# What is "engine braking" on 18-wheelers and why is it banned everywhere? **URL:** \ **Category:** Factual Questions\ **Created:** [November 1, 2005, 12:40am UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830 "2005-11-01T00:40:11Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [November 1, 2005, 9:04pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/21 "2005-11-01T21:04:26Z")
> [@CynicalGabe](#): > > > [@DSYoungEsq](#): > > > > P.S.: It’s a potential Trademark violation to use the term “Jake” brake when not speaking specifically about “Jacobs Engine Brakes”) > > Bah. > > Anyway, I need to go Xerox some paperwork… Worrying about that now is like putting a Band-Aid brand adhesive bandage on a major flesh wound. ---
**Author:** ![rpinrd](https://avatars.discourse-cdn.com/v4/letter/r/b3f665/32.png) [@rpinrd](https://boards.straightdope.com/u/rpinrd)\ **Post date:** [November 1, 2005, 9:48pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/22 "2005-11-01T21:48:22Z")
> [@Incubus](#): > > I’m guessing that they don’t scale down as well. A big eighteen wheeler with a trailer is going to have a lot of inertia. A small coupe with one passenger is not going to have nearly the kind of inertia, and typically can handle slowing down properly with its own brakes. Also, according to the Mailbag answer, they (only?) work on deisel engines due to the much greater compression used in those engines. One question that came to mind as I read the Mailbag answer: the engine brake works in part by allowing cylinder gasses to escape and thus preventing the braked cylinder from firing. Does this result in a bunch of unburned fuel being blown out the exhaust, or is this fuel captured somehow? ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [November 1, 2005, 10:39pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/23 "2005-11-01T22:39:41Z")
> [@](#): > > One question that came to mind as I read the Mailbag answer: the engine brake works in part by allowing cylinder gasses to escape and thus preventing the braked cylinder from firing. Does this result in a bunch of unburned fuel being blown out the exhaust, or is this fuel captured somehow? I think the injector does not turn on, so no fuel goes in. Also ‘Jake Co’ makes other braking devices, such as electromagnetic driveshaft brakes which are totally quite so engine brake is a better term. ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [November 1, 2005, 10:42pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/24 "2005-11-01T22:42:30Z")
> [@Polycarp](#): > > Worrying about that now is like putting a Band-Aid brand adhesive bandage on a major flesh wound. Didja ever notice that the phrase “Band-Aid brand adhesive bandage” perfectly fits the meter of the opening line of “Anything Goes”? ---
**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:** [November 2, 2005, 12:48pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/25 "2005-11-02T12:48:35Z")
> [@tracer](#): > > Didja ever notice that the phrase “Band-Aid brand adhesive bandage” perfectly fits the meter of the opening line of “Anything Goes”? Slow day at the office **Tracer**? 😉 ---
**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\ **Post date:** [November 2, 2005, 3:07pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/26 "2005-11-02T15:07:16Z")
> [@CookingWithGas](#): > > Why haven’t they ever been marketed on passenger cars? If they save brake wear and cause no additional engine wear, it would be better than downshifting to slow down. Engine braking also refers to something you can do with your small car. You drop the gear down maybe two below what you would normally be driving at. This sends your revs way up, and so long as you do not use the gas it will slow you down. Particularly good for not boiling your brake fluid on long downhills. ---
**Author:** ![beergeek279](https://avatars.discourse-cdn.com/v4/letter/b/7ea924/32.png) [@beergeek279](https://boards.straightdope.com/u/beergeek279)\ **Post date:** [November 2, 2005, 4:39pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/27 "2005-11-02T16:39:22Z")
> [@askeptic](#): > > Since you’re up could you bring me a Band-Aid? Sure, I’ve got them on top of the TiVo. ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [November 2, 2005, 8:08pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/28 "2005-11-02T20:08:10Z")
> [@beergeek279](#): > > Sure, I’ve got them on top of the TiVo. Can you use “TiVo” as a verb? I don’t know, I’ll have to Google for the answer. ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [November 2, 2005, 8:22pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/29 "2005-11-02T20:22:21Z")
