaterial' without actually discussing them.

The article name is 'Atkinson cycle', which is shorthand for 'Atkinson thermodynamic cycle'? As pointed out above, the Otto cycle can be implemented in different manners (conventional crank engines and rotary engines for 2 examples). Therefore, it is reasonable that the Atkinson cycle can also be implemented in different manners that obey the same thermodynamic cycle. If we were discussing an article titled 'Atkinson patent' then we would have to agree that the linkages outlined in the patent are definitive and the discussion would be closed. If the article title was 'Atkinson engine' then we could have a discussion about whether we are talking about a thermodynamic cycle or a particular method to implement it as given in the patent. But the article is about the thermodynamic cycle and the article is therefore free to talk about multiple ways to implement it. A cycle is not bound by one particular method of implementing it.

I will give a further example of how engines can implement different cycles. In my day job we take a diesel engine from a manufacturer. This of course implements the Diesel thermodynamic cycle. We remove the injectors and insert spark plugs in their place. We then change the manifold to a new one that we designed that has CNG injectors and a throttle. We then add appropriate plumbing and electrics to control these. This engine now runs the Otto thermodynamic cycle using CNG. Note that we did not change anything else internal to the engine - external bolt-on changes only. The same internals can run both Diesel and Otto cycles depending on the external bolt-on parts. The engine manufacturer then implements our design on their own production line. I have previously pointed out that thermodynamic cycles can be implemented multiple ways and I have now pointed out that the same set of linkages can implement different thermodynamic cycles. Thermodynamic cycles are not necessarily limited to a particular method of implementation.

Wikipedia etiquette for these discussions is detailed at WP:BRD. We normally don't change an article while it is under discussion. If you feel we are stagnating then you can ask for more input from Wikipedia talk:WikiProject Automobiles or any other project you think might be appropriate.  Stepho  talk  00:10, 18 July 2016 (UTC)

"I see your debating technique is to hand wave your opponent's arguments as 'immaterial' without actually discussing them." Stepho, I was trying to simplify things for you because you keep trying to complicate things are have your conditions accepted and your needs met. I think you are quite malicious and your intent is not in the interests of those trying to learn, or in the spirit of Wikipedia. Imposing 'thermodynamic cycle' over "*" cycle is straight garbage. I'll say it again, "an engines thermodynamic characteristics do not define its type", unfortunately for you, that is something you cannot control/change! — Preceding unsigned comment added by 59.100.214.26 (talk) 23:56, 19 July 2016 (UTC)

Since we are having trouble convincing each other, I have asked at Wikipedia_talk:WikiProject_Automobiles#Atkinson_cycle for other editors to comment here. Please feel free to ask at any other project for others to comment.

If you think I am malicious and acting against the interest of Wikipedia then you should report me to the Wikipedia administrators. You can do this at WP:Administrators' noticeboard/Incidents. You can also read WP:DISPUTE for other possible actions.

You have stated your position a number of times. But you have not explained why your position is right or why my position is wrong. Can you provide some support for your argument.  Stepho  talk  01:53, 20 July 2016 (UTC)

No comments from the guys at the Automobiles project to help us resolve our stalemate, so I have put the same post at Wikipedia_talk:WikiProject_Engineering#Atkinson_cycle. Please feel free to ask at any other project for others to comment.  Stepho  talk  08:03, 23 July 2016 (UTC)

Are you guys serious? If you talk about the Atkinson Cycle Engine, you mean the patent of 1887 with its linkage. If you refer to an Atkinson-cycle engine you are talking about any kind of engine following the thermodynamic cycle, starting with Atkinson's own Utilite Engine. — Preceding unsigned comment added by 2A02:8070:21A2:A700:9284:DFF:FEF5:C9F8 (talk) 13:37, 4 January 2017 (UTC)

Torque?

I've seen some sources say that Atkinson cycle engines have comparatively poor low end torque. There's no mention of torque in this article (odd for an engine article). Any reason to doubt these sources? --Juventas (talk) 01:55, 7 June 2017 (UTC)

Do you mean real Atkinson engines, about which I know nothing, or modern 'over expanded' engines, ie short intake long exhaust timing? They'll be gutless compared with a normal valve timing at the same rpm and capacity because they suck in less mixture. Greglocock (talk) 03:54, 7 June 2017 (UTC)

Can actual efficiency numbers be provided?

This article and related articles make multiple statements along the lines of "The Atkinson cycle is designed to provide efficiency at the expense of power density." Can some comparative numbers be provided here or elsewhere? Thanks. — Preceding unsigned comment added by 23.29.213.104 (talk) 21:20, 22 October 2019 (UTC)

The nature of an open wiki is that if you can find those numbers then you can add them yourself. We can help you with the formatting side.  Stepho  talk  22:19, 22 October 2019 (UTC)