Talk:Expansion chamber

Tuned pipe

Absolutely not "tuned pipe" is street language not engineering language. The tuned pipe article itself is full of errors and half baked misconceptions. "Tuned pipe" should be deleted not merged.--=Motorhead (talk) 22:31, 13 April 2009 (UTC)

I see the point, but deletion is not the answer. Redirect, maybe? Andrewa (talk) 19:10, 15 May 2012 (UTC)

rename to tuned pipe

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was No move. This move request has become a mess, but it's clear to me that there's no consensus that the current article (Expansion chamber) should be moved to the title Tuned pipe.Cúchullain ^t/c 15:29, 30 May 2012 (UTC)

Expansion chamber → Tuned pipe –

I support the merge, because there was major duplication across the same topic (although was anything actually merged, or needed merging?). However the name tuned pipe is much better than expansion chamber. It is also the rather more common everyday name for such a system.

A tuned pipe is a system used for two-stroke engines with inertial scavenging or the Kadenacy effect. An expansion chamber is one component, albeit a necessary one, of this. However expansion chambers are also found in other exhaust systems, including four-stroke engines where the expansion chamber is only used for silencing (by simple expansion) or for the balancing of exhaust pulses between banks of a vee engine. Neither of these are tuned systems, or have any relation to scavenging. Andy Dingley (talk) 01:09, 30 April 2012 (UTC)

• Comment the edit history of the current Tuned pipe (edit | talk | history | protect | delete | links | watch | logs | views) will have to be moved somewhere... 70.49.124.225 (talk) 03:59, 30 April 2012 (UTC)
• Comment I have no strong views on this, the only point I will make is a merge should be done properly. On balance I would say that Expansion chamber is the better article but there are one or two errors there not present at the existing tuned pipe article. It is that as much as anything else I have objected to on procedural grounds in the past. I'll comment more fully in the next day or so but it's gone time to be clocking off here. Crispmuncher (talk) 16:08, 30 April 2012 (UTC).
• Comment Tuned pipe(s) can also mean:

1. two stroke exhaust system (aka expansion chamber),
2. tuned length exhaust manifold (typically used on 4 stroke car engines),
3. tuned length inlet manifolds (tunnel rams being just one example),
4. pipes in a pipe organ,
5. pan pipes
6. and probably a few more things I can't think of right now.

Perhaps 'Tuned pipe' should be a disambiguation page.  Stepho  talk  04:27, 1 May 2012 (UTC)

Tuned pipe only needs to become a disambig if and when some of those other topics appear as articles, and not before. We don't (and don't need to) disambiguate before we have the articles to require it. Andy Dingley (talk) 11:51, 3 May 2012 (UTC)

• Comment suggest merge and maybe a name change to reflect what is meant as both terms have multiple uses.NealeFamily (talk) 04:52, 1 May 2012 (UTC)

• Oppose. Lots of things to sort out here. These are two distinct and encyclopedic topics, and both deserve articles. Oppose both the move (which doesn't seem to be a well formed proposal anyway) and the merge. Andrewa (talk) 17:59, 9 May 2012 (UTC)

What are these two topics, and what relevance do they have for the articles we have at presenet here? To quote their leads, "A tuned pipe is a part of a two-stroke engine's exhaust system." and "An expansion chamber is an exhaust system used on a two-stroke cycle engine ". Whatever other uses there are for either term (and I agree, there are plenty), then the content of these two articles is pretty clear, and pretty clearly a near-duplicate in scope. Anything else is a matter for other articles, and disambiguation in names. Andy Dingley (talk) 20:19, 9 May 2012 (UTC)

No, the scopes of these two articles are anything but clear. But that's not the main issue for this RM.

What is the eventual desired result? I think you'll find for example that the best solution ends up with two articles.

If that is agreed, then we can proceed to ask, where should the histories of the existing two articles end up, what should the two articles be called, lots of things.

And only then, having worked out what we want to end up with, we can ask how to get there. I can't imagine how this particular move proposal can be a helpful part of that process, but happy to be proven wrong. Andrewa (talk) 00:48, 10 May 2012 (UTC)

Maintaining the same conversation on two pages is awkward. Since both articles point the merge discussion to Talk:Tuned pipe#Merge to Expansion chamber, may I suggest the discussion continue there and not here.  Stepho  talk  03:57, 10 May 2012 (UTC)

Where to discuss

Agree that discussion should continue at talk:tuned pipe rather than here.

But there's a procedural question here... we need to do something with this RM. Is there really any support for it?

The current formal proposal is to move the content and history currently here at expansion chamber over the top of that at tuned pipe. This doesn't seem to help with any solution currently proposed.

I think this RM should be closed, and if needed, another RM can be raised when the direction is decided. Alternatively, we can relist this with an alternative proposal, but any such move proposal I can imagine is premature. Andrewa (talk) 21:17, 10 May 2012 (UTC)

"a procedural question" Alternatively we could do something useful. Andy Dingley (talk) 21:46, 10 May 2012 (UTC)

Andrew, Yes there are a number of problems to discuss. I see them as follows:

1. Two articles containing nearly identical information about an exhaust system for 2-stroke engines.
2. Need for much improvement of accuracy and references. This would be much, much easier if it was done once to a single joined article instead of to two separate articles.
3. Terminology: Should it be called 'Tuned pipe', 'Expansion box' or something else. Also, the phrase 'tuned pipe' is used for a different phenomena in 4-stroke exhausts and yet another phenomena in 4-stroke inlets but at the moment there is no article covering the 4-stroke versions.

Item 2 is easiest when done after a merge - why do the work twice when it can be done once?

If item 1 makes 'expansion box' the main article then 'tuned pipe' can be a disambiguation page to 'expansion box' (for 2-stroke exhausts) and inlet manifold and exhaust manifold for the 4-strokes (I volunteer to making sure those articles mention the phenomena).

If item 1 makes 'tuned pipe' the main article then the 4-stroke systems can have either a disambiguation hatnote at the top or a few sentences near the top directing readers to those 4-stroke articles.

