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  1. #1
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    Default Smartbrake Opinions

    I asked in another forum and didnt get much help so Im trying here. Does anyone have any experience with Smartbrake. Please give me opinions or experiences. thanks.


  2. #2
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    You got a detailed list of questions that could help you out in the other post that you have not answered yet. An exhaust brake is a simple device, it is adjusted to whatever PSI backpressure the manufacturer of the engine will allow (say 60 psi in my case). One exhaust brake's 60 psi is not going to slow you down any better than another one's 60 psi so the first thing you need to do is make sure it is adjusted right. That backpressure measurement is taken at maximum engine speed (and braking engine speed is usually a bit higher than max goverened speed). Once you have that, you have all you are going to get from exhaust braking.

    I assume you are looking at the variable feature, that seems to be a relatively new development. It will hold you back better at lower engine RPM but it still will not hold you back as well as keeping the engine at full speed while braking (driver training issue) and the full speed performance will be unaffected.

    I was unaware of the Smartbrake until you posted but I priced a Pacbrake PRXB which is more or less the same thing to add to one of our trucks and it cost a little over $500, cheap compared to the other options but likely ineffective. I will tell you how it works in about 6 months because I will probably do it after fire season ends.

    Birken

  3. #3
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    Thanks for the reply. I have not answered the other things because I dont know the answers yet. I am in a time crunch to get an answer to my chief on the Smartbrake. I havent received much info on it. I know you are saying it probably wont work any better than the exhaust brake I have now, but I am giving the Smartbrake the benefit of the doubt. In their sales info I believe they say it works better at slower RPMs that a standard butterfly valve so stopping power is improved by 30%. I was hoping this is correct but it doesnt seem that many people have first hand experience of it, which is what I want. Is the brake you are talking about a guillotine brake like the smartbrake? Is it supposed to be better than Jacobs? Thanks

  4. #4
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    We are currently running the smart brake on one of our navistar 4300 ambulances. There are two more waiting on us to install them as time allows. the folks from smart brake came in and helped itstall the first one. the install took about 8 hrs with the truck on an inground lift. We opted to weld the pipe joints instead of using the supplied clamps. This has really helped slow down the brake wear. These trucks new were going through front pads every 4000 miles or so. After navistar came in and did a bunch of testing we got 8000 miles out of our brake pads. we currently are at 6000 on the set of pads that were installed at the same time as the smart brake and they look very good. This system is 3 months old as of right now.
    The only thing we were not expecting in the process of installing this system was taking the truck to a certified allison trany shop to have the exhaust brake feature activated in the trany ecm. It took the folks we use in Louisville Ky about five minutes with a lap top to do this.
    I hope this helps you out. I would be happy to talk with you if that would be more helpful. god bless and stay safe.

  5. #5
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    Quote Originally Posted by bartnamerif
    I havent received much info on it. I know you are saying it probably wont work any better than the exhaust brake I have now, but I am giving the Smartbrake the benefit of the doubt. In their sales info I believe they say it works better at slower RPMs that a standard butterfly valve so stopping power is improved by 30%. I was hoping this is correct but it doesnt seem that many people have first hand experience of it, which is what I want. Is the brake you are talking about a guillotine brake like the smartbrake? Is it supposed to be better than Jacobs? Thanks
    The idea of a variable exhaust brake is still relatively new but as I stated, maximum braking performance will be exactly the same (assuming your existing system is set properly) the only advantage you will see is if the drivers are letting the engine RPM get too low while braking. It seems a lower cost solution to me to first verify that the back pressure of the existing units are at maximum spec, then train the drivers to drive properly before throwing parts and money at the problem. From what I understand this problem has been several years in the making so why rush all of a sudden. Do it methodically and be certain that the first solution you choose is going to work and be the last solution.

    As I stated my money is on the Telma, I have them on ambulances with less than ideal alternator/battery systems and they work great. Just make sure to get somebody who understands the emergency vehicle electrical system to be in on the project and expect to upgrade some alternators and wiring, if you have 4 batteries already you are probably good on that count.

    Birken

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    Please explain how you keep the RPMs high as you are stopping. Thanks

  7. #7
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    Hey Streetwise, are you saying that you went from no exhaust brake at all to the smartbrake, or did you go from a traditional exhaust brake to the smartbrake. thanks

  8. #8
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    Quote Originally Posted by bartnamerif
    Please explain how you keep the RPMs high as you are stopping. Thanks
    You either program the automatic transmission to call for 2nd gear on throttle being lifted, or maybe when the brake pedal is depressed, or else you manually select 2nd gear on the selector. The electronic transmissions do it pretty smoothly and the hydraulic ones are supposed to, but I have seen them over-rev engines before so I will instead manually select each lower gear as it becomes appropriate.

    Birken

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    Ok, what was confusing was people kept saying that keeping the RPMs up was a driver training issue when it is actually a vehicle transmission setting. All of our trucks shift down when you let off the gas pedal. That is working properly. Thanks.

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    It is both. On ours it would be too annoying since we have long stretches where you might want to coast or just let the Jake come on for a little while to drop a few MPH. So it becomes a driver training issue when you tell them to think ahead, if there is a stop sign coming reach over and push the "2" button.

