Talk:Two-stroke engine

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Somebody should join the pages two-stroke cycle and two stroke cycle - 2004/04/04 20:11 CET

Morven: (... removing part about 2 exhaust strokes since it didn't make much sense.)

it makes sense.. the noise an engine produces depends on the number of exhaust strokes. A two stroke engine has twice as many exhaust strokes as a four stroke engine (at the same rpm) and so produces twice the noise. MH 2004/05/06
But a 4 stroke engine will have more capacity for the same power, and thus will often have more cylinders, and thus the difference will be erased.
Except the 2 stroke burn cycle is interrupted by the exhaust cycle, while the 4 stroke completes the burn cycle before the exhaust cycle. iow, the fuel gases explode out of the chamger into the exhaust system.

Were there any 2-stroke diesels that were valveless? I've never heard of any, which must mean that at least it was rare. Any references, Andrewa? —Morven 20:13, 7 May 2004 (UTC)

There was a to-stoke diesel called Wichmann that were valveless, this was a big 2500 bhp diesel engine commonly used in the fishing fleet of Norway. (unsigned).

Also Crossley and Napier deltic diesels were valveless. Biscuittin (talk) 17:54, 27 December 2007 (UTC)

There were/are many tiny (typically 1.0cc) model aero engines which were compression-ignition valveless two strokes. Surely these count as diesels ? Cabinscooter 20:47, 18 July 2006 (UTC)
Not really, see model engine. Biscuittin (talk) 17:54, 27 December 2007 (UTC)
Disagree, they are compression ignition, liquid fuelled, reciprocating engines. Therefore in all essential respects they are diesel engines.Greg Locock (talk) 20:00, 27 December 2007 (UTC)

Does anyone have resources re: fuel efficiency/emissions of gasoline 2 stroke outboards? —Amgine


The "Basic Operation" section is contradictory. Does the air-fuel mixture enter the cylinder as the piston rises or as it falls? Also, a graphic would be most helpful.

Typically a bit of both, around about bottom dead centre. There's no induction stroke, nor an exhaust stroke. Instead these processes both occur independent of the piston movement, and overlap. That's the essence of the two-stroke cycle. Andrewa 17:07, 23 November 2005 (UTC)

[edit] bidirectional running causes damage not true

This passage. "It is true that Two-stroke engines will start and run in either direction, however running one in reverse will cause internal damage." is not correct. I have an Mercury outboard that uses "direct reversing." In other words it runs in both directions without causing damage. This was the first consumer straight six Mercury made and the chief engineer, Carl Kiekhaefer, was not sure a shifting gear case could take the increased horsepower. To get around this he merely had the outboard run forward or backward. William (Bill) Bean 14:56, 21 November 2006 (UTC)

Although it wont cause damage on engines designed to do it, it can over time cause problems with an engine not designed to run backwards for the reasons stated in the article. When designed to do so there is no problem at all.--=Motorhead 23:36, 21 November 2006 (UTC)

[edit] reference for 2 stroke emissions

-Design and Simulation of Two-Stroke Engines Gordon P. Blair -The internal combustion engine in theory and practice by C.F.Taylor -Internal combustion Engines and Air Pollution by Edward E. Obert --=Motorhead 19:38, 1 Apr 2005 (UTC)


Bombardier and Rotax both have direct-injection marine outboard 2-strokes that run on straight gasoline and meet the strict California Air Resources Board emission standards. Information about this technology might be a useful addition to this article.

[edit] Reed valve

Can these be made of fibers alone, or are the fibers always bound into a resin to form a composite material? If the latter is the case, please re-link from carbon fiber to graphite-reinforced plastic. You might also want to do the same for glass fiber, re-linking to glass-reinforced plastic.--Joel 03:09, 16 Jun 2005 (UTC)

[edit] Use of both valves and ports in one engine

See the graphic at How Stuff Works for a design with inlet ports in the sides of the cylinders, and exhaust valves in the head. It looks very credible to me, but we don't describe this variation at all, in fact we more or less imply that it's one or the other. Who is right? Andrewa 17:07, 23 November 2005 (UTC)

The arrangement shown on the link you supplied is described in the “Valve in head” section. The fact that the ports are in the cylinder sidewall is assumed because that’s the only place they can be. The engine type is used by detroit diesel and others.(http://en.wikipedia.org/wiki/Dugald_Clark)(.--=Motorhead 06:46, 28 November 2005 (UTC)

