*very well

+Brandon Shafer, or 'very nicely'

Sprieken sie duetsch ?

hablo español

+Gofrin Bicelis 我也是！

Nice !

+ChrisFix Haha should've know you watch EE :D

+ChrisFix Thanks Chris!

Engineering Explained Thanks for explaining this, never thought that it was the vacuum not the compression in gas cars. Just one question tho, when you put a car in gear to hold the vehicle on an inclination when engine is off, is it the compression that holds the car instead of vacuum in this case since pistons aren’t moving.

Engineering Explained actually i think it’s both the compression and power stroke in two different cylinders that created the force to hold the vehicle, since the cylinders at intake and exhaust stroke has open valves which would not create any pressure in this case to counteract the force.

Would trucks be burned at the stake for witchcraft? If so, I feel it would be a punishment for both the truck, and the people watching since watching a perfectly good truck go to waste hurts my soul.

Wait. There is no switch mentioned in any of this ... just let off the gas (diesel) and the Jake system uses the compressed air to slow it down. NO SWICH RIGHT?

@@scottmonfort no, the jacobs brake has a switch to activate it.

I like your explanation better! WITCHCRAFT HAPPENS!

@@markflierl1624 yeah. Its witchcraft alright, she is sucking you to a stop..

I'm glad it became the Jake brake instead of cum brake xD

Really? I had to read the comments to understand where the term "jake" came from? Thanks to the Wizz. But tell me this ... it is not a switch right? .... just let off the gas, and the system does it (jakes) right?

@@scottmonfort You have to usually flick a switch on the dash to engage the Jake Brake then let off the accelerator then it does it's thing. Some have 3 settings off on or standby for the Jake brake the standby mode works when you take your foot off the accelerator pedal and disengages when you put your foot back on the accelerator. The on setting you have to flick the switch off before you can move forward. I may of got some of that wrong but that is how I understand how it works by riding with my father who use to drive trucks as part of his excavation company job well until the state of Vermont took his CDL away for his epilepsy even though at that time I was in my teens and never had I seen him have a seizure but they felt the need to take it away. They even tried to take his drivers license away but after my father said he was going to go on disability because of it they sent the drivers license back he was intending to drop his CDL but what pissed him off was having it taken.

Mr. Cummins gave his patent to his daughter and son in-law as a wedding gift. The son in-law was of the Jacobs family.

@@02091992able mostly right, except they all have an on/off switch, when on, the jakes will usually only activate when APP is read as 0%, which is when the process wxplained in the video is carried out. Some systems are optioned with a 2 or 3 positon switch, 2 position switches activate either half or all cylinders (3 or 6 in the case of an inline 6) and 3 pos switches activate 2, 4 or 6 cylinders. Gives greater control over braking effect and with prolonged use oil temps can increase, so can be used to prevent that on long downhill runs with brake modulation

+wayde philpot Agree 100%!

I've nursed my worn brakes like this for awhile while I'm saving for a brembo upgrade 😂

+wayde philpot I wish people on the freeway understood this concept. For some odd reason people think brake lights= I need to slam on my brakes, when in reality you can simply let off the throttle and let physics slow you down. Saves traffic, time, and money (from brake wear)

+wayde philpot They even teach this in driving schools over here, arguing that you save some fuel and prolong the life of your brakes in the long run.

+MrElpajita The weight of the vehicle keeps it rotating along with the mass of the flywheel. Most engines won't completely shut the injectors off but will open them for a much shorter time so that there is less fuel going in to the cylinders. As the car slows to idle or once you press on the gas to start going the computer sees the increased load and will start to turn on the fuel injectors for longer periods.

Best explanation ever!

Hahaha yes indeed!

thats not the sound it makes

🤣

nice joke with a jake brake

+Adrian Foekens 14.5 litre on 6 cyl? That's insane...

14.5 liters of beast, that's awesome, glad you enjoyed the video!

Whenever I engage the Jake brake on my Peterbilt, country girls throw their panties at my windshield.

+Adrian Foekens Is this why some trucks are doing such a huge noise when decelerating ?

