Talk:Hemispherical combustion chamber

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Archives of past discussion[edit]

Archive 1

Cars[edit]

Wich car models used the hemi engine?

French hemi?[edit]

I recall reading (somewhere...) of a French-built, Chrysler-designed hemi, around 130ci, intended for armored cars or something in France in the '40s, being sold in SAm (Brazil?) into the '70s... Can anybody substantiate? TREKphiler hit me ♠ 02:48, 7 February 2009 (UTC)


Factually inaccurate disaster[edit]

Why all the pent-roof content? A pent-roof combustion chamber is by definition NOT hemispherical. And ironically, Aston Martin engines that actually do have hemispherical combustion chambers aren't mentioned at all. Benefits/drawbacks is incomplete, "Supersession in modern engines" is flawed, many historically/technologically significant hemi engines aren't mentioned, the Lotus section doesn't actually say anything about Lotus's engines, Alfa's 4-cyl hemi (second only to the Jag engine for longevity of production, 1953-1993) isn't mentioned, and the Porsche section erroneously claims that recent 911s utilized hemispherical combustion chambers! And why do these Mitsubishi engines warrant inclusion (has anyone verified that they actually have hemispherical combustion chambers?) when inexpensive 4-cyl pushrod hemis from Renault and Toyota (both of which are arguably of more historical/technological significance on account of racing victories) are omitted? Good grief. Jelliott4 (talk) 15:10, 14 November 2010 (UTC)

Thank you for your suggestion. When you believe an article needs improvement, please feel free to make those changes. Wikipedia is a wiki, so anyone can edit almost any article by simply following the edit this page link at the top. The Wikipedia community encourages you to be bold in updating pages. Don't worry too much about making honest mistakes—they're likely to be found and corrected quickly. If you're not sure how editing works, check out how to edit a page, or use the sandbox to try out your editing skills. New contributors are always welcome. You don't even need to log in (although there are many reasons why you might want to). Wikipedia has this cool idea...if you see a problem, fix it. As to pentroof chambers being hemis or not; when Mopar was developing its DOHC "hemi", it called the four valve pentroofed heads "hemi pentroof" chambers (according to a 1967 "Mopar Muscle" article)
I did find some time to make a couple such minor improvements in June 2012, but it appears that they were promptly undone by people who preferred the less accurate prior versions. (This is sort of what I suspected might happen if I went ahead and started investing time in improving this article without running it by the ′Talk′ page first...) Jelliott4 (talk) 00:14, 28 October 2014 (UTC)
I don't know that a sentence and a picture is all that much content. And it shows the evolution of the hemi chamber. A pentroof is a cross-flow head, just like a hemi and the only reason it isn't a true hemispherical combustion chamber is because it has 4 flat-headed valves in each ""corner"".
It could be said of any cross-flow combustion chamber design that ″the only reason it isn't a true hemispherical combustion chamber is because [insert distinguishing characteristics here].″ So what? I don't understand the apparent desire to confuse the meaning of a technical term like this. If you're going to stray from the long-established and very specific meaning of such a term, the term loses essentially all technical value; why maintain an encyclopedia entry at all? Jelliott4 (talk) 00:14, 28 October 2014 (UTC)
If you think benefits/drawbacks is incomplete, complete it to your satisfaction. Same goes for fleshing out the Lotus, Alfa and any other manufacturers you may want to add to the list.
The ′Benefits and drawbacks′ section does appear to have been substantially improved over the last two years. That said, I'd still be inclined to remove much of the second paragraph (since it erroneously discusses drawbacks associated with large valves in general [i.e. in no way inherent to hemispherical combustion chambers]) and the entire fourth paragraph (since it erroneously discusses drawbacks associated with adapting a pushrod valvetrain to work with hemispherical combustion chamber design [i.e. in no way inherent to hemispherical combustion chambers]). But if I went ahead and did any of that today, I wouldn't have much confidence that my revisions wouldn't be undone tomorrow. Jelliott4 (talk) 00:14, 28 October 2014 (UTC)
I believe the concept here is for everyone to add their bit. It sounds like you have some bits to add, so go to it.Marshmallowbunnywabbit (talk) 01:03, 30 November 2010 (UTC)

"Today,"hemi" is more of a trademark than a description of a combustion chamber." It's either a trademark, or it's not. Let's not use the term 'trademark', which has a particular legal meaning, to mean 'characteristic term'. — Preceding unsigned comment added by 207.189.106.4 (talk) 17:36, 15 June 2012 (UTC)

