# Are there other types of combustion engines other than internal? **URL:** \ **Category:** Factual Questions\ **Created:** [March 14, 2001, 5:36am UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912 "2001-03-14T05:36:46Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [March 14, 2001, 5:36am UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912/1 "2001-03-14T05:36:46Z")
I don’t really understand how the combustion could be anywhere but internal, so why do they bother specifying it? ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [March 14, 2001, 5:42am UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912/2 "2001-03-14T05:42:18Z")
Stirling cycle engines are external combustion. [External Combustion Engines](http://www.geocities.com/Yosemite/Rapids/2068/) ---
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [March 14, 2001, 5:44am UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912/3 "2001-03-14T05:44:44Z")
Sure, there are external-combustion engines - any steam engine, for instance, or Stirling-cycle engines. The difference is that the working medium (the liquid or gas that pushed on a piston or turbine or something mechanical) in an EC engine isn’t directly produced by combustion and then dumped overboard; instead it’s heated externally. The advantage of such a system is that you can use almost anything for fuel and can optimize your combustion system for thermal efficiency and emissions. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [March 14, 2001, 5:45am UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912/4 "2001-03-14T05:45:30Z")
You can find some more Stirling Cycle links [here.](http://www.uni.edu/darrow/frames/externalc.html) ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [March 14, 2001, 2:32pm UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912/5 "2001-03-14T14:32:11Z")
Whoa, hey, kewl stuff! 😃 How it works (the short version). [http://www.sfu.ca/~sfungc/stirlingengine.htm](http://www.sfu.ca/~sfungc/stirlingengine.htm) How it works (the Big Brain version). [http://electron6.phys.utk.edu/phys136/modules/m3/m3ex1.htm](http://electron6.phys.utk.edu/phys136/modules/m3/m3ex1.htm) Build a Tin Can Stirling Engine in your basement! [http://comptune.com/tincan.htm](http://comptune.com/tincan.htm) So, tell me again why I don’t have one of these marvelous engines as the pusher in my soccer mom Caravan? 😃 ---
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [March 14, 2001, 2:42pm UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912/6 "2001-03-14T14:42:36Z")
The swashplate mechanism has a lot of problems to face with friction losses and basic reliability. Also, the high lateral loads placed on the pistons affects the sealing and life of the rings. The operating medium has to be kept well sealed from the outside, limiting your ability to provide lubrication where you need it most - your car engine can run fine a quart low, but not a Stirling. The theoretical thermodynamic efficiency of the cycle, and the ability to use anything as a fuel, are attractive, but people have been working on the concept for a century or so without adequately fixing the practical problems. ---
**Author:** ![SavageNarce](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@SavageNarce](https://boards.straightdope.com/u/SavageNarce)\ **Post date:** [March 14, 2001, 6:26pm UTC](https://boards.straightdope.com/t/are-there-other-types-of-combustion-engines-other-than-internal/57912/7 "2001-03-14T18:26:31Z")
There’s a lot of talk and rumour around right now about Dean Kamen and his new “Ginger” invention which, as nearly as anyone seems to be able to determine, is a Sterling-powered urban commuting scooter. See [http://GINGER.patentcafe.com/](http://GINGER.patentcafe.com/) for details… such as they are 🙂