+Yak Eru Yes, That's typically the performance muffler or even straight piped crowd. A Jake Brake sounds fantastic through 10" straight stacks Alot of cities, well, pretty much all of them, technically have bylaws against the uses of engine brakes within city limits because of them lol. thats one of the perks of the silly aerodynamic eco friendly truck I drive, Jake brake is so quiet i can use it everywhere and no one knows. Also driving a straight piped truck 11 hours a day (13 in canada) gets pretty old after the first week. its alot of noise.

what car do you own?

+Colin Dowd Sell it immediately, I foresee big problems down the road.

+The Channel of Stuff if it's a BMW, there is no fix for that.

***** yeah there is..its called a trade in!

+The Channel of Stuff omg! You just killed me 😂😂😂

+XxCORNFEDxX Happy to hear it!

Very good point

+RobWhittlestone Man, that name is a mouth full.

"Compression release" is a whole different thing. Long ago they were on engines to reduce "compression (ratio each revolution) while less effective starters tried starting cold engine (when oil was cold& difficult to pump by starter as well. Todays 12 volt gear reduction starters are FAR MORE EFECTIVE so compression release no longer are used cept maybe in extremely cold climates? Haven't seen one in decades. (did help start my tractor after leaving driving lights on one night in Weed, CA as I recall)

+James Tennier No, I mean the whole term "compression release retarder". I know what you mean: I have compression release on my Yamaha SR500 motorcycle - it's a little lever to open a valve so I can position at TDC to kickstart the 500cc single cylinder engine. Old diesels (eg cement mixers) had this too. All the best, Rob

Nice informative video. 2 stroke compression release is much simpler. I have a lever on my 4 stroke 1970 Ducati 450 Scrambler that opens the exhaust valve for starting. I also put one on my 2 stroke 1972 Bultaco 250 Alpina that used the crankcase compression to brake the rear wheel for muddy downhills or when the brakes were wet.

Dammit! I wanted to make a very similar comment

Yes, this is the exact reason why I no longer have any friends names "Jake". But since I do most of my trucking along the Texas/Mexico boarder, I've adapted to using the "Juan brake" it's quite effective and there is an abundance supply down here. 😂😂😂

+Dunkaccino25 Trump makes THE BEST brakes.

+Engineering Explained I guess you can say, it Trumps all other brakes.

+Engineering Explained Donald Trump Owns Brembo Braking Systems?

+Leofred A company I worked for (US) had Hino brand trucks (Toyota's large truck and bus division) that had a retarder type of engine brake. Key feature user-wise is that it was not loud, so it could be used in areas that normally prohibit Jake brakes due to noise issues. They were actually pretty good trucks - virtually trouble free.

+Leofred I knew someone would mention these... Imagine a garden hose, water on... Engine is just moseying along. Now try to bend the hose to minimize water flow; really tightly now... Engine brake on. The difference is the "retarder" uses engine oil and directs it through a smaller orifice within an appendage to the engine/ transmission "connection" Decrease the flow and "braking action" occurs though it also heats the engine oil. Another aside: there are electrical retarders too but that is another story. Imagine a Prius "regenerating electricity to it's battery when throttle is released or brakes are applied...

+Tiger Sharma Thanks Tiger! :)

James Tennier. That is interesting. I had never looked up the history of Jacobs Brakes. We had a 76' 4300 series International that came out of the factory with a 318 Detroit and true Jacobs brake. Had a lot of problems with them from what I can remember as a kid, so we had them removed. The truck was a flat lander and didn't really need them. When I first drove for CFI in the 90's, none of the fleet had compression brakes. We ran 48 states and Canada. Old school mountain method for downhill was one gear lower than the last gear you topped the hill in.

James Tennier The grapevine was a nemesis for many, be it semi or pickup and trailer driver ! 😊 Too many times did I get to the bottom with a STRONG amount of suction on the seat ! 😫 If you know what I mean !

cummins himself invented it after almost hitting a train testing a truck, Jacobs drill and chuck just made the ting cause the had the mills to do it.

Clessie cummins designed it after he retired

+James Dean Youngs That's not a good thing actually. The Ford Explorer isn't equipped with an engine brake, so that 'braking' you experienced was due to internal friction of driveline components (like your transmission), which kills your fuel economy during normal use.