It's true that Chrysler has somehow registered ″Hemi″ as a trademark in the USA, despite the fact that this clearly contravenes the legal prohibitions on the registration of descriptive and/or generic terms as trademarks. That they got away with it was probably just a matter of no one objecting (note that other car manufacturers have typically not made a big marketing deal out of the shape of their combustion chambers); if I were an intellectual property attorney with time on my hands, I suspect I could get Chrysler's trademark registration thrown out under section 706.01 of the USPTO's Trademark Manual of Examinging Procedure. But I'm not an attorney, I'm a mechanical engineer, so I'll just refer you to Trademark distinctiveness to draw your own conclusions. (And I would love to see a section of this article dedicated to Chrysler's spurious trademark of ″Hemi,″ but I'm really not the one to write it.) Never mind that the current crop of Chrysler ″Hemi″ engines arguably aren't hemis at all, since their combustion chamber design is only slightly concave... Jelliott4 (talk) 00:14, 28 October 2014 (UTC)

Possible improve to lead section[edit]

I am not knowledgeable enough about this subject to write about it, but I would like to suggest how the lead section could be improved. I think that is should mention what the hemi design is an alternative to . It should also explain if it is a relatively uncommon design; maybe something like "In 2012 hemi engines were used in only 2% of new cars". Some of these things may be covered in more detail later on in the article, but I think the lead should provide some basic context for the casual reader. ike9898 (talk) 15:38, 23 July 2012 (UTC)

Benefits and drawbacks improvements[edit]

As the Hemi is talking about a specific type of engine which is used in specific cars and advertised as a recognizable name, I expected the benefits and drawbacks section to discuss the benefits and drawbacks of the hemisphere design compared to other, more conventional designs. Instead, it only talks about the pros and cons of variants on the engine, with a slight section talking about weight and how they have fallen out of favor. However, the new Dodge Durango is advertised as having a HEMI option so it still seems to have some favor.

Whoever wrote the Benefits and Drawbacks section studied English as a 47th language. I'd clean it up, but I have no idea what meaning it intends to convey. --76.21.157.203 (talk) 19:00, 27 September 2014 (UTC)
if a hemispherical combustion chamber can't have four vpc then the examples cited such as the 1912 GP Peugeot can't have had hemispeherical combustion chambers. Either than or there CAN be 4-valve hemispherical combustion chambers, coz they can't both be right. Mr Larrington (talk) 12:53, 13 October 2014 (UTC)
Well, strictly speaking, you could develop a true 4-valve hemi, but (to my knowledge) no one has done so (due to the valvetrain complexity that would be required). The 4-valve examples cited in the ′History′ section do not have hemispherical combustion chambers, and their inclusion there is egregiously misleading—but it looks like last time someone tried to correct that, their correction was almost immediately undone. Jelliott4 (talk) 00:14, 28 October 2014 (UTC)

Requested move 20 May 2015[edit]

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: moved. Number 57 17:57, 21 June 2015 (UTC)


Hemi engineHemispherical combustion chamber – This is what the article is about. "Hemispherical combustion chamber" would be a more accurate and more general title, while remaining perfectly understandable. Hemi is a Chrysler trademark and closely associated with Chrysler engines; hemispherical combustion chamber engines were used a wealth of different manufacturers. --Relisted. George Ho (talk) 05:52, 30 May 2015 (UTC) Cloverleaf II (talk) 11:58, 20 May 2015 (UTC)

