Engine Brake / J Brake

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Some folks leave it ON all the time when traveling,, I use it when needed,, I find that leaving it on results in slowing when NOT NEEDED only means that I have to regain that speed at a cost.>>>Dan
 
That may be rig dependent, also. My Beaver wouldn't allow the cruise control to operate with the compression brake on. My Ventana lets me leave the engine brake (a VGT, actually) on all the time, if I wish. But I find there are times I wish to let off the throttle but no brake, and for those times I need to turn the VGT off, otherwise I mostly leave it on. So it depends on your needs and on the coach.
 
I assume you mean Jake Brake, or Jacobs Engine Brake. They are normally left on at all times, except when traction is questionable.

Turning the Jake Brake off means that it's not available when you need it the most, during an emergency braking situation.

On wet roads, use the low setting. On icy roads, turn it off. The braking action could cause skids and loss of control.

Edit: The question was related to motorhomes, but those towing trailers should be extra careful on wet roads. If the Jake Brake engages slowing down the truck, but the trailer brakes are not applied, the result could be a jackknife.
 
I do all my emergency braking with the right foot!  I don't have the engine brake but I do have the exhaust brake and use it to slow my descent on a hill to improve control and I do leave it on most of the time. 
 
It is intended as an assist in normal driving and is not just an "emergency" brake. Just how much and in what circumstances you use it is mostly a personal preference thing. Generally it should NOT be used in slippery road conditions because it may apply braking when you may not expect it and cause a skid. It can also become a nuisance in rolling terrain or city driving, braking every time you take your foot off the accelerator, so many people turn it off then.

Definitely use it when descending long grades, where it greatly assists in slowing the RV.
 
So does this mean I'm using mine wrong as I have never used it yet?

I also have never been on any big hills or mountains YET.

I was under the impression that when you climb a good size hill (aka mountain) when you get to the top (or JUST before)
then you turn on the exhaust brake before you start to descend the downside of the hill and downshift as needed too.

I guess I thought the exhaust brake was used to slow you down going down big hills and if that was true then using it on level ground
would make the engine work harder to overcome the effect of the EB.
But after reading some of these comments about leaving it on all the time except when wet - I have to wonder if my
thinking is screwed up? 

So am I the only one that would (plan on) only using it on the downside of a mountain?   I hope this isn't a dumb question.

IF I'm wrong I can handle that, but someone would have to give me some kind of proof that it didn't hurt fuel mileage or
wear out the EB faster then not using it all the time.

One more thing is - I'm the kind of guy that if no one is behind me, I take my foot off the gas or disengage the cruise and coast
to a stop sign or stop light if it's red.  If using an EB all the time would keep the coach from free coasting without feathering the gas pedal,
then I'm not sure if using it would be a benefit to me. 
 
There are exhaust brakes and engine brakes. I don't know all of the differences between them, but I do know that our Jake Brake works by re-timing the engine's exhaust valves, using back-pressure to slow the coach. It works great and I will frequently descend miles of 6% or 7% grades without touching the service brakes. We live out west and often have to climb and descend grades.

I never turn ours off - even when it's raining. We weigh in at about 40,000 lbs so traction is rarely a problem. I would turn it off on snowy roads, because that's what the owners manual says to do, but I leave it on its lowest setting in the rain. I wouldn't intentionally cross our mountain passes when it's snowing anyway, so snow would rarely be an issue. Our Jake Brake also works with our cruise control.

Here's something else to consider. If you're towing a car, make sure its auxiliary brake does not start braking, just because the brake lights are on. Someone on this Forum told me their older system did. Our coach's brake lights come on when the Jake Brake is braking, so our towed vehicle's brake lights come on too. If the towed vehicle's auxiliary brake started braking, just because the brake lights were on, the towed vehicle's brakes would get really hot when descending grades. The newer auxiliary breakng systems don't brake, just because the brake lights are on. They're programmable and have sensors to prevent that.

Kev
 
Good point Kev.  Our brake lights come on with the exhaust brake so I sold our SMI plug n play and went to a RVi2 brake that works only on inertia.

You have the nicer 2 level engine brake on your Tour.  Winnie only put a exhaust brake (pac) on ours.  I think both do the brake lights now as part of a new requirement. 
 
I have an exhaust brake on my Ram and I leave it on all the time , it works great down to 20 MPH at which point it turns off, if you have not used yours you don't know it will work when needed so I would try it and make sure it is operational.
 
Definitely use it when descending long grades, where it greatly assists in slowing the RV.
Click to expand...

And it saves the service brakes so you have them if needed.  We use ours to slow when exiting a freeway so we save the service brakes.

We have some very long grades where I put the Jake on at the top and leave it on all the way down.  Two grades in particular are steep enough with curves that I also engage the service brake to slow more if I start to pick up too much speed.  In our motorhome the "need to slow more" tends to be at 34 mph, 44 mph, 54 mph and 64 mph - in other words just before the "5" point where it changes gears.  Yours may vary so you have to experiment to learn about it.  We also had a Pak brake on our previous motorhome and used it the same way.

ArdraF
 
An exhaust brake (aka Pac Brake) works by closing a flap inside the brake unit located in the exhaust system, causing increased back pressure. Standard operation means that the exhaust brake is activated at zero accelerator position. Some of us have an after-market foot pedal allowing the driver to determine when braking action is applied (i.e. at other than zero throttle, eliminating the automatic downshift of the transmission).

A Jake engine brake, so called because of the Jacobs name of the original manufacturer, turns the engine into a compressor. Exhaust valves are opened near the top of the compression stroke, releasing the highly compressed air through the exhaust system, with little or no energy returned to the piston. The net effect is a significant braking/retarding action, and the pop, pop, pop sound some communities find objectionable. Most (all?) Jake brakes have a selectable braking action by choosing the number of cylinders to perform as compressors.

Meanwhile, technology moves on, and newer developments in exhaust and engine braking are discussed on the Jacobs web site.
 
Have run across that sign often on our travels in the west, "do not use engine brakes in city limits".. We use ours as well going down hills, but it will not work while cruise is engaged.


Bill
 
  One correction Tom,,the "jake brake" as it is now known as, was invented by Clessie Cummins,,He took the invention to the Jacobs machine Co. to be produced and later sold it to Jacobs.>>>Dan
 
Thanks for the clarification Dan; I wasn't aware of that part of the story.
 
Be careful on your first drive with the engine or exhaust brake.  I was test driving a MH with the two speed engine brake on high and as I approached a red light I let it slow the MH down and was amazed at how effective it worked - then at 10 or 20 mph it let go and that sudden lunge forward resulting from freewheeling after such an effective slow down can surprise you!  I almost rolled through the light! Not as dramatic as it sounds, but it can catch you off gaurd :)
 
LOL... yep, it'll do that. IMO the high setting is just too much braking for normal driving. Generally, the only time I use it is when we're descending grades. It'll actually slow the coach too much on 6% grades, so I have to switch to the low setting to avoid getting too slow. Yeah that surge that occurs when the high setting kicks off would definitely get your attention if you weren't expecting it. :)

Kev
 
  A properly set up Jacobs "brake" can make as much horsepower slowing you down as the engine is able to make speeding you up.>>>Dan
 
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