Talk:Four-stroke engine

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Serious concerns about terminology

I have looked through the engine section on Wikipedia and I have some serious concerns about the terminology, which I feel is misleading or inaccurate. I should mention that I have no problems with the content of the articles. I have a degree in mechanical engineering and a strong background with engines, which alone should not give me unquestioned authority here. But rather, I'm hoping that my opinion and research will at least be considered and discussed. I have outlined below my list of problems with the terminology here:

• A four-stroke engine is NOT the same as an Otto cycle engine. There are four-stroke cycles that are NOT Otto cycles, mainly the Diesel cycle. This is, in my opinion, the most serious error.
• I submit that an Otto cycle engine does not necessarily need to be four-stroke. The generally accepted definition of the Otto cycle (which is an idealized cycle) is based on the thermodynamic cycle - isentropic compression, constant-volume heating, isentropic expansion, constant-volume heat rejection. This cycle is concerned only with the compression and power strokes. Whether or not there are intake and exhaust strokes is irrelevant. (Of course, adding boost or backpressure changes the cycle but these are not ideal for a naturally aspirated engine.) The very first paragraph in Internal Combustion Engine Fundamentals by Dr. John B. Heywood (which is considered to be one of the premier authorities on engines) reads, "The internal combustion engines which are the subject of this book are spark-ignition engines (sometimes called Otto engines, or gasoline or petrol engines, though other fuels can be used) and compression-ignition or diesel engines." This quote is being posted under fair use policy. Dr. Heywood (and I) equate the Otto cycle to an ignition by spark, and NOT to a particular number of strokes. Additionally, he equates the Diesel cycle to compression ignition. Throughout the rest of his book, he uses the terms "spark-ignition" and "compression-ignition" almost exclusively to differentiate between engine types. It is my opinion that this terminology is the most accurate and most descriptive way to categorize engines, and I suggest that it be used throughout all Wikipedia engine articles.

Any responses to my request?

Signed User:Fyre4ce

It is nice to have an automotive engineer here. I, for one, do not have the depth of knowledge about engines that I do about some other articles to which I have contributed. If I am at fault about four stroke and Otto, compression ignition seems a refinement rather than a departure from the principle that shocked apart Otto's early engine. Wikipedia needs to be consistent with modern technical terms, without loosing the readers in them. To the extent that it does not interfere with looking deeper into the technical literature, it seems that how real engines work is more appropriate here than idealized thermodynamic definitions. This is pointed out by the apparent failure of Carnot to lead the way to compression. (Being a physicist who has worked with engineers, I can imagine his frustration.) David R. Ingham 07:07, 17 January 2006 (UTC)

David,

Thanks for the reply. I'm very new to Wikipedia and, if nothing else, it's nice to know that someone out there is listening. :-) I think it's entirely possible to use a standard in terminology that will be both informative and not stand in the way of more in-depth research. I also think it's important to make reference to the idealized thermodynamic cycles, because I think understanding how a real engine relates to its idealized cycle is an important part of understanding how the engine works (and this was how it was taught at the university where I studied - ideal model first, how the real world situation differs next). What do you think should be my next step? Before I would consider making sweeping changes to the naming and organization of the information in the engine section, I would want to go through all the main articles carefully and lay out a new standardized and corrected scheme. This will take some time. I would like to get approval from other editors but I also don't want to find myself patiently waiting for months for a "sure, that sounds good" that may or may not ever come, and that may or may not be from someone with a background in the subject. Since you seem to have experience writing on Wikipedia on technical topics, I am hoping you can give me some advice.

Thanks, Fyre4ce 23:12 Jan 17, 2006 EST

• You're not likely to find any definitive editor of this article to approve your endeavor. Even if one or two people tell you it's okay, that's not how it should work. The process is a bit different. Just make the changes, and as frustrating as it may be, others will come along and change whatever they think is not right. Like they say, be brave about editing... --flyhighplato 05:07, 18 January 2006 (UTC)

"....Scalpel!" (It will actually take me a while before I'm really ready to start cutting and pasting.) Fyre4ce

