Thread: Pac brake

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    Default Pac brake

    Im looking for some input on the pac brake , we currently are using jake brakes and have no problems, but we also like to look around at other produts that may work better for us , your input is greatly appreciated

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    I know that Pac Brake is a specific manufacturer of an exhaust brake- the only aux. braking device available on the smaller engines- "C" series cummins, 40 or 50 Series Detroits, etc; as these engines are too small for Jake Brakes.

    The Pac Brake is an exhaust retarder. While I have no experience with Pac Brake, I have driven several trucks with exhaust retarders- a C Block Cummins and a 40 series Detroit. The exhaust brakes worked pretty good, and I would reccomend them on the smaller engines. I honestly dont know if they are even available on the larger engines.
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    Jake brakes are exhaust brakes. Jacobs engine brakes are just a trade name really. Any diesel can have one. We have jakes on two rigs and they work well, but remember in wet or icy conditions they shouldnt be used.( I know I dont follow that rule I cut it back to 4 or 2 cylinders and just go slower)
    Honestly most fire trucks dont really need jake brakes . They work in mountains and steep hills the best ( that being said I used to annoy people in the flat lands with mine when I drove truck) but they do help slow you down in a hurry on the flatlands. Keep in mind some locales are outlawing their use in cities and towns unless an emergency exists.

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    Jake brakes and exhaust brakes are definitely not the same thing. A jake brake might be generically called a "compression brake" that works by modifying valve timing while an exhaust brake is a flapper that closes off the exhaust.

    A true jake works much more effectively than an exhaust brake. I would never specify another fire engine without one. Besides being the most effective, they also do their job without compromising any other system or the reliablity of the apparatus. The noise can be dealt with by the use of better mufflers to the point where it is not even distinguishable.

    Exhaust brakes are available on all sizes of motors but are generally used only on the smaller ones where a jake is not available because the cost of a real jake installed at the time of building is nominal.

    If anyone thinks they are not essential especially with today's weights and speeds they must have slower drivers and less runs than we do. I spend a good portion of my time working on brakes that are severly abused.

    Birken

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    Quote Originally Posted by bfdtruckie12
    Honestly most fire trucks dont really need jake brakes .
    I strongly disagree with this.
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    Default Re - NFPA on braking

    Quote Originally Posted by bfdtruckie12
    Honestly most fire trucks dont really need jake brakes .
    FYI

    NFPA section 12.3.1.7

    "All apparatus with a GVWR of 36,000 lb (16,000 kg) or greater shall be equipped with an auxilliary braking system."

    I think that covers just about every fire truck - other than mini pumpers maybe, or light duty vehicles.

    You decide....

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    Smile Imho

    Exhaust retaders are old technology, but still work well. HOWEVER - I much perfer the newer magnetic retarder systems. Much smoother and more reliable if maintained properly!
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    The problem with Telmas is they are a drain on your electrical system. Depends on your operation and situatuion whether this is an issue. They are also heavy for an apparatus that may be having weight issues. They do work nice though.

    There may be some confusion between an exhaust butterfly brake which is old and generally not very effective and a Jacobs brake which works off the exhaust valves which is also old but works extremely effectively (and noisily depending on the muffler). The Jacobs brake is the best of all situations because it adds no electrical load or heat load to the engine, doesn't weight much of anything, and is effective.

    Birken

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    Quote Originally Posted by bfdtruckie12
    Jacobs engine brakes are just a trade name really. Any diesel can have one.
    I must respectfully disagree. To the best of my knowlege, the only fire rated engine that carries a true Jacobs engine brake is the Detroit series 60. Jakes are also available are Mack E-7 and Cat 3406 engines, though neither is popular with the fire service.

    A real Jake pounds the crap out of the engine, provided its built for it that's not a problem, but Cummins refuses to certify their heads and turbos. For those and other lighter engines you'll see an exhaust brake (not an engine brake) which is the damper in the stove pipe. Its better than nothing, but does not compair to the true stopping power of a Jake.

