Talk:Compression release engine brake

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Why so much noise?[edit]

Q: why do these things cause so much noise?

A: The compressed gas in the cylinder at the top of the compression stroke is released abruptly and explosively. Why does this cause more noise than the release of exhaust gases on the exhaust stroke in normal engine operation? It is because, in the latter case, the gas is not compressed but rather simply pushed out of the exhaust port by the motion of the piston. There is no abrupt, explosive release.

There is an explosive release, in that the combusted mixture creates pressure, but it only happens once every 2 crank turns (multiplied by no. of cylinders), not every crank turn (x cylinders), and its at a higher pressure during jake (engine) braking, 7legs 090206

First and Foremost, jakes are an essential tool in stopping and slowing a rolling semi (often 75,000 lbs) Second a jake brake should only be used on a DECLINE,, used in an incline it hinders shifting into another gear, and can lead to a drive being able have powered control of his vehicle, while he attempts to put it back into gear... Often a novice will forget to switch the jake off for and incline and will stall out.. necessitating them to creep up a hill in only 3rd or 4th gear.. Myself as a current active driver appreciate the added help, slowing my rig down when a four wheeler cuts me off then slows down to talk on their cell phone.. Unassisted a semi can take about as long to slow down as they take to get to up to speed.. aDo drivers like the sound probably. But is there a valid reason to use jakes, without question, YES..-- (talk) 22:11, 4 March 2008 (UTC)Caveman.otr

"used in an incline it hinders shifting into another gear, and can lead to a drive being able have powered control of his vehicle, while he attempts to put it back into gear"

The phrase "can lead to a drive being able have powered control of his vehicle" is ungrammatical and makes no sense. Can somebody who knows about this please correct it? Thanks ---Dagme (talk) 16:42, 3 April 2015 (UTC)

This is my best guess to clarify the apparent confusing statement which "Dagme" has noted and w/which I agree...! I believe the phrase was intended to say: "...can lead to a drive(r) being (UN)able have powered control of his vehicle..."

Comment/Any relationship to incline?[edit]

yes: there is a very real relationship to incline/decline:
In general, anyone who has driven heavy trucks in hilly terrain - or even just in traffic - will tell you what a huge effect on safety the development & use of engine brakes has been!
Engine brakes - 
(e.g., the Jacobs engine brake, aka, the "jake brake" a term now used generically over a variety of other such devices all of which operate by various means to augment mechanical brakes by slowing/retarding engines and valve functions, shutting off fuel to the cylinders, for example, etc.)

- are designed to use the much higher compression of the diesel engine - as opposed to that of the gasoline engine - to slow/constrain the wheel speed of a heavy truck as use of the wheel brakes alone will cause them to overheat and fail, resulting in 'runaway' truck on a 'decline', ie., downhill, on a downgrade.

However, the engine brakes are all dependent upon the truck being maintained - in gear - in order to transmit the braking energy from the engine which is transformed into a compressive mechanism to slow/restrain wheel speed on a downgrade, through the transmission & the drivetrain, to the wheel sufficient to overcome/restrain/control the speed generated by the gravitational downhill force on the vehicle, rather than to generate speed & power to drive it on the gentler terrain and on uphill sections.
Use of an engine brake on incline, i.e., an uphill grade, is counterproductive as it prevents engine from developing the very power required to propel truck up the hill - as the engine speed/power is suppressed by the braking effect of the engine brake. If the mis-use of the engine brake results in the driver taking it out of gear the result is Not good...! Engine can stall, truck slows/stops, rolls backward downhill. This can have critically problematic effects as one might imagine - runaway truck going backward - downhill & out of control - in the UPhill lanes!  — Preceding unsigned comment added by Ed-do-u-ardo (talkcontribs) 03:48, 19 August 2015 (UTC) 

Comment/Any relationship to incline?[edit]

Comment on the article: This is the best explanation of the Jake Brake I have seen and has cleared up for me a mystery of 30 years standing.

