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Old 06-17-2015, 01:09 AM   #15
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"FIRE UP"......I'm going to burst your bubble. Many of us on the Monaco forum added a foot pedal. I wired it in series to my dash switch. On short descents I used the pedal. On longer ones, I used the dash switch.
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Old 06-17-2015, 09:02 AM   #16
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Quote:
Originally Posted by FIRE UP View Post
ever heard of an "Exhaust Brake Pedal". I'm not saying it can't exist. All I'm saying is, no one has ever mentioned on here or, any other RV forum about having an exhaust brake pedal.
I'm sorry, pedal was the wrong word, it implies a mechanical linkage. I should've said an exhaust brake switch.


pacbrake C11745 Foot Switch


From the pacbrake web site:
Quote:
The convenient floor-mounted ON/OFF switch provides easy access for exhaust brake activation.
HOWEVER, based on later posts it sounds like migkiller might have a transmission retarder? An easy way to tell is to get up to a reasonable speed, and activate that brake switch:
  • An exhaust brake will tend to downshift the transmission, rev up the engine, but not make much significant noise other than the revving engine.
  • An engine (compression) brake will make that braa-aa-aa-aap sound out of the exhaust that is so common when semitrucks are going down a hill or slowing down
  • A transmission retarder will just tend to slow you down without doing either of the above (although I have no personal experience with one, if someone who has one can correct me, please do!)
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Old 06-17-2015, 09:15 AM   #17
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Quote:
Originally Posted by Migkiller View Post
Ok folks please enlighten me on the Pac Brake ? We recently bought our 1st motorhome. Have been checking it out and reading the owners manual,etc. Our coach has a Pac Brake that is a pedal on the left side of the drivers floorboard. So this being a form of engine exhaust brake, do you just push on the pedal when going down hill, after letting up on the throttle first ? Do you hold the Pac pedal down until you no longer need the exhaust brake action ?
Thanks for any help !
Chuck
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See: Exhaust Brake Use
Or Google "how to use an exhaust brake".
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Old 06-17-2015, 09:22 AM   #18
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Quote:
Originally Posted by ShapeShifter View Post
I'm sorry, pedal was the wrong word, it implies a mechanical linkage. I should've said an exhaust brake switch.


pacbrake C11745 Foot Switch


From the pacbrake web site:


HOWEVER, based on later posts it sounds like migkiller might have a transmission retarder? An easy way to tell is to get up to a reasonable speed, and activate that brake switch:
  • An exhaust brake will tend to downshift the transmission, rev up the engine, but not make much significant noise other than the revving engine.
  • An engine (compression) brake will make that braa-aa-aa-aap sound out of the exhaust that is so common when semitrucks are going down a hill or slowing down
  • A transmission retarder will just tend to slow you down without doing either of the above (although I have no personal experience with one, if someone who has one can correct me, please do!)
That photo is what i have...expect it is chrome. I do think you have hit the nail so to speak ! Yes...it is wired to the transmission and brake lights through relays and also the Eaton ABS relay box. The coach is in Tenn. at our other home as i live near Chicago because i am still WORKING.... Anyhow, i will take it out and test it on the hilly and one 7% grade near the house. Seems like these engine brakes are not a basic one size fits all...but rather whatever the manufacture wanted to install.

Thanks everyone for their input...mystery solved !!
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Old 06-17-2015, 09:35 AM   #19
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I have written to PacBrake and asked for info on how their system works. Will post their reply when i get it !
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Old 06-17-2015, 09:48 AM   #20
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In response to the OP's question, I use Pacbrake synthetic lube several times a year. Haven't had any issues to date.
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Old 06-17-2015, 09:56 AM   #21
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Quote:
Originally Posted by Dutch Star Don View Post
I made lubing the PacBrake part of my yearly oil change and service so I wouldn't forget.


"Migkiller"......You need to find out what you have. I'm guessing it's and Engine Brake, not Exhaust Brake. An exhaust brake blocks off the exhaust forcing the engine to build up pressure and slow the coach down. An engine brake closes off the engine valves causing backed up pressure. Engine brakes are more effective than exhaust brakes, usually come with two speeds and are installed in coaches as they typically reach a certain price level like your Dynasty.
A valve train Engine brake/retarder does NOT hold the valves closed, It holds the Exhaust Valves OPEN..
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Old 06-17-2015, 11:24 AM   #22
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Quote:
Originally Posted by DMTTRANSPORT View Post
A valve train Engine brake/retarder does NOT hold the valves closed, It holds the Exhaust Valves OPEN..
Actually, it operates the exhaust valve almost normally, with one slight change:
  • Intake stroke: intake valve open, exhaust closed
  • Compression stroke: both valves closed
  • Power stroke: normally the exhaust valve would be closed while fuel is injected and burned, but the engine brake opens the exhaust valve at this point
  • Exhaust stroke: intake closed, exhaust open
The idea is that it takes in air, then closes the valves while it compresses that air. The act of compression takes energy, which slows down the coach. Then, right around top dead center, the exhaust valve opens. This lets out the compressed air, causing the distinctive sound, and prevents the compressed air from acting like a spring and returning the energy to the piston when it expands.