My recommendation is to merge as soon as possible because it doesn't hold anything up and because delaying the merge makes the cleanup in item 2 much harder. To me item 3 (which name to use) is a coin toss as long as the 4-stroke systems get links to appropriate articles. We can always do a name change in the future if something clashes - or add more hatnotes/disambiguation links. I see nothing that holds up the merge - objections raised so far can easily be handled after the merge.  Stepho  talk  04:49, 11 May 2012 (UTC)

Expansion chamber, not expansion box. Expansion chamber is a well-referenced 1950s-1960s term for these resonant two stroke exhausts, even if tuned pipe is (IMHE) the more common name for them today. Expansion box (and not chamber) is a common term for a minor non-resonant component in four stroke exhausts, which is broadly unrelated to what's discussed here.

I've never heard a four stroke exhaust, manifold or header described as a "tuned pipe". Nor are there any such things - the resonant scavenging behaviour described here just can't happen with four stroke engines, as their valve overlap is too small. Yes, gasflow in four stroke exhausts is important, but it doesn't work this way. Given the international variation in terminology, and the misunderstood rubbish spouted by shade tree mechanics, I'm sure that the term is in use somewhere, but probably only between cousins. Either way, no sourcing has yet been offered for these "four stroke tuned pipes" and whatever they are isn't the same thing as what's described for the scope within these two articles.

Four stroke engines belong nowhere near these two articles. If any four stroke exhaust coverage appears in the future, it needs to be referenced first and we shouldn't start messing with the name of this article to make space for it until we're damned sure we need to and that the four stroke content is real.

Now I admit I know little about two strokes, and even less about small petrol two strokes - but I'm getting a strong sense of WP:RANDY here. Andy Dingley (talk) 08:37, 11 May 2012 (UTC)

Apologies, expansion box was my mistake. Since the four stroke part is getting in the way, I'm happy enough to drop it so that we can move ahead with merging. Could you clarify which of us is being called Randy Boise?  Stepho  talk  09:16, 11 May 2012 (UTC)

I searched around a bit and found the term "tuned length extractors" and "tuned length inlet runners" matched what I was thinking of for 4-stroke engines (which use reflected negative pressure waves to promote flow as opposed to reflected positive pressure waves limiting the flow in a tuned pipe). Apologies for confusing the two terms.  Stepho  talk  12:11, 11 May 2012 (UTC)

A fundamental difference between two- and four-stroke engines is the time available for their valve opening, in terms of the overall cycle. The valves are open for longer, and thus have more overlap, in the two stroke. The four stroke engine has strong exhaust pulses of themselves, driven by the piston acting as a scavenge pump. Two strokes though (at least for the small crankcase compression engines relevant here) do not have a strong exhaust pulse, they require resonance from the exhaust system to assist with this - this is the function of the tuned pipe. In a four stroke though, which is probably a multi cylinder engine with a shared exhaust system, the problem for the exhaust design is rather the opposite of this - leaving the engine's exhaust pulses unaffected and in particular, stopping adjacent cylinders from interfering with each other. The manifold is often "tuned" for length to achieve this, but the goal is about avoiding exhaust system effects on the engine, rather than encouraging them.

There are some claims for resonant pipes on four stroke systems - most of which are nonsense. It's hard to do this, as you describe, by using reflected negative pressure. More seriously though, resonance in a four stroke would then mean a narrowed power band and there are few installations that can cope with that, as it demands closer gearbox ratios, bigger gearboxes, more complicated driving. It's accepted for a two stroke, as part of getting such high power from such a small engine, but for four strokes it's more trouble than it's worth. Andy Dingley (talk) 12:33, 11 May 2012 (UTC)

It depends on the application. Tuned pipes are pretty standard for F1 engines, and occur on many other four-stroke racing engines. The phase 3 Falcon had them for example. Andrewa (talk) 12:34, 12 May 2012 (UTC)

Some F1 engines with tuned pipes

• 
  Peugot
• 
  Ferrari
• 
  BRM
• 
  Aston-Martin

Discussion

Mainly for the benefit of the closing admin, note that this RM has as its background a minor edit war [23] [24] [25] [26] [27] [28] . The proposed move seems to me to merely muddy the waters, and most of the above discussion appears irrelevant to the move as currently proposed. Andrewa (talk) 21:55, 11 May 2012 (UTC)

OK Mr Ego, it's your article. You know the subject inside it, you know all about tuned pipes for diesels, you know all about tuned pipes for four strokes. You do what the hell you want with it. I do _not_ appreciate my addition of an entirely proper merge tag for discussion, following a merge that had admittedly gone off the rails, being described as "edit warring".

And yes, WP:RANDY.

Andy Dingley (talk) 23:30, 11 May 2012 (UTC)

The most revealing thing you can do is to describe someone else's thought processes; Invariably, you describe your own instead. So simmmer down.

It's neither my article, nor yours. And I'm not claiming to be an expert on two-stroke vehicles, I have owned only one (a Suzuki L60V), but I did service that vehicle myself over several years so I'm not entirely ignorant of them. And I have also owned and maintained a four-stroke with a tuned extractor manifold (an Austin-Healey Sprite mark IIa). And I used to admire the the odd Suzuki Swift... hmmm, there was an Australian car by that name when I had the van, it was a very hot drop indeed with a two-stroke engine and an adjustable tuned exhaust, and the owners used to frequent the same parts suppliers as I did at one time for obvious reasons, but our article doesn't seem to cover that particular model. Anyway, that's the limit of my expertise, and elsewhere you say that you know little about two strokes [29] but you do seem to have and claim some knowledge, so maybe we're in much the same boat.

My definition of an expert is somebody who has already made most of their mistakes. And I do claim some expertise in Wikipedia procedures and policies, and I'm committed to making them work usefully, that's my responsibility as an administrator. And I'm still making mistakes and learning from them, that's how I gained this expertise. But you don't seem to think I have any [30]. Oh well, I tried. Andrewa (talk) 19:06, 15 May 2012 (UTC)

Progress

There seems to be no prospect of consensus for this move, but I can't close it myself as an involved party.

Note that there now exist tuned pipe (disambiguation), expansion chamber (disambiguation) and tuned exhaust.

