To start this thread off I have a question, if you use your jake brake does it cause your truck to use more feul ? Secondly, How much should it be used and when. First time owner of a truck with one by the way... appreiciate any input....thanks.
A jake brake releases compression at the top of the stroke, it doesn't use fuel so no, it will not effect your fuel economy. It can be used any time you want to slow the truck, but it's especially helpful on long down grades. Select the proper gear to hold the truck back and you won't need to use your brakes the whole way down. In my opinion, jakes add a lot of safety to a truck, keeping the brakes cool for when you really need them. You just need to be careful you don't overrev the truck when slowing, that's about it.
The way that I understand how it works would have nothing to do with fuel usage. The Jake brake made by the Jacobs Company (the same as Jacobs drill chucks) changes the exhaust valve timing so that it dumps the compression at TDC, and maybe even creates a vacuum on the down stroke (the power stroke), both of which will use up energy. However, no fuel is used in the process, unless having a Jake makes you rush up to stop signs, keeping your foot in the throttle longer! If I am wrong about that, someone please correct me! Understand that I am not a vocational trucker, but just a farmer and part time hauler, so what do I know? However, when I am in a truck with a Jake, I use it anytime that I don't think that it will bother the neighbors, sometimes even when shifting quickly. For what it's worth... Paul
does it make a lot of noise?
On straight piped trucks they can be pretty loud, but through muffled trucks they aren't too bad. Some municipalities have prohibited their use on local streets due to the noise.
Around here using a jake in a town or city is against the law, and they have signs up to warn you when you enter the town. They can be pretty loud, even with a muffler. I have driven one volvo truck when I took my license and you couldnt hear the jake at all! Is it just me or do the louder jakes seem to work better?
Music to my ears :drinkup
Yeah jakes sound great, so does the factory brake on my dodge. Some areas do have signs that say no jakes. And come on Wolf you've never heard a jake heading into the jobsite?
It get's annoying listening to some of these guys running jakes. Most of the time these guys run straight pipes just so they can make noise. It's obnoxious and annoying. As to yer question here's a little article for ya. hope it helps. http://en.wikipedia.org/wiki/Jake_brake
My granite with the AMI-370 Mack motor really roars, I didnt realize how loud it was unitl my buddy went for a ride and had his window open. It works way better than the old dynatard did on an R model we had, low is about all you ever need it seems, when it's on high it really slows you down. I use low most of the time loaded or not, then high when I am in big hills.
Just to add: A Jake Brake should not be confused with an Exhaust Brake http://en.wikipedia.org/wiki/Exhaust_brake But "Jake" has become a Generic term of sorts which people use to refer to engine brakes. Sometimes I hear people referring to a Jake when I know their truck does not have a decompression device......its a small thing I know....but it bugs me
The Jacobs site has a pretty good "how it works" page. http://www.jakebrake.com/technology/engine.php BTW - If you ever see signs that say "No Jake Brake" they want to know about it since "Jake" is a brand name. If it says "No Engine Brake" they can't do anything about it, but you can thank all the guys running straight pipes for the ordinances.
When you say straight pipes, is that with or without mufflers?
I think thats what kinda was getting at as far as over use or inproper use of the jake brake resulting in more feul consumption. I know when I roll into town and forget to shut it off and instead of just coasting allong the jake comes on and slows me down too soon there fore loosing momentum. Now Having to get back on the throttle to get speed back up. Just have to get use to using it I guess...:beatsme
Do you have a multiposition switch for your jake? They make 1, 2, and 3 stage jakes. A 3 stage jake activates 2, 4, or 6 cylinders whereas a 2 stage activates 2 or 4 cylinders. With a 3 stage jake, you can switch back and forth between 1, 2, and 3 stages depending upon how much braking force you need. If you only have a on/off switch, it is probably activating all 6 cylinders and giving you maximum braking.
Don't forget that engine brakes are just that BRAKES not SHIFTING TOOLS. It really bothers me when you get that fool who seems to think that VRRROOOOMM, BBBRRRAAAPPPP, VRRROOOOMMMM, BBRRRRAAAAPPP is necessary.
