Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 06-21-2016, 03:00 PM   #1
Member
 
Krash's Avatar
 
Join Date: Nov 2014
Posts: 99
Pacbrake and Cruise Control

I have read in many posts that some coaches cannot use their Pacbrake and cruise control at the same time. This confuses me a little? Of course, your cruise control would disengage as soon as you touch the service brake, and on my coach, if the exhaust brake switch is on, the EB engages and the transmission starts downshifting.

But I am getting the feeling that I may be missing something? Are some coaches configured that if the cruise control switch is even on (but not actively on cruise control) the EB cannot be used? I mean I can’t understand why this would be?

I also have read the both the EB and cruise control can work together? Meaning that you can be on cruise control at 55 MPH and if you start going downhill and your speed increases, the EB will activate to keep your speed down close to 55 MPH. When this occurs, does the transmission start to head toward the target gear (in my case 2nd gear) and display 2 on the gear selection panel?

This is a feature I would like to have. Can anyone tell me if this is programmable? If it is, would Cummins or Allison be the ones to do it?
__________________

__________________
Krash is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 06-21-2016, 03:17 PM   #2
Senior Member
 
Join Date: Jun 2016
Location: Nine Mile Falls WA / Arizona City AZ
Posts: 524
Let me try and clarify this for you... I was a PacBrake distributor for 20 years before retirement... over the years we sold and installed many, many units....

If the PacBrake is linked to the ECM of the engine.... and the engine is programed to support an exhaust brake.... than the ECM will turn on the PacBrake when the programing calls for that...

With that said... some ECM programs support PacBrake (exhaust or engine) engagement with the cruise control ON when the program calls for it... some ECM's don't support that feature and need to have the cruise control in the OFF position...

And of course... if you don't have your PacBrake linked to the ECM (normally because the ECM doesn't support it), the exhaust/engine brake can be wired directly with manual controls.... with this style of wiring, its suggested you link a relay into the cruise control circuit so that you don't go down a hill, and the ECM calls for speed and your exhaust brake is still trying to slow you down....

And in the case of Cummins and Allsion... most engines and transmission built after 2006 supports inputs to the ECM for an exhaust brake.. in some transmissions that needs to be turned on... of course there are so many possible configurations of engines and different transmissions I can't quote which are which...

I hope this helps...

BTW - in some cases, you can add to the programing of the Allsion Transmission so that when the transmission ECM sees the input from an exhaust brake... the transmission ECM looks at the vehicle speed senor and will downshift the transmission to give you the very best results with either an engine or exhaust brake...

And finally... the use of an exhaust brake is based on the ENGINE and what kind of exhaust valve springs are in that engine... so some brakes can provide more retarding HP on one engine... and less on other engines... its because of the exhaust valve spring in the engine.. In some cases, mostly in Cummins, you can upgrade the exhaust valve springs to provide more retarding HP...
__________________

__________________
jelag is offline   Reply With Quote
Old 06-21-2016, 03:21 PM   #3
Senior Member
 
znt1186's Avatar
 
Join Date: Nov 2014
Posts: 490
I use the cruise and eb on mine together. With the cruise on, the eb will engage and target 2 gear at about 5 mph above the target cruise speed. I still need to brake sometimes on some grades because rpm's are too high for a downshift. Anyway, they do both work together on my 2003 Allegro Bus with a 350 Cummins and Allison 3000MH
__________________
znt1186 is offline   Reply With Quote
Old 06-21-2016, 04:12 PM   #4
Member
 
Krash's Avatar
 
Join Date: Nov 2014
Posts: 99
Quote:
Originally Posted by znt1186 View Post
I use the cruise and eb on mine together. With the cruise on, the eb will engage and target 2 gear at about 5 mph above the target cruise speed. I still need to brake sometimes on some grades because rpm's are too high for a downshift. Anyway, they do both work together on my 2003 Allegro Bus with a 350 Cummins and Allison 3000MH
Yep, this is what I would like to have. I have a 2002 Diplomat with Cummins 330 ISC. I would love to hear if any others have this set up on their similar coaches. Also, if it could be done to mine.
__________________
Krash is offline   Reply With Quote
Old 06-21-2016, 05:49 PM   #5
Senior Member
 
jacwjames's Avatar
 
Monaco Owners Club
Join Date: Jun 2014
Posts: 4,597
I own a 2002 Monaco Windsor with 350 ISC.

I have a PacBrake that is programmed to work when the cruise control is not active. If I leave the PacBrake switch on I can engage the cruise control and as soon as I tap my brakes or cancel the cruise (I have a VIP steering wheel so not hard to control). the PacBrake will engage.

