# What is a HEMI? And, why a TM? **URL:** \ **Category:** Factual Questions\ **Created:** [July 25, 2006, 12:15pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941 "2006-07-25T12:15:36Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [July 25, 2006, 12:15pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/1 "2006-07-25T12:15:36Z")
As I understand it, a “hemi” is engine technology (geometry, to be specifi) to make the combustion of the fuel more efficient by directing veritably all that energy into moving the pistons. But, moreso, how can Chrysler have a trademark ™ on this terminology? Is it unique to Chrysler? I thought it was well-known, public domain teminology…like piston or cylinder… So, what’s the scoop on HEMI ™? - Jinx ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [July 25, 2006, 12:18pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/2 "2006-07-25T12:18:49Z")
A trademark does not prevent someone from making an engine with the hemispherical tops for the cylinders. It just prevents them from marketing and referring to it as a hemi. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [July 25, 2006, 12:20pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/3 "2006-07-25T12:20:46Z")
I remember asking the same, its to do with the air-fuel mixture and how it combusts. Its been replaced by more effective engine management IIRC. Obligatory wiki link to [the Hemi Engine](http://en.wikipedia.org/wiki/Hemi) and [the Chrysler Hemi](http://en.wikipedia.org/wiki/Chrysler_Hemi_engine). ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [July 25, 2006, 12:49pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/4 "2006-07-25T12:49:41Z")
Ah, in my haste to answer I misunderstood the OP, unlike gazpacho :smack: The answer I suppose is much the same as why Honda have a variable valve timing technology called VTEC, Toyota VVT-i, BMW VANOS. They all have unique designs certainly, but the branding is trademark and associated with that company only. ---
**Author:** ![R.P.McMurphy](https://avatars.discourse-cdn.com/v4/letter/r/7993a0/32.png) [@R.P.McMurphy](https://boards.straightdope.com/u/R.P.McMurphy)\ **Post date:** [July 25, 2006, 1:46pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/5 "2006-07-25T13:46:54Z")
I presume that Chrysler has trademarked the word “Hemi” for a type of engine that they build. The term for the design is “hemispherical combustion chamber”. Basic HCC design has been used by other manufacturers. As far as I know, Chrysler was the first to mass produce and market an engine with an HCC design so they probably had the forsight to trademark the word “Hemi” and hold on to the trademark even though the original Hemi went of of production. ---
**Author:** ![Airman\_Doors\_USAF](https://avatars.discourse-cdn.com/v4/letter/a/e36b37/32.png) [@Airman\_Doors\_USAF](https://boards.straightdope.com/u/Airman_Doors_USAF)\ **Post date:** [July 25, 2006, 1:54pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/6 "2006-07-25T13:54:07Z")
The real irony is that the current HEMI engine does not have hemispherical heads. It’s simply a gimmick to sell more engines, and it’s quite a good one because it evokes historical images of raw power, which creates quite an emotional appeal. ---
**Author:** ![Cluricaun](https://avatars.discourse-cdn.com/v4/letter/c/bb73d2/32.png) [@Cluricaun](https://boards.straightdope.com/u/Cluricaun)\ **Post date:** [July 25, 2006, 2:09pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/7 "2006-07-25T14:09:53Z")
> [@Airman Doors](#): > > The real irony is that the current HEMI engine does not have hemispherical heads. It’s simply a gimmick to sell more engines, and it’s quite a good one because it evokes historical images of raw power, which creates quite an emotional appeal. Wait, the new Hemis aren’t…Hemis? How can they call it and sell it as such? That’s almost akin to calling your new six cylinder engine a “V8”, just for marketing purposes. ---
