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Old 12-11-2013, 11:15 PM   #29
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Quote:
Originally Posted by 1985 Bounder View Post

_"These(exhaust) brakes are also recommended to be left on so there will be there when needed and so the flapper in the brake will actuate every time you drive to keep it from sticking due to exhaust residue."
Would you please identify exactly which companies make that recommendation? I know Winnebago and Cummins do not.
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Old 12-12-2013, 07:55 AM   #30
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Based on what I see in my town, you are supposed to remove your muffler and then ride the engine brake all the way down the not very steep hill in our town. You should try to do this late at night or early in the morning. Just ignore the "No Engine Brakes" sign - it's never enforced.
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Old 12-12-2013, 08:36 AM   #31
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Ok looking at it; Cat 7.2 330hp

It says Jake like piston.
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Old 12-12-2013, 08:55 AM   #32
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Quote:
Originally Posted by Ray,IN View Post

Would you please identify exactly which companies make that recommendation? I know Winnebago and Cummins do not.
I know PacBrake makes that recommendation and I do also. But each RV owner has the right to choose how they want to drive their rig.

There has been much discussion and many threads posted on this topic. Bottom-line it's up to the owner/driver.

Why would Cummins not recommend leaving the Exhaust Brake Switch on which BTW does NOT mean that the Exhaust Brake is active ALL the time? It would be difficult to drive a rig that had the Exhaust Brake flapper closed all the time.

Here's a cut & paste from their web site and the link to the page.

"Direct Turbo Mount PRXB Exhaust BrakeInLineMount PRXB Exhaust Brake
Controlled by a master ON/OFF switch, Pacbrake’s exhaust brakes provide whisper quiet supplemental braking that allows service brakes to be used much less, ultimately saving you money. They have the ability to be left on all the time, making it ideal for in-city driving or for steep, downhill grades. This product pays for itself as less wear on the brake pads means fewer brake jobs."


Diesel Exhaust Brakes and Retarders | Duramax, Cummins Turbo Diesel, Powerstroke Brakes

I know that the Spartan people DON'T recommend it. People who own a Spartan chassis should listed to them. BUT I would like to know WHY Spartan's reasons behind their statement.

The Monaco S-Chassis is so strong and unique that I am guessing it doesn't matter to them as they haven't stated any such thing about the use of Exhaust Brakes.

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Old 12-12-2013, 10:30 AM   #33
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Ray, I don't know what the MH manufacturers tell their owners. The recommendations I was talking about are from the brake manufacturers.

When I said the brake was left on all the time, I was referring to the dash switch. The engine brake will never actuate during a fueling condition barring a malfunction. The exhaust brake however does in some instances actuate during fueling, such as when it is being used to speed up the warm up process. Sorry if my language was not clear on that.
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Old 12-12-2013, 10:35 AM   #34
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Explain this method?

Quote:
Originally Posted by 1985 Bounder View Post
Ray, I don't know what the MH manufacturers tell their owners. The recommendations I was talking about are from the brake manufacturers.

When I said the brake was left on all the time, I was referring to the dash switch. The engine brake will never actuate during a fueling condition barring a malfunction. The exhaust brake however does in some instances actuate during fueling, such as when it is being used to speed up the warm up process. Sorry if my language was not clear on that.
Can you explian the "warm up" method ? I never heard of such a thing........
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Old 12-12-2013, 10:47 AM   #35
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A signal from the engine temperature is wired into the control system of the exhaust braking system. Until the engine temperature reaches a predetermine temperature the brake will stay actuated. For those that just fire the engine and go, they will notice a reduction in power until the engine temperature comes up. The earlier Powerstrokes in the Ford pickups were like this from the factory. Jacobs and BD were all able to be set up in this manner.
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Old 12-12-2013, 01:20 PM   #36
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Quote:
Originally Posted by 1985 Bounder View Post
Ray, I don't know what the MH manufacturers tell their owners. The recommendations I was talking about are from the brake manufacturers. When I said the brake was left on all the time, I was referring to the dash switch. The engine brake will never actuate during a fueling condition barring a malfunction. The exhaust brake however does in some instances actuate during fueling, such as when it is being used to speed up the warm up process. Sorry if my language was not clear on that.
It's really hard to find any definitive statement in print about compression brake operation. I found this excerpt from a Manuel on line:

Jacobs Engine Brake Operation
The Jacobs Engine Brake depends on the free flow of
engine oil for operation, so be sure to let the engine reach full operating temperature before switching on the engine brake. Normally, the engine brake is then left in the “On” position whenever you are driving. The exception is when roads are slippery due to bad weather conditions. Refer to the section entitled “Slippery Pavement” for specific operating instructions.

Here is the PDF file:

http://www.blackwoodfire.org/docs/dr...Ops-manual.pdf

I think lawyers may have more influence over what you find from various chassis builders and/or motorhome builders than anything else. I've heard the argument that Spartan supposedly makes about the service brakes getting glazed from light use and I personally don't give it any credence. I have now driven my full time coach for 7 years and about 60 k miles. The coach is 11 years old now with 100k on the clock. My service brakes still have a great deal of pad thickness and they stop great. I use my Jake almost every time I wish to slow my coach. If I had a Spartan Chassis, I would closely question them concerning this position. If I attend the FMCA Perry event I may go to a Spartan seminar.

