Engine Brake and Cruise Control - RV-Dreams Community Forum

PrairieRV · RV-Dreams Family Member

Engine Brake and Cruise Control

bjoyce · RV-Dreams Family Member

Our cruise control and engine brake work together, so I am surprised to hear that is not always the case. We mostly use cruise control to keep our speed down, since it is easy for it to creep up if not paying attention.

NorCal Dan · RV-Dreams Family Member

That's how I ran mine...engine brake off. I didn't like having the brake engage every time I lifted off the gas pedal.

Barbaraok · RV-Dreams Family Member

PrairieRV wrote:
(I apologize ahead of time if this is just a dumb question.)

I know using cruise control isn't the best idea for good mileage and all that. But I tried it out with my new (to me) motorhome on the interstate here in central Kansas. So there's not really big hills or anything. But I found that after it accelerated to go over a higher area, as it descended the other side and the cruise control let up on the accelerator, then the engine brake would kick in and throw the cruise control off. So I'm assuming that the engine braking should be turned off if using cruise control.
Does anyone else have experience with this? Is that the right solution?

I'm not sure why you think cruise control is bad for your mileage? Most humans can't match the computer is adjusting fuel flow to keep the speed at a constant, predetermined level. The key is to pick a speed that is the sweet spot for your rig and get the 'lead foot' off the pedal by using the cruise control. We use the cruise control all of the time EXCEPT when we are climbing big passes, where we down shift before the engine starts to lug down using our RPMS as our guide. 4% or greater grade and we start downing shifting to keep the RPM between 1800 and 2000. At the top of the pass, with our speed down to 40-45 is when we engage the exhaust brake for the descent.

Terry and Jo · RV-Dreams Family Member

Patti,

It has been said here before, but likely a long time ago. There are NO dumb questions, however, one can certainly receive a smart-alecky answer once in a while. If a question prevents one from making bad decisions, it is ALWAYS a good question.

Personally, I don't have a lot of experience in the Plains states much, so I seldom use the cruise control when towing the fifth wheel. But, as other stated, when I do use it, it is to keep ME under control.

Terry

Bill and Linda · RV-Dreams Family Member

Patti:

Actually that's a very good question.

General statement - use the engine brake ANYTIME you are coming down a mountain / hill with the cruse control off Do not "ride the brakes." Let the engine brake due to work and safe the vehicle brakes.

I leave engine braking on all the time for better vehicle control and minimum use of brakes. Save the brakes for when they are needed by keeping them cool.

Different manufactures implement the interaction between cruse control and other drive train (transmission / engine/turbo brake) functions. You haven't indicated the type of engine or transmission. Doesn't matter the brand and model of the motor home. It's the engine and transmission builder that determine proper operation.

Read the manual and see what it says.

I do not recommend cruse in mountains. On flat land, like BillJ said, its good to maintain and keep the speed in check.

Do not, IMO, even think about fuel mileage when driving. Drive the vehicle as it should be driven for best safety, speed and vehicle control. Actually if one pays attention they can get better fuel mileage without the cruse control because one can look out the window and anticipate what is the best for power and braking and not over do the power when cresting a hill, etc. I've proven this over and over many time in mountains. On flat land cruse will maintain a steady speed. But not in the mountains or rolling / up and down Interstates.

PrairieRV · RV-Dreams Family Member

Thanks for all your responses.

Bill Joyce, I also want to use the cruise control to keep me from stepping in it based on traffic around me. I guess I need to read the manuals again about how/if they are linked.

NorCal Dan, I'm basing my original premise on just a few times I've used it. I'm wondering now if the engine brake didn't really throw off the CC. I know it startled me, and I decided not to use CC if it was going to be like that. Or turn off the engine brake.

Dave (or Barb?), I was thinking about the only other time I drive anything heavier than my pick-up, when I'm towing a trailer. It seems I can do better without CC and have better control. I don't have a real basis in data. Thanks for the tips. I'm going to try to condense it to a list to keep handy when driving in the mountains.

Terry, it's in the flat-land in particular, I know I'll need it. It's really easy to be complacent about the speed.

Bill (or Linda?), my 'bago has a Cummins diesel and Allison transmission. I need to read the manuals again. Thanks for the tips.