> [@kanicbird](#): > > Also ‘Jake Co’ makes other braking devices, such as electromagnetic driveshaft brakes. Holy Crap, did everyone see the lightbulb going off over my head. In all my 41 years I have never had such a ‘duh’ moment. Such a simple and obvious device. Wish I had thought of it. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [November 2, 2005, 9:26pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/30 "2005-11-02T21:26:44Z")
The signs say “engine brake” because the earlier Jacobs Co. patents have become public domain, so other companies can make similarly noisy devices, but due to trademarking, can’t call them “Jake” brakes. The people who author the anti-noise signs want to cover all bases. As noted, Jacobs also makes braking devices that are NOT engine brakes, but may still be refered to as “jake” brakes. The electromagnetic devices are one such, but valves which restrict the exhaust are also common. These are called exhaust brakes rather than engine brakes, and they are not nearly so noisy. Engine braking devices could work fine on a SI (spark ignition) engine, but the existing throttle valve already provides a good deal of compression braking…which is NOT available on a diesel. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [November 2, 2005, 11:16pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/31 "2005-11-02T23:16:19Z")
> [@flight](#): > > Engine braking also refers to something you can do with your small car. You drop the gear down maybe two below what you would normally be driving at. This sends your revs way up, and so long as you do not use the gas it will slow you down. Particularly good for not boiling your brake fluid on long downhills. Particularly good for burning up a clutch surely unless you do it properly, either give the accelerator a blip before you change down gear or slow down and change gear before going downhill. ---
**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\ **Post date:** [November 3, 2005, 5:31pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/32 "2005-11-03T17:31:54Z")
> [@Pushkin](#): > > Particularly good for burning up a clutch surely unless you do it properly, either give the accelerator a blip before you change down gear or slow down and change gear before going downhill. Yeah, ideally you rev the rpms up to where they will be once you engage the clutch. Hmm, you can’t really do that with an automatic though. Do you have to slow down as you say first? ---
**Author:** ![beergeek279](https://avatars.discourse-cdn.com/v4/letter/b/7ea924/32.png) [@beergeek279](https://boards.straightdope.com/u/beergeek279)\ **Post date:** [November 3, 2005, 5:53pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/33 "2005-11-03T17:53:20Z")
> [@tracer](#): > > Can you use “TiVo” as a verb? I don’t know, I’ll have to Google for the answer. I use it all the time in that sense, as in “I’ll TiVo the game tonight”. That was inn the sense that TiVo has become the generic name for all DVRs (my Adelphia DVR was made by Scientific Atlanta and isn’t licensed, but I still call it a TiVo). ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [November 3, 2005, 8:42pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/34 "2005-11-03T20:42:07Z")
> [@flight](#): > > Yeah, ideally you rev the rpms up to where they will be once you engage the clutch. Hmm, you can’t really do that with an automatic though. Do you have to slow down as you say first? But the auto does that automatically if you’re not a wussy with it. Punch the accellerator to the floor, and nothing at all happens except that the engine revs up. Once it’s good and revved up, the torque converter catches up, and then you’ve got power. Well, I’ve been driving an underpowered car lately… I don’t seem to recall this with my own car at home – it seems to drop into the right gear and get up the right RPM instantly with no lag for the torque converter. ---
**Author:** ![askeptic](https://avatars.discourse-cdn.com/v4/letter/a/eb9ed0/32.png) [@askeptic](https://boards.straightdope.com/u/askeptic)\ **Post date:** [November 3, 2005, 8:53pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/35 "2005-11-03T20:53:02Z")
> [@Polycarp](#): > > Worrying about that now is like putting a Band-Aid brand adhesive bandage on a major flesh wound. How did I end up on your ignore list? (see post #16) 😉 ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [November 3, 2005, 9:29pm UTC](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830/36 "2005-11-03T21:29:25Z")
Signs here say something like: _RESIDENTIAL AREA LIMIT COMPRESSION BRAKING_ Some of these are at the bottom of long grades, and the sign hints that sometimes the truckies might have little choice, especially if the cab is filling with the smell of freshly toasted brake linings after coming down a mountain. It also allows the use of other, quieter, engine braking technologies. [Previous page](https://boards.straightdope.com/t/what-is-engine-braking-on-18-wheelers-and-why-is-it-banned-everywhere/328830.md?page=1)