There is lots more to do, but I still can't see any prospect of this particular move proposal helping things. Andrewa (talk) 10:42, 29 May 2012 (UTC)

The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Lots of issues

For a start, this article assumes that any two stroke engine is petrol fueled. Not so.

There's lots of good material here, but it needs to be rewritten to clarify this and many other similar assumptions. Andrewa (talk) 17:59, 9 May 2012 (UTC)

Yes so. This article isn't about two stroke engines, it's just about crankcase compression two strokes. Those are petrol. Andy Dingley (talk) 21:45, 10 May 2012 (UTC)

Exactly. But it doesn't say that. See Talk:Tuned pipe#Lead. Andrewa (talk) 22:03, 11 May 2012 (UTC)

Failed merge

Okay, we started with two nearly identical articles (Tuned pipe and Expansion chamber) and now we have:

• Tuned pipe covering the two-stroke exhaust system
• Expansion chamber nearly identical to the above
• Tuned exhaust giving an overview of both two and four stroke exhausts and linking to both of the above nearly identical articles.
• Tuned pipe (disambiguation)
• Expansion chamber (disambiguation)

I don't have a problem with the disambiguation pages but now we have 3 articles explaining the two-stroke system (although Tuned exhaust also includes the four stroke system). This is obviously not a good situation to be in. Possible ways forward are:

1. Leave Tuned exhaust as it is (a general overview article) but merge Tuned pipe and Expansion chamber into a single article without (I don't care which name is used).
2. Copy the cleaned up content of Tuned pipe and Expansion chamber into Tuned exhaust and make those two articles simple redirects to Tuned exhaust.
3. Shift Tuned exhaust content to a section in Exhaust manifold (leaving behind a redirect) and merge Tuned pipe and Expansion chamber into a single article (again, don't care which name).
4. Shift cleaned up content of all 3 articles into Exhaust manifold (leaving behind a redirects).

I favour #4 but I could live with any of them. Comments?  Stepho  talk  04:03, 31 May 2012 (UTC)

I'm skeptical that tuned pipe undisambiguated is a good name for any article on exhaust systems, given the broader usage of the phrase in acoustics. I just did a Google Books search [31] and my first result was Understanding The Pipe Organ, the first page of ten hits admittedly contained six relating to exhaust systems, but the other four related to pipe organs as noted, to loudspeaker design and to other areas of acoustics (your results may vary). I think we should seriously think of making tuned pipe the location of the DAB, rather than an article or even redirect concerning exhaust systems.

I'm also wary of merging material to tuned exhaust, see talk:tuned exhaust. I don't own that article of course, but currently it is approachable by someone not familiar in the field or with the jargon, and I think it should stay that way. Also, while it's not well-referenced, I think it is accurate. On the other hand, it's been claimed before that the material currently in tuned pipe [32] and expansion chamber [33] seems to contain a great deal of motorcycle enthusiasts' jargon and folklore, and that's my impression too. I realise that this proposal talks about cleaning up the material, but I wonder whether there will be very much left!

Exhaust manifold also needs work... it currently [34] doesn't even mention two-stroke or four-stroke engines, but most of the article is currently only applicable to four-stroke engines, while Exhaust manifold#Dynamic exhaust geometry is similarly about two-strokes.

I'm not sure which of the four solutions is best... another thing that might be relevant is that while zoomie headers are commonly called a type of exhaust manifold, they're actually not a manifold at all, as there's one to each cylinder. And in some parts of the world a collector is not called a manifold either, rather it's an alternative to a manifold in that dialect. But in the broader sense, a collector is a type of manifold. That's one of the reasons I chose tuned exhaust as a name; So far as I know it's unambiguous and accurate in all regional dialects of English, which none of the other potential article titles seemed to be.

Very pleased to see some more hands involved, thank you! Andrewa (talk) 03:13, 1 June 2012 (UTC)

Process

I'm not altogether sure that the merge proposal has failed. The requested move has failed, with the closing admin noting this move request has become a mess. IMO it was a mess from the start... the intention all along seems to have been a merge not a move, so WP:RM wasn't an appropriate process.

The only opposition to a merge of tuned pipe and expansion chamber so far has been from me I think, and I've now retracted that [35].

See also Talk:Tuned pipe#Merge to Expansion chamber. Andrewa (talk) 10:21, 1 June 2012 (UTC)

Merging the two articles is what I asked for all along. The move was a side issue that was never officially asked for (every tag I put on the articles was for discussing a merger). Nevertheless, since you have removed your objection to merging then we can at least merge the two original articles together. Since 'tuned pipe' is contentious, I recommend that 'Expansion chamber' remains a proper article and that 'Tuned pipe' becomes a redirect. I have no objection if 'Tuned pipe' also gets a rename. Other issues can be tackled afterwards.  Stepho  talk  13:05, 1 June 2012 (UTC)

I agree that you didn't ask for the move, but it was quite official [36]. That's how I got involved in fact... at the end of the seven days I looked at it with the view to closing it, either as a move as requested, or as rejected.

What I found was already a mess. The move proposal was ill-formed in several ways. My first reaction was to oppose the merge too, in the hope that the tuned pipe article could be expanded to include the use of tuned exhausts on four-stroke engines, which are after all also tuned pipes in a sense, as it seemed possible that both articles had significant edit history. Preserving edit histories is one of the things that admins particularly bear in mind in helping with merge and move requests, and this seemed a good solution.

It proved not to be that simple, there was opposition to the idea of broadening the scope of tuned pipe on the grounds that the four-stroke application wasn't significant (There are some claims for resonant pipes on four stroke systems - most of which are nonsense [37]). Pointing out that all non-turbo Ferraris (as just one of many, many examples) have used them both on road and track for more than half a century and continue to do so didn't seem to budge this view, and another thing admins are supposed to be big on is consensus. So I changed tack, gave up on the simple solution to the edit histories (which was my main reason for opposing a merge), and created a new article at tuned exhaust instead.