So far, I've only done a short "shake-down" trip. Later in August I'll take it a couple hundred miles to Councel Bluffs, Iowa, and boondock a few days during a Spyder event. Then, in September I'll be heading from Kansas to northern California. That's the one I'm sure I'll get to use all these tips on.

I love these boards. Ya'll are great.

Barbaraok · RV-Dreams Family Member

PrairieRV, it is Barb (Dave doesn't post on forums) kind of thought the screen name was a dead give away.

Our exhaust brake will not cut in until we are down around 45 or less - - it immediately drops us into 4th if we aren't already there. And we don't try mountain passes on the cruise control - - I know some of the really big DPs practically race of the mountains, but we don't. The service manager where we take the coach pointedly looked at me and told me to start down shifting when climbing anything remotely close to 4%, if not before. Even just shifting down to 5th will bring up the RPMS to the 1700 - 2000 range where we like to be for climbing. Once you get to the Rockies you will find that you will become very familiar with your exhaust brake and how it works. In normal driving, we just set the cruise control and go, don't have the exhaust brake on.

PrairieRV · RV-Dreams Family Member

Thanks again, Barb!

(I was looking at signatures for hints on how to address folks. My apologies.)

arcaguy · RV-Dreams Family Member

Has anyone here used an exhaust brake in slick conditions such as rain, snow and ice? If so, how do they work?

Neil and Connie · RV-Dreams Family Member

arcaguy wrote:
Has anyone here used an exhaust brake in slick conditions such as rain, snow and ice? If so, how do they work?

Better than the regular breaks as the wheels are free to rotate and hence less likely to lose traction.

Barbaraok · RV-Dreams Family Member

We don’t drive in snow or ice and try to be in sunshine areas.

Bill and Linda · RV-Dreams Family Member

Neil and Connie wrote:
arcaguy wrote:
Has anyone here used an exhaust brake in slick conditions such as rain, snow and ice? If so, how do they work?
Better than the regular breaks as the wheels are free to rotate and hence less likely to lose traction.

X2 - I agree with Neil and to add, the exhaust brake will be "braking" only the rear wheels - actually just "retarding them" as Neil said so less lightly to have the front steering set loose traction.

Had to do a lot of this coming home solo from "up north" with the 5500HD and the exhaust brake was a tremendous help. Not recommending anyone do it, but sometimes ya just get caught and we did in a blowup out of now where snow and ice storm. Cars were slipping and spinning all over the place but our truck was solid. Our 5500 HD has anti-skid as well and that was a benefit.

As with all equipment, its use is based on conditions and experience.

Terry and Jo · RV-Dreams Family Member

I'll chime in with agreement with Neil and Bill. Experience is the big thing with respect to such things. Otherwise, follow Barb's advice and don't even travel under those conditions.

Sad to say, I broke one of my own rules. When we went to leave Kanab, Utah, it was on a Sunday. I discovered when I did the "brake and pin lock" test that I didn't have trailer brakes. However, there was no place in Kanab where I could find brake fluid. So, we drove from Kanab to Green River, Utah (roughly 267 miles) with me using the F450's Tow/Haul feature and insuring that I was leaving plenty of room between myself and any traffic in front of me. I was also on high alert for any traffic situations that might require me to need to brake heavily.

As soon as we got set up in Green River, we went and found some brake fluid, and I topped off the reservoir that night. I then pumped the brakes the next morning before doing the brake and pin lock test, and then I topped off the reservoir again.

Terry

Russ Ranger · RV-Dreams Family Member

After traveling in a gas power motorhome the last five years, we switched to a diesel pusher this year. At first I didn't fully understand how much I had missed by not having an exhaust break.

We just spent the last week dry camping in the Big Horn Mountain of Wyoming. To exit these mountains you must come down a 20 mile switchback 6% grade.

In my old rig I would have been white-knuckling it all the way. With the exhaust brake I just picked a speed and let the Cummins/Alison take control.

There is probably a price for peace of mind. For that half hour it was priceless.

By the way, Highways 16, 14, 14A and 37 are amazing roads in an awesome area. Don't just zoom around them to get to Yellowstone. Slow down and have a talk with a Moose or Big Horn Sheep.