1. #1
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    Default Compression Vs. Exhaust Brake

    I would like to know some details from some of you mechanics and engine gurus about the upsides and downsides of both types of engine brakes. Thanks.

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    Rather than try the full explanation here go to www.pacbrake.com or http://en.wikipedia.org/wiki/Jake_brake and you will get the explanations there. Or post at www.evta/forums.com for more from the mechanic side.

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    I have used both, the compression brakes seem to slow you down quicker without using the brakes as much, especially on long grades. although they are quite loud, they are doing many things to try to muffle them now these days, the exhaust brake does an ok job, it will tend to hold you at a desired speed on a small downhill grade, but if you ask me I would go with the compression brake aka "Jake brake"

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    I would agree that the "Jake Brake" is the way to go. One thing to be mindfull of is how it is programmed. They can be programmed to call for downshifts at different points. The faster they downshift the higher the rpms and the more braking effect it has. Fire0099881 is correct that they can be much quieter now than in the past, but to me the only thing that sounds better is the sound of an old 4barrel carb. sucking the hood down.

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    Thank you for the info so far. The dilemma here is on a new engine we are specing we are trying to incorporate verbage into our section about the motor that allows more than one manufacturer of motor to be eligible. We have looked at Cat and Cummins (the meduim duty engines). The cummins ISL and Cat C-9 are our two possibilities. I just discovered that the C-9 is only offered with an exhaust brake. I wonder why? I don't know alot about engines, so thats why I come here to ask. We had said no exhaust brakes in the beginning, but the engine is a big ticket item. We can save about 7 grand going from an ISL to a C-9 but that limits us to an exhaust brake.....kinda in a dilemma, we are up against a very very tight budget and 7 grand means alot. What do we do???

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    Look at the overall unit size, weight, etc and the territory you are running in to see if the engine brake is really needed. My personal feelings are from a safety standpoint as well as brake life; so then the numbers of runs could be a factor. I fully understand budget restraints but then again way safety and all the rest of the factors in before cutting yours and the crews and citizens throats by not getting something to save money that might wind up saving lives.

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    I would do some checking on the cat c-9 engine. We just spec'd a new pumper. I went to our local heavy truck garage and talked to the service manager and he told us to stay away from Cat. Local town highway departments have been having big trouble with them. Dropping turbos, loose oil pumps and so on. They recomended we go with Cummins. Also when I was at SeaGrave Canada they told us same, stay away from Cat.
    We have a Rescue truck with a Volvo chassis with a Volvo engine \ exhaust brake, very impressive when you let off. Tranny is programed to go into second gear.

    If I had a choice I would go with a Jake Brake.

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    Not to steer you in one direction or the other but the C-9 is now available with a compression brake for 2007.

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    If I had a choice, I would spec. my fire apparatus with a Telma brake retarder... FDNY has used them for years on their fleet of apparatus with little to no problem.

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    Quote Originally Posted by NozzleNutz View Post
    If I had a choice, I would spec. my fire apparatus with a Telma brake retarder... FDNY has used them for years on their fleet of apparatus with little to no problem.
    We have them, they suck

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    We have been using Telma Brake Retarders for over 20 years, without a problem. Look at that as an option.

    http://www.industrialautomatic.com/html/telma1.htm
    I have only 2 allegiances, to my country and to my God. The rest of you are fair game.

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    Default Telma retarders

    I don't have any personal experience with Telmas, but from fleets and what I've been able to learn by studying them for possible use on our engine, this is my understanding. Like anything else, there are applications where they're great, and others where they're not.

