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Old 10-31-2005, 07:40 PM
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What is "engine braking" on 18-wheelers and why is it banned everywhere?

I often see signs in smaller towns that say "no engine braking!" in reference to trucks. I'd imagine that it's noisy or somehow dangerous. Google searches only turn up manufacturers of engine brakes.

What is it? Why's it banned everywhere?
Old 10-31-2005, 07:45 PM
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They're referred to more commonly as "Jake brakes," and here's a good explanation.
Old 10-31-2005, 07:46 PM
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And the Straight Dope mailbag article on Jake brakes from a few years ago.
Old 10-31-2005, 07:57 PM
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Engine brakes are devices, installed on the head of diesel engines, that basically turn
the engine into an air compressor. This makes the engine much more efficient in
slowing the truck. Some truck owners run modified, or straight, mufflers in the belief
that it improves engine performance. It probably does the opposite on modern,
computer controlled, engines. When using the engine brake w/ stock mufflers the
increased noise is minimal, but w/ more open exhaust systems they can be very loud.
There are, of course, some who like this effect, but it is very annoying to residents of
homes near truck routes, especially during early morning hours. You may notice that
many of these signs specify no "unmuffled" engine brakes.
The engine brakes are an important safety feature, as they aid in controlling downhill
speed w/o excess braking, which can result in overheating and failure of the brake
shoes.
Old 10-31-2005, 08:01 PM
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Sorry, I'm a slow typist. Cecil's article nailed it.
Old 10-31-2005, 08:24 PM
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Slight hijack:

I've noticed in recent years that all the signs I've seen in California that used to say "Truckers: Easy on the Jake BrakeNext 5 miles" or something to that effect, now say "Engine" brake. The word "engine" is obviously a sticker/fresh paint or something that is covering up "Jake" since it is on a slightly different color background.


Whats up with that?
Old 10-31-2005, 08:40 PM
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Quote:
Originally Posted by CynicalGabe
Slight hijack:

I've noticed in recent years that all the signs I've seen in California that used to say "Truckers: Easy on the Jake BrakeNext 5 miles" or something to that effect, now say "Engine" brake. The word "engine" is obviously a sticker/fresh paint or something that is covering up "Jake" since it is on a slightly different color background.


Whats up with that?
Read the Mailbag column, linked above.


(P.S.: It's a potential Trademark violation to use the term "Jake" brake when not speaking specifically about "Jacobs Engine Brakes")
Old 10-31-2005, 08:45 PM
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Quote:
Originally Posted by CynicalGabe
Whats up with that?
The link supplied by [i]tracer[\i] explains it.

Basically, the Jacobs company doesn't want their neame to be shorthand for "noisy trucks".
Old 11-01-2005, 07:38 AM
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Quote:
Originally Posted by Xema
Basically, the Jacobs company doesn't want their name to be shorthand for "noisy trucks".
Too late....
Old 11-01-2005, 09:32 AM
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I used to wonder this, myself. Then last year when driving in Boston while on vacation, I heard this godawful loud "thwacka-thwacka-thwacka-thwacka" sound coming from the semi in the next lane. I exclaimed aloud to my husband, "What the hell is that?!" He said, "Engine braking." My immediate response was, "No wonder you see all those signs forbidding it!"
Old 11-01-2005, 11:15 AM
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Having grown up at the end of a street, that had a sand & gravel pit at the other end of it, I think they should be outlawed, removed from all trucks, and destroyed in a public ceremony.

I can't tell you of the number of times, I had to say "Wait a minute, a truck is going by... " as one kicked it's Jake Brake on directly perpendicular, and only 30yds away from my bedroom window. My window seemed to be the spot at which EVERY truck decided, "Time to slow down for the stopsign ahead."

Actually, I know why we need them on the big trucks, and don't REALLY want them actually outlawed, but some consideration would have been nice.

Now I live far away from that street, and NEVER have a truck begin braking just outside my bedroom window!


-OP : Banned because they're trying to keep me from blowing up trucks, after I snap from "One too many" trucks slowing in front of my house.

BRRRRRRRAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA <chugg chugg of the gear shift>

-Butler
Old 11-01-2005, 11:21 AM
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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.
Old 11-01-2005, 11:29 AM
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Quote:
Originally Posted by 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...
Old 11-01-2005, 11:48 AM
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Quote:
Originally Posted by 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.
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.
Old 11-01-2005, 01:04 PM
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Quote:
Originally Posted by CynicalGabe
Bah.

Anyway, I need to go Xerox some paperwork...

On your way back will you grab a few Kleenex for me? I have a runny nose.
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Old 11-01-2005, 01:11 PM
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Quote:
Originally Posted by The Chao Goes Mu
On your way back will you grab a few Kleenex for me? I have a runny nose.
Since you're up could you bring me a Band-Aid?
Old 11-01-2005, 01:13 PM
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And on that note:

The Straight Dope mailbag article on trademarks used as generic terms

Old 11-01-2005, 02:00 PM
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Quote:
Originally Posted by askeptic
Since you're up could you bring me a Band-Aid?
I just listen to my walkman when the loud trucks go by
Old 11-01-2005, 02:20 PM
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A Pepsi would probably make your nose feel better.
Old 11-01-2005, 03:31 PM
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Quote:
Originally Posted by GaryM
A Pepsi would probably make your nose feel better.
Personally, I don't like that brand of coke.
Old 11-01-2005, 04:04 PM
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Quote:
Originally Posted by CynicalGabe
Quote:
Originally Posted by 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.
Old 11-01-2005, 04:48 PM
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Quote:
Originally Posted by 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?
Old 11-01-2005, 05:39 PM
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Quote:
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.
Old 11-01-2005, 05:42 PM
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Quote:
Originally Posted by 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"?
Old 11-02-2005, 07:48 AM
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Quote:
Originally Posted by 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?
Old 11-02-2005, 10:07 AM
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Quote:
Originally Posted by 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.
Old 11-02-2005, 11:39 AM
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Quote:
Originally Posted by askeptic
Since you're up could you bring me a Band-Aid?
Sure, I've got them on top of the TiVo.
Old 11-02-2005, 03:08 PM
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Quote:
Originally Posted by 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.
Old 11-02-2005, 03:22 PM
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Quote:
Originally Posted by 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.
Old 11-02-2005, 04:26 PM
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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.
Old 11-02-2005, 06:16 PM
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Quote:
Originally Posted by 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.
Old 11-03-2005, 12:31 PM
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Quote:
Originally Posted by 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?
Old 11-03-2005, 12:53 PM
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Quote:
Originally Posted by 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).
Old 11-03-2005, 03:42 PM
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Quote:
Originally Posted by 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.
Old 11-03-2005, 03:53 PM
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Quote:
Originally Posted by 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)
Old 11-03-2005, 04:29 PM
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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.
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