This is certainly a personal individual driver issue, but my feeling is that if I were to limit the use of my Jake, I would not be using the tools at my disposal to best advantage.

Opinions will almost certainly vary.
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Old 12-12-2013, 02:23 PM   #37
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X-2 Steve!

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Old 12-12-2013, 06:37 PM   #38
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I wonder how many owners that have experienced exhaust manifold cracking run the exhaust brake switch on continually? Cummins says the manifolds crack from excessive heat, which is one result(higher manifold temp) of exhaust brake overuse.
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Old 12-12-2013, 06:40 PM   #39
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We were told at the Spartan Chassis owners training course last year to avoid using the jake brake constantly or we might experience problems with lack of use on service brakes. They said the service brakes need to be used and given the low mileage on motor homes we should use jake brake genedally only in mountainous areas. I dont recall the technical reasoning but that is what they told us.
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Old 12-12-2013, 06:51 PM   #40
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If that was truly the case then I had better stop using my expensive Banks Power Pack kit that was recently installed otherwise it may crack my Exhaust Manifold.

My EGT sensor which has been installed in the Exhaust Manifold can get to 1350F before the computer throttles back the juice.

I would think that if anything, the Banks System probably gets the Exhaust Manifold a lot hotter than any PacBrake Exhaust brake use. Although what goes up must come down so the Exhaust Manifold will get a double whammy on any significant grade and I have certainly have done my share of them.

Although I have read that if the exhaust gasses get too hot the pistons start to melt. Not sure about the Exhaust Manifolds but maybe those get cracked due to negligence of some sort.

Do you have any resources to look up?

I'll do some rooting around the Cummins Engine web sites to see what they have to say.

Thanks for the warning.

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Old 12-12-2013, 07:07 PM   #41
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I have no references. Just memory from an in class session in Charlotte. Up to then I had been using Jake brake 100% of the time. The guys at Spartan say we should not. I assume/hope they know what they are talking about.
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Old 12-12-2013, 07:43 PM   #42
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Well, after looking around the Cummins Engine web site I wasn't able to find anything about not using your Exhaust Brake too much for fear of cracking an Exhaust Manifold.

However, I did find a very good article written by the Gale Banks Engineering department regarding the use of Exhaust Brakes and how they actually work.

Here's a clip from that article but I have also listed the link below for people who want to read the entire article which is well worth the time.

BTW, Gale Banks is one of the leading engineers who knows Cummins Engines inside and out.

To understand how an exhaust brake works, we first need to understand how a diesel makes power – or more specifically, torque. After a diesel has ingested air on the intake stroke and compressed it on the compression stroke, fuel is injected directly into the cylinder. The heat of compression ignites the fuel, and combustion occurs releasing more heat to increase the pressure of the compressed air in the cylinder. This pressure then pushes the piston down on the power stroke to generate torque on the crankshaft. The more fuel that is burned, the more heat that is generated and the greater the pressure acting on the piston. And of course, more pressure means more torque.

Now let’s look at the exhaust stroke for our diesel. Normally the piston just pushes the exhaust out past the open exhaust valve, and through the remaining exhaust conduits until the exhaust gases reach the atmosphere. When the driver releases the fuel throttle, almost no fuel is being injected into the cylinders, so there is very little more than the air that was initially ingested on the intake stroke to be expelled on the exhaust stroke. In fact, if we put a pressure sensor in the exhaust system, we’d find that the exhaust pressure is very close to zero during deceleration because the exhaust system can easily handle the exhaust flow. This means the pressure in the cylinder is also very close to zero on the exhaust stroke under these deceleration conditions, and zero pressure on the piston top during the exhaust stroke offers no resistance to the piston as it rises.

Now let’s add an exhaust brake downstream from the turbocharger. An exhaust brake is basically a valve that can be closed in the exhaust system to restrict (but not totally close off) exhaust flow. This valve closes when the driver releases the fuel throttle. Under these conditions, the exhaust flow from the cylinders is bottlenecked and rapidly builds pressure in the exhaust system upstream from the exhaust brake. Depending on engine speed, this pressure can easily reach up to 60 PSI maximum working pressure. Maximum working pressure is limited as part of the design of an exhaust brake. In this example, that same 60 PSI also remains in the cylinder for the entire exhaust stroke (exhaust valve open) and exerts 60 PSI on the piston top to resist its upward movement. We can think of this as negative torque, slowing the engine for a braking effect. We might even think of this as just the opposite of the power stroke, and in effect, it is. Thus, you can see that simply restricting the exhaust flow can generate substantial braking. That’s what makes an exhaust brake so effective.


Banks Power | How An Exhaust Brake Works


So the important information that I came away with after reading the entire article is that when an Exhaust Brake has been activated there is hardly any combustion going on inside the engine as there's no fuel being delivered to the pistons. Therefore any HEAT factor from having the Exhaust Brake on is minimal.

You cannot have POWER coming from the engine at the SAME time as Exhaust Compression. It's either one or the other but not BOTH at the same time.

So I would venture to say that Cummins is correct in that excessive heat will crack your Exhaust Manifold. HOWEVER, it will most likely happen on the way up the mountain versus on the way down using your Exhaust Brake.

So that's my story and I'm sticking to it but I am open to other opinions however list data not hearsay or I was told by a someone, etc.

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