Proper use of jake brake

Discussion in 'Questions From New Drivers' started by Detel555, Mar 23, 2020.

  1. Detel555

    Detel555 Bobtail Member

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    Mar 23, 2020
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    I just got my cdl through cr England's premier trucking school, and now I've been driving with a trainer. Anyways, I've been using the air brake by switching to the appropriate setting for the hill grade, and using the throttle to engage and disengage the air brake, which allows me to keep my speed exactly where I want it and not use the service brake at all while going down. It also enables me to keep it smooth, steady and keep my rpms from revving up super high. Anyway, my trainer gets mad about it and says its inappropriate and should not be used this way.
    Going through colorado, his advice was to target 68 mph, throw on the brake and use the service brake to slow my speed. It sends the engine into super high rpms, and he told me when this happens to downshift or use the service brake to bring down the rpms. I dont believe its safe, easy on the engine or the way I'm supposed to do this. Anyway he told me I'm no longer allowed to drive with him for doing what I believe is the right and safe way. I need experienced drivers to tell me what they think. I'm trying to get out of the truck asap. It's an automatic dt12. I notice as well that how I use the engine brake is very similar to what the truck sounds like when it is in it's set mode for descent control so long as it's set before allowing the truck to accelerate excessively before hitting the service brake, downshifting and turning the truck into the brake settings like he told me to do. Is there something wrong with using the throttle pedal to regulate the air brake? Does it hurt anything if I'm not constantly turning on and off the brake while going up and down the mountains? I believe I'm doing it correctly. This guy seems like he hasn't had his own appropriate training. Everything I do while riding with him is a huge problem. I cant even drive in metro traffic without him yelling at me constantly for adjusting my speeds to what I think is appropriate for conditions.
     
  2. gentleroger

    gentleroger Road Train Member

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    You are not doing it correctly.

    The engine brake should go off before you get back on the throttle. By using the fuel pedal to disengage the engine brake you are wasting fuel and "confusing" the transmission.

    Do a search for mountain driving and limit the time to the last year, you will find a couple of good threads.
     
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  3. Detel555

    Detel555 Bobtail Member

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    Mar 23, 2020
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    See that doesnt make sense either. If its staying in the same gear, retaining the same speed, how is that confusing the transmission. My trainer admitted he is completely self taught on it
     
  4. RailRoad Guy

    RailRoad Guy Light Load Member

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    Regarding high rpms, the Volvo manual for the 2018 model I drove a ways back specifically indicated that up to 2,200 rpms was considered safe and normal operating range for using engine brake on downhills. Obviously, revving that high for power would not be good for it, but engine braking that high on downhills is fine. Sounds like your trainer was a moron... so many of them out there, so good luck.
     
  5. Atlaw4u

    Atlaw4u Medium Load Member

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    You may want to d a search for mountain driving. There was a long discussion posted previously that discusses this in detail.
     
  6. sirhwy

    sirhwy Light Load Member

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    The engine brake is designed to be turned off and on, and it can be adjusted by switching between 1,2, or 3 cylinders. On larger hills the cruise can be disengaged and the engine brake allowed to slow the descent of the truck. I say use the engine brake as you see fit, I haven’t torn one up in 23 years. The whole idea is to use the service brakes as little as possible.

    Find a different trainer. You know more than he does.
     
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  7. AModelCat

    AModelCat Road Train Member

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    Its an engine brake, not an air brake.
     
  8. blairandgretchen

    blairandgretchen Road Train Member

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    Your trainer is a numty head.
     
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  9. TravR1

    TravR1 Road Train Member

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    I think most of us are self taught. Trainers dont say much about the engine except to say "there it is."
     
  10. Brandt

    Brandt Road Train Member

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    On the DT-12 transmission it designed to run very high RPMs the engine and transmission work together as one. If you drive it like regular engine brakes you get all kinds of weird things basically you are telling the transmission to go back regular mode. Like it will shift gears and when you take food off the pedals will go back high RPMs and be shifting cazy amount and you probably will feel like it you don't have control of the transmission.

    The DT-12 is designed to give you maximum engine bakes when you ask for it. Because a computer controls the engine and transmission it can do thing you would never to in manual transmission. First you need to know the shift points when you run the engine brake on the DT-12. Stage 1 and stage 2 will ALWAYS keep the engine RPMs between say 1100 and 1750. Stage 3 is special because it will ALWAYS keep RPMs 1750-2200.

    Say you going downhill and you turn on stage one. Then go to stage 2 and it still not enough to hold truck back. You turn on stage 3 it will downshift a gear probably and raise the engine to 1750-2200 RPMs because you are telling the truck you want maximum engine braking. You just ride down the hill at 1750-2200 RPMs you won't even need to touch the regular brakes.

    Here's the part most people mess up. Let's say you got stage 3 going and the truck is actually slowing down because the engine brakes is so strong. You remember the transmission will downshift at 1750 RPMs in stage 3. So at 1800 RPMs switch to stage 2. This will stop the transmission from dropping anther gear. The truck will start to go faster downhill. Let the truck go faster and when the RPMs reach 2100 or 2200 switch back to stage 3. Keep doing that all the way downhill. You only use stage 3 on big hills because it has so much engine braking power. If you notice that the same way Descent Mode works.

    That's why you need to know the shift points of the engine brake. Because you might not want it to downshift the transmission. Because it will never give up slowing down the truck. It will keep dropping gears as the truck slows down and keep giving you maximum engine brake if you want it. If it snow or ice then you don't use the engine brake because you already know how it will downshift on you automatically.
     
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