I was hoping someone could help me understand how these work. I get that it holds the exhaust valves open to release the compression so that it does not force the piston back down. I know I am missing something, but I dont understand how that slows the truck down. It seems like putting it in neutral would do the same thing. Thanks for the help, Joey
Well if you put it in neutral your just free wheeling and you will pick up speed. When you downshift your revving the engine up and then cutting off fuel and making your momentum turn over the engine which slows you down. If your aren't in a gear your engine isn't connected to the drive line.
It's The exhaust valves opening on the top of the compression stroke.The engine turns over with the resistance of the compression stoke but looses the stored compression energy on the power stroke when the exhaust valves open releasing the pressure suddenly.So the piston goes down on the compression stroke without any compression ,making the engine have more resistance.The loud poping noise is the compression being released suddenly through the exhaust valves.
You beat me to it 25c, but I'll add a little more.Yep, your missing one key operation of the Jake; it stops the injector from injecting fuel while Jake Brake is in operation. The braking action is actually very simple, it's making use of braking energy that the engine inherently has, that is, compression. It takes energy to force each piston up on compression stroke. When your going down a grade and backed off the throttle, the compression of the pistons is creating hold back force. But then at TDC you get ignition of fuel and the subsequent forcing the piston back down, which minimizes the effect of the compression braking. The Jake Brake allows compression of each piston, but at TDC, there's no fuel injected. And, that's when the exhaust valve opens and releases the compression (which is the noise you hear), and now the compression and fuel ignition that would force the piston back down on power stroke is gone. Efficient engine braking.
Very good explanation there guys. Just thought I would mention that engines with higher compression ratios, and also larger displacement engines, will provide a larger braking force.
Need to ammend my original post. I seem to be reminded that most Jake's don't prevent the fuel injection. When the fuel is injected at TDC, ignition and burning of fuel happens, but then the exhaust valve opens and releases the energy of compression and ignition.
I've got another question concerning jake brakes. Can you use a jake on a automatic transmission, like a big allison or ZF style. I know about the retarders in automatic transmissions and have used them, but they heat up really fast. The telma brakes are another style I've seen, but they are really expensive. I've just never seen a jake on a rig with a automatic. Can the tranny's take it?
Most fire trucks nowadays have automatics as well as jake brakes. The brain that controls the jake also keeps the torque converter locked. If the torque converter was unlocked, you would not get the full benefit of the jake brake.
Lol, I feel like a moron. For some reason my brain wasn't thinking about the resistance created when the piston is going up on the compression stroke. I need some coffee... Thanks guys, Joey
One should never feel like a moron when one is asking a question about how something works. That's how you get edjumacted about things! :yup
So if a Jake brake is a highly effective system used to slow down a truck, why is it illegal to use it coming down steep grades like Vail Pass on I-70?.......OH YEAH! because rich guys in their mansions need peace and quiet More than truckers need to keep fully loaded trailers under control. Better to use a runaway truck ramp than wake up the neighbors. What a world.
Yeah, I've been down that grade Muffler Bearing, it's a pretty good one. I tend to agree with you in places like that and banning Jake's because of noise. I can understand the ban in quiet neighborhoods, Downtown strips, and the like, but a place like the grade on I-70 at Vail Pass???? Hmmm, if'n ya want peace and quiet in the Colorado Rockies... then why in the #%@* have you chose to live next to an INTERSTATE HIGHWAY???? That's kinda like someone moving into a house near an airport and complaining about the noise!
Every explanation in here is good. One way I explain to the drivers that come in my shop is think of the engine turning into a big air compressor. When that exhaust valve is open all the air is trying to get compressed into the exhaust pipe.
Yes, Vail Pass is a good one. One of the trucks I used to drive had a 3408B and the "Brakesaver." That brakesaver works extremely well with no noise. It will heat the engine oil up if you leave it on very long. MK Eby had some trucks with jakes (Trigger Type) and automatic transmissions. They also had the retarder. Those trucks would shut down in a hurry. :guns
Engine Brake Related Signs We would like to thank all of you who have let us know about brand specific signs like the one below. Since "Jake Brake" is our registered trademark, we like to know where it is being used. If you see any signs that use the brand name like this, please let us know what Route number, City/Town and State you saw the sign by sending an E-mail to: [email protected] . Digital photos are very much appreciated also. Thank you! Like to post this wherever I can. Love the sound of a Jake and a straight pipe.
Okay, I'll claim I'm feeling like a moron to. I've only worked on older jakes, and their isn't much "brain" to them. A switch on the dash, which controls the power (12v) to the "jake's" on the heads that grabs the valves. You also have switches on the clutch and accelerator pedals, so that if either is depressed, it cuts out the jakes. How is this connected into a torque converter, to keep it locked up in a automatic? New jakes may have a brain, but I'm kind of feeling like I don't! Help me out!
