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holstein13's avatar
holstein13
Explorer
May 05, 2016

Easy Mountain Driving

When I lived full-time in Florida, I rarely thought about mountain driving. For the one trip out west or through the Smoky Mountains, it was trivial to simply take off the cruise control and turn on the tow/haul mode on my gasser and later, the Jake Brake on my DP.

But now that we are full-time traveling, it seems as if we are very often in the mountains or high plateaus and constantly working the brakes and throttle was a little tiresome. I would inevitably pick up too much speed going downhill and end up applying the service brakes too often.

So I decided to look into the features of my cruise control and jake brake and found that with very little effort, I could setup the cruise to automatically apply the Jake Brakes in stages to finely control the speed.

Now, I set the cruise control slightly below the speed limit and relax while the Cummins ISX15 maintains my speed within 6 miles per hour while I concentrate on the road ahead. I set the system to allow it to go 6 MPH over my set speed so that it would allow the coach to pick up speed on a descent to use on the way back up a mountain.

It makes mountain driving much more enjoyable and safer for me. I often wonder why the manufacturers don't set this up in advance and why more folks don't set it up after the fact when it's fast, easy and free on all recent Cummins engines.
Class A

14 Replies

  • holstein13's avatar
    holstein13
    Explorer
    May 05, 2016
    DSDP Don wrote:
    If the speed continues to rise, I'll move the engine brake from LOW to HIGH. If it still picks up speed, the trans will down shift and the unit will start even heavier braking.
    You shouldn't have to move the switch from LOW to HIGH. The Cummins ISL should do this automatically for you if you set the "Cruise Control Speed Delta for Minimum Engine Brake - Parameter" and the "Cruise Control Speed Delta for Maximum Engine Brake - Parameter"

    Please see: https://cumminsengines.com/powerspec-isl-engine-brake-features-and-parameters

    The way it works is the engine will apply the minimum engine brake at first but if the vehicle starts moving too fast (above the set speed) it will apply the maximum. Have you tried leaving it on HIGH and seeing if it only applies the minimum on slight speed increases?
  • holstein13's avatar
    holstein13
    Explorer
    May 05, 2016
    DSDP Don wrote:
    "holstein13".....You keep saying that you activated the features like they were programmable somewhere. Is that what you mean or that you just started using the features that were already there? I don't know if the King Aire has some cruise control features that are different than my Dutch Star.

    My Dutch Star has a two speed engine brake that works with my cruise control. Once I set the speed on a grade, with cruise control, and turn my engine brake on either HIGH or LOW, they will engage once I exceed the set speed by about 5-6 mph. If the speed continues to rise, I'll move the engine brake from LOW to HIGH. If it still picks up speed, the trans will down shift and the unit will start even heavier braking.

    What I just described is standard on the Freightliner XRC Chassis at the Dutch Star level. Does yours do something different than that?
    Those features are standard on all Cummins engines but the parameters were not enabled on my chassis. Maybe it's a Spartan Issue. I asked about it and Newmar said they would not enable them for me.

    So I plugged into the ECM and enabled them myself. There are lots of great settings in the ECM that you can adjust such as how much speed you can pick up without engaging the engine brake and at what point the maximum braking will be applied (this could automatically switch from low to high in your case).

    The ISX 15 has a three stage engine brake 2,4 or 6 cylinders. At the max setting, it will generate 600 HP of braking power.

    That's interesting that it was enabled on your Dutchstar (as it should be). I wonder why they don't enable it on the King Aire.
  • DSDP_Don's avatar
    DSDP_Don
    Explorer
    May 05, 2016
    "holstein13".....You keep saying that you activated the features like they were programmable somewhere. Is that what you mean or that you just started using the features that were already there? I don't know if the King Aire has some cruise control features that are different than my Dutch Star.

    My Dutch Star has a two speed engine brake that works with my cruise control. Once I set the speed on a grade, with cruise control, and turn my engine brake on either HIGH or LOW, they will engage once I exceed the set speed by about 5-6 mph. If the speed continues to rise, I'll move the engine brake from LOW to HIGH. If it still picks up speed, the trans will down shift and the unit will start even heavier braking.