Normally I don't leave the PacBrake on, I will hit the switch as I'm starting to descend a hill and the PacBrake will start working and the transmission will start the downshift sequence, initially showing 2 on the display. My coach is heavy so I sometimes have to pulse the barks to help slow me down. I try not to ride the brakes.

I would check with a Cummins shop as to whether you could install the PacBrake. It mounts between the Turbo and the Exhaust, installation looks pretty simple but don't know about the programming and whether there is existing wiring to make installation easy. The PacBrake itself isn't overly expensive but once you get Cummins involved the cost will escalate quickly.
__________________
Jim J
2002 Monaco Windsor 38 PKD
2005 Jeep Grand Cherokee w/5.7 Hemi
jacwjames is offline   Reply With Quote
Old 06-21-2016, 06:07 PM   #6
Senior Member
 
FIRE UP's Avatar


 
Join Date: Dec 2009
Location: Out there, somewhere
Posts: 5,283
I use the cruise and eb on mine together. With the cruise on, the eb will engage and target 2 gear at about 5 mph above the target cruise speed

Well,
A question to you. Are you saying that your cruise is ACTIVE and when you start a decent down a grade, the E/B will engage automatically? Or, are you saying that your cruise is on but, NOT ACTIVE, and when you start a decent down a grade, your E/B engages and starts to slow you down?

On our coach, an '04 Itasca Horizon 36GD with the 330HP C-7 and Allison MH3000 trans, if the cruise is active (using it) and the E/B switch is ON, and I start a decent down a grade, the E/B will NOT activate. That coach will gain speed, faster and faster UNLESS, I momentarily step on the brake pedal which, at that time, will disengage the cruise and, activate the E/B.

On our coach, just having the cruise switch ON, has no effect on the E/B. It will start slowing me down, each and every time I let off the accelerator pedal. If I'm actively using the cruise, the E/B will NOT activate, even with my foot completely off the accelerator.
Scott
__________________
2004 ITASCA HORIZON 36GD, 2011 GMC Sierra 1500 4x4 Toad '08 GL 1800 Gold Wing
Retired-29.5 yrs, SDFD, Ham - KI6OND
Me, Karla and the Sophie character, (mini Schnauzer)
FIRE UP is offline   Reply With Quote
Old 06-21-2016, 06:18 PM   #7
Member
 
Krash's Avatar
 
Join Date: Nov 2014
Posts: 99
FIRE UP It sounds like your cruise and Pacbrake work exactly like mine does.

jacwjames I already have a Pacbrake. My question is about having the Pacbrake slow me down when I am coasting too fast while on cruise control. Some have this feature, and I would like to see if I can get mine working that way. like znt1186 post above.
__________________
Krash is offline   Reply With Quote
Old 06-21-2016, 06:57 PM   #8
Senior Member
 
FIRE UP's Avatar


 
Join Date: Dec 2009
Location: Out there, somewhere
Posts: 5,283
Well,
Here's my thought(s) on this. In many diesel coaches, if equipped with either a "Pac Brake" or Exhaust brake (to me, those are one and the same), and it activates as you descend down a grade, that will also activate the BRAKE LIGHTS. And that means, it's a form of braking and, that, to me, also means it SHOULD disengage an active cruise control. But, this is just my thoughts, not necessarily the way things happen.

We used to own an '07 Grand Cherokee Overland model with the 5.7L Hemi and just about every bell and whistle you could possibly get on one of those. It was the only car we've ever owned that when using the cruise control on a flat road, and then started a descend down a grade, that car would actually SLOW you down, to keep your intended speed at what you set the cruise at. No other car/truck/motor home/motorcycle etc. we've owned, has ever done that.

Now, maybe there are motor homes that have the correct programming in both the Cruise and the ECM etc. to handle both flat ground and descending and keep the cruise on and active. Now, if that's true and, the E/B actually activates while descending down a grade and, the BRAKE LIGHTS are activated, then at the bottom of the grade, the E/B stops and, the cruise takes over, that's news to me.
Scott
__________________
2004 ITASCA HORIZON 36GD, 2011 GMC Sierra 1500 4x4 Toad '08 GL 1800 Gold Wing
Retired-29.5 yrs, SDFD, Ham - KI6OND
Me, Karla and the Sophie character, (mini Schnauzer)
FIRE UP is offline   Reply With Quote
Old 06-21-2016, 06:59 PM   #9
Senior Member
 
jacwjames's Avatar
 
Monaco Owners Club
Join Date: Jun 2014
Posts: 4,597
OK, understand.