Not so. There could be both inlet and exhaust valves in the cylinder head, and no ports at all. That's what I assumed this section was describing, and I still think it's the more natural reading of the section as it stands. Andrewa 09:58, 28 November 2005 (UTC)

Link above corrected to point to version before changes - Andrewa 09:54, 12 December 2005 (UTC)

There is no case I am aware of which uses both intake and exhaust valves in the head for a 2 stroke engine. The problem of scavenging would be nightmarish with such a system but I wouldnt doubt that someone somewhere tried it without success. The intake and exhaust have to be open at the same time in a 2 stroke. There is no system in operation which can have both intake and exhausts in the head and be open at the same time and still scavenge with any reasonable efficiency. The valve in head may be intake or exhaust but not both. I think you are confusing 4 stroke diesels with 2 stroke diesels. The only "natural" reading would be to assume uni flow , cross flow or loop scavenged flow when considering a 2 stroke engine, as all systems fall into these 3 types. In all cases there are ports in the cylinder wall.--=Motorhead 04:01, 6 December 2005 (UTC)

Exactly. I think your new version eliminates this confusion, which is common elsewhere on the www, not just on Wikipedia. Thank you! Andrewa 09:54, 12 December 2005 (UTC)
Hmmm. Perhaps one reason for this confusion is that the first two-stroke engines were Clark cycle diesels, which have no ports in the cylinder walls, see Dugald Clark. Perhaps all modern two-stroke engines (whether diesel or not) do have cylinder wall ports, but these first ones did not. The article still seems to need some work IMO to make this clear - if I've finally got it sorted out! Andrewa 16:23, 16 December 2005 (UTC)

I havent been able to find much detail on Sir Dugald Clerk's (not Clark) engine except that it used a second cylinder to pump fresh mixture through a one way valve into the working cylinder. Nevertheless, at least from the time of Alfred Scott and Day,cylinder sidewall ports were used.--=Motorhead 18:42, 18 December 2005 (UTC)

If the title of the Dugald Clark article is wrong, please fix it, or at least cite your sources and I will.
Frankly, there's a lot of misinformation about engines of all sorts (steam, gasoline, diesel, proposed) on the web. Many engine enthusiasts (I may even be one of them!) seem to write webpages, including Wikipedia articles. It's easy to pick up folklore from people who specialise in one particular type of engine, and assume for example that all two-strokes are the sort that they know intimately, or that all V-8 engines are crossplane. I'm currently looking closely at every v-twin motorcycle I see (and I see lots in my current work) to try to come up with the best set of examples for that article... it's a lot more complicated than many think! I think however that the inline twin article is mainly sorted out.
There's also a certain amount of deliberate misinformation spread by engine and vehicle manufacturers and proposers of new designs, and going back several centuries!
But I think we are making progress here. Andrewa 20:21, 20 December 2005 (UTC)

I put some sources in the talk page of the Clark page.Its a very widespread error but I think the Clerk sources have it. Vtwins? I'd definately include early harley and must have vincent maybe indian. I'd include that the vtwin was an offshoot of the WW1 radial design with most of the cylinders missing!

I guess all we can do is our best. Myths really annoy me and they spread faster than real facts do. Today I heard from my bro-in-law about adding acetone to your gas for a miraculous milage increase of 35%! (like no one ever tried that eh? hehe) Sigh.......it never ends--=Motorhead 03:31, 21 December 2005 (UTC)

AFAIK the big shallow-V twins such as Harley and Crocker are well covered by what the article already says. The myth that needs exploding is that all v-twins are this common big-end configuration. The Yamaha Virago, for example, has an enormous offset between the cylinders, strongly suggesting a double-throw crank, but I've yet to find any citeable source that describes its internals. Andrewa 10:09, 21 December 2005 (UTC)

[edit] Refactor

I think this page needs a general refactor. The headings overlap, particularly on diesel engines. We need a clearer structure. Andrewa 01:48, 25 December 2005 (UTC)

I've started this with a new history section. More to follow. The diesel engine article also needs some work. Andrewa 20:56, 25 December 2005 (UTC)

[edit] graphics

could someone find a bigger graphic of the two stroke engine with color to show the gas?

[edit] Crap article

This article has been edited into garbage! It is now a mere thumbnail definition instead of an informative article. Someone has to go back through the revisions and restore the plentyfull information that was here and now is gone.

[edit] Outboard Motors

I changed 'small outboard motors' to 'outboard motors' in Applications. Yamaha currently makes a 300hp 2-stroke, Mercury makes a 250hp, BRP makes a 250hp and Tohatsu's largest, a 115hp, is also a 2-stroke. Their small outboards are almost universally 4-stroke. So this would seem to be an obvious error.