    Telma retarders normally go into the driveline. That is, the driveshaft is cut and the Telma is placed in between, sort of like a pump transfer case. So, first, you have to have space for it. The retarder unit has to be supported and placement of it for driveline angle purposes is critical. There is another version of it that was developed with Rockwell (now Meritor) that bolts to and becomes integral with the rear. That eliminates or reduces the placement/angle problem. I don't know, but I think that's the version that FDNY uses. One of their people or FWDbuff could probably shed more light on that point

    Unlike all of the other retarders, the effectiveness of the Telma is not dependent on engine speed. They are extremely powerful and are capable of bringing the vehicle nearly to a stop without using the service brakes. They can be modulated more than the others. But they are very heavy, require large amounts of electrical current, and generate lots of heat when they are in use.

    I remember being at an ATA truck show in Chicago in the early '70s and hearing of an electric retarder that did not require any power input. It actually generated power as it functioned. How and where it dissipated the power is something I never learned or have long since forgotten.

    Like others have said here, exhaust retarders are generally not as effective as compression brakes. But on the smaller engines (C9 Cats, ISC Cummins, 40 Series Detroits and the like), compression brakes aren't usually available.

    Hope this helps you make your choice.

    Stay safe out there, everyone goes home!

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    I don't think anyone here will argue that a true Jake brake will perform better than a compression brake. And like Sam said, you won't see a true Jake on the smaller diesel motors many of us are forced to use for our engine choices.

    Keep in mind, if your rig exceeds a GVWR of 36,000 pounds, the thing must have some sort of auxillary braking system per our friends with the NFPA, so you will have to have something if you exceed that weight. I don't think you're debating about having some sort of additional braking capability at this point, but I thought I'd throw that out there.

    We have three engines all with exhaust brakes, and they all work well for our application. No doubt we'd try to have true Jake's if the motors were large enough, but the exhaust brakes are a lot better than nothing.

    For those who read my original reply, I've been without sleep too long...let me fix this. Sorry guys and gals.
    Last edited by npfd801; 12-30-2006 at 02:02 PM.
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    Joel, recheck your terminology here, correct me if I'm wrong. Jakes (and C-brakes), unless I've been in outer space for some years, are the compression brakes. They work on changing the valve timing in order to make the engine into a big air compressor. Exhaust retarders, (Pacbrake and the like) work by partially blocking the exhaust so as to create resistance in the cylinders.

    Stay safe out there, everyone goes home!

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    Thanks for the heads up. Between looking through my quoting software, on the net to try and make sense of what's out there, I really screwed this up...

    Sorry.
    "Share your knowledge - it's a way to achieve immortality." - Stolen from Chase Sargent's Buddy to Boss program

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    one thing i would seriously consider is how close are the cat and cummins service centers to you. i dont mean truck dealers either. Alot of truck dealerships work on them but many are not true service points i.e. warranty work, specailty tools, and service literature. Also do you have experience with these shops? good or bad?

    i know someone mentioned stay awya from the cats but honestly in 07 its fair game as far as ia m concerned. now cat is gettin away from the huei fuel system in 07 and going to a common rail which is what most are using now anyways. much more efficient, less moving parts, and easier to troubleshoot.

    Take it easy, jon

    p.s.- the reason smaller engines dont have them is because the heads arent big enough to take that kinda torque

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    Our primary reserve engine is a "93 Pierce with a Detroit 450hp and a Telma. The Telma will pretty much stop the rig by itself, and works better for stopping then either of the the engine-type bakes.

    But from what I understand it generates alot of heat and does something to the transmission that requires more frequent service. Im not a mechanic, so I have no idea why, but thats the reason we went away from the Telmas.

    On our new quint with a Detroit 500hp we went with the Jake brake. With our new pumper with a Cummins 370hp, we went with an exhaust brake. Both types work well for the particular size of vehicle. So I guess your answer would be in the size of your rig. The heavier the rig, the more I would lean towards the Jake brake.
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    I believe the transmission retarders that Allison offered required more maintenance and generated more heat.

    We have had 3 Telmas for the last 12 years, never a problem. We also have 4 wheel abs and disc brakes, if the driver panic stops you better be belted or your launched.

