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Old 07-04-2016, 05:27 PM   #1
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Is your rigs exhaust brake set to latch mode?

I am in the process of upgrading to the Pacbrake PRXB and have a question for those who have an exhaust brake that is set to latch mode. I am also considering reprogramming to latch mode. As I understand it, in this mode, the exhaust brake, when switched on, will only activate when the service brakes have been applied. It then releases as soon as the accelerator is depressed and stays off until the service brakes are applied again.

For those whose exhaust brake works in this manner, I have a question.

When going down a steep grade, if you have activated your exhaust brake by using the service brakes, can you then toggle you EB switch (usually on the left console) on and off to control your speed? Or if the switch is turned off and back on, do you need to use your service brakes again to activate the EB?

Thanks for any input.
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Old 07-04-2016, 05:47 PM   #2
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SO I ASK YOU... with one of the best features of an exhaust brake, or engine brake is to extend the life of the service brakes... why would you use both... when with planning the exhaust brake will do most of this work for you..

I sold and installed PacBrake for 20 years.. I suggest that you install the brake so that it interfaces with your engine ECM if your engine and transmission supports that function.. the factory ECM and programing will give you the best use and function of use...

The key to use an Exhaust Brake or Engine Brake is to extend and preserve the use of the factory service brakes... thus the factory service brakes stand in reserve when you head down a large hill... this will usually double or triple the life of the service brakes...

I tell most customers to install the brake and interface with the ECM.. if the brake comes on when you don't care for it... either flip the switch and turn it off... or touch the throttle and the brake will turn off...

Also when its interfaced with the engine ECM, most engine ECM's talk to the transmission ECM and will usually downshift to maximize the benefits of the exhaust brake....

I suggest you take it.. use it as its designed and if your not happy bring it back to us and we'll change it... but get used to how it works... in all the years.. we never had a customer bring one back...

If your vehicle's ECM doesn't support an exhaust brake... than wire it to interface so it won't come on if the throttle is open and install either a dash switch, shifter switch, or foot pedal to active the brake as needed....

KRASH... I don't fully understand your questions at the end of the text to address them directly but would be happy to if I better understood what you were asking... Have I helped...
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Old 07-04-2016, 06:24 PM   #3
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Jelag, Perhaps I didnít make myself very clear.

The exhaust brake can be configured in many ways. Mine is currently configured, as many others, to come on when my foot comes of the accelerator pedal if the switch is on. This, as many others have noted, can be a little annoying as the coach immediately starts down shifting and applies the EB, when all a person may want to do is coast, not start slowing down dramatically.

I leave my EB switch on most of the time because I cannot foresee when I may want maximum braking in an emergency stop.

However, it feels pretty uncomfortable if you are going up and down some rolling terrain for example.

So, the latch mode allows for the exhaust brake to only activate when the service brakes are applied, or merely momentarily touched. It will then stay on, (say for long grades), until the accelerator pedal is pushed. But, it will not come back on until the service brakes are used again.

This is all fine, and I believe will work better for me.

The only time I think it might require a lot of back and forth on the pedal is on a grade where no EB make the coach go too fast, and using the EB constantly pulls my speed down too much. In this situation, I currently toggle the EB on/off switch to control may speed, say in 4th gear. In other words, off to gain speed down the hill to a comfortable level, then on, to slow back down to a comfortable level.

With latch mode, I guess briefly touching the accelerator, then going back to the service brake pedal, then back to accelerator accomplishes the same thing as just using my on/off switch does now.

I hope that is a little clearer. I am hoping anyone who has had both modes may understand my question.

Oh, and I never use my service brake when the EB will do the job. I am at max load of 32,000 lbs on the coach, and pull a 10,000 lb trailer always. So, GCVWR of 42,000, and that's max for my coach.
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Old 07-04-2016, 07:24 PM   #4
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Is your rigs exhaust brake set to latch mode?

Quote:
Originally Posted by Krash View Post
...The exhaust brake can be configured in many ways. Mine is currently configured, as many others, to come on when my foot comes of the accelerator pedal if the switch is on. This, as many others have noted, can be a little annoying as the coach immediately starts down shifting and applies the EB, when all a person may want to do is coast, not start slowing down dramatically....

The fix for this is to have your transmission reprogrammed so it does not shift down when the brake engages. I had Allison reprogram our transmission so it stays in whatever gear it's in when the brake comes on. Best mod I have made to our coach.
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Old 07-05-2016, 12:41 AM   #5
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"Krash"......I like the latching method because it can allow you to coast on some grades without turning the EB on and off. I understand your question and I think it's really your choice as to how you function the exhaust brake. You can either switch the brake on and off or tap the brake and throttle. If you turn the switch off, you will have to tap the brakes once you turn it back on, to engage the EB.

As I said, I like the latching method, but never took the time to change to this method on my previous coach. I learned to just feather the throttle to disengage the EB.