Keep at current page. Hemi engine is the common name. That some one owns a trademark on the name is not sufficient reason for a move. Google books search for Hemi engine: About 27,500 results, Google books search for Hemispherical combustion chamber: About 16,800 results. Spshu (talk) 13:38, 20 May 2015 (UTC)
You've proved my point! Almost all of these books (Google books search for Hemi engine) are about the Chrysler Hemi engine, not hemispherical combustion chamber engines. That demonstrates "Hemi engine" is the common name of a Chrysler V8, not that it is the common name of the technology discussed in this article. —Cloverleaf II (talk) 16:58, 20 May 2015 (UTC)
No, I do not. The first book [How to Build Max-Performance Hemi Engines indicates on page 9 that he uses "hemi" as the generic term and "Hemi" when refering to Chrysler's. Hemi Muscle refers to "Hemi clone cars" on page 11. Chrysler originally used Firepower name in 1950's for Hemi engine (Hemi Muscle] (Page 9). Other early books are Chrysler manuals. --Spshu (talk) 19:51, 20 May 2015 (UTC)
Books (and some newspapers) that use the word this way exist, but aren't they outnumbered more than 10 to one by those that use Hemi for Chrysler and hemispherical for other brands? When I search books for "hemispherical head engine" I get book after book about non-Chrysler engines, but search for "Hemi engine" and it's Chrysler, Chrysler, Chrysler, with only one or two exceptions. --Dennis Bratland (talk) 20:04, 20 May 2015 (UTC)
  • Move Hemi engine should redirect to Chrysler Hemi engine (or vice versa). The shorthand "Hemi" refers to Chrysler's engine. A general article about all hemispherical combustion chamber engines needs a different title. "Hemi" is not the common name of all such engines, only the Chryslers. It's true that sometimes the term is used figuratively, as a synecdoche: someone will say the name of Chrysler's engine, "Hemi", intending it to stand for all such engines, like saying "a Coke" to refer to any soft drink. But we shouldn't use such imprecise figures of speech in article titles. --Dennis Bratland (talk) 17:46, 20 May 2015 (UTC)
Comment: however that is precisely how WP handles article titles per Wikipedia:Official names and common name, as it is Bill Clinton not William Jefferson Clinton, as it is how people would search for the info. Redirects can be used for official names or other common names (using the most common). Chysler's engine could just be a section at Hemi engine. Spshu (talk) 19:32, 20 May 2015 (UTC)
I'm sorry, but I can't follow your reasoning at all. If your argument were inverted, then it would make sense to me. Bill Clinton is not relevant because nobody ever refers to ex-presidents as Bill Clintons. They do refer to Pepsi, Sprite and Coke as Cokes, but that figurative use would break the encyclopedia badly. Maybe someone else can read what you're saying and explain it to me. --Dennis Bratland (talk) 19:46, 20 May 2015 (UTC)
In other words you don't know what your reason is for moving as I followed your reasoning: "But we shouldn't use such imprecise figures of speech in article titles." Bill Clinton is not precise as it isn't his official name (William Jefferson Clinton) and as there are other Bill/William Clintons. You are mixing "ex-president" with "Bill Clinton". Spshu (talk) 21:23, 20 May 2015 (UTC)
Nope, but I can see there is a great deal of misunderstanding here. Bill Clinton simply isn't a relevant example. You're saying we should redirect Coke to Soft drink or Xerox to Photocopier. At least in those case you could at least show a substantial number of uses of the words that way. In the case of Hemi, the overwhelming majority refer only to Chrysler engines, so there is even less reason to to use the genericized trademark as a a title of a generic article. The next best alternative to the move proposal here would be to make Hemi engine a dab page, similar to Coke. --Dennis Bratland (talk) 21:33, 20 May 2015 (UTC)
  • Support. I'm getting 18,100 Google Books hits for "hemispherical combustion chamber" compared to 4840 for "hemi engine". The latter does appear to be closely associated with the Chrysler Hemi engine, which has its own article.--Cúchullain t/c 14:53, 9 June 2015 (UTC)
  • Support move - At this time, "Hemi" means Chrysler, and doesn't reflect the technology itself. Make this a redirect, put a hat note on the Chrysler Hemi article pointing to the full, proper name. Dennis Brown - 00:53, 14 June 2015 (UTC)

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

2 valve - 4 valve innacuracy[edit]

The article states that the design of a hemispherical combustion chamber only allows 2 valves per chamber, but in the history there is mention of a 4 valve engine.

One of these statements is inaccurate. — Preceding unsigned comment added by 50.121.72.11 (talk) 18:50, 1 June 2015 (UTC)

The BMW Apfelbeck [[1]] engine was a 4 valve hemispherical engine. Certainly 2 valves are easier but 4 vales can be done (with great effort). My German doesn't exist but the engine is mentioned on the German hemi page [[2]]. I suspect there are others but most would be 2 valve engines. I think many SOHC and DOHC 2 valve motors were also hemi in shape. Ironically the current HEMI V8 does not have a hemispherical combustion chamber. Springee (talk) 03:28, 28 July 2015 (UTC)

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Aircraft?[edit]

Why are only autos mentioned here? Hemis have been used in recip aircraft emgines almost from day one. They are essential for high power to weight. Also, all motorcycles use a hemi or pentroof (derivation.) Harley since 1937; almost all makes at least since the 'thirties. Indian was only notable exception. Harley stopped producing flatheads in what 1964 I believe. Also Boats. Many use Hemis in 4 stroke applications--PT boats used 3 V12 Allison aircraft engines, again, hemis. — Preceding unsigned comment added by 184.99.135.215 (talk) 13:53, 26 April 2017 (UTC)