If my cruise is on it the EB will not engage.
__________________
Jim J
2002 Monaco Windsor 38 PKD
2005 Jeep Grand Cherokee w/5.7 Hemi
jacwjames is offline   Reply With Quote
Old 06-21-2016, 07:28 PM   #10
Member
 
Krash's Avatar
 
Join Date: Nov 2014
Posts: 99
"Now, maybe there are motor homes that have the correct programming in both the Cruise and the ECM etc. to handle both flat ground and descending and keep the cruise on and active. Now, if that's true and, the E/B actually activates while descending down a grade and, the BRAKE LIGHTS are activated, then at the bottom of the grade, the E/B stops and, the cruise takes over, that's news to me."

Thanks Scott,

But this is exactly what I have been reading on this, and other, forums. I am not sure about the brake lights, as some manufacturers only activate the lights with the service brakes. But yes, my brake lights come on with the Pacbrake, so I assume some of these people who have the cruise and exhaust brake working in harmony, also have brake lights come on when on cruise and the Pacbrake is activated.

I have come across the situation often when I am on cruise at 55 MPH and come to short downhill stretch. My coach starts to scream down the hill, and I have to get on the brakes which cancels the cruise control, and activates the Pacbrake. Then 30 seconds later I have to reset the cruise control again.

My workaround to this is to just drop it a gear or two until I get down the very small hill while not touching the cruise control.

But as I have read, some other coaches do this automatically by activating the exhaust brake while on cruise when the coach reaches a few miles an hour over cruise set speed. Then when the set speed is reached, the EB is released and the cruise continues on its' merry way.

AT least, that my understanding.
__________________
Krash is offline   Reply With Quote
Old 06-21-2016, 08:37 PM   #11
Senior Member
 
Join Date: Jun 2016
Location: Nine Mile Falls WA / Arizona City AZ
Posts: 524
so I didn't read all the posts since my last post, but would like to answer this...

jacwjames.... just a second...

remember I said it was how the vehicle ECM was programmed.... on one of my rigs the cruise control can be set.... and when you descend a hill the exhaust brake will engage and slow you down.... on one of my other pickups... you have to turn OFF the cruise control for the exhaust brake to work....

when we installed them... we would play all of the different scenarios so we could teach the owner... honestly this was always a crap shoot... so we couldn't promise certain functions when we sold the units... as we just didn't know until we tapped into the ECM and tested it... it changed from vehicle to vehicle and year to year...

One last thought... we found that when you have the cruise control set.. and descend a hill.... the range of the cruise control allows a wider range of control than I personally want... in other words... it lets the vehicle roll faster than I'd like... so personally I turn off the cruise and turn on the exhaust brake...

krash...

your right... some ECM's will down shift and lock the transmission in a lower gear... some ECM's won't do that.... so in your case.. if your ECM won't do that... your right to change gears and get the best retarding HP that you can achieve...

with my pickup, with a manual transmission... I hunt for the correct gear, to allow my PacBrake to control the load... for me... its all about the size of the load and the hill...

take as an example, the Teton Pass heading WEST out of Grand Teton National Park... that's like 5-6 miles of 10% downgrade... for me to feel safe... my pickup is in 3rd gear at about 20 MPH... and I go down that hill without the use of the vehicle brakes.... on other hills I might go down in a different gear and feel comfortable to use the vehicle brakes... when I don't know the grade or how long it is.... I side with safety and just go slower....

Any other specific questions...
__________________
jelag is offline   Reply With Quote
Old 06-22-2016, 01:18 AM   #12
Senior Member
 
DD788Snipe's Avatar


 
Newmar Owners Club
Spartan Chassis
Join Date: Jun 2013
Location: Apple Valley CA
Posts: 914
It can be programmed to work in different senerios. My rig the EB will engage when the cruise is set on low percentage down grades and not down shift unless I tap the brake. I have it as a gauge on my ScanGauge and in monitoring it I can see it kick in up to 85%. If I start to over speed I'll tap the brake so that the Trans will down shift and hold my speed. It works very efficiently. I would think that any Cummins shop with the Insite software can program your ECM and TCM to do what you want it to do.
__________________

__________________

Craig & Carolyn Roberts Apple Valley, CA
2006 Newmar 3910 KSDP 400 ISL Cummins Spartan Mountian Master Chassis
Toad: 2017 GMC Canyon 4X4 Crewcab
DD788Snipe is offline   Reply With Quote
Reply

Tags
brake, cruise control



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Eco Cruise Cruise Control LSepulveda iRV2.com General Discussion 6 03-30-2016 07:52 AM
Cruise control out of control bjreynolds Newmar Owner's Forum 6 05-11-2014 01:12 AM
Pacbrake/Cruise/Fast Idle rpk Class A Motorhome Discussions 1 10-28-2012 02:20 PM
Banks PowerPack and PacBrake PRXB Install recurry Cummins Engines 8 05-23-2011 10:44 PM
Cruise Control/Wiper Control/Bright Light Control cnjcampione Winnebago Industries Owner's Forum 2 05-21-2011 08:38 PM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 02:29 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.