I also added the PRXB to my Monaco Diplomat. I was looking for more braking at higher speeds so that I wouldn't get run over by semis on a grade, 50mph - 55mph. I found the PRXB was an improvement, but added nothing at higher speeds. It improves braking when rpms are high, something you don't want at higher speeds. So.....it worked better at 45 mph and under, but there was no improvement above that.....it's just the way an EB works.
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Old 07-05-2016, 05:51 AM   #6
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I am in full agreement with Dutch Star Don for the same reason he gave. Our previous '14 Phaeton had the EB that would activate as soon as you took your foot off the throttle. Because of that, I did not use the Phaeton's EB as much as I should have because I like to plan my stops, and enjoy coasting. Our current Bus has the latching EB setting, and I absolutely love it... in fact, I generally keep it on all the time now since the only time it activates is when I tap the brakes. On mine, it even works with the cruise control without tapping the brake to stop down hill runaway (above the set speed), so latching mode is the way to go for me.
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Old 07-05-2016, 07:18 AM   #7
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I guess it's driver preference. My pacbrake switch is easy to reach (can hit it without looking) and I'd never want it tied to the brake pedal as I want my brakes nice and cool when I really need them.
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Old 07-05-2016, 07:24 AM   #8
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Quote:
Originally Posted by Krash View Post
I am in the process of upgrading to the Pacbrake PRXB and have a question for those who have an exhaust brake that is set to latch mode. I am also considering reprogramming to latch mode. As I understand it, in this mode, the exhaust brake, when switched on, will only activate when the service brakes have been applied. It then releases as soon as the accelerator is depressed and stays off until the service brakes are applied again.
Thanks for any input.
Krash
On my Cat powered coach, (with the Allison MD3060 6 speed and a PacBrake), the Exhaust Brake Mode in the Cruise Control Perimeters of the Cat ECU, (electronic control unit), can be set to any 1 of 3 modes.
1.) MANUAL MODE
2.) LATCH MODE
3.) COAST MODE

Originally mine was set to MANUAL.
In 2012 had a Cat shop change it to LATCH, (which I tried for a year).
In 2013 I had it changed from LATCH MODE to COAST MODE, (which I prefer).

In "COAST MODE", (with the Pacbrake ON/OFF switch in the ON position), the operation of the PacBrake is controlled with the brake pedal and the throttle pedal.

Application of the service brakes turns the PacBrake ON.
Tapping the throttle pedal, (or accelerating), turns The PacBrake OFF.

When the PacBrake ON/OFF switch is in the ON position the PacBrake remains OFF until/unless the service brakes are applied.
When neither pedal is being touched the coach COASTS... (and the cruise control also operates as it should).

Mel
'96 Safari, 146k miles
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Old 07-05-2016, 09:51 AM   #9
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Quote:
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I guess it's driver preference. My pacbrake switch is easy to reach (can hit it without looking) and I'd never want it tied to the brake pedal as I want my brakes nice and cool when I really need them.
Not an agrument, but I met my brake pads never get any warmer than your given the circumstances. A tap of the brake pedal to activate the EB literally means a "tap", the EB will remain activated until the throttle is tapped, or pressed.
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Old 07-05-2016, 10:02 AM   #10
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Not an agrument, but I met my brake pads never get any warmer than your given the circumstances. A tap of the brake pedal to activate the EB literally means a "tap", the EB will remain activated until the throttle is tapped, or pressed.
I didn't catch the "tap the pedal" part...I mistakenly read that the EB was on when you had the brake depressed. That actually sounds like a better solution than I currently have. I wonder if this is something that can be enabled without an ECU (I have a Cummins 8.3C which thank goodness has no computer). MY EB works with a tps that talks to the allison..no computer on the engine.
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Old 07-05-2016, 12:52 PM   #11
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Wow! Thanks for all the great responses. Dutch Star Don, you actually answered my exact question. Thanks!

I guess I will have to use my brake and exhaust pedals to control the speed with just a tap on either. I also have definitely decided to switch to the latch mode if I can find someone to do it. I am mostly in the Denver area, so if anyone knows who can program a 2002 Cummins 330 ISC with Allison to the latch mode in the Denver area, please let me know.

Also, I am upgrading to the PRXB because my original Pacbrake is only developing 18 PSI of back pressure. It seems it has seen its last days. Hoping to get 60 PSI with the new brake.
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Old 07-05-2016, 01:38 PM   #12
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Enjoyed reading your comments. We have a 2005 Safari Cheetah with eng oil pressure zero on 20psi or more boost ,and 40psi or better at cruise or eng brake on or off on descent. I am mech. inclined but don't get this reverse relationship. anybody ever seen this ? 25psi OP at hot idle steady , and 55psi cold start steady. Oil 7/8 full no loss, Hot eng. water 190F stable all the time. OP sending unit 1 yo , terminations clean and tight.
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Old 07-05-2016, 03:23 PM   #13
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Quote:
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I guess I will have to use my brake and exhaust pedals to control the speed with just a tap on either.
What I meant was I will just have to use the service brake and throttle pedals to control speed. Just a tap on each!

Sorry about that, I have exhaust on the brain.
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Old 07-05-2016, 06:41 PM   #14
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Quote:
Originally Posted by mel s View Post
Krash
On my Cat powered coach, (with the Allison MD3060 6 speed and a PacBrake), the Exhaust Brake Mode in the Cruise Control Perimeters of the Cat ECU, (electronic control unit), can be set to any 1 of 3 modes.
1.) MANUAL MODE
2.) LATCH MODE
3.) COAST MODE

Originally mine was set to MANUAL.
In 2012 had a Cat shop change it to LATCH, (which I tried for a year).
In 2013 I had it changed from LATCH MODE to COAST MODE, (which I prefer).

In "COAST MODE", (with the Pacbrake ON/OFF switch in the ON position), the operation of the PacBrake is controlled with the brake pedal and the throttle pedal.

Application of the service brakes turns the PacBrake ON.
Tapping the throttle pedal, (or accelerating), turns The PacBrake OFF.

When the PacBrake ON/OFF switch is in the ON position the PacBrake remains OFF until/unless the service brakes are applied.
When neither pedal is being touched the coach COASTS... (and the cruise control also operates as it should).

Mel
'96 Safari, 146k miles
this is a good info. i have a pacbrake. when it's turned on, the gear will drop from 6 to 4. if i press the fuel pedal, the gear will not change upward, stays in 4. does cummins or chassis shops do the programming so that the gear remains in 6 though the pacbrake is turned on? only then will coast mode make sense i assume.
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