    Jake has been working on a "whisper Jake" and as of a few months ago (last I heard of it) that was supposed to offer better action than an exhaust brake without the torure testing required of the full engine brake. (Exhaust valve opens sooner, smaller gap, works with turbo waste gate to create optimum braking) Known as the Diamond Logic Engine Brake the new brake is available with International engines at this time.

    http://www.jakebrake.com/products/

    I don't know much about the electric brakes, look interesting but I don't think they'd last long in the grit and grime of a Northeast winter. Done right they have the potential to be much more powerful than even a real Jake, but that would be a huge motor mounted on the drive shaft.
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    Jakes are available on the Cummins ISL and ISM which are both used in the fire service...also some of the smaller Cats as I recall...Not the C7 for sure though and the Detroit 2-cycles though that is pretty much a dead issue at this point though I did have one added to my old Pierce.

    As for pounding anything on the engine, well, the exhaust brake is worse...it can cause valve/piston contact and turbo seal failures as well as increased blow-by when in use...plus they don't work worth a hoot.

    The real root cause of the problem is that they specify engines that are too small for the horsepower produced for use in the fire service. Around here about every other year something needs major repair because of this and we don't run that many miles nor have that many pieces. But over the course of a normal fire apparatus lifetime it should be able to run without any major engine repairs because the base engines are designed to run 2-3 times as long as any fire apparatus body will be in service. But they uprate the horsepower above and beyond the commercial rating and make it unreliable. The reason you can't get Jakes is because they are not available on the small engines, ISC and C7 basically.

    In my opinion, fire apparatus should get lower HP ratings on their engines than commercial, not higher. We need things to be reliable and not hot rods

    Birken

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    Quote Originally Posted by BirkenVogt
    Jakes are available on the Cummins ISL and ISM
    well, I think we're both right on that one, the ISL and ISM are available with the "Cummins C-Brake by Jacobs" but it is not a real Jake by any measure. In fact, I just spent 15 minutes googling it to try and figure out exactly what the "C-Brake" entails, I find all sorts of references to it but no specifics. As for the others, I was mostly talking about new trucks.

    Cummin's lit claims at full braking on an ISC you'll get about 60psi back pressure on the exhaust system of the engine, compaired to about 500psi when the exhaust valve opens on a series 60. Its still a lot of pressure and I too have seen it blow out seals and make a mess of the turbo, but that's what Cummins is willing to live with.

    I could not agree with you more about the HP ratings. Smoke and mirrors. HP is more about cooling the engine than the power you get. In the fire service we get away with the higher continuos ratings because our engines start cool and have huge aux coolers while running at a fire scene. An over-the-road hauler only has the radiator. You take an engine like the vernable Cat3208, rated 165HP to 230Hp with a 250HP fire rating, the same engine can be had with 475HP in a boat where cooling is unlimited (scarey little engines).

    A lot of it is slick marketing and advertising.
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    The C-brake is Cummins' term for a real Jake, in other words it is a real Jake. It utilizes the usual "Jake heads" under the valve cover. On the ISL it is the only true Jake available, but the ISM has both it and the 411, I don't know the difference there. And of course there are exhaust brakes for all engines too including the N although I don't know why you'd bother.

    A Jake brake opens the exhaust valve into a pressurized cylinder it's true, but the turbo shaft seal doesn't see any of that pressure. All of the Jake action is upstream of the turbo, operating the valves, into pressures that are not even as high as they normally operate when the engine is at full power. The turbo is actually working as normal when jaking, it is making boost off the hot exhaust gas (actually only air) that comes out. This contrasted to an exhaust brake which chokes off the output of the turbo only.

    Birken

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    Well, I'll take you word for it on the C-Brake, but I've driven a number of trucks with those and A) they don't sound like Jakes, and B) they don't work like Jakes.