    There are different settings for downshifting as well. Are yours downshifting as agressively as possible, i.e. running the engine up to max RPM with each downshift? If not, they should be for maximum effect. If they are, then back to the orignial question, you will see no difference in braking performance from one manufacturer's properly set exhaust brake to the next.

    Birken

  11. #11
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    Talking braking

    Birken, we have the aggressive downshift on the heavier units to 2nd and the rest are at the 3rd gear level. I also preach downshifitng manually but only if the operator feels safe doing it by taking one hand off the wheel. Some operators don't feel comfortable about it. In order for our guys to not be confused by the touch buttons ours are with the gear select lever for the job. Some people can't push buttons.

  12. #12
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    lvwrench,

    Tell me that you're kidding. Can't take one hand off the wheel for 5 seconds, can't push buttons???

  13. #13
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    We still spec and will continue to spec manual transmissions in the really large vehciles (water tenders) so drivers that can't take a hand off the wheel, well, they would have a hard time with that...

    Also we run one man engines most of the time so running the siren, horn, radio, etc is kind of important....

    I can tell you that going through a busy intersection with that tender trying to shift gears, change the tone on the siren, honk the horn and answer the radio that is yapping can be a challenge sometimes though.

    Do your guys use the blinkers when they go around corners?

    Birken

  14. #14
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    Talking one handed

    C'mon guys this is the big city. You really expect some of these new guys and even some of the older ones who have wreecked to take one hand off the wheel to do something? That's why we have a four man crew. Two guys in the back to suit up to fight fire, a Captain to look at the MDT,operate the spotlight, talk on the radio, etc.etc. and a Engineer to drive and play with the air horn and siren and eventually run the pump. I can remember my days in the USAF driving O-10's and 11's and such with the stick shifts and not having any brakes. Then again we could chew gum and walk at the same time while patting our heads and rubbing our stomachs.

  15. #15
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    Default Smartbrake

    Sorry came to this forum a bit late, but for what its worth :

    I have read your reply requests for information regarding Smartbrake and noted your comments. I think it worth while to correct a couple of misunderstandings, firstly modulating exhaust brakes are not a recent innovation and were first patented in the late 1980s early 1990s By the manufacturers of Smartbrake.



    Secondly performance, of course it is true that one manufacturers 60 Psi is the same as another’s, however a modulating exhaust brake that is fully closed until this pressure is reached allows the maximum pressure to be obtained in the cylinder earlier in the pistons stroke towards T.D.C, increasing the braking stroke.



    The constant bleed through the fixed orifice in the butterfly brake can also reduces the volume of air that is available to supercharge the cylinder when the exhaust valve is floated from its seat by the manifold pressure; this reduces the “start pressure” at B.D.C which also affects the length of the braking stroke.

  16. #16
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    Pure bull$#!+.

    Do you expect me to believe that your exhaust brake works back and forth with each individual piston stroke or something?

    Either it is a fixed orfice or it is modulated based on engine RPM/backpressure. The only factor that can change retarding effort is backpressure PSI. And the common theme with exhaust brakes is they all work lousy.

    Tell you what. I have a 56,000 lb truck that has some real pucker marks in the seat since they though an exhaust brake would be "good enough". You set me up a chassis dyno run that shows your brake has significantly more retarding HP than the lousy one I've got now, within engine manufacturer's spec of course. I'll buy it and recommend your product too.

    Birken

  17. #17
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    Birken.



    I agree pure bull$#!+ but who is talking it?



    One of our engineers picked up on the fact that you appeared to be offering advice on our product without any knowledge of it, and as it is not our policy to promote our product on any forum , he decided to correct your errors off his own back.



    First you stated that modulating exhaust brakes are relatively new, sure they are if you consider early 1990 recent,

    Smartbrake is a derivative of the first modulating brake that has been engineered on over the years.



    Secondly, just how you managed to arrive at the conclusion from his simple explanation of the factors that affect exhaust braking, that he was saying that the Smartbrake works back and forth with each individual piston, is a mystery to us, as it would be to any engineer, it is so plainly a nonsense. I guess that this means a more detailed explanation is needed.



    Going back to your statement that one manufacturer’s 60 P.S.I is the same as another’s is of course self evident; however as regards performance that is only one part of the equation. Take for example the Cat C9 this has a allowable back pressure 60 P.S.I a bore of 4.41” and a stroke of 5.87,” in common with all volume specific engine brakes which include both exhaust brakes and compression release (Jake type) brakes, the start pressure (before the piston begins its upward travel) with piston at B.D.C is of cardinal importance. In the case of the exhaust brake this is the volume /pressure that will be compressed against the exhaust brake when the engine exhaust valve is open producing the braking stroke.



    Taking the position of the piston at B.D.C with gauge zero, a standard atmosphere of 14.695903 is available for compression, now applying Boyle’s law this shows that at 2.935 inches (half the stroke of the C9) the pressure is 29.39 P.S.I Half the braking stroke used and still only half way to the 60 P.S.I allowed.