PS In fairness, I must say that there are also claims for aftermarket extractor manifolds sold in accessory shops in Australia most of which are nonsense, and I guess it's the same in the USA. There are exceptions, some of the extractors still popular for the VW beetle engine work well for example, as do aftermarket copies of the performance manifolds developed by the makers for the BMC A-Series engine and Ford 335 engine, and I expect it's similar for other makes. But many bolt-on so-called extractor manifolds are designed mainly for show, as the engine development work required to make them effective as extractors has simply never been done. They may help in reducing back pressure, but they're not tuned at all! Andrewa (talk) 20:14, 1 June 2012 (UTC)

And also created some DABS as you have noted. The one at expansion chamber (disambiguation) is marginal at present, but as keen student of nuclear physics back in the late 1960s, to me the primary usage of that term expansion chamber was in connection to cloud chambers, bubble chambers and similar devices. This usage seems to be at least partly historic, and there's little about it in Wikipedia or on the Web (and Wikipedia seems to place the demise of the cloud chamber as a little earlier than I remember it! Probably the American universities had the money to replace them a bit before we Australians did), but I'll dig out my old textbooks one day and fix that. But the one at tuned pipe (disambiguation) is important IMO. The usage in acoustics goes back to the first translation of Sensations of Tone and continues to be mainstream.

Yes, in some ways this made the mess even messier, but the dialogue on the talk pages was getting nowhere, and this seemed a way forward. Apologies if I've made it even more complicated, and let's move on. Andrewa (talk) 19:29, 1 June 2012 (UTC)

OK, if you're going to disparage my contributions here, then let's go fo it.

We started off with two articles that were simple duplicates, of different qualities (one poor, one really bad), but they did at least describe a single important and notable topic: that of resonant exhaust systems used with crankcase compression two-strokes to improve exhaust scavenging. They do not cover four-strokes: four-strokes do not use exhausts of this type.

There was a merge proposal. This was rejected by one editor: an editor with evidently no knowledge of the topic and who kept trying to derail discussion by bringing in irrelevant issues such as diesel engines, or even more so, that of organ pipes. Organ pipes just aren't a content issue here, they're a trivial disambiguation naming issue where basic policy explains how to sort it, end of story.

We no longer have two duplicate articles. Now we have five overlapping articles. One of these, tuned exhaust, is a feeble mish-mash written by sticking text strings into Google and with no hint of an editorial structure. We also have two disambiguation articles that go out of their way to not mention the lead articles under their own name.

Here's a technical heads-up: tuned pipe and expansion chamber should be merged, and as expansion chamber is the better article, we should merge into that. Edit history is a red herring, or at least a long-solved problem on WP, just read the policy guide at WP:MERGE. Then name the results as "resonant exhaust systems used with crankcase compression two-strokes to improve exhaust scavenging", or some shorter and snappier version of this, maybe tuned pipe or expansion chamber as both of these are referenced terms used for exactly this system.

Technical point #2: there are no four-strokes using this system, there are no diesels using this system. None. Nada.

Four-stroke exhaust systems work differently: they may be tuned, but not in the same way. In general, four-stroke engines use exhausts that are deliberately de-tuned, not to emphasise resonance. They're multi-cylinder and the purpose is to reduce disruptive effects between cylinders. In a few cases, four-stroke engines do have their exhausts tuned for resonance. This makes them difficult to drive outside of racing cars and also (for the purposes of this article) it's still not the same thing as resonant exhaust systems used with crankcase compression two-strokes to improve exhaust scavenging.

We're still back were we started, but now with two extra disambig pages that aren't even disambig pages: a disambig page per WP is a disambig across lexical overlaps, these are across homonyms at most. Per WP practice, this isn't an overlap that even needs disambiguation: the fact we could describe organ pipes as being "pipes that are tuned" doesn't mean they need disambiguation, until we get to the point where articles exist under titles like tuned pipe (organ). As for excluding tuned pipe from tuned pipe (disambiguation), that's sheer WP:POINT. Andy Dingley (talk) 20:43, 1 June 2012 (UTC)

Some valid points made here, and some things that should be included in the articles. But much of it I disagree with too, and I stand by my earlier comments. I made them as gentle as I could, and avoided naming you.

I think you have a problem. I'm not trying to disparage your contributions, just the opposite, but I do get the feeling you're trying to disparage mine. What else does let's go for it mean?

See also this diff and my reply [38]. As I've said before, you have obvious knowledge. But there are gaps in it, just as there are in mine. That's why Wikipedia is collaborative, and why the note below the edit box reads If you do not want your writing to be edited, used, and redistributed at will, then do not submit it here.

You don't know it all. Get over it. Sorry if that's blunt, but we need to move on. Andrewa (talk) 21:14, 1 June 2012 (UTC)

References, or STFU. Your tuned exhaust article is the sort of crap that a car magazine wouldn't even run. "Crankcase scavenging" is more of a misnomer term than you clearly realise. Andy Dingley (talk) 21:24, 1 June 2012 (UTC)

Agree that a car magazine wouldn't run such an article. But Wikipedia caters for all readers, including those who don't have the background of the intended readership of car magazines.

Agree that crankcase scavenging is a misnomer (always have), and that you see it as a more serious misnomer than I do. But it's also a common term, and I have given references supporting that, and also for the wider usage of tuned pipe, while you have given none supporting the seriousness of the misunderstanding that you see underlying the term crankcase scavenging. Andrewa (talk) 21:59, 1 June 2012 (UTC)

One of the valid points was that tuned pipe (disambiguation) didn't point to tuned pipe, as of course it should have. Fixed. I've also similarly modified expansion chamber (disambiguation).

But I'm not entirely happy with the results. The lead to the expansion chamber article currently [39] reads in part It is the two-stroke equivalent of the tuned pipes (or headers) used on four-stroke cycle engines (wikilink as in the article). But as we all know, the tuned pipe article is currently [40] also about two-stroke engines. Andy D above described these two articles as previously being one poor, one really bad. Have they changed all that much?

Whatever the faults of the tuned exhaust article, it is a clearly defined topic with clear and accurate contents (please, someone other than Andy D check this!). People coming to the tuned pipe and expansion chamber articles should be able to get to it, surely? And I'm not quite sure how they do this at present. Andrewa (talk) 00:31, 2 June 2012 (UTC)

A detailed reply

I think I should reply in detail to one of the posts above [41].