This article makes no mention of direct fuel injection, which is is a serious omission since it is clearly necessary to the future of 2-stroke engines. The emissions info also appears to be out of date. EPA awards '04 Paul Moir 20:52, 5 March 2007 (UTC)

64.7.137.64 00:35, 13 April 2007 (UTC)

[edit] Tuning a Chain Saw

If I have a chain saw and it has idle, Lo and High adjust. The engine starts and roars to life only to be suffocated by the brake. I frantically adjust all the screws and nothing happens except it dies out, when I turn it too far. High throttle all the time. How can I adjust it nicely to hum and the throttle can actually be used.


First you must insure the idle speed is adjusted correctly. Sounds like your throttle is open too far even at idle. Could be idle speed much too high or throttle simply stuck open. Check to see that the Throttle butterfly actually closes all the way(NOT the choke butterfly). Then gently close high and low speed mixture screws and then open each about 1 1/4 turns and adjust the idle speed so the throttle just begins to open for a start. If you have a manual use those numbers instead. For the saw to rev as you decribe it must have air and its getting it from somewhere. --=Motorhead 16:13, 13 April 2007 (UTC)

[edit] Two stroke outboard oil injection leakage

My 30 HP Yamaha outboard (3 cylinder) has currently extensive oil leakage in the lowest carborator. It literally has oil coming out of the carborator intake and I have no idea where it comes from. What might be the cause?

[edit] Schnürl porting

I'm not sure if [1] should be on the links list, but it explains Schnürl porting as having the transfer and exhaust ports "overlap" in timing, to use the term for the 4 stroke equivalent. Other sources, such as [2] say that it is multiple "focussed" transfer ports, or the like. (Good thing it wasn't used soon after the patent. It would have been a headache for the patent office and courts.)

[edit] Sierra club full of it

I'm pretty sure that the Sierra club's claim that 8 hours of a jetski running will pollute more than a car going 100k miles is absolute crap. I'll say that a jetski consumes an incredible 50 gallons of fuel in 8 hours. The real number is much less, but 50 makes it even. Assume a car with a more-or-less average fuel economy, say 20mpg over it's 100k miles. At 100k miles that's 5000 gallons. I'm not sure that it's possible for the cleanest-burning engine to burn 5000 gallons and put out less pollution than the dirtiest engine burning 50 gallons. Even with 2-stroke oil in the mix (35:1), that's about a gallon and a half of oil, total. With the Sierra club figure or 30% going unburned, you get 15 gallons of gasoil unburned. Does the Sierra club honestly mean to say that 100000 miles of driving puts out less pollution than 15 gallons of fuel? Come on now. They're smoking something. Probably they compared the jetski to a solar car and didn't bother to include that detail. Phasmatisnox 05:56, 20 August 2007 (UTC)

Your opinion and open bias are sure to get your changes made!Athene cunicularia 14:28, 20 August 2007 (UTC)
Suddenly, having a strong opinion has become wrong. Interesting. Phasmatisnox 02:46, 21 August 2007 (UTC)

[edit] mercury 2 stroke engine

I have been told that if 2 stroke fuel is left in the tank for a period of about 3 months or so that the oil in the mixture can separate and restrict fuel flow in the system and make starting etc difficult, is this true? I have just bought a second hand engine and even after changing the plug it is difficult to start. Compression seems OK. Advise welcome. —Preceding unsigned comment added by Jakey77 (talk • contribs) 09:21, 2 September 2007 (UTC)

Hello my name is Blake Carlson

This is cool thanks —Preceding unsigned comment added by 168.212.125.173 (talk) 19:03, 30 October 2007 (UTC)

[edit] Why no small two-stroke diesels?

Ok so I understand why we don't use two-stroke gasoline powered cars anymore (Trabant), but why can't I have a two-stroke diesel in my Jeep? It seems that two-stroke diesel technology shows up only in large scale diesel engines, but if the pollution problems don't exist as they do for two-stroke gassers, then whats the hold up? Every article I have read (including this one) gives no explanation why, it only states that two-stroke diesels are large and four-stroke diesels are small (relatively speaking). Madzyzome (talk) 17:57, 21 May 2008 (UTC) diesel and gasoline engins should be discussed seperately LUB Two-stroke gasoline engines etc.24.146.23.84 (talk) 06:43, 10 June 2008 (UTC) wdl