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Open Roads Forum  >  Fifth-Wheels

 > Jake Braking A 5er Down Long Steep Incline

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4x4ord

Alberta

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Posted: 11/25/21 08:43am Link  |  Quote  |  Print  |  Notify Moderator

ReneeG wrote:

rhagfo wrote:

ReneeG wrote:

Retired JSO wrote:

I tow in tow mode and use cruise control all the time with the exhaust brake engaged. The OP has a 2019 F-350, I have a 2018 F-350, my exhaust brake has no auto, it’s either on or off.


We have a 2011 F350 and the true engine compression brake (not exhaust) is only off or on with setting the Tow Haul Mode.


I agree with Ron, please explain all recent HD pickup use an exhaust brake, which uses some means of restriction of the exhaust gases.
Now PacBrake offered a Load Lash device for the Cummins 6.7, that was more like an engine brake.


It's not a true exhaust brake, but merely uses the transmission and the back pressure of the engine. It works and it's efficient, but Ram owners , I beleive, have true exhaust braking.


The 2011 through 2014 Powerstroke didn’t have an EB switch but did have a turbo that was capable of creating some back pressure. In 2015 the Powestroke turbo was upgraded, an EB switch was added and the EB performed considerably better. The Cummins EB works very similar to the Powerstroke in that it is the turbo that is creating back pressure. However, because Cummins engines use stronger exhaust valve springs the EB can be used to generate higher back pressure without danger of the exhaust valves “floating” and coming into contact with the pistons. For this reason the Cummins can generate the same negative horsepower at 3000 rpm that the Powerstroke can at 4000 rpm.


2022 F350 SRW Platinum short box 4x4.
B&W Companion
2008 Citation Platinum XL 34.5

Cummins12V98

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Posted: 11/28/21 09:37am Link  |  Quote  |  Print  |  Notify Moderator

I gave the "AUTO" mode a shot. I was descending I-15 to I-215 from Barstow, I would guess it's 5-6% grade. I let off and tapped my brakes at 60 mph. It only took seconds for my speed to increase to 70. I hit the brakes and set cruise to 55 and locked in 4th. I adjusted the cruise up and down to stick close to 60.

Lighter loads may work on AUTO but 35k combined is No Bueno.


2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

4x4ord

Alberta

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Posted: 11/28/21 11:15am Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

I gave the "AUTO" mode a shot. I was descending I-15 to I-215 from Barstow, I would guess it's 5-6% grade. I let off and tapped my brakes at 60 mph. It only took seconds for my speed to increase to 70. I hit the brakes and set cruise to 55 and locked in 4th. I adjusted the cruise up and down to stick close to 60.

Lighter loads may work on AUTO but 35k combined is No Bueno.


If you think about what auto EB is doing you’ll better know how to use it. Auto EB on the Ram is capable of producing exactly the same back pressure as “full on” EB which is 60 psi. The amount of braking the EB can do is a function of the back pressure x the engine rpm. If you let off the throttle at 60 mph the auto EB would have closed and been creating 60 psi back pressure. If the truck starts slowing down the auto EB would open to prevent slowing dow … it’s trying to maintain the speed you were travelling when you let go of the brake. As soon as the truck started accelerating it should have been apparent that the EB could not hold your rig back at the rpm the engine was turning. You could have locked out 6th and 5th gear. If it couldn’t hold back in fourth you could have slowed down enough to lock out 4th gear. If your truck holds back your rig in 4th gear using cc but won’t hold back your rig in 4th gear using auto EB it is because cc is applying your wheel brakes. On the Ford, auto EB will not apply the wheel brakes until the engine rpm reaches the red line…. The Ford cruise control will apply the wheel brakes shortly after the truck accelerates above the travel speed set point.

Cummins12V98

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Posted: 11/28/21 01:00pm Link  |  Quote  |  Print  |  Notify Moderator

It did not down shift into 4th I just let it do it’s thing. Next time I will lock out 5-6 and see what happens.

Using cc it applies more back pressure the lower I set cc to a point. Seems like I am hitting around 170-180 back pressure hp.

4x4ord

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Posted: 11/28/21 01:51pm Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

It did not down shift into 4th I just let it do it’s thing. Next time I will lock out 5-6 and see what happens.

Using cc it applies more back pressure the lower I set cc to a point. Seems like I am hitting around 170-180 back pressure hp.


170-180 reverse hp sounds like the right number to maintain 55 mph on a 5-6% grade with 35,000 gross combined weight. I think the Ram exhaust brake should be able to create that amount of braking without using wheel brakes. The advantage of using the Auto setting rather than CC is that "Auto" just works ... ie you don't really have to do any thinking about it. If you're going too fast you simply brake a bit to slow down, or, if you want to pick up your speed a little you step on the throttle a bit to get to the speed you want. If you want "auto" to help slow you down, as soon as you touch the brakes the EB goes into full on mode until you release the brake pedal. I think after you use the auto EB setting a bit you might get to like it better than CC.

Cummins12V98

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Posted: 11/28/21 06:05pm Link  |  Quote  |  Print  |  Notify Moderator

4x4ord wrote:

Cummins12V98 wrote:

It did not down shift into 4th I just let it do it’s thing. Next time I will lock out 5-6 and see what happens.

Using cc it applies more back pressure the lower I set cc to a point. Seems like I am hitting around 170-180 back pressure hp.


170-180 reverse hp sounds like the right number to maintain 55 mph on a 5-6% grade with 35,000 gross combined weight. I think the Ram exhaust brake should be able to create that amount of braking without using wheel brakes. The advantage of using the Auto setting rather than CC is that "Auto" just works ... ie you don't really have to do any thinking about it. If you're going too fast you simply brake a bit to slow down, or, if you want to pick up your speed a little you step on the throttle a bit to get to the speed you want. If you want "auto" to help slow you down, as soon as you touch the brakes the EB goes into full on mode until you release the brake pedal. I think after you use the auto EB setting a bit you might get to like it better than CC.


Thanks for opening my eyes and I will give it a shot.

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