Mark LaPointe Oh well. Sold it two years ago for 300 bucks.

why are cars so cheap in the US?

CRGamingHD if it was sold for $300 it was a pos.

Mark LaPointe "comes with an engine brake"? Have you watched the video...?

Some on the clutch. There is very little wear on engine and transmission components while driving.

You win love!

+ckarsenal yep...

+ckarsenal No need to downshift when you brake, unless you want to practise heel-toe or rev matching.

Yup. In an automatic, don't put it in neutral. Some allow you to choose gears now and also rev match automatically. In a manual, you can stay in gear until you don't have enough torque and the engine begins struggling and put it into neutral. Another option is to downshift every gear. The last option is to block shift. The latter two options require you to know how to rev match.

***** No you don't have to downshift while you brake. You can downshift after you brake, unless you like doing heel-toe rev matching. As long as the rpm is above idle and the throttle pedal is not depressed, even in 6th gear @1500 rpm the engine will not use fuel.

+xXxMartin96xXx I tend to downshift to third and then brake to a stop. I find if I simply brake from 5th to a stop, I am using my brakes too much and missing out on the effects of engine braking.

+MultiTerpen kzfaq.info/get/bejne/pNyVpKZ-s7rYmGQ.html

Engineering Explained So for example.. I know that the compression ratio for my 69 mustang 351w is 9.5:1 But what does that actually mean? I did not really understand by watching the video. Is it like it becomes 9,5 times as small before it ignights? But what is really a high compression and what specifies a low one? Also what is the difference between NA and forced induction like a turbo?

+MultiTerpen The compression ratio isn't necessarily how small the cylinder can get before it ignites, but rather, how small the cylinder is designed to get in a regular cycle. In most gasoline engines, they use a spark to ignite the fuel when the cylinder is in its compressed state. However, in many diesels engines, they rely on autoignition, so the compression ratio in diesels *could* give an indication of how much compression you can get before ignition. Because in diesels, you rely on autoignition, you typically have higher compression ratios than on gasoline engines. When you add a turbo, however, some of the air that enters the cylinder is pressurized, so the autoignition point is at a lower ratio of compression. So to prevent premature ignition, turbo powered gasoline engines typically run have a lower compression ratio. Say for instance, you decide to add a turbo system to your inline 4 or straight V6 engine, which has a compression ratio of 10:1 but may experience knocking if the compression ratio was set to, say 15:1. Due to the turbo, the pressure of the inlet air will be higher. If the pressures increase 100%, then you can only compress the air 7.5 times before ignition. So the 10:1 compression ratio needs to be adjusted, or you should select a different turbo to prevent knocking.

+MultiTerpen Compression "ratio" is the factor by which air is compressed from the bottom of a cylinder to the top of the cylinder, during each "compression cycle." Example: assume your tachometer displays 6000 revs per minute. This would equal 3000 compression strokes (up). 3000 power strokes, (down), 3000 exhaust strokes (up) and 3000 intake strokes (down). Where both valves have or are closed at that moment. Near the end of compression stroke, 14 to 30or32 degrees of rotation before the piston actually reaches top dead center (of the crankshaft rotating the (rod) up & in turn pushing "up" the piston, either fuel is injected or (in a carbureted engine, fuel/air is "ignited" by the spark plug. There is a formula (Google, Summit Racing etc) that takes cylinder bore, piston (crown) stroke, head-gasket thickness and cylinder-head combustion chamber capacity in grams usually to determine the total difference between the amount of air in a sealed cylinder with the piston DOWN and the compression ratio in turn is referenced by the number arrived at when the piston crown is UP, at the very other end of it's travel. Octane of gasoline, propane, natural gas all have different numbers, depending on their propensity to be ignited by the spark plug. Diesels on the other hand, compress air to a greater degree, hence much higher compression ratio, and that air heats quickly;y when compressed and fuel under "high" pressure is litterly squirted into combustion chamber and explodes, driving piston down and rotating crankshaft... rather than burns (out in a flame front from the spark plug.) Sorry you asked?