So the valves are neither held closed nor open, they are both opening and closing on each stroke, it's just that the exhaust valve timing has been changed so that the engine absorbs energy by compressing air, and then releases that energy to the air through the exhaust.
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Old 06-17-2015, 12:28 PM   #23
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Quote:
Originally Posted by Dutch Star Don View Post
"FIRE UP"......I'm going to burst your bubble. Many of us on the Monaco forum added a foot pedal. I wired it in series to my dash switch. On short descents I used the pedal. On longer ones, I used the dash switch.
Don,
No bubble burst here. There are "MacGuyvers" all over this RV world, myself included. If you've "added" something to assist in your coach operation that helps you accomplish your goal, that's great. And you state that MANY have added a foot pedal for the same operational tactics. Well, again, if it works, outstanding. My statements were primarily directed at what, if any, FACTORY "Third Pedal" installments and, WHAT, EXACTLY do they operate? As stated, my only experience with a THIRD pedal in any diesel (mostly fire trucks) and I think maybe one test drive in a coach that I cannot remember year/make/model/engine, is that it is a pedal to control a TRANSMISSION RETARDER.

But, if there's been ever been FACTORY installed third pedals to control either the EXHAUST BRAKE or, a COMRESSION BRAKE, I've just never seen or, been in any coach that had one.

One of the folks we occasionally travel with has an '01 Itasca Horizon 36DL with the 3126 CAT 330 and he also added one of those "floor buttons" to operate his EXHAUST brake.

To the OP here. Sorry for any deviation of the original topic. Sometimes this happens. It's not intentional, about 99.9% of the time, it's by accident, one thing leads to another and so on. As for lubing our Pac/Exhaust brake, yep, purchased that same little tube from Ebay and, have taken the time to lube it at least twice in the last year. I know those components DO get severely warm, I'm suspecting that there is at least some of that lube that remains in place to aid in the ease of operation of those pivoting points.

Many of us think that just because those components in that area i.e. all exhaust/turbo/pack brake etc. parts get extremely hot that, there's nothing on this planet that can withstand those temps and remain in place as a lubricant. Well, I don't have any proof that it does, or doesn't. All I can do is use it as directed and, hope it preserves some free movement in all those pivot points.
Scott
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Old 06-17-2015, 01:11 PM   #24
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Quote:
Originally Posted by ShapeShifter View Post
Actually, it operates the exhaust valve almost normally, with one slight change:
  • Intake stroke: intake valve open, exhaust closed
  • Compression stroke: both valves closed
  • Power stroke: normally the exhaust valve would be closed while fuel is injected and burned, but the engine brake opens the exhaust valve at this point
  • Exhaust stroke: intake closed, exhaust open
The idea is that it takes in air, then closes the valves while it compresses that air. The act of compression takes energy, which slows down the coach. Then, right around top dead center, the exhaust valve opens. This lets out the compressed air, causing the distinctive sound, and prevents the compressed air from acting like a spring and returning the energy to the piston when it expands.

So the valves are neither held closed nor open, they are both opening and closing on each stroke, it's just that the exhaust valve timing has been changed so that the engine absorbs energy by compressing air, and then releases that energy to the air through the exhaust.
So is this different than stating the Pac Brake/Jacobs Brake when operating holds the "EXHAUST VALVES" open....
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Old 06-17-2015, 03:34 PM   #25
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Quote:
Originally Posted by FIRE UP View Post
But, if there's been ever been FACTORY installed third pedals to control either the EXHAUST BRAKE or, a COMRESSION BRAKE, I've just never seen or, been in any coach that had one.
I've heard so many people mention exhaust brake foot switches that I assumed some come from the factory that way. I can't imagine that every single one of them are factory add-ons, especially since I've seen posts from people asking what is that switch? If they have to ask, they obviously didn't add the switch themselves. So I assumed at least some came from the factory, but you know what happens when one assumes...

Quote:
Originally Posted by DMTTRANSPORT View Post
So is this different than stating the Pac Brake/Jacobs Brake when operating holds the "EXHAUST VALVES" open....
Maybe it's just semantics? When I see the word "holds" in your statement, to me that means they are opened up and stay open. Of course, that's not the case: they are still opening and closing, just with different timing to cause the braking action.
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Old 06-17-2015, 04:07 PM   #26
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Quote:
Originally Posted by DMTTRANSPORT View Post
So is this different than stating the Pac Brake/Jacobs Brake when operating holds the "EXHAUST VALVES" open....
DMTTRANSPORT

A PacBrake brand/make of "exhaust brake".
Exhaust brakes are installed in the exhaust system.
There are other brands/makers of exhaust brakes including Jacobs.

"Compression brakes", (aka: engine brakes), although they accomplish similar auxiliary braking, do the braking differently.
Compression Brakes, (which are internal to the engine), are often called Jake Brakes or Jacobs Brakes.

See: Exhaust Brake Vs. Jake Brake | eHow

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Old 06-17-2015, 04:53 PM   #27
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Quote:
Originally Posted by mel s View Post
A PacBrake brand/make of "exhaust brake".
While we're on the topic of semantics...

PacBrake is a manufacturer of both exhaust brakes and compression brakes. But they are best known for their exhaust brakes, so that's what people think of when they hear the name.

Jacobs also makes both exhaust brakes and compression brakes. But they are primarily known for their compression brakes, which are often referred to as Jake brakes (Jake for Jacobs.)

So while a PacBrake is usually an exhaust brake, and a Jake brake is usually an engine brake, there are exceptions, as is so often the case in this world.
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Old 06-17-2015, 05:08 PM   #28
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Originally Posted by ShapeShifter View Post
While we're on the topic of semantics...

PacBrake is a manufacturer of both exhaust brakes and compression brakes. But they are best known for their exhaust brakes, so that's what people think of when they hear the name.

Jacobs also makes both exhaust brakes and compression brakes. But they are primarily known for their compression brakes, which are often referred to as Jake brakes (Jake for Jacobs.)

So while a PacBrake is usually an exhaust brake, and a Jake brake is usually an engine brake, there are exceptions, as is so often the case in this world.

Mel
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