We started off with two articles that were simple duplicates, of different qualities (one poor, one really bad), but they did at least describe a single important and notable topic: that of resonant exhaust systems used with crankcase compression two-strokes to improve exhaust scavenging. They do not cover four-strokes: four-strokes do not use exhausts of this type.

Agree.

But as I have pointed out, the articles weren't (and aren't as I write) entirely consistent even in this. The expansion chamber article does refer to four-strokes, when it says in its lead It is the two-stroke equivalent of the tuned pipes (or headers) used on four-stroke cycle engines (my emphasis).

There was a merge proposal. This was rejected by one editor: Yes, and that was me, and in hindsight I made a mistake, and I've reversed my position.

an editor with evidently no knowledge of the topic

Wrong, baseless and a personal attack. I haven't owned such an exhaust myself. I have worked on several bikes that use them.

and who kept trying to derail discussion by bringing in irrelevant issues such as diesel engines, or even more so, that of organ pipes. Organ pipes just aren't a content issue here, they're a trivial disambiguation naming issue where basic policy explains how to sort it, end of story.

At the very best a failure to assume good faith, and some debatable points.

We no longer have two duplicate articles. Now we have five overlapping articles.

I've created one more, yes. Where did the other two come from? I think you might mean the DABs I've created. DABs overlap other articles, yes, otherwise they wouldn't be DABs!

Or perhaps you mean exhaust manifold, or several other overlapping articles? These already existed of course. And overlaps aren't always a bad thing, otherwise we wouldn't link to main articles at all. Tuned exhaust is an overview article, and should link to more detailed articles on two-stroke and four-stroke engines with {{main}} tags, and does already but the targets need some work, to say the least.

One of these, tuned exhaust, is a feeble mish-mash written by sticking text strings into Google and with no hint of an editorial structure.

Disagree. And the tone here (and elsewhere) is IMO an unacceptable violation of several Wikipedia policies. Tone it down. Please.

We also have two disambiguation articles that go out of their way to not mention the lead articles under their own name.

Good point. Fixed. (More needless speculation about my motives, and still contrary to WP:AGF but I guess there's some justification here.)

Here's a technical heads-up: tuned pipe and expansion chamber should be merged, and as expansion chamber is the better article, we should merge into that.

Agree.

Edit history is a red herring, or at least a long-solved problem on WP, just read the policy guide at WP:MERGE.

My attempt to simplify the process was ill-advised and counterproductive, but again it was in good faith.

Then name the results as "resonant exhaust systems used with crankcase compression two-strokes to improve exhaust scavenging", or some shorter and snappier version of this, maybe tuned pipe or expansion chamber as both of these are referenced terms used for exactly this system.

Agree with some of this, but there do seem to be problems with tuned pipe as a title that still need to be clarified. Someone at least thinks that tuned pipes (or headers) are used on four-stroke cycle engines, see above, and there are other ambiguity issues.

And there may be problems with expansion chamber as a title too. You did say earlier However expansion chambers are also found in other exhaust systems, including four-stroke engines where the expansion chamber is only used for silencing (by simple expansion) or for the balancing of exhaust pulses between banks of a vee engine. Neither of these are tuned systems, or have any relation to scavenging. [42] (my emphasis).

Technical point #2: there are no four-strokes using this system, there are no diesels using this system. None. Nada.

Agree.

Four-stroke exhaust systems work differently: they may be tuned, but not in the same way. In general, four-stroke engines use exhausts that are deliberately de-tuned, not to emphasise resonance. They're multi-cylinder and the purpose is to reduce disruptive effects between cylinders. In a few cases, four-stroke engines do have their exhausts tuned for resonance. This makes them difficult to drive outside of racing cars and also (for the purposes of this article) it's still not the same thing as resonant exhaust systems used with crankcase compression two-strokes to improve exhaust scavenging. (your emphasis removed and mine applied)

I'm sorry, but some (not all) of this is rubbish, and rubbish you've asserted before [43] and which seems to be the important issue. Many luxury performance cars use resonant systems, for example. Why do you think it's only in a few cases? And are these cases unimportant?

We're still back were we started, but now with two extra disambig pages that aren't even disambig pages: a disambig page per WP is a disambig across lexical overlaps, these are across homonyms at most. Per WP practice, this isn't an overlap that even needs disambiguation: the fact we could describe organ pipes as being "pipes that are tuned" doesn't mean they need disambiguation, until we get to the point where articles exist under titles like tuned pipe (organ). As for excluding tuned pipe from tuned pipe (disambiguation), that's sheer WP:POINT.

I have to agree that the DABs did look pointy. But I'm just trying to make Wikipedia useful to readers. We seem to agree that the two original articles are not all that useful. Where we disagree is, I think that the tuned exhaust article is useful, and I'd like to help readers to find it.

We haven't made nearly as much progress as I'd like, but I think we've made some, and the DABs are part of this. If they aren't justified, then they should be deleted and I'm sure they will be in time. I think they are helpful, but I've been outvoted before and won't take it personally if it happens again. You've said Whatever other uses there are for either term (and I agree, there are plenty)... [44] (my emphasis), so I think the DABs are at least a helpful interim in working the titles out.

But I think there are far more pressing issues. Andrewa (talk) 01:41, 3 June 2012 (UTC)

Clearly the only thing you're interested in is hooting your trap off. Andy Dingley (talk) 01:45, 3 June 2012 (UTC)

Proposal

See Talk:Tuned pipe#Proposed redirect which is essentially the first step towards proposal #1 above. Andrewa (talk) 07:27, 4 June 2012 (UTC)

Yet again, you oppose a correct merge proposal. This immediate redirect would be tantamount to deleting the article instead, which is not the goal required.

No, it's not a deletion because it preserves the history. What is the goal required and how does the proposal fail to address it? And what correct merge proposal am I opposing? I think I'm supporting it.

As the article doesn't have much content to offer to a merge to expansion chamber, then this does seem like a route to the same end result though.

I think that means that you agree with the proposal.

