Engine braking

[Jim]

Like most diesel engines, my coach has a compression brake. (CUMMINS 6C 8.3 330hp ISC Turbo Diesel with 330hp. ) I’ve heard it called an “engine brake”, “Jake brake”, or other names as well. From reading, it appears there is a difference between the compression brake on my coach, and the Jake brake on an 18-wheeler. But regardless of the name, the result is to use the engine to slow the vehicle down and save the actual brakes.

Since this is the first vehicle I’ve owned with an engine brake, I’m curious if I’m using it correctly, and to what extent I can use it without damaging the engine.

When leaving home, the highway descends from 4,000 foot to 2,000 foot elevation over a distance of about 5 miles. The signs say 8% elevation drop but I swear, it looks like a roller coaster ride from the top. I start my decent about 25 mph and push the “brake” button on. The braking is quite evident and when the coach starts to exceed the 25 mph, I touch the foot brake just a little bit and the coach slows back to my desired speed.

When the coach is going down these steep grades, the engine brake starts to bring the RPM’s up, and when they reach (what I consider to be) an uncomfortable point, I depress the foot brake until they come back down to where I’m comfortable. Repeat, repeat, repeat.

Is this the correct method? As I said, this is my first encounter with an engine brake and although it seems to work well, I’m not sure I’m using it correctly.

 

[stang37]

Your method is what I use also, but I gear down first. Once the RPM reach 1800 I use the coach brakes. Works great for maintaining my desired speed without major use of the coach brakes. I believe this is the goal of the engine/exhaust brake system. (IMO)

 

[NWIP]

I am by no means an expert or anything else on this matter. I normally select the gear I want that will assist in maintaining the speed I want and use the engine brake to help maintain the speed. In my coach I have variable setting to the engine brake, ie low, medium and high. I will then adjust engine brake setting as I descend down the grade as needed, if I am unable to maintain desired speed then I figure I selected the wrong gear. I recently went down a 6% grade that is about 13 miles long and never touched the brake pedal, maintaining 50 mph +/-5 mph.

If your engine brake is single stage, you will be limited. Assuming that is what you have I think you are doing it exactly right with what you have available.

 

[TJ&LadyDi]

I'd say your technique is pretty much textbook, @Jim. As @NWIP noted, the new 3-stage brakes are a little more convenient, but a single-stage will do what needs to be done. Moderate driver intervention is needed periodically, but selecting a lower gear and using the foot brake when needed is the right way to go.

TJ

 

[Buly]

Like most diesel engines, my coach has a compression brake. (CUMMINS 6C 8.3 330hp ISC Turbo Diesel with 330hp. ) I’ve heard it called an “engine brake”, “Jake brake”, or other names as well. From reading, it appears there is a difference between the compression brake on my coach, and the Jake brake on an 18-wheeler. But regardless of the name, the result is to use the engine to slow the vehicle down and save the actual brakes.

Since this is the first vehicle I’ve owned with an engine brake, I’m curious if I’m using it correctly, and to what extent I can use it without damaging the engine.

When leaving home, the highway descends from 4,000 foot to 2,000 foot elevation over a distance of about 5 miles. The signs say 8% elevation drop but I swear, it looks like a roller coaster ride from the top. I start my decent about 25 mph and push the “brake” button on. The braking is quite evident and when the coach starts to exceed the 25 mph, I touch the foot brake just a little bit and the coach slows back to my desired speed.

When the coach is going down these steep grades, the engine brake starts to bring the RPM’s up, and when they reach (what I consider to be) an uncomfortable point, I depress the foot brake until they come back down to where I’m comfortable. Repeat, repeat, repeat.

Is this the correct method? As I said, this is my first encounter with an engine brake and although it seems to work well, I’m not sure I’m using it correctly.

Jim,
I'm with Stang37 on the issue. I down shift as I was driving a manual transmission car. Then use the engine brake, and help with the brake pedal.
One thing to consider is, that if you already braking with the engine brake or down shifted, the drive wheels are the only ones slowing down the coach. When you apply brake with the pedal, all the wheels are breaking, meaning the drive wheels receive additional breaking force on top of the engine brake, and may lock up and start skidding. Go easy on the brake pedal when engine brake is active. Me thinks

 

[sheridany]

Is it correct that you should use engine brake cautiously or not use it in wet weather to avoid skidding? i recall @TJ&LadyDi giving me some good advice on this topic over "there" a while back.

 

[Tjdave]

You are doing it right. Always start off in a lower gear before your decent on a steep grade. I can't tell anyone how a DP engine brake works, because I have never owned one. But, I have driven commercial vehicles for decades. At the gov site I work at, we drive many trucks of all types. New and old, dump trucks, water trucks, equipment haulers, cranes, flat beds, specialized shipment vehicles, all of it.
What I can tell you from the new trucks vs the older ones, is that the cruise control has a effect on the engine brake. If the cruise is off, the engine brake kicks in as soon as you let off the accelerator. If the cruise is on, but not set, the engine brake will not kick in unless you press on the brakes. On mild grades, while the cruise is set, the new trucks will engage engine brake automatically to keep you in the set range. Of coarse if you just head over the crest of a steep hill on cruise, and your engine brake can not keep up, it will be too late to downshift and you could be in for a ride!

 

[RandyB]

I agree with everything advised here thus far. The point I would like to make is using the service brakes. The one operated by the driver and the brake pedal. On a descent, make sure to NEVER ride the brakes (light, long application of brakes) or even have your foot on the pedal. You want to operate the brakes in a firm and meaningful manner to rapidly slow down the vehicle, then let off entirely. Let the engine brake and the transmission do their job and as the speed increases, once again, firm braking and release.

 

[Jim]

Hey, great! And thank you everyone. Been driving this thing around for the last 9 months and really didn't know for sure that I was doing it right. Again, thank you all.

Jim

 

[NWIP]

Is it correct that you should use engine brake cautiously or not use it in wet weather to avoid skidding? i recall @TJ&LadyDi giving me some good advice on this topic over "there" a while back.

@sheridany You are correct that use of engine brake on wet or slippery roads should be avoided per the manual. I think that @Buly explains the reason about additional braking on drive wheels when applying the foot brake.