James Tennier Thanks :D, but when it is like 9.5:1... Is the space inside the sylinder getting smaller by 9,5 times from when it is at the bottom to when it is at the top then? Is there a difference between saying compression and compression ratio?

You are absolutely correct!

Jacobs invented vise grips?? I did not know that, thank you. very interesting

I'm going to stroke my beard - invented by Herbert Beard in the late 1800s.

If you bore your beard, you might get more torque out of it.

Cummins had Jacobs make them because the board of his company said no, he wanted engine brakes so he could go faster on downgrades and break the coast to coast record.

With many modern engines, yes. Though it's possible to still burn a very small amount, depending on the setup. Ideally you would burn no fuel since it's completely wasted. The inertia of the car passes through the wheels/transmission to keep the engine running without fuel.

+edguiterrez yep.

+Engineering Explained you actually still burn fuel on overrun because of tip-out driveability filters which act on brake torque to give it a smooth deceleration feel (this is done by injecting ever decreasing quantities of fuel to generate a bit of indicated torque). These filters are used pretty much throughout the industry because driveability has become one of the most important customer requirements.

+Engineering Explained does engine braking wear down your car at all? The compression doesn't seem like it would be good for those small parts

Ethan Arpin you're compressing either way.... Think of it like this instead of fuel making explosions in your engine to make it move road is turning it. I'd say you're getting even less wear then when you're on throttle.

+Sho Bud Actually the noise is a by-product of the driver using engines compression to reduce brake heat buildup. Smoking brakes are a sign that the truck may well be under less control than the driver might wish!

+One Day I don't think that is the only reason. Cars just are not that heavy compared to serious trucks, thus downshifting is sufficient. Except for mountain downgrades or long hills, simply wind drag and brakes usually are sufficient to limit speed. Trucks carry a lot more weight, thus downshifting + Jake brake is needed for sufficient safety and braking options. But I do have a question that maybe somebody could answer for me? Do truckers abuse the Jake brakes? Why not downshift more and Jake brake less? Jake brakes make so much noise, it can be heard a mile away, not so good within the big city, where people are trying to sleep. Also, is Jake brake, on/off, or is it of a variable amount of braking power? Are some Jake brakes quieter than others?

+Yosef MacGruber I used to drive with Jake brake on when not in city all the time, it's just laziness. release gas - it engine brakes for you, don't have to shift the foot. seems like nothing but when you are driving for 12 hours a day for few days you become lazy. Volvo trucks have 3 positions for Jake brake: light, medium, heavy braking. Freightliner, Kenworth have just on/off switch for Jake brake.

+Yosef MacGruber also Volvo's engine brake is a gentle purr in comparison to newer Freightliners or old rust buckets "classic" Petes, KWs.

+Mod Mark No, unless the driver changes down too early and habitually redlines or over revs the engine. Just change down as normal and no additional wear or stress will occur. Engine braking is an advanced driving technique. And I've just remembered that most American vehicles are auto trans, so engine braking isn't as effective as it is on a manual box. Although some of the more advanced auto trans probably have configurations that work like a manual.

Skye13 Can a driver be expected to constantly push the accelerator all day? Surely they must have some adaptive cruise-control for trucks by now? It is bad design if merely taking one's foot off the accelerator for just 1 second, to switch feet, causes a noisy Jake brake to sound? But then I am not a truck driver, so I do not know enough how a truck cab differs from that of a car? I also read somewhere that a Jake brake, properly mufflered, is not all that loud, at least not on all trucks. And I think the other day, I heard a Jake brake on a passing truck, and it wasn't even all that noticeable, as it was not loud.

Older trucks sometimes were ordered without mufflers and that is why the engine brakes were so loud. No mufflers is a cool factor to some drivers, other trucks just had crap mufflers. Newer trucks are mandated to have a DPF, a special type of filter that takes the place of the muffler and makes the soot from the engine go away and the gasses from the engine safer. Think Volkswagen and their recent scandal, it involved the DPF and the software in them. Anyway a truck with a DPF is very quiet and so are the engine brakes on the truck. I normally cant hear the engine brake on mine over the radio. I always use the engine brake even if the sign says no to, police dont care as long as you have a DPF or an older truck with a good muffler. Just unmuffled is a problem because it sounds like a gatling gun going off. For the record I am a licensed truck driver who also has a degree in criminal justice. Many cop friends have told me their views on engine brakes and they are all positive.