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    Default Cummins

    My Pierce Enforcer being built, is coming with an ISL 400 with a Jacobs Brake and 4 wheel disc brakes. We stayed away from the trans retarder because we were told it would require maint more often with the heat generated and such. Plus with the disc brakes all the way around and 600 gallons of water on board, she should stop just fine.
    The standard on the ISL 400 in a Custom Contender is an exhaust brake.
    The Jake brake option was aprox $ 3,000 more than a exhaust brake and $ 3,500 less than the transmission retarder on the 3500 series Allison transmission.

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    CE11 has it about right.Small engines will generally have an exhaust brake,the true"Jake"compression brake is not offered.Nor are exhaust brakes as effective as a compression version.The jury's still out on the Thelmas,some folks love 'em most mechanics hate 'em.Now,like everything else,the rules are changing.As the "mini mouse"cummins(ISC/ISL) gets "pumped up" there may be a change in the future on auxiliary braking systems.Cat is already headed that way.I wouldn't be fearful of "yellow"engines although I do not favor engines under 10 liter for Fire service work REGARDLESS of mfg.That's just my personal preference. We run exclusively ISM Cummins and have had very good service from them sans a couple software issues.T.C.

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    Default Jake Brake

    Braaaaaaaaaaaaaaaaaaaaaaaaaaa-tat--tat---tat----tat-----tat------tat

    Enough said!

    Sung in the style of a Detroit 8v92TA with a straight-stack.
    (gotta love those 2 stroke Detroits)
    I can't believe they actually pay me to do this!!!

    One friend noted yesterday that a fire officer only carries a flashlight, sometimes prompting grumbling from firefighters who have to lug tools and hoses.
    "The old saying is you never know how heavy that flashlight can become," the friend said.
    -from a tragic story posted on firefighterclosecalls.com

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    Quote Originally Posted by IronsMan53 View Post
    Braaaaaaaaaaaaaaaaaaaaaaaaaaa-tat--tat---tat----tat-----tat------tat

    Enough said!

    Sung in the style of a Detroit 8v92TA with a straight-stack.
    (gotta love those 2 stroke Detroits)
    Yep that is one of the greatest sounds to hear! I believe the neighboring dept has that engine in their tanker, I am sure HEYVERN will let me know if I am right or not! Our station is about 4-5 miles away from their station and you can hear it leaving there station!

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    One thing I've noticed on the Telma is the lag from when you step on the gas to when the Telma shuts off. It's just around a second, but when you're used to a Jake that instantly shuts off and you have instant throttle, then go to a rig that lags, it's quite an adjustment. The Telma does work extremely well. But as others have mentioned there is a heat issue.
    FTM-PTB-EGH-RTB

    Stay low, keep pushing in, and stay safe.

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    Quotes from another magazine.....

    The C9 has been given a larger 9.3-liter displacement to produce ratings of 365- to 425hp with peak torques of 1,250 to 1,350 foot-pounds. The new engine configuration has a dry weight of 1,650 pounds, which makes it about 1,000 pounds lighter than some other engines in this power range.

    To complement the new models, Caterpillar has a new engine brake and two new automatic transmissions. The Cat engine brake is a compression-type brake option that can be specified on the C9 and C13 engines. It meets the NFPA 1901 requirements for auxiliary brakes on apparatus with GVWR of 36,000 pounds or more.

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    Quote Originally Posted by IronsMan53 View Post
    Braaaaaaaaaaaaaaaaaaaaaaaaaaa-tat--tat---tat----tat-----tat------tat

    Enough said!

    Sung in the style of a Detroit 8v92TA with a straight-stack.
    (gotta love those 2 stroke Detroits)
    What he said!

    I prefer the Jake for the simple reason that if needed it can be used on high, med., low depending on road conditions.

    "They" do say that the Telma's are the most effective of the bunch.

    I will say that if you program the Allison transmission with the agressive down shift into the Jake you do not need the brake pedeal either.

    I think it comes down to what you and your department prefer and what works best for your needs.

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