    A modulating exhaust brake until the set pressure is reached is, for all intents and purpose fully closed, whereas a fixed orifice has a constant bleed and this can be quite substantial, obviously dependant on size of the orifice. This constant bleed past the exhaust brake affects the distance that the piston will travel before compressing the air in the cylinder to the maximum allowed. Having a continuous leak past the exhaust brake also reduces the volume of air that is available to supercharge the cylinder when the exhaust brake back pressure lifts the exhaust valve off its seat as the piston moves back towards B.D.C. after the compression stroke,



    To emphasis the importance of the start pressure, again taking the C9 at the beginning of the braking stroke with a start pressure of 14.5 P.S.I the piston travels 4.4025” before reaching 60 P.S.I leaving a maximum effective braking stroke of 1.4675”. Increase the start pressure by just 5 P.S.I. and the piston travels 3.80” to produce the 60 P.S.I. leaving a maximum braking stroke of 2.07” an increase of just over 40%.



    I have kept this as short as I possibly can and have only addressed some of the factors affecting exhaust brake performance, so I apologize for the lack of depth.



    We are not trying to sell you anything, as I said we do not promote our products through open forums. We do have a number of endurance braking tests that are carried out by Government approved testing stations for European vehicle type approval, these are on a variety of engines. So if you tell us what engine, gear box, back axle, and tire sizes your vehicle has we will send you a matrix of speeds and percentage slopes that you can descend, without use of the wheel brakes.

    We understand that you have had a bad experience with butterfly exhaust brakes but don’t let that color your opinions before at least riding in a truck with a Smartbrake.

  18. #18
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    Quote Originally Posted by mahsreh
    Going back to your statement that one manufacturer’s 60 P.S.I is the same as another’s is of course self evident; however as regards performance that is only one part of the equation. Take for example the Cat C9 this has a allowable back pressure 60 P.S.I a bore of 4.41” and a stroke of 5.87,” in common with all volume specific engine brakes which include both exhaust brakes and compression release (Jake type) brakes, the start pressure (before the piston begins its upward travel) with piston at B.D.C is of cardinal importance. In the case of the exhaust brake this is the volume /pressure that will be compressed against the exhaust brake when the engine exhaust valve is open producing the braking stroke.



    Taking the position of the piston at B.D.C with gauge zero, a standard atmosphere of 14.695903 is available for compression, now applying Boyle’s law this shows that at 2.935 inches (half the stroke of the C9) the pressure is 29.39 P.S.I Half the braking stroke used and still only half way to the 60 P.S.I allowed.



    A modulating exhaust brake until the set pressure is reached is, for all intents and purpose fully closed, whereas a fixed orifice has a constant bleed and this can be quite substantial, obviously dependant on size of the orifice. This constant bleed past the exhaust brake affects the distance that the piston will travel before compressing the air in the cylinder to the maximum allowed. Having a continuous leak past the exhaust brake also reduces the volume of air that is available to supercharge the cylinder when the exhaust brake back pressure lifts the exhaust valve off its seat as the piston moves back towards B.D.C. after the compression stroke,



    To emphasis the importance of the start pressure, again taking the C9 at the beginning of the braking stroke with a start pressure of 14.5 P.S.I the piston travels 4.4025” before reaching 60 P.S.I leaving a maximum effective braking stroke of 1.4675”. Increase the start pressure by just 5 P.S.I. and the piston travels 3.80” to produce the 60 P.S.I. leaving a maximum braking stroke of 2.07” an increase of just over 40%.
    OK, the illogic of your argument should be evident to anyone who knows how these things work. When calculating the retarding effort of an exhaust brake you do not consider the exhaust stroke to have started with 0 psig or 14 psia. When the exhaust brake valve closes the other cylinders of the engine quickly bring the exhaust manifold pressure up to the setpoint of the valve. Therefore when the exhaust valve opens at the start (bottom) of the exhaust stroke, it is opening into 60 psig already. Then the piston continues up through the exhaust stroke continuing to work against this 60 psig until the top is reached and the valve closes. This continues with the other cylinders in their firing order as long as the valve remains actuated.

    No valve in the outlet of the exhaust manifold, that is operating within the engine manufacturer's specification, can hope to offer any more retarding effort than any other.

    Birken

  19. #19
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    Default manual transmissions

    I'm amazed you have members that can actually drive a manual transmission tanker(tender). After getting tired of replacing blown and burned clutches in the two tankers(tenders) we have. 4 or 5 times I think, we had them converted to allison automatics. Expensive but worth it in the long run!









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  20. #20
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    Though you don't say specifically, I suspect you might have one of the smaller manuals. 5 speed or 6 speed. They tend to have not as low a first gear and are just generally not as nice to drive as a full-on, non-synchronized, big truck tranny. The mistake most fire departments make on stuff like that is that they buy lighter duty stuff.

    With ours the clutch is only used incidentally for starting and stopping and then very briefly. The transmission has very low gearing and so it is not even necessary to apply throttle before the clutch is fully engaged on even the steepest hill. It just goes. You would have to work very hard to burn out a clutch on this one.

    Birken

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