The term 'four-stroke' is widely used as a synonym to the Otto cycle, but I agree with you when you say this is incorrect terminology. I urge you to start editing. This article as well as the Diesel-related articles all require some major reconstruction, as much of the terminology is incorrect and the loose connections between an idealized cycle and a real world engine application needs to be set straight. - Victor van Poppelen (talk • contribs)

The Otto cycle and four-stroke cycle are different things. I came to this article hoping to explain to a friend the difference between the diesel and otto cycles, and instead found a rough description of the four-stroke cycle that conflates the diesel and otto cycles as if they are the same thing. I agree with a move to reconstruct - this article would make a good base for the definition of four-stroke and the otto cycle could be described properly.

mnemonic paragraph

I'm removing the following paragraph since it looks unencyclopedic to me. I can't see any way to fix it and, honestly, no reason for such a mnemonic in an encyclopedia (it's not a high school clue sheet) --- cbraga 20:40, Jun 9, 2004 (UTC)

One way to remember the four strokes and their functions is the series "suck, squeeze, pop, phooey", or alternatively "suck, squeeze, bang, blow". The four "strokes" are also present at each stage of a jet engine, where they are performed simultaneously rather than as a sequence.

Desmodromic valve timing

I'm thinking of doing the same to the Desmodromic valve timing section. Does anyone have and idea about how to fix it?

Acegikmo1 01:13, 11 Jul 2004 (UTC)

I've rewritten it - see what you think. Incidentally I thought that the mnemonic above was actually quite worth keeping - it's a common phrase and including it to my mind doesn't subtract from the "encyclopedicness" of the article, whatever that means. Graham 03:28, 11 Jul 2004 (UTC)

If you'd like to reinstate it, I wouldn't object.

Acegikmo1 03:35, 11 Jul 2004 (UTC)

Hello, I'm french, and read this article. I'm sorry to say that i disagree with the interest of the desmodromic valve train. The only advantage of this device is to avoid the problem of inertia at high speeds. The advantages you explain is the one of VVT (variable valve timing) or VTEC from Honda. (I'm motorist, see the Page of Rémy in the french wikipedia)

• Hello. Are there factual inaccuracies in the desmodromic section? The article currently states that the advantage of desmodromic valves is that they perform better at high speeds, which you seem to agree with. I don't know anything about it, though, so if you see inaccuracies, please feel free to fix them or point them out. -- Wapcaplet 15:48, 24 Oct 2004 (UTC)

For reference : http://scarbsf1.com/valves.html Ericd 21:50, 16 May 2005 (UTC)

Desmodromic valves have the advantage that the force varies according to the speed (the valve acceleration) instead of depending only on the lift and the spring stiffness. At least in principle, this means low wear and friction at low speed combined with no valve float at high speed. It may only save reciprocating mass if materials like carbon fiber, that can't make good springs are used. Otherwise, like with Panhard's torsion bar valve springs, the lever will weight as much as the spring would have. Another option is sleeve valves (as Panhard used earlier) that rotate instead of reciprocating, but coil valve springs work better than anyone would have expected. David R. Ingham 17:02, 6 January 2006 (UTC) For reference : link title End problem off valves

Animation

The 4-stroke animations are broken. They don't run in Windows Media Player 9 or Winamp, as far as I can determine. They should be fixed or removed. Quicksilver 19:15, 15 Jun 2005 (UTC)

Has this animation been nominated as a featured animation or picture or whatever? It is very nice. David R. Ingham 06:02, 6 January 2006 (UTC)

Animation Direction

Cool animation!! I would like to point out that 99.99% of all IC engines rotate clockwise when looking at them from the front. The "funny" rotation immediatly seemed un-natural to me. However, this view could be looking at the engine from the flywheel end, or the 2nd engine in a contra rotating marine application.

The monikers: suck, squeeze, bang, blow were taught in the U.S. military. 69.213.205.190 18:03, 5 October 2005 (UTC)

That number seems too large. In two piston-engine airplanes, unless costs of stocking pars are cut, one goes clockwise and the other counterclockwise. In one engine airplanes, German-Swiss and Anglo-American engines turn, or turned, in opposite directions, as seen in photos showing the propellers. Reed valve two strokes can run either way. The Messerschmitt KR200 and Spatz Kabinenroller used this instead of a reverse gear. Small model airplane engines can be used as pushers or with left or right propellers, by starting them in the opposite direction.