I suspect that what you're really trying to do here is to avoid merging tuned pipe and expansion chamber correctly, and instead to redirect to your new madeup at tuned exhaust, because you still refuse to recognise the importance of "resonant exhaust systems used with crankcase compression petrol two-strokes to improve exhaust scavenging" as the most notable and referencable topic within this. Your past exclusion of both from disambig pages under the same name suggests that too. Andy Dingley (talk) 08:40, 4 June 2012 (UTC)

Yes, that's one possibility, as described at Talk:Tuned pipe#Proposed redirect. Perhaps you'd like to comment there, or is there some reason to prefer discussing it here instead? Andrewa (talk) 09:50, 4 June 2012 (UTC)

Done [45], and appropriate hatnote added here [46]. Andrewa (talk) 07:35, 13 June 2012 (UTC)

Lead

I've had a go at cleaning up the lead [47]. All mention of four-stroke engines has been removed as both unsourced and inaccurate [48] [49]. Andrewa (talk) 07:35, 13 June 2012 (UTC)

Waves

Some very interesting edits [50] by an anon with no previous contributions. (I'll post a welcome, and if you see this first, we were all new once, see User:Andrewa/Creed. So neither being new nor using an IP address is a criticism, in fact I think you're doing very well and the article now reads far better for your attention, thank you!)

Welcome posted [51]. Andrewa (talk) 21:03, 26 September 2012 (UTC)

On the whole I'm very impressed... but I'm not an automotive engineer, just an amateur who once owned and maintained a two-stroke van (without a tuned exhaust AFAIK but I never played with that part of the engine).

Two of the many things that have been significantly modified are the history in the lead and the terminology throughout.

The lead already had the only two references in the whole article, but it's not clear whether they support the material now added. More citations definitely needed, both here and elsewhere. Not a new problem for this article! The latest edits simply follow the pattern already established here, which therefore still needs fixing.

The substitution of acoustic wave for pressure wave is even more interesting. I suspect it's quite correct... long ago I seem to recall hearing that pressure waves could travel faster than sound; Acoustic waves obviously can't. But I'm very vague on whether they may even be the same thing in this context. My formal physics training ended at first year university level in 1971!

Again, citations would probably fix this. Andrewa (talk) 20:34, 26 September 2012 (UTC)

File:Exhaust with minimal expansion chamber.jpg

This picture is of a 4 stoke motorcycle. the mechanics of the exhaust stroke on a 4 stroke engine are completely different to that of the two stroke engine and as such may not be relevant to the rest of this article which draws reference to two strokes. --121 11:04, 1 December 2012 (UTC)

I wondered about that... but I can't tell from the photo whether it's a two-stroke or four-stroke. As I understand it the article is entirely about two-stroke engines, and the lead currently [52] reads On a two-stroke engine, an expansion chamber or tuned pipe is a tuned exhaust system used to enhance its power output by improving its volumetric efficiency.

The photo is originally from flickr [53] and there's no clue there as to the exact model of motorcycle. Can you identify it? Or does it just look like a four-stroke to you?

In any case, if we can't tell, it's not a suitable photo to illustrate the article. Andrewa (talk) 10:10, 30 November 2012 (UTC)

The configuration of the water cooled barrel "no fins" cylinder head valve cover and the resemblance to modern 4 stroke motocross bikes makes me sure this is a modern overhead cam motocross bike. The minimal expansion chamber just visible near the boot is also called a "bulb" "mega bomb" "power bomb" It reduces the sound of the engine which is a major issue today with the closure of motocross facilities due to noise nuisance. Their is a performance claim which I do not want to go into. This device could also be called an expansion chamber or as the photo's caption states minimal expansion chamber. To maintain this article I do believe it should be Titled "2 stroke expansion chamber". Also could someone upload pictures of the prototype motocross Suzuki's and the works bikes that Joel Robert and Roger De Costa raced in the late 1960's and early 1970's as this period is significant to this article. --121 11:04, 1 December 2012 (UTC)

Nice new relevant picture [[54]]--121 11:04, 1 December 2012 (UTC)

You're welcome. Have a nice day. Now, all we need to do is get rid of all the unreferenced crap in the article and add some good quality referenced material to support it. --Biker Biker (talk) 11:05, 1 December 2012 (UTC)

The article has been problematical for some time, and it's no wonder considering the agro some editors have been allowed to use defending it. Good luck. Andrewa (talk) 19:24, 1 December 2012 (UTC)

Or the unreferenced nonsense that one editor has persisted in adding to it. Andy Dingley (talk) 12:27, 2 December 2012 (UTC)

Sorry you think it's nonsense but frankly I think this reflects more on your understanding than on mine. Agree that more citations are needed, for your material as well as mine. I've borrowed a copy of The Design and Tuning of Competition Engines, by Philip H. Smith, which seems well respected [55]. Other suggestions? Andrewa (talk) 14:25, 4 December 2012 (UTC)

Agree with most of this.

When you say could be called an expansion chamber I assume you mean that this is established usage. This was also suggested by another editor above, in very similar terms... expansion chambers are also found in other exhaust systems, including four-stroke engines where the expansion chamber is only used for silencing (by simple expansion) or for the balancing of exhaust pulses between banks of a vee engine. But the same editor was elsewhere adamant that these systems should not be covered by this article (which all the time had the 4-stroke photo in its lead). Evidence attesting to the usage would be good, I don't think we have any either way so far despite much discussion.

I doubt that there's enough material to justify separate articles on two-stroke and four-stroke expansion chambers. But I could be wrong there.

Perhaps the first thing to do is to either create a new stub article on the four-stroke case, or refactor this article (mainly with a new lead) to deal with both.

If the intent is to have two articles we could move this article to a title that refers only to the two-stroke case, such as you suggest above. This can be done either by proposing a move at WP:RM or by boldly moving it if you're reasonably sure of your ground and the new title is available. See WP:AT for the article naming policy.

I favour the refactor, but note the previous strong opposition to this.