Straight pipes = no mufflers
3 stage is used on comaparts 1,2,or3 heads. two stage on motors with 2 heads or 2 rocker boxes eg. cat mack detroit . motors with ohc and small diesels use exhaust brake which is a valve in exhaust pipe which closes and backs up exh. in motor.
Although I will use the first stage once in a while for shifting in low range; 13 speed...pre-electronic 855 Cummins... I have never read a better description of the sound, than you wrote. All 3 on, straight pipes, every gear. Classic...
It can also help you catch a gear climbing a hill from a stop.
Especially with a 13 speed behind a slow to wind down Cummins... And thanks to you, Steve, and the mods. for providing such an outstanding forum...It's got it all...:usa
The older lower compression diesels(like my Mack at 15:1) had less effective jakes because they didn't build as much compression. The newer higher compression motors(20+:1) work much more effective. Yes, a stock muffled truck is not terrible for noise with the jake on...it's just all the BBR 's with 8" pipes and no mufflers that have ruinied it for the masses.
compression dosen't matter! it is the neg. press. that matters. so it is cubic inches. that is why it works on big cu. in. motors. jake brake was designed for comeaparts originaly but cummins rejected it assuming no one would buy such a thing.
Brake on the Cummins engine brake was invented by Clessie Cummins after a near death trucking moment whilst demonstrating a Cummins powered truck, the manufacture deal with the Jacob's Chuck people was a son = daughter thing from the two Co's (Cummins-Jacob's ) the brake system is a total masterpiece of great engineering, it works on both multi head and single head engines, e.g. the 855 =3 heads L10/m11=1head, it can also be fitted to a wide range of different manufacture engines,it is not sold /marketed as it should be in the U.K.sadly its worth is not realized, finaly if you touch the throttle (gas pedal) the engine brake is switched off so no fuel is wasted, the service brakes enjoy an extended life with low lining/drum wear The exhaust brake or snubber is a very poor item, being crude in its component parts, with operational limits e.g. often only 2 minute max constant use before engine damage may happen, also increasing the engine crank case pressure and possibly pushing exhaust gasses into the inlet manifold side of the engine, Scania have offered a hydraulic retarder built into their gearbox for about 15 years, this is a large amount of parts even needing a larger water pump on the engine,but the sum of all the bits does not beat the Cummins engine brake " The Jake " blowing it on, tctractors
The amount of pressure is dependant on the compression ratio of the motor. Yes, a larger bore/stroke will enable more volume, but if it was only compressed to 14:1(1960's motors) then it would not react as well as if it is compressed to 22:1(late model motors). For a 'for instance', leave the intake valve just open a touch on that big motor and the jake won't work very well, as there isn't much compression(piston at TDC). So it takes both high compression AND large volume to produce enough "neg pressure" to slow the truck down.
the jake anchor. Most Cummins motors are classed as low compression, the VTA17-10 I think is about 13.5 to 1,the later engine VTA -28 is 14.5 to 1, this is a V12 engine of 28 ltr capacity the bore size is the same, the pistons look the same only the top ring position is slightly higher making the compression ratio greater,the difference in brake effect would be hard to gauge by the average driver who has grasped the correct way to use the Cummins brake saver,the piston has to first compress the air inside the cylinder(all valves closed), then at about TDC the exhaust valves are made to open (via the injector rocker arm) compressing oil in a master cylinder directly above the adjuster screw, this cylinder forces oil into the slave piston that presses down on the exhaust valve crosshead opening the exhaust valves letting all the compressed gas escape out to atmosphere passing no energy on to the downward stroke of the piston, the engine brake effect is logrithmic and a small engine only pulls a light load a big engine with a large swept volume would be used on a heavy load,opening the inlet valves would be a usless task as the brake effect of compressing gas/air inside the cylinder would not happen, the thing to remember about the "JAKE" is the way you get the best effect, with the engine spinning slowly its only a noise device, tctractors. I may be only a Brit, but I know a bit about CAT, & CUMMINS, the bigger the better, tc
I use my jake on low to shift my Mack, especially in hills, if you have to start up in a hill you almost have to use it with a Mack motor/trans. combo unless you want to be in the same gear until the top of the hill.
