Educate me-exhaust brake

[turbojet]

I know enough about one to be dangerous. Are they primarily for slowing down quicker once you let off the pedal and to help on downgrades? How exactly does it work?

 

[Dean Upson]

The ebrake is just a valve that is mounted in back of the turbo. When you let off on the throttle, the valve closes and the resulting compression slows the engine and thus the drive train down. The higher your rpms are the more effective the braking. Its like stuffing a potato in the exhaust pipe. They save on your service brakes. In my opinion you really don't need one if you are not towing or carrying a heavy load. Normally you would turn it off if road conditions are slippery. You can find out quite a bit more on the Cummins or Jacobs Brake sites.



Dean

 

[Wiredawg]

Yep!

Turbojet:



The exhaust brake assists in slowing down grades without using brakes and for coming to a stop, downshifting thru the gears.



The exhaust brake creates back pressure in the engine, much the same way a butterfly on a throtle body does in a gas engine. You basically install a butterfly (the exhaust brake) in your exhaust system, the most common types replcing the elbow behind your turbo. They are vacuum operated thru an electric silinoid. The silinoid can be activated by your ECM and a switch in you truck (Pacbrake) or thru an accelerator pedal switch and shifter switch (BD).



You want to be careful using it on slippery surfaces. I wouldn't use it in snow and ice.



The 03s don't have a vacuum pump, so you have to buy a kit that includes one (Jacobs).



I think I covered it. hope this helps

 

[turbojet]

Thanks Dean and Dawg, that clears it up for me.

 

[Carlton Bale]

There is an additonal feature of the Cummins/Jacobs exhaust brake that is new for '03 and hasn't been mentioned. Since it is controlled by the ECM (engine control module), the exhaust brake interacts with the ECM-controlled cruise control. If you top a hill with the curise set to 65 mph and start to speed-up when going down the hill, the brake will cycle on and off to try to keep vehicle speed between approximately 65 and 68 mph.



Keep in mind, the brake switch has to be in the ON position! Also, it may be necessary to downshift if you're pulling a heavy load. As Dean stated, the higher the engine speed, the more the braking horsepower.

 

[dtrevathan]

Is the Cummins/Jacobs exhaust brake an item that you order with the truck or is this an after market part? I plan on ordering a new 3500 HO, 6 speed in about a month. I’ll only pull a 8,000 pound trailer for the first 3 years, but will upgrade to a fifth wheel in the 14000 pound range after that.



Any ideas?

 

[pstillo]

How does exhaust brake sound on the HO?

 

[Carlton Bale]

Originally posted by dtrevathan

Is the Cummins/Jacobs exhaust brake an item that you order with the truck or is this an after market part? I plan on ordering a new 3500 HO, 6 speed in about a month. I’ll only pull a 8,000 pound trailer for the first 3 years, but will upgrade to a fifth wheel in the 14000 pound range after that.

The exhaust brake can be ordered as a dealer-installed option with your new truck, but not as a factory-installed option. It's my understanding that dealer-installed options can be included with truck financing.



For the 14000 pound trailer, I would definitely want an exhaust brake. The more you drive over hills/mountains, the greater your need for an exhasut brake would be, even for lower trailer weights. 'm sure other owners can give more specific expamples to help you make your decision.

 

[Carlton Bale]

Originally posted by pstillo

How does exhaust brake sound on the HO?

The brake acutally sounds more-or-less the same for the both engine horsepower configurations. It is very similar to previous exhaust brakes on previous model years if you have heard them.

 

[kbarlow]

Hi Carlton Bale,



Thank you for joining the TDR.



Will the new E-Brake be shipped with a boss for a pyro install? If yes, which size is recommended? If no, will later models have it?



Thank you

Ken

 

[Carlton Bale]

Originally posted by kbarlow

Will the new E-Brake be shipped with a boss for a pyro install? If yes, which size is recommended? If no, will later models have it?

Ken,



The new brake does not have a port for a pyro. If we revise the brake in the future, we will take a pyro port into consideration -- it's something we'd never thought of adding before. As long as the cost impact is minimal, it shouldn't be hard to do.



For the existing brake, if you decide to drill and tap a hole for a pyro, you should be able to find a flat area that doesn't interfere with the butterfly movement.

 

[kbarlow]

Thanks Carlton,



One more question, if I may, regarding heat buildup. On a long downhill with a heavy trailer pushing, is heat a concern and how is it controlled?



Thank you Ken

 

[Carlton Bale]

Originally posted by kbarlow

One more question, if I may, regarding heat build-up. On a long downhill with a heavy trailer pushing, is heat a concern and how is it controlled?

Heat is not a concern for the exhaust brake because the ECM stops injecting fuel before the brake is activated. Because there is no fuel being injected, cylinder temperatures are much lower.



The air in each cylinder is still compressed and expanded before going into the exhaust manifold when the brake is on. This does heat the air to temperatures well above ambient temperature. However, this cylinder temperature is still lower than it would be if combustion were occurring.



When the brake is on, airflow through the engine decreases because the brake keeps some air in the cylinder during the exhaust stoke (this is what slows the engine. ) Coolant flow remains unchanged, easily removing any heat caused by braking.



Let me know if you have any other questions.

 

[kbarlow]

Thank you Carlton



Ken

 

[Blue Goat]

Carlton



Please explan the interaction of the two (2) ECM pins used for the exhaust brake operation.

 

[Carlton Bale]

It's pretty straight-forward. One wire tells the ECM whether or not to engage the brake when a braking condition occurs. The other wire tells the brake to actuate when all conditions-for-braking are met, including the cab switch being in the proper position. (FYI, the signals used by the ECM are a proprietary TTL-type. )

 

[Steve G]

Carlton,

I talked to DC today and was told that they have heard nothing with regards to the E-Brake application for the new 48RE. Also called Cummins and found out that the E-Brake kit is $1276. 00 and labor is $999. 95. Is this new kit that labor intensive? Seems at that price they do not want to do this.



Steve

 

[Carlton Bale]

Originally posted by Steve G

I talked to DC today and was told that they have heard nothing with regards to the E-Brake application for the new 48RE.

It is up to DC to test the brake with the 48RE transmission and to make the compatibility announcement. This testing is planned and may already br in process. Unfortunately, that's all the info I have right now. I will post as soon as I have anything official from DC.

Originally posted by Steve G

Also called Cummins and found out that the E-Brake kit is $1276. 00 and labor is $999. 95. Is this new kit that labor intensive? Seems at that price they do not want to do this.

You can view the installation manual on the Jacobs website to see what steps are involved and judge for yourself. Installing the vacuum pump is an additional installation step. Each dealer/distributor determines their own pricing for the brake and the installation.

 

[Dean Upson]

I read the installation manual and I think a quy could make a pretty good living installing them for a thousand bucks a whack! That is a nuts price. If the garage was getting $70/hr that would be nearly 2 days work for one man. No way!



Dean

 

[Casey Balvert]

Now I don't build rockets for a living but I was a licenced Class A mechanic in Ontario for a number of years before going into EMS. I have read that installation manual as well and I figured that if one studied that manual real well first, maybe four hours of honest work tops. At a thousand bucks a crack maybe I should have stayed in the business. I am all for a shop making a reasonable profit but I agree, that seems excessive. Dean, drive on over, I'll put it in for ya and buy the coffee to boot.



Happy Holidays,

Casey