Delightfully interesting!

In addition to what Stewie said, compression brakes are much quieter than Jake brakes. And there is also the option of a retarder which is mostly silent.

+Keith Fox Feel free to ask questions! :)

You have to know what's surrounding the explanation given here in the video to fully understand. I drive a semi tractor trailer truck so let me just give you an overview on more what it's doing. With some exceptions, on a diesel engine, you do not have a natural vacuum by design (in the video's first example) like a gas engine does that slows the engine down when you take your foot off the accelerator. Instead, air will continue uncontrolled into the engine when you take your foot off the accelerator, which transfers air pressure to the engine similar to both air and fuel but with less power because fuel is not being injected and ignited. Large trucks oftentimes have a compression release brake that is added to the engine called a Jake Brake in reference of Jacob's patented system. The Jake Brake opens the exhaust valves at a time when they would normally be closed - the time when air and fuel are usually being compressed in the engine and are about to ignite. When you take your foot off the accelerator, you are no longer adding diesel fuel into the engine but it's still getting uncontrolled air. As the air is nearly completely compressed, the Jake Brake opens the exhaust valve, letting out the compressed air so that the air pressure doesn't drive the engine. Instead, the friction of the engine and other sources of friction in the drivetrain slows it down because it's not being propelled by air compression. It can be oftentimes used in differently levels (anywhere from 1-4 levels) that determines how much engine braking is used. Whenever you hear a large truck - usually on the highway - make a loud "bop-bop-bop-bop" noise while it's slowing down, that noise caused by the Jake Brake and is the air pressure exiting the exhaust. The higher the level of Jake being used, the louder the noise. The reason it's so loud is because the action of the compressed air suddenly escaping the engine is similar to a gunshot. I hope this helps you to understand what this system is actually doing in the real world with reference to the video.

@@danieldeaseweitzelwalker well trained idiots, they have made of us...they have you believing all that crap... Once the compression is vented, (and a diesel is always compressing air), there is no air in that cylinder, and the piston starts down.. it has to pull a vacuum, until the valves are sucked open... That's the popping you hear, is the exhaust valves being sucked open.. Jake not working right? Replace the worn out valve springs, and it will work great again. A Jake shortens engine life.

Simple instead of using your brakes just let you foot off the gas and the car will slow.

Im confused about if you the throttle body closed and it created a vacuum wouldnt that mean the car would stop firing and you would here no noise from the engine when you took your foot off your petal? I feel like im missing something obvious.

+Ian Thompson Hm, I am guessing here (gasoline engine): Downshifting results in a higher RPM. Also, the vacuum gets built over time, until it's strong and actually causes a noticable breaking effect. So, only a small percentage of that vacuum-time is actually effecting breaking-time. I hope I am making sense here - Accountant and Author :-) Now, the higher the RPM, the greater the breaking time per minute - and that's why downshifting causes a greater engine breaking effect. Was that halfay right? :-)

+Christian Breitenstein Downshifting will also put you in a lower gear, meaning more braking torque will be applied to the wheels.

+Christian Breitenstein In lower gears, the amount of air being moved and restricted, is a greater amount of air per mile traveled, thus the kinetic energy or speed of the vehicle, is more efficiently converted into heat which the engine can handle far better than can the easily-overheated brakes. Thus the braking effect is increased in lower gears. That is why automatic transmissions have those low numbers, 3, 2, 1, as those set a limit of the maximum gear that the automatic transmission should engage. Those selections are mainly for engine braking, but perhaps a slightly lower gear should also be selected for towing? Otherwise, just ever leave it in Drive or Overdrive if there is an Overdrive selection, for best fuel economy.