    The turbo actually does contributes some braking effect on a Jake, I read about it on their sight the other night. As more air escapes the engine you end up with boast which increases the pressure in the cylinders, increasing the braking effect. Though you're right, by the time the air gets down to the shaft seals its no worse than regular exhaust impulses.

    The big deal with the Jake and pressures it that you're opening the valve with that pressure on it. A 3" exhaust valve opening at 500PSI with a 1/2" shaft will have to have 3000psi applied to get it opened. Lesser built engines will bend valve shafts. True its a fraction of combustion pressure, but that pressure is distributed along the valve seat, not the shaft. Stems, rocker arms, pushrods, all have to be very strong.

    If you look at the dry weight of an ISM vs. a series 60 you'll see you get a lot more metal in the latter. Light weight engines and high HP to weight ratios are great in race cars, me, I want a huge hunk of honking horse power for my fire truck.
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    I hadn't made it clear enough but I was referring to exhaust valve opening pressure in normal operation, not peak pressure. Even after the piston has reached the bottom on the power stroke there is still a lot of pressure left in that cylinder because of the fuel that has been burned in it, increasing its temperature and pressure and therefore the exhaust valve is always opening into a high pressure cylinder be it BDC on the power stroke or TDC when operating the Jake. In any case Jakes have been around for a long time and exahust valve problems are not one of their known issues, in fact they have almost no issues whatsoever except noise.

    A series 60 to an ISM is not an apples to apples comparison either, a S60 is more similar to an N14/ISX. You can get those in fire apparatus too if you have the bucks. The main reason S60s are popular is because of their predecessors the 92 and 71 series that were so popular and those were mainly popular because they were cheap.

    Nevertheless no engine, large or small seems to hold up very good any more. They don't even seem to make it through warranty without some sort of major failure....

    Birken

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    I thought about this subject some more and it occurred to me that the C brake is used on engines that do not have Mechanical Unit Injectors. You see a normal Jake uses the injector rocker to actuate the exhaust valve on the same cylinder which opens it at the optimal time. However some engines do not have inejector rockers but use a different system such as the PLN (Pump-Line-Nozzle) system which means that there is no injector rocker to use to actuate the exhaust valve with. So they use the exhaust valve off a different cylinder which results in longer oil line length and less optimal timing resulting in a less effective Jake. But still much better than an exhaust brake.

    Birken

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    Quote Originally Posted by BirkenVogt
    A series 60 to an ISM is not an apples to apples comparison
    In some ways I feel it is, if you buy a big red truck your options for engines are an ISM or 60 if youre looking in the 400-500HP range. I agree they are very different engines, but on the street that's your choice right now.

    The main reason S60s are popular is because of their predecessors the 92 and 71 series that were so popular and those were mainly popular because they were cheap.
    I think a lot of people poo-poo the old 2 strokes unfairly. In their day, the 92, 71 (and to a lesser extent the 53) series Detriots were extremely reliable. Sure they were messy, but what engine doesn't leak after 5 years? DD's just got head start . They ran (sometimes too well like when you lost scavenger seal, hehehe) and they also had fantastic torque ratings, all things equal a 2 stroke will have nearly double the tourque of an otherwise simular 4 stroke. The torque gave the old gal decent acceleration compaired to their peers of the day. The only real downsides to them was the inhearent inefficiency of the the 2 stroke, which is why we don't have them as an option any more (emmisions).

    The USCG just built a whole new series of 47' surf boats and rather than put a modern high tech engine in it they hung a pair of 500HP 8V92's. I was shocked that in 2000 I was seeing brand new Gov paid vessels with 1947 era engines until I realized the 92 series has the highest angle tolerance of any diesel engine on the market (these boats are designed to roll over and keep going, lets see an ISM do that).

    And to this day, there is nothing that gives me an audio thrill like the sounds like a 8V92TA pounding down the road with striaght pipes and a Federal Q2B wailing. I feel bad that my kids will never get to hear that sound and feel the goose bumps rise on their arms.