Anyway, I don't see anything showing wether the annimation is from the front or the back (or the engine is transverse mounted). David R. Ingham 05:56, 6 January 2006 (UTC)

This looks correct as viewed from the flywheel (rear) end, assuming a left hand drive USA vehicle, with: 1. an inline engine, transversely mounted with the transaxle toward the driver's side. 2. the driver's side bank of a V engine mounted classically. 3. the forward bank of a V engine mounted transversley with the transaxle on the driver's side. The spark plug is centered in the combustion chamber, and there appear to be separate intake and exhaust camshafts, so I would assume this matches #1 above. (very common DOHC arrangement) BobJones 23:48, 20 June 2006 (UTC)

Output Limit paragraph

The last paragraph in this article specifically states that it applies to four-strokes. Piston speed, however, is the limiting factor on all reciprocating engines, not only four-strokes. Shouldn't someone move this section to reciprocating engine page? - victorvp (talk)

History

According to

• Hardenberg, Horst O., The Middle Ages of the Internal combustion Engine, Society of Automotive Engineers (SAE), 1999

the 1862 Otto (O#O) engine did not have exactly the modern four stroke cycle and did not work for long.

Also it says he knew nothing about Carnot and discovered the advantages of compression by turning the flywheel backward by hand! David R. Ingham 06:13, 6 January 2006 (UTC)

The statement that he invented the four stroke cycle was not exactly what the German courts found. His patent was not held to cover internal compression or even the four stroke cycle. See internal combustion engine#history. David R. Ingham 06:02, 10 January 2006 (UTC)

terminology and focus problems

I agree with Fyre4ce about the problems with this article. The "four-stroke cycle" describes a particular operating concept for an internal combustion reciprocating piston engine; it is not a synonym for the Otto cycle (despite the fact that Otto's first engine was indeed a four-stroke).

The Otto cycle is an idealized thermodynamic model of the processes taking place in a gasoline, spark-ignited engine; the title "four-stroke cycle" should be restricted to a page describing the details of operation of a real four-stroke piston engine (e.g. valve timing, output limits, volumetric efficiency, etc.), and a page describing the Otto cycle should be far more focused on the ideal thermodynamic cycle (isentropic compression/expansion, constant volume heat addition, constant volume heat rejection, and the analyses that fall out of that simple model). See the page on Carnot Cycle to get an idea of what I'm talking about. It's fine to enumerate the differences between reality and theory, but in writing about a theoretical construct, the focus ought to be on the details of that construct.

I'd be happy to help rewrite an article, but I don't know anything (yet) about the shorthand used in producing things like integrals and section headings. IOW, I'm not ready yet. I will need to study the "how to edit a page" guide first.

Joe Frickin Friday 18:14, 27 January 2006 (UTC)

"Output limit" paragraph

There is a lot of confusion here, and this does not seem the best place to discuss these things. Rod/stroke ratio seems independent of which cycle is used. Without supercharging, the output limit depends most on the air intake. I suggest starting over. David R. Ingham 07:04, 7 March 2006 (UTC)

I agree with that. There are other limiting factors which predominate depending on context. Piston speed limitations are real enough but it never stopped shortening the stroke and spinning it like a turbine anyway. Overall air flow is a more important limiting factor. The rod/stroke ratio thing is a somewhat overblown pet theory of Smokey Yunik but it shouldn’t be presented as the ultimate power secret. The section should be tweaked.--=Motorhead 00:52, 10 March 2006 (UTC)

motor fetishism

The reverted edit [[1]] reminds me of Coleman's abnormal psychology textbook (I think that may be Coleman, James C. (1964). Abnormal Psychology and Modern Life (3rd ed.). Illinois: Scott, Foresman and Company. Or the first edition, 1950.) His example was a boy who was sexually aroused only by exaust pipes. This edit is similar. David R. Ingham 04:41, 8 March 2006 (UTC)

Efficiency

Some typical and maximum efficiency levels would be useful. Tobyw 12:29, 8 March 2006 (UTC)

valve clearance adjustment

Some formatting needs to be fixed in this section, there's a random "Headline Text" thing and some writing that goes on forever off to the right (at least in Safari) Thetrump 23:06, 6 April 2006 (UTC)