It is vacuum that causes engine braking in a gasoline engine, not compression. The piston is trying to draw air through a restricted port (intake). Connect a vacuum gauge to the intake manifold and you'll see 22"+ of vacuum with the throttle closed during deceleration. Since there is less than normal air pressure in the cylinder during the intake stroke, there's less than normal air pressure for the compression stroke, there is little compression to resist the piston to cause "compression braking". You can't compress a vacuum (even though it isn't a perfect vacuum).

Vacuum....sucks you to a stop

This is not true at all. The vast majority of the energy used to compress the air will go right back into the engine during the power stroke, making the energy loss very minimal (even without fuel). It's critical to either create a vacuum, build backpressure, or release the potential energy stored at TDC for the compression stroke. There's a reason these devices exist.

+Brice Eychenne That's a good explanation. But obviously, there must be a flaw in that system for them to facilitate the exhaust valve mechanism. I think the reason why your explanation isn't actually put to practice is that the engine might not be able to compress that air to such high pressure due to the momentum and therefore stop the engine suddenly causing a 'stall'-like situation which is pretty dangerous.

+Engineering Explained Just explain then, why it's so hard to turn an engine over with a spanner? Is it the vacuum in the intake? No it's the compression.

Oh now that EE has explained it, I feel quite silly trying to hypothesize a solution. My page didn't load when EE answered it here.

davidrobert2007 True, but once you turn it over, it follows through effortlessly right? It's because the pent up energy during compression is released after reaching TDC, right Engineering Explained ?

+Joel Flores gas engines make vacuum at idle

Yeah, I can see that as well. What with the throttle being closed and all

+Tomas Prado engine braking uses no fuel, conserves brakes(puts less pressure on air brakes in semis and lorries) and slows you down. does that answer your question?

No. It's not good to break your engine. Using it to brake can be useful though.

+Andrew Barcomb yes, thanks

+timpaul paintballisbetterthanairsoft why is it not good?

to engine brake in a bigger vehicle yes, but not really needed to in a smaller one like a coupe/ suv. the other guy just said that because you misspelled break instead of brake.

Really! He did that, I like that! I always figured it was someone in khakis but I figured they were green I think Jake wears Khaki colored khaki's so I think you may have the wrong Jake!

+Ola Håkansson I can't breathe in this thing!

+MrRexQuando diesel engines have no throttle plate it's always wide open

crowmagg1 Agreed! This is proof it isn't the "vacuum" that causes the braking. Its using the engine as a compressor.

+MrRexQuando i have driven 18 wheelers (diesel) and gas v8's the disesl had almost no engine breaking effect (there is some but not that much) without a jake we had to engage the cooling fan clutch that is because the air that is getting compressed only rebounds during the power stroke then it is pushed out the exaust while on the gasoline engine the intake stroke is pulling from a manafold with a closed throttle butterfly if you put a vacum gauge there you will measure about 30" of mercury the piston is using energy at that part of the stroke because of the differencial between the top (near vacum ) and the bottom (at crankcase pressure (near atmospheric) that energy is returned during the compression stroke but then again lost on the power stroke during the exaust stroke the valve opens and the vacum is lost by a inrush of exaust gasses and almost at once pushed back out during the exaust stroke now with the exaust valve closed the process repeats when the intake valve opens so there is more engine braking effect in gasoline engines than a diesel without additional equippment installed to provide this the engineer here is wrong about the heating effect with a gasoline engine it's more of a cooling effect but both take energy

crowmagg1 nope- again you can test this yourself with a gas-er. drive down a hill in gear with the ignition off. Opening the throttle increases the engines resistance. The vacuum effect is rubbish.

+MrRexQuando i do it every day when i ride my mtorcycle on some engines the effect is so strong they make slipper clutches to keep inexperienced riders from crashing both effects we discuss have braking effect but chopping the throttle is stronger and is enough to cause rear wheel lock-up and cause a low side crash experienced riders know to keep some throttle applied when in a turn to prevent this and yes i can cut the ignition any time there a switch for that right next to the throttle but when i do that i notice np extra braking effect with the throttle open i do notice there’s a little less

Hahaha. Too bad it's wrong

+Melric Chico when you drive a 18 wheeler they start training without the jake those engines have almost no braking effect without them