The Engine computer knows all and see's all. Do you want to know about specific input sensors on the trans and engine?
Actually, I was looking at a used truck crane. The crane was a late 90's with a cummins 8.3, and a allison auto, but with no jake's. Where I live, jake's are a needed item, they really save on brakes, and I was just exploring if a guy could put a jake on this sort of application. I imagine it would make a difference on the particular engine and tranny combo, and if the computer could be reprogrammed, or maybe that age of equipment has no brain for the tranny, and then this isn't possible. Thanks for the help guys!
That's the Catch 22 - The sound you love is making other people put up the signs. Even Jacobs asks that everybody run mufflers... As far as I know there is no engine brake made for the 8.3 or ISC. They do make an exhaust brake for it though. Or maybe look into getting a driveline retarder?
A few years ago a town near me put up a No Engine Brake sign that read 100 dollar fine if used in village limits. A driver got a ticket and went to court over it saying that it is a safety hazard because most trucks require the use of the engine brake for efficient stopping. The court ruled in his favor and now in this state you can't get a ticket for using your jake. Now the sign say's please don't use engine brake. So if your in this state, Leave em on!
I leave it on anyway when it's the middle of the work day. If it's late I usually just pick a hill that doesn't have noise laws.
Your are right, you will have to go with an exhaust brake on the 8.3 or ISC. I installed one on a motorhome when I worked for Cummins.
This is another case where a few idiots make it rough for everybody else. In our area all the little towns came up with the idea of "no engine braking/jake brakes/ect inside city limits." What brought this on was almost every Billy Bigtrucker Bullhauler had to have dual 8" straight pipes and the only way to get the pipes to cackle was to rev the engine up against the governor and max out the jakes. The stacks would really bellow. People began to get sick of this when a fleet of 8 trucks rolls into town at 2 AM. I've never heard of anyone getting a ticket by using jakes, but I suppose these laws give the law enforcement officer a change to write a ticket to someone being obnoxious when they are coming into a town on a flat road. I DO NOT support the laws concerning Vail pass--a fully loaded truck needs all the help it can get in the stopping department. Sadly, the trucker following the law and not operating his jakes (or other retarders) will be just as much at fault when he can't stop to avoid an accident due in part to hot brakes. I almost think I'd take my chances on getting caught running the jakes rather that deal with the aftermath of an accident caused in part by hot, faded brakes.
There are a few signs I have seen around here, but not many. I agree with the above though, a little noise is worth potentially saving lives and avoiding accidents. I also love the sound of straight pipes and jakes, but I also understand that in some areas some people have to constantly hear it at all hours.
Mufflers are cheap , Ive always had full use of my Jakes without being inconsiderate to others trying to sleep . Just because I'm awake doesn't mean everyone else has to be . Everyone likes the muffled growl of a Jake , but these wankers going through towns with no mufflers sounding like ack ack fire destroy people's quality of life .
We have a young guy at work who was issued a brand new Pete in 2004. It had the 550HP Cat, and he was dissapointed in how quiet the exhaust was. After he asked several times for straight pipes, and being told no, he looked for other options. About a month later, the exhaust and engine brake started to get pretty loud. The owners office was right by the gate where the trucks come in, and he was tired of telling the driver to back off the noise, and respect the neighbors. About 5 minutes with my laptop, he had no more jakes, and a 65 mph speed limit. Talk about humble, he was. About 2 years later, I found out he dropped 4 D-Cell batteries down the stacks, and it ate the baffles out of the muffler.
There are Drivers and then there are Drovers .
In all actuality the jake brake, compression brake, engine retarder, or what ever the manuf. calls it is a BRAKE on a COMMERCIAL vehicle which is under FEDERAL regulation! I have beat a muni ticket for Jake use where prohibited! Since it is a brake, and up to the drivers digression as to when it is needed, no government agency can lawfully decide when you use any braking device. I ask the judge if he really wants to have his Court looked at by the Federal DOT, too see if your ordnance is legal? Just like setting the parking brake. That air shot can be heard for blocks! But a cop can't ticket you for setting your parking brake if you are parking waiting for a place to open! If you need that extra braking help from the Jake, their ticket is illegal! And a noise ordnance is just that "Unnecessary noise of excessive exhaust, loud music, yelling in a fight, barking dogs, NOT Jake brakes! All it will take is for one driver to testify the :if I could have used my jake brake, I wouldn't have had the accident, and I wouldn't be suing the municipality
For those of us getting udemacated here- What about the tales that using your Jake ups the fuel consumption over not using it. Anything to that?
I can't even imagine the logic behind that one... Since it only works when the throttle is off I'm gonna say no, fuel use isn't affected.
Using your Jakes has no effect at all on fuel consumption, fuel is shut off when your foot is lifted off the throttle.