**Author:** ![Tastes\_of\_Chocolate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tastes_of_chocolate/32/3232_2.png) [@Tastes\_of\_Chocolate](https://boards.straightdope.com/u/Tastes_of_Chocolate)\ **Post date:** [July 25, 2006, 3:27pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/8 "2006-07-25T15:27:14Z")
> [@Cluricaun](#): > > Wait, the new Hemis aren’t…Hemis? How can they call it and sell it as such? That’s almost akin to calling your new six cylinder engine a “V8”, just for marketing purposes. _scurries off to trademark “V8”_ Dang. I’m going to make a mint off this. A “V8”[sub]TM[/sub] with good gas mileage. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [July 25, 2006, 4:14pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/9 "2006-07-25T16:14:47Z")
I don’t think V8 has mint in it. It’s mostly tomato juice. ---
**Author:** ![The\_Chao\_Goes\_Mu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_chao_goes_mu/32/3191_2.png) [@The\_Chao\_Goes\_Mu](https://boards.straightdope.com/u/The_Chao_Goes_Mu)\ **Post date:** [July 25, 2006, 5:23pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/10 "2006-07-25T17:23:42Z")
Check this out. [How HEMI’s work](http://auto.howstuffworks.com/hemi.htm) Can they really advertise something as a HEMI when it doesn’t have and engine with hemispherical heads? I hates false advertising. :mad: ---
**Author:** ![Omegaman](https://avatars.discourse-cdn.com/v4/letter/o/e480ec/32.png) [@Omegaman](https://boards.straightdope.com/u/Omegaman)\ **Post date:** [July 25, 2006, 5:29pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/11 "2006-07-25T17:29:08Z")
> [@Airman Doors](#): > > The real irony is that the current HEMI engine does not have hemispherical heads. It’s simply a gimmick to sell more engines, and it’s quite a good one because it evokes historical images of raw power, which creates quite an emotional appeal. Dual spark plug over the top of the cylinder head, dead center of the valve cover ,and canted valves Perhaps you have access to more complete technical information than I do . Site ? ---
**Author:** ![Airman\_Doors\_USAF](https://avatars.discourse-cdn.com/v4/letter/a/e36b37/32.png) [@Airman\_Doors\_USAF](https://boards.straightdope.com/u/Airman_Doors_USAF)\ **Post date:** [July 25, 2006, 5:40pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/12 "2006-07-25T17:40:36Z")
> [@Omegaman](#): > > Dual spark plug over the top of the cylinder head, dead center of the valve cover ,and canted valves Perhaps you have access to more complete technical information than I do . Site ? [Here you go.](http://www.allpar.com/mopar/new-mopar-hemi.html) > [@](#): > > The Hemi design combustion chamber is one of the poorest designs for emissions - why do you think it took so long to get it into production? It almost did not make emissions test requirements even with the modifications. … Today’s Hemi is that (a “Hemi”) in name only. [Editor’s note: Bob is referring to the head design. It is not a true hemispherical head, but looks vaguely like a hemispherical head with parts filled in.] Right above that quote is a close-up picture that will prove to you that it is not truly a Hemi. It’s amusing that they continue to maintain throughout the page that it is, though. It’s not. ---
**Author:** ![Omegaman](https://avatars.discourse-cdn.com/v4/letter/o/e480ec/32.png) [@Omegaman](https://boards.straightdope.com/u/Omegaman)\ **Post date:** [July 25, 2006, 5:54pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/13 "2006-07-25T17:54:19Z")
> [@Airman Doors](#): > > [Here you go.](http://www.allpar.com/mopar/new-mopar-hemi.html) > > Right above that quote is a close-up picture that will prove to you that it is not truly a Hemi. It’s amusing that they continue to maintain throughout the page that it is, though. It’s not. Because it was improved , you say it’s not a Hemi. Your’e right it’s interesting how every chance they get they refer to it as a Hemi. Hmmmmmmm. ---