    BTW, thanks for the info on the C-Brake, I was talking with my regional mechanic about it yesterday, and he too was unsure of the difference, only that compaired to a "real" jake it was enimic at best.
    Last edited by Fire304; 03-31-2006 at 02:48 PM.
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    Quote Originally Posted by Fire304
    In some ways I feel it is, if you buy a big red truck your options for engines are an ISM or 60 if youre looking in the 400-500HP range. I agree they are very different engines, but on the street that's your choice right now.
    .
    Caterpillar has the C13 in the same HP range..most manufacturers offer it also.

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    True enough, the C-13 is available, but of twenty some trucks sold in Maine by my salesman last year, not a single one had the Cat in it.
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    When we got our new 3000 gallon tanker, it had a jake but no muffler. I swear, I think you could shatter windows with that thing if you wanted to. We've since put a muffler on it, which also increased the braking performance. One of our engines and our heavy rescue also have jake brakes. Driving with vs without them is night and day. I would NEVER want to drive a fire apparatus without one (unless it is slippery).
    Even the burger-flippers at McDonald's probably have some McWackers.

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    Quote Originally Posted by Fire304
    ...
    The USCG just built a whole new series of 47' surf boats and rather than put a modern high tech engine in it they hung a pair of 500HP 8V92's. I was shocked that in 2000 I was seeing brand new Gov paid vessels with 1947 era engines until I realized the 92 series has the highest angle tolerance of any diesel engine on the market (these boats are designed to roll over and keep going, lets see an ISM do that).
    ....
    Interesting discussion. If successful with our fire grant app for a tanker pumper will have to come back to this.

    Current production Oshkosh M1070 HET, M977 HEMTT, and M1074 PLS trucks for the Army also have 8V92TA engines/Allison auto. Detroit must still have these in production somewhere. There Army sure uses a lot of them. Fire trucks exempt from the EPA BS?

    I have a couple of M911 Oshkosh HET in my parking lot planned for conversion to jumbo tenders, 8V92TA engines/Allison. 1978 production with 4600mi and 8200mi.

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    Quote Originally Posted by nmfire
    I would NEVER want to drive a fire apparatus without one (unless it is slippery).
    Just remember that just because it is slippery out, does not mean the brakes will not overheat because of over-use. My policy is if conditions are so bad that the Jake needs to be turned off, then the truck should not be going over 25 mph (some people used to think it needed to be turned off whenever it rained)

    Quote Originally Posted by neiowa
    Current production Oshkosh M1070 HET, M977 HEMTT, and M1074 PLS trucks for the Army also have 8V92TA engines/Allison auto. Detroit must still have these in production somewhere. There Army sure uses a lot of them. Fire trucks exempt from the EPA BS?
    No of course not We get EGR, the $10,000 upgraded particulate trap muffler with fuel injector, urea injection SCR, etc., just the same as the rest of the trucking industry...lovely isn't it

    Birken

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    Quote Originally Posted by neiowa
    Detroit must still have these in production somewhere.
    My understanding was that there are wharehouses full of "replacement" engines purchased years ago which are now being used in new installations.
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    Most obsolete engines of recent vintage have remans available, you could get them and just eat the core charge but I think some of the two-cycles are still in low volume production for just this sort of reason. May be some sort of spin-off manufacturer, that's how it goes these days

    Birken

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    Quote Originally Posted by BirkenVogt
    some sort of spin-off manufacturer,
    Yeah, there certianly is no secret of building a 92series block, take one enormous hunk of metal, bore 6 or 8 cylinders of "X" by "Y" dimensions... LOL It would not be hard for a small foundry to set up a mould and cast a few each year.

    I know there is a used Detroit dealer in my area that pays pretty good money for any and all 2 stroke blocks from 2-53 up to 16V-129 series, even ones that have been on the bottom of the ocean for a while. Fishermen who have one want to keep it and I don't blame them.
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