Hang in there. This is long-overdue progress. Andrewa (talk) 20:21, 1 December 2012 (UTC)

My own enthusiasm for the development of the two stroke exhaust in motocross deflected my judgement and in hind sight reference to motocross hero's and bikes probably would not benefit this article. Motorcycle exhaust development is moving fast and new terminology has yet to be established for the new header pipes which are being designed for 4 stroke motocross bikes reference the "change in volume along its length" which was on the original photo, who's caption read "minimal expansion chamber". However with the change in photo which shows to my mind what I understand to be a 2 stroke motorcycle expansion chamber my initial concern has been settled. However remember the search term "expansion chamber" will raise this page result which describe a 2 stroke motorcycle expansion chamber.121 22:25, 1 December 2012 (UTC)

Yes, the four stroke case is not currently covered and should be. If the article is to remain at this name, this could be either by broadening this article or by a hatnote leading to another article. Andrewa (talk) 20:05, 4 December 2012 (UTC)

Why do you still think that four strokes belong here? Their exhaust systems work differently, they do not use this type of exhaust. Even though they have components termed "expansion boxes" those are unrelated to the behaviour here. Even though the term "expansion chamber" is sometimes applied (largely erroneously), that doesn't mean that they gain the same function.

All through this mess you have been convinced that the definition of a mechanism is the result of its name, rather than its function. Such a simplistic view is harmful to any encyclopedia trying to produce comprehensible articles – that is more the function of disambiguation pages. Andy Dingley (talk) 21:35, 4 December 2012 (UTC)

I really am sick of sorting out attacks such as simplistic above (which is there applied to a view which is being falsely attributed to me) from the valid discussion points.

Above I said I doubt that there's enough material to justify separate articles on two-stroke and four-stroke expansion chambers. But I could be wrong there. Do you disagree with that? Why?

If there is such material, then we need two articles.

In either case, there seems no reason that the four-stroke case should not be mentioned in this article, if only to link to wherever the four-stroke case is described. Andrewa (talk) 02:29, 5 December 2012 (UTC)

If you don't like "simplistic" as applied to your understanding of how to structure tutorial or encyclopedic material, then try "clueless" and "utterly wrong" for your understanding of the technical issues.

If you still think that the exhausts of four stroke engines work in the same way as two stroke engines, as described here, then you're welcome to find some credible references to back up your misunderstandings and then add them. Andy Dingley (talk) 02:35, 5 December 2012 (UTC)

But I don't think that. Andrewa (talk) 02:47, 5 December 2012 (UTC)

Four stroke engines

Try United States Patent 5,050,378 September 24, 1991 [56] In a spark ignition or compression ignition four cycle internal combustion engine, an exhaust expansion chamber is sized to produce a reflected exhaust pressure wave timed to an auxiliary reopening of the exhaust valve after the intake valve has effectively closed. Interesting?

The current article topic (restricted to two stroke engine applications) may of course still be the primary meaning, but it does IMO raise the question. Andrewa (talk) 02:47, 5 December 2012 (UTC)

OK, now that's an interesting patent. It does indeed describe the combination of a four stroke engine, together with an expansion chamber exactly as described here for the two stroke engine. Now, is this patent in use? Does it even apply to four stroke engines, as we know them today? No.

It's a complex patent. It seems to depend (I haven't read it in enough detail to know if this is a requirement or merely their context of description) on engines using the Miller cycle. Now that, along with turbo-compound engines, is pretty much a dead duck (and no, the Prius doesn't use an Atkinson cycle either). It's just easier to use a turbocharger and do the lower part of the useful expansion cycle outside of the cylinder. Still, if someone did show an interest in Miller cycles, it might come in handy.

Today though - this is not a patent that's in use by today's four stroke engines. Andy Dingley (talk) 03:24, 5 December 2012 (UTC)

Do you have any references to back all this up? Andrewa (talk) 05:31, 5 December 2012 (UTC)

Which bit? The problem of getting enough expansion in a highly supercharged engine belongs under turbo-compound engine (long overdue for a rewrite – it's pretty meaningless at present) and can be sourced from the 1950s edition of Ricardo or Caxton Press' High-Speed Oil Engine. The problem is that it's possible to supercharge an engine (if it's strong enough) to maybe 6 bar, whilst its combustion processes and basic thermodynamic efficiency continue to function and even to improve (mostly because some losses remain constant and thus shrink proportionately). However the piston engine's ability to extract this power relies on the gas doing work against the piston, and the piston stroke just isn't long enough to allow for enough expansion. As a result, the exhaust gas still contains appreciable energy, energy that would then be wasted. This can be captured by adding a second stage turbine – a turbo-compound engine – and letting the exhaust gas do its work against that. However it takes substantial power to drive the supercharger too. It's also useful (for materials reasons) to make both centrifugal supercharger impeller and exhaust turbine smaller, which then requires higher rotational speeds. Turbo-compound engines already require a complex transmission, and giving this two high/low speed gearboxes as well becomes a serious mechanical problem. So if one simply couples the turbine and compressor together, and careful design can make that power demand much the same as the exhaust turbine output power demand, then you abandon the gearboxes and invent the direct-drive turbocharger instead.

I can't think of good sources for Miller or Atkinson offhand. They're pretty obscure – a mechanical linkage that changes the piston motion from being the usual simple harmonic motion to being something asymmetric with the overall effect of having a longer expansion phase. This is a similar fix to the turbo-compound, but it's done for different reasons. Mostly these ideas belong to the original Diesel cycle engines (which are not the same as diesel engines today) where the constant pressure expansion phase was particularly long – especially with slow-burning heavy oil or coal dust fuels. I haven't heard of either being used in the last half-century.

Some recent engines use peculiar timing diagrams (and commonplace connecting rod linkages) to make their behaviour especially suitable for use in hybrid cars. This has nothing to do with the Atkinson cycle, but because looking at a simple valve timing diagram (without also seeing the piston's movement that is the core of the Atkinson concept) is similar to that of the Atkinson engine, it has produced a widespread misnomer that the Toyota Prius has an Atkinson engine inside it, funny crank linkages and all. It doesn't.