I was only saying leave the intake valve open in reference to lowering the compression available, not in actually doing it as in braking effort. I was trying to make a comparison between a lower compression motor and a higher compression motor when you use it as back pressure. It will make a difference in "jake" affect as that compression is what you are building and using to slow the truck.
yes but you are also taking advantage of neg. energy on missing power stroke
I am with you on this one. Nuttin better thab an ole 855 with a set of jakes and straights :cool2:thumbsup
If you are using the Jake excessively and slowing down more than you want or need .. yes, you will use more fuel, as you have to regain the momentum you lost, as with any excessive braking. Good drivers look well ahead (100's of yards, not just 20) .. never use any brakes (Jake or foot brake) more than absolutely necessary .. and anticipate moves by other vehicles. If you use this techinique, along with a light throttle at all times, your fuel consumption will definitely improve. It always amazes me in a time of expensive fuel, to see people pedal-to-the-metal away from the lights .. then standing her on her nose with the brakes, at the next set of lights. Using a Jake when not really needed, is definitely a way to use more fuel. Remember also, that Jakes are braking assistance, not a total braking device. They are there to keep your brake wear down, and your brakes cool, especially on steep downhill slopes. tctractors has outlined the Jakes operation well, they are an excellent device if used according to Jakes instructions .. Here is the Jake brake, operators manual, in .pdf format .. I'll wager a lot of drivers have never read one .. http://www.jakebrake.com/products/docs/Operators-manual.pdf
The Jake brake short history .. The Jacobs brake was invented by Clessie L. Cummins .. but not perfected .. until long after, he underwent a "near death" experience in 1931 .. which was when he put his mind to inventing a brake that utilised the potential power in the engine. Although the Jacobs Engine Brake has been on the market since 1961, the need for it was terrifyingly demonstrated to its inventor, some thirty years earlier. In August of 1931, Clessie himself, Ford Moyer, and Dave Evans were driving a Cummins diesel powered Indiana truck, from NY to LA, in an attempt to set a new truck speed record across the continent. All went reasonably well, until the descent of the Cajon Pass, on old U.S. 66 leading into San Bernardino, California. A long, winding and steep gravel road, criss-crossed by a busy mainline railroad, almost led to the demise of the truck, its driver Clessie, and all the crew. In Clessie’s words: “About dusk on the fifth day, we reached the top of Cajon Pass west of Barstow, California. Before retiring to the sleeping compartment, Dave had warned me against this thirty-five-mile stretch of mountainous downgrade. I failed to register when the sign for the Cajon Pass appeared. Soon, however, I realized my error. The brakes wouldn’t hold. Now running in third gear, I tried desperately to get into a lower speed. Nothing doing, I saw I would just have to ride it out. I suddenly saw something moving across the road ahead. I realized with new alarm that a freight train was cutting across our path! As we raced inexorably toward the crossing and doom, the train’s caboose loomed out of the darkness. Its red lights cleared the highway, just as we reached the tracks. We had escaped certain death by inches.” Clessie spent over two decades on the design of the engine brake, and didn't produce the final design until 1954. He then shopped it around, but found little interest in it, from the major engine manufacturers. In 1957, Clessies brothers son introduced him to the Jacobs Chuck manufacturing Co, which had been in business since 1903, and who produced the famous 3 jaw Jacobs drill chuck. Jacobs expressed great interest in manufacturing Clessies engine brake, and drew up a deal with him .. and the Jacobs Engine Brake appeared on the market in 1961. In 1986, the Jacobs company split into two separate businesses; Jacobs Chuck, who make the drill chucks in Clemson SC - and Jacobs Engine Systems, who build the engine brakes in Bloomfield CT.
Very interesting!! Thanks so much for the post Oz!!
According to the USDOT this IS an extention of the breaking system which is a federally regulated safety device! No municipality has the right to limit your breaking power, or tell you can't use additional brakes, regardless of the noise! It's a local noise orrdinace that effects the safe operation of a commercial motor vehicle! Do you think the mayors court want to get into a p'ing contest with the state or the feds? Ask Norton Ohio what happens when the municipality goes against the state!