    What I just described is standard on the Freightliner XRC Chassis at the Dutch Star level. Does yours do something different than that?
  • Kayteg1's avatar
    Kayteg1
    Explorer II
    May 05, 2016
    Don't sweat it :)
    We live in times where it takes bachelor degree to operate most of every day stuff.
    I read Mercedes forum a lot and my understanding is that >90% of owners have no idea they have hill descent and hill holding.
    While hill descent is not crucial for a car, hill holding is very nice option, especially in California hills as you don't need to hold the brake when waiting for green light uphill.
    What is stupid IMHO is that Mercedes makes the option available only on Comfort setting, that moves the car with 2nd gear.
  • holstein13's avatar
    holstein13
    Explorer
    May 05, 2016
    Kayteg1 wrote:
    You did admit that you discover the option long time after the purchase, didn't you?
    Meaning you never ask for it.
    I'm ashamed to admit this, but I scrutinized every single feature and parameter on the ISX15 engine and Spartan chassis for two weeks before I purchased my coach. So no, I knew the features were there (I just didn't know they weren't activated by the OEM and I didn't know how to activate them right away). But I don't do that for every purchase I make (depending on my interests) and I certainly understand that most people would have very little idea about this subject.
  • holstein13's avatar
    holstein13
    Explorer
    May 05, 2016
    Mr.Mark wrote:
    If I'm near the end of the hill and see the next hill coming, I can move the retarder stalk to zero and start to pick up speed to 'get into' the next hill. If you only allow a 6 mph increase, you are not utilizing the hill to your advantage and your engine will kick in sooner.

    Since I drive about 60 mph in a 70/75 mph zone. I'll let the coach coast up to 70-75 into the next hill.
    Mountains always frustrate my ideal plans for fuel economy. On small, straight descents, I like to wind up as much speed as possible before approaching the next ascent, but it rarely happens that way. I typically find myself on windy curves at the bottom of the descent where I wouldn't want the additional speed anyway.

    Like you, I set my cruise control below or well below the speed limit for a couple of reasons. 1st, it's much, much safer on winding mountain roads to go slowly and 2nd, it allows me to pick up speed safely and within the speed limits when I want to.

    The way I do that is I simply hit the cancel button on the cruise control. That prevents the brake from coming on and allows me to pick up speed. Then I'll hit the resume button on the way up.
  • Kayteg1's avatar
    Kayteg1
    Explorer II
    May 05, 2016
    holstein13 wrote:
    Kayteg1 wrote:
    I think the technology holstein is talking about is available for over 20 years, but nobody made the demand, so why worry about supply?
    I guess that's really my question. Why is there no demand for this? Do people just not know how great it is or what? Maybe they don't know it exists. My guess is that A) They don't know it exists and B) They can't imagine how much easier it makes driving up and down mountains.


    99% of US costumer have 3 things on their mind when they are shopping for stuff.
    -cheap
    -shiny
    -cheap
    I just observed a Bay Area house, who is sliding down the hill with lower subbasemet wall at 80 degree.
    It was nicely decorated, so 1.7 mil asking generated 2+ mil multiple offers.
    When I can understand that not too many can afford Prevost, it always amaze how people buying new RV with $7 faucets, 50 cents cabinets locks and no safety.
    I think hill descent will be somewhere past #1000 on demand list.
    You did admit that you discover the option long time after the purchase, didn't you?
    Meaning you never ask for it.
  • Mr_Mark1's avatar
    Mr_Mark1
    Explorer
    May 05, 2016
    holstein13 wrote:
    Mr.Mark wrote:
    Our new Volvo has the 6 speed retarder that I can set with the stalk. Or, the minute I hit the service brakes, it automatically activates the retarder at full 'holdback' (can't think of the correct word).
    Yes, but why hit the brakes at all? Can't you setup your cruise control to control the throttle and the engine brakes? It's so much easier. I wonder if the Volvo will let you program it this way.


    I actually don't have to hit the brakes and can control the descent with the retarder stalk. The retarder is much stronger than the two stage brake we had on the Dynasty (which worked fine).

    If I'm near the end of the hill and see the next hill coming, I can move the retarder stalk to zero and start to pick up speed to 'get into' the next hill. If you only allow a 6 mph increase, you are not utilizing the hill to your advantage and your engine will kick in sooner.

    Since I drive about 60 mph in a 70/75 mph zone. I'll let the coach coast up to 70-75 into the next hill.

    Safe travels,

    MM.
  • -Gramps-'s avatar
    -Gramps-
    Explorer
    May 05, 2016
    The cruise control on my coach along with the tranny grade brake works very much the same way.
  • holstein13's avatar
    holstein13
    Explorer
    May 05, 2016
    Kayteg1 wrote:
    I think the technology holstein is talking about is available for over 20 years, but nobody made the demand, so why worry about supply?
    I guess that's really my question. Why is there no demand for this? Do people just not know how great it is or what? Maybe they don't know it exists. My guess is that A) They don't know it exists and B) They can't imagine how much easier it makes driving up and down mountains.

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