Talk:Engine braking

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This page needs reworking, in my opinion, and I'll try to do so soon if there are no objections. In an engine, the compression of air in the cylinder is approximately a reversible process. Yes, it takes energy to compress it on the compression stroke, and the gas heats up, but on the downstroke that energy is returned to the crankshaft and the gas cools back down. In a gasoline engine, engine braking during closed-throttle operation comes mainly from maintaining a partial vacuum in the intake manifold (between the closed throttle and the cylinders). Diesel engines are unthrottled, so they don't incur these "throttling losses" and don't provide much engine braking (it's also one reason they tend to be fuel-efficient); a jake brake on a (presumably diesel) truck provides engine braking by opening the exhaust valves at the top of the compression stroke, so that the energy used in compressing the air is lost, instead of being returned to the crankshaft. - Coneslayer 05:01, 2005 Mar 5 (UTC)

Sounds like you know about the subject, no objections here. Raazer 16:44, 8 Mar 2005 (UTC)

Contents 1 Brakes, brakes, brakes 2 question 3 Don't Merge 4 "Compression Braking" 5 Risks?

[edit] Brakes, brakes, brakes

OK, we've got Engine brake (AKA Compression brake), Exhaust brake, Air brake (rail), and Jake brake (plus multiple suffixes for each e.g. -e , -es, -ing). Is there a better way to organize it? Just adding a category might not elucidate one as to the differences, if there are any, between the various types. Ewlyahoocom 10:51, 30 July 2005 (UTC)

- Jake brake seems like a popular name for an exhaust brake made by Jacobs, and could be a subset of that article. However, the jake brake article seems to describe the mechanism in clearer detail (and perhaps more correctly) by saying how the energy is dissipated by the release of the air from the cylinders.

The exhaust brake article is more extensive in mentioning the competitor of Jacobs, Pacbrake but seems confused as to the mechanism, and makes it seem the air never leaves the engine.

An air brake (rail) is very different from everything else and should remain in its own article. It mentions trucks, but refers to applying pneumatic pressure to activate regular friction braking. Also, compression brake probably is fine as a redirect. Exhaust brake/jake brake is a mechanism that does not exist in regular cars, but engine braking is possible in any car, so they are also distinct.

To remedy the number problem, I guess I'll, or someone else will come back to merge parts of exhaust brake and jake brake, hopefully maintaining all the information in the jake brake article. But Jake brake is actually an indivudual product, and merits its own article.Raazer 23:01, 23 August 2005 (UTC) -

Could we merge a lot of these pages together, including the section from Air brake (rail), into a new page about truck braking technology? Or maybe "large vehicle" braking systems? In some respects trucks and trains have more in common than trucks and cars. Ewlyahoocom 10:35, 4 February 2006 (UTC)

Agree that the section Other applications from Air brake (rail) be removed from that article; material not about railroad/railway air brakes does not belong in an article titled Air brake (rail). While I am certain that the section is out of place where it sits today, I'm not certain where the material does best belong. Since truck braking is not an area of particular interest or expertise for me, I won't offer an opinion on this material's eventual home — those with more knowledge about that subject matter should decide.

I thought I'd point out that the disambiguation page for "Air Brake" lists a page (which is not created) for Air brake (commercial vehicle) which would be a good place to put all the truck-related air brake information. There is quite a bit over at Semi-trailer (now semi-trailer truck ENeville), which would be better put there, in addition to the stuff on Air brake (rail) and elsewhere. I don't think it should be moved to the Engine brake page though, since it's not really engine-brake related (it's about air brakes, which aren't engine brakes). I think there is enough stuff to have separate pages for the air braking systems of trains and trucks (and planes, and a separate page for anything else that uses them). We just need to condense all the truck stuff onto one page. There's definitely enough content, I think. -Kadin2048 02:26, 1 May 2006 (UTC)

I concur, Air brake (rail) should be just that, and not involve trucks at all.UbiquitousGeep 22:20, 15 February 2006 (UTC)

I will add, however, that the term Engine braking may deserve to be better qualified. There are a lot of different types of engine in the world. — JonRoma 18:59, 4 February 2006 (UTC)

I'll add to the mix by saying I added an article on retarders a little while ago(Retarder (mechanical engineering)), which also covers an overlapping area of this topic. I just thought I would bring it to people's attention in case a major rewrite/clean up of this topic area takes place.WLD 08:49, 15 February 2006 (UTC)

My two pence:

• Rename air brake (aircraft) to speed brake, which as far as I'm aware is the more commonly used name.
• Rename air brake (rail) to air brake, put a disambig link to speed brake at the top, and leave the section on trucks there. Air brakes on trucks are basically the same thing as air brakes on trains, and a completely different subject from engine braking.

FiggyBee 23:47, 9 June 2006 (UTC)

I disagree. In my experience, "air brake" is used far more often than "speed brake" to refer to brakes on aircraft. Balfa 18:16, 11 December 2006 (UTC)

[edit] question

Why are compression release engine brakes so loud? I'm also confused about whether there's combustion going on when the exhaust valve is opened at compression stroke (If anyone would care to answer). —The preceding unsigned comment was added by 71.10.233.117 (talk • contribs) 05:47, 9 September 2005.

I realise this answer is a bit late. In a normal engine cycle, the exhaust valve opens at the bottom of the stroke, when the gasses in the cylinder are under relatively low pressure. The rising piston then pushes the exhaust gasses out. However, with the compression release brake, it pops the exhaust valve at the top of the compression stroke, when the air inside is at many times normal atmospheric pressure. This sudden release of pressurised gas is what makes all the noise - it's like firing a gun. The compression release brake also turns the fuel injection off (and there's no pressurised air in the cylinder any more to ignite it anyway), so no, there is no combustion. FiggyBee 23:15, 10 June 2006 (UTC)

[edit] Don't Merge

I don't understand why some of the Wikigeeks love to combine pages. This page is fine on it's own for several reasons:

• Jake Brakes are a distinct item in trucking and vehicular braking
• Jake Brake is a genericized trademark
• The issue of compression brakes being banned on certain roads due to their noise has become a hot-button issue in many communities

I can't believe I'm actually taking the time to write my opinions on a Wikipedia article on friggin' JAKE BRAKES, but come on guys. It seems like every other article on here has some knob pushing for merging with another, semi-related article. Why not combine the articles on lard and apples, because together they make a pie? —The preceding unsigned comment was added by 72.57.241.84 (talk • contribs).

[edit] "Compression Braking"

Is "compression braking" just a bad synonym for "compression release braking"? Compression release makes sense, but as the Jake Brake article tells, the compression itself is entirely countered by the spring effect in the inevitable expansion that follows, thus no net braking occurs. Balfa 18:23, 11 December 2006 (UTC)

[edit] Risks?

Are their any possible risks to the engine when breaking? For example if you use engine breaking on an steep hill, is there a point where you should use your regular breaks to prevent too much strain on the engine? amRadioHed 23:41, 10 January 2007 (UTC)