**Author:** ![Airman\_Doors\_USAF](https://avatars.discourse-cdn.com/v4/letter/a/e36b37/32.png) [@Airman\_Doors\_USAF](https://boards.straightdope.com/u/Airman_Doors_USAF)\ **Post date:** [July 25, 2006, 6:14pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/14 "2006-07-25T18:14:15Z")
Look, I’ve given you visual evidence and an admission from the editors of a Mopar fanboy page that it does not have hemispherical combustion chambers. Therefore, it is not a Hemi. It is a HEMI, Chrysler’s trademark name for the engine. Hmmm… indeed. ---
**Author:** ![silenus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/silenus/32/166_2.png) [@silenus](https://boards.straightdope.com/u/silenus)\ **Post date:** [July 25, 2006, 6:23pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/15 "2006-07-25T18:23:55Z")
Has Chryler done any print advertising that makes the distinction? Because you can’t tell the difference between hemi and HEMI™ when someone says it on TV. It’s cheating, but it’s legal and not false advertising. Print would be a different matter. ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [July 25, 2006, 6:29pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/16 "2006-07-25T18:29:32Z")
I’m guessing to most people, “HEMI” just means “big, powerful engine.” That the “HEMI” is derived from a term that no longer applies to the engines called by that name doesn’t bother me. ---
**Author:** ![Airman\_Doors\_USAF](https://avatars.discourse-cdn.com/v4/letter/a/e36b37/32.png) [@Airman\_Doors\_USAF](https://boards.straightdope.com/u/Airman_Doors_USAF)\ **Post date:** [July 25, 2006, 6:38pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/17 "2006-07-25T18:38:13Z")
> [@garygnu](#): > > I’m guessing to most people, “HEMI” just means “big, powerful engine.” That the “HEMI” is derived from a term that no longer applies to the engines called by that name doesn’t bother me. Like I said, emotional appeal. 🙂 ---
**Author:** ![Omegaman](https://avatars.discourse-cdn.com/v4/letter/o/e480ec/32.png) [@Omegaman](https://boards.straightdope.com/u/Omegaman)\ **Post date:** [July 25, 2006, 6:46pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/18 "2006-07-25T18:46:44Z")
> [@Airman Doors](#): > > Look, I’ve given you visual evidence and an admission from the editors of a Mopar fanboy page that it does not have hemispherical combustion chambers. Therefore, it is not a Hemi. It is a HEMI, Chrysler’s trademark name for the engine. Hmmm… indeed. I was hoping for something a little more legitimate than a mopar “fanboy” page. ---
**Author:** ![Airman\_Doors\_USAF](https://avatars.discourse-cdn.com/v4/letter/a/e36b37/32.png) [@Airman\_Doors\_USAF](https://boards.straightdope.com/u/Airman_Doors_USAF)\ **Post date:** [July 25, 2006, 7:10pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/19 "2006-07-25T19:10:41Z")
Yeah, I guess the picture lies, too. I guess you could take the engine apart and see for yourself, but it’s easier to look at the visual evidence and weigh the fact that even the rah-rah crowd, in moments of honesty, will admit that it’s not a Hemi. I suppose you could look it up on [Wikipedia](http://en.wikipedia.org/wiki/Chrysler_Hemi_engine#Modern_Hemi): > [@](#): > > The modern Hemi is not really a Hemi at all - it has a polyspherical combustion chamber similar to that in many other modern engines. A true hemi head was considered in the design phase, but it was rejected and only the near-perpendicular valve arrangement remains. The Hemi replaced Chrysler’s large LA family of engines, particularly the Magnum 5.9, in the early 2000s But if what I gave you isn’t good enough, that certainly won’t be good enough either. ---
**Author:** ![control-z](https://avatars.discourse-cdn.com/v4/letter/c/eada6e/32.png) [@control-z](https://boards.straightdope.com/u/control-z)\ **Post date:** [July 25, 2006, 7:17pm UTC](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941/20 "2006-07-25T19:17:07Z")
That would suck if it’s true, yet another fake thing in the world. But either way the horsepower and torque the Hemis put out is very decent. [Next page](https://boards.straightdope.com/t/what-is-a-hemi-and-why-a-tm/365941.md?page=2)