Question: is there a relationship between the grade of the highway and the weight of the truck which necessitates the use of Jake Brakes? Is it necessary for a loaded 18 wheeler to use Jake Brakes on a 6% grade? How about a 3% grade. Is there an economic reason - use of Jake Brakes increases longevity of brake linings? Somehow I get the impression that Jake Brakes are equivalent to non-mufflered autos - the driver likes the sound. Gary A. McDaniel

I have to laugh - I think you've hit it right on the head! lol. Crabapplecove 13:42, 31 August 2006 (UTC)
Man, I used to love driving rigs with Jake brakes. Drove a cabover Freightliner once that had no mufflers. Just straight stacks. The Jake was loud enough to cause an avalanche. Haven't driven in years, but I still have my CDL. Fun stuff. - Lucky 6.9 07:11, 4 October 2006 (UTC)
absolutely! Use of service brakes alone will cause them to overheat and fail VERY quickly, and simply gearing down will not be effective, as diesel engines lack a throttle plate. The idiots that come up with those "No Jake Brake" laws have NEVER driven a semi before and don't know or care that the engine brake is our primary source of braking power on grades. The engine brake's job is to hold back the weight of the trailer.Lpimlott (talk) 16:26, 10 September 2008 (UTC)

Recommendation to rewrite the article[edit]

I recommend that this article is rewritten/changed/replaced by an article about engine compression brakes as it is Jake centric and doesn't really reflect well on actual technology in use today e.g. other manufacturers examples (Mack's Dynatard anyone?) also it sources an exhaust brake equipment manufacturer, where clear distinction between these two systems must be made to inform the readers. I think its OK to have an article about Jake as generic term but more useful article about the subject(compression engine brake) is essential. Stonufka (talk) 12:16, 28 February 2008 (UTC)

Some "internationalization" wouldn't hurt either, for exampl I have never heard of "Jacobs brakes" or whatever it is called. I suppose it is a US company? There should be such information available in the artcle. What about other companies? And other countries? :arny (talk) 08:28, 5 June 2008 (UTC)
The Jacobs brake is used on the Paccar MX engine which powers DAF trucks as well as Kenworth and Peterbilt. The new Detroit Diesel DD15 and DD16 will feature a Jacobs designed Jake Brake. The DD15/16 will power all of Daimler's truck lines including: Freightliner, Western star, Mercedes Benz and Mitsubishi Fuso. The Hino 13 liter engine is also equipped with a Jacobs designed engine brake. Also Jacobs designs other engine technologies such as variable valve actuation and EGR systems. Those systems are used by other companies such as Iveco, Daewoo and Hyundai.

The Volvo D11, D13 and D16 power a number of truck brands including: Renault, Mack and SISU. They employ a Jacobs like compression brake but it was not designed by Jacobs. —Preceding unsigned comment added by Thaddeusw (talkcontribs) 00:11, 31 August 2009 (UTC)

Relationship to Jacobs chuck corporation[edit]

If you look at the circa-1970s-vintage Jacobs Engine Brakes logo, it seems obvious that this product line was made by the same Jacobs corporation of drill chuck fame. I'd imagine that the lines of business are probably completely spun off into separate corporations today (see and Would be nice to fill in the historical info a little. is interesting although rather sparse. Regards, — ¾-10 03:43, 4 May 2010 (UTC)


"A compression release engine brake uses an extra lobe on the camshaft to open a second exhaust valve at the top of the compression stroke. The stem of this valve telescopes during normal operation so the valve remains closed, but is locked at full length by a solenoid when the engine brake is engaged so that the valve opens as directed by the cam."

Is a separate solenoid built into the stem of each of these special valves?

Dagme (talk) 01:53, 14 November 2010 (UTC)

Good question. I don't know, not being as familiar with diesel-mechanic work as I'd like to be. Another question it would raise in my mind is, if you've got a solenoid, do you even need a cam at all? At least within the past 25 years, since ECMs have been common, it would seem that a signal, a solenoid, and a hot lead would be all you need (look Ma, no cams). Of course I am talking out of theory not experience. Maybe someone (like a diesel engineer or mechanic) can set me straight. — ¾-10 02:47, 17 November 2010 (UTC)
The solenoid is merely to engage the poppet valve, not to actuate it (that is, to actually push it down into the "open" position). Valves in internal combustion engines are held closed by very heavy valve springs. The springs have to be heavy because they must quickly close the open valve at the appropriate time during each engine cycle. Moreover, because engines rotate rapidly, the inertia of the valvetrain tends to want to keep the valve open, thus also necessitating a very strong spring. And on top of that, when the time comes to open the valve again, it must also be done quickly (again, in opposition to the valvetrain's inertia), which requires a lot of force. And again, this is in addition to the heavy closing force of the spring.
As a result, the force needed to open these valves is tremendous -- far exceeding what a solenoid could bring to bear. Only a steel cam can provide the amount of force necessary to rapidly open engine valves against the forces of valvetrain inertia and strong valve springs. Captain Quirk (talk) 02:17, 1 June 2017 (UTC)

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