The valve timing of Miller and Atkinson engines is strange (and unfamiliar to me). It's entirely likely that they get to a point of overlap, similar to a two stroke engine, where a resonant exhaust system starts to be helpful, and for just the same reasons as it does with a two stroke. That's still of little relevance to "real world" four strokes though.

Your thesis is, "Four stroke engines use exhausts with resonant expansion chambers to improve their scavenging, as for a two stroke engine". I contest this, as four stroke engines don't use such exhausts. The patent here then becomes "the exception that proves the rule". It shows that when four stroke engines do use such exhausts, just what a convoluted stretch we have to be looking at before we find "a four stroke engine" that does so. This isn't an engine that's terribly close to the commonplace four stroke, or to what our readers recognise as a four stroke. One might as well go to Cat and add "Cats' eyes have round pupils" because Pallas cat does. You can cite a reference to show that it's "true", but it's neither realistic, relevant or helping our readers to understand what a cat (or an exhaust) looks like. Andy Dingley (talk) 10:45, 5 December 2012 (UTC)

No, my thesis is not this and never has been. If I had said that, I would understand your concern for my competence to make any contribution on the subject. But your attempted rephrasing of my understanding here is not even close.

And I admit I don't understand your argument here. My referring to the patent (which is a primary source, so it might help us to establish what is accurate, but it's not a good reference for the article) was simply to point out its usage of the phrase expansion chamber. The fact that this particular technology might not be notable is irrelevant to the point I was making regarding the meaning(s) of the phrase expansion chamber. And comparing it to Miller and Atkinson cycles and to turbo-compound engines, which are similarly not in common usage in current vehicles but are all clearly notable, seems to argue against your case, not for it.

One specific thing you might provide a reference for is the opinion that that, along with turbo-compound engines, is pretty much a dead duck. This seems to be what all the technical matter above is supporting. You obviously feel qualified to make such a prediction, but is it just yours?

And it might not even be too good a prediction... New Holland still seem to be promoting this technology, Turbo Compound technology improves fuel efficiency by 5 percent compared to conventional turbocharged engines [57]. Or have I missed something there? Andrewa (talk) 12:22, 6 December 2012 (UTC)

But I'm not sure it's particularly relevant anyway. The question here is simply whether the two-stroke case is the primary meaning of expansion chamber, or the only automotive meaning of expansion chamber, or neither or both. The evidence is, it's neither. Andrewa (talk) 20:03, 5 December 2012 (UTC)

But the other thing is that even if these opinions about miller cycle and turbo-compound engines are supported by authorities, that would not be a case for deleting the articles concerned. They're still of interest. We don't try to predict whether they will have further widespread application, we just report the opinions of authorities on this, and even if we did regard them as obsolete we'd still be interested in them historically.

Similarly the four-stroke expansion chamber technology described here is of less interest than it would be had it already reached production, but it's still of interest. It may not be notable enough for an article of its own, but it could still be part of another article. Andrewa (talk) 10:22, 5 December 2012 (UTC)

See also POPULAR 4 stroke engine kit/ new exhaust pipe/new expansion chambers [58], an aftermarket exhaust, apparently. Andrewa (talk) 05:39, 5 December 2012 (UTC)

OK, that's clearly WP:RS. You want chapter and verse before you'll believe me saying that exhausts are loud and get hot, but one line on a Chinglish website and you'll believe anything 8-( That's just Alibaba. It could be a saxophone for all I know. Andy Dingley (talk) 10:45, 5 December 2012 (UTC)

Yes, I have asked for references for some of your more controversial claims. Most notably, your claims that tuned extractors aren't very useful on four-stroke engines, and that turbo compound engines are dead ducks. I think you should tell us whether this is your own WP:OR or whether you are relying on authorities, and if the latter, what these are. But only for the controversial claims, not for the mountain of elementary material with which you surrounded one of them above. And I am quite happy to trust you that exhausts tend to be loud and get hot, I even think that this is the common experience of those of us who have worked with them. (;->

Yes, I think Alibaba is useful evidence in that the term expansion chamber is used there for the four-stroke case, a usage that you have agreed with in the past, but seem now to reject. I'm only citing this website for this one piece of relevant data, and your deriding it as Chinglish is I think offensive to those users of English Wikipedia whose native language is not English. We are here for all English speakers.

It's important that we come to some consensus on the automotive meaning of expansion chamber. What evidence would you consider valid, and why would it be better evidence than this sales literature? Bear in mind we are not seeking to verify article content, we are trying to decide current English usage in order to match the name to the topic and scope of an article. WP:OR applies to content. WP:RS applies to both but it's also primarily written with content in mind.

Or, perhaps I should first ask, what is your current view on the matter? Andrewa (talk) 07:07, 7 December 2012 (UTC)

Speed of sound

Very interesting article and a good read since I am interested in performance enhancement of normally-aspirated engines. Not sure how this "post" will come across as totally inexperienced with Windows-type programming syntax. I note one obvious mistake in section 2.4 Complicating Factors, para 2, where it is stated incorrectly that the speed of sound is reduced in areas of elevated temperature. In fact the reverse is true, since the speed of sound is equal to the square root of the product of the ratio of specific heats, the specific gas constant for air and the local static temperature. Thus, concerning the influence of temperature, the speed of sound is predominantly proportional to the square root of the local static temperature. Every text book on aerodynamics and thermodynamics refers, also the Wikipedia page on Speed of Sound. Hope this is useful comment. Aero-joe (talk) 22:20, 29 May 2013 (UTC)

No argument there. Someone edited it to say Decreased. I changed it back.--=Motorhead (talk) 01:29, 18 June 2013 (UTC)

Royal Pioneer had expansion chamber in 1910

The earliest example I'm aware of is the American Royal Pioneer not German engineering in 1938. https://books.google.com/books?id=na4yAQAAMAAJ&lpg=RA1-PA292&ots=7YD06BLfpd&dq=royal%20pioneer%20expansion%20chamber&pg=RA1-PA292#v=onepage&q=royal%20pioneer%20expansion%20chamber&f=false Cycle and Automobile Trade Journal, Volume 14 - 1916 — Preceding unsigned comment added by 75.88.144.67 (talk) 13:58, 20 April 2015 (UTC)

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