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Old 09-05-2014, 06:57 PM   #15
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[QUOTE=D Lindy;1863187]Question??? Why are you using your engine brake at such slow speeds?????[/QUOT

That's what it's for.....
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Old 09-05-2014, 07:07 PM   #16
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I use mine whenever I am above the threshold for it to engage and work. It's on ALL the time and never gets turned off.

I think it disengages around 15-20 mph.

Obviously if my foot is on the treadle my exhaust brake is disengaged. If my foot is resting on the treadle but no pressure, I am coasting. If my foot is off the treadle the exhaust brake is engaged.

From the PacBrake Internet web site.

PRXB Exhaust Brakes:

Our Pressure Regulated Exhaust Brake (PRXB) offers the highest retarding power for the lowest price available. Although the PRXB’s retarding power is comparable to that of a compression release engine brake, the manufacturing and installation costs are significantly less.

Conventional exhaust brakes experience a reduced exhaust backpressure at low engine speeds, resulting in an unnecessary loss of braking power. Pacbrake’s innovative PRXB addresses this issue with a patented wastegate design that regulates exhaust backpressure as engine speed changes. The valve maintains near constant engine backpressure throughout the entire RPM range, providing maximum exhaust braking power at all times.

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 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.


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Old 09-05-2014, 07:31 PM   #17
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[QUOTE=DMTTRANSPORT;2215834]
Quote:
Originally Posted by D Lindy View Post
Question??? Why are you using your engine brake at such slow speeds?????[/QUOT

That's what it's for.....

If you are referring to my post, an exhaust brake would typically be expected to operate at freeway speeds, but ours has been intermittent as described. Further, using an exhaust brake at any speed, of which I use 'low' which engages fewer cylinders versus 'high', is beneficial in my experience to significantly reduce the need for applying wheel brakes.
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Old 09-05-2014, 07:33 PM   #18
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Richard, I concur with your references on the use of exhaust brakes. As such, I look forward to our throttle pedal assembly being replaced and getting back on the road. Best regards, Chris
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Old 09-05-2014, 08:34 PM   #19
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Chris,

If you have a High/low switch versus an On/Off switch you have an Engine Brake versus an Exhaust Brake. The Engine Brake is far better than any Exhaust Brake made.

HowStuffWorks "How Engine Brakes Work"

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Old 09-05-2014, 08:42 PM   #20
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Chris,

If you have a High/low switch versus an On/Off switch you have an Engine Brake versus an Exhaust Brake. The Engine Brake is far better than any Exhaust Brake made.

HowStuffWorks "How Engine Brakes Work"

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And a Retarder?
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Old 09-05-2014, 09:08 PM   #21
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And a Retarder?
AFAIK only the most expensive RV's may have a retarder. BUT then there are RV companies that will use the term Retarder in place of Engine Brake or Exhaust Brake when it reality they are not TRUE retarders.

Most RV's have only one of three different type of auxiliary braking systems.

Exhaust Brake, Engine Brake and Variable Geometry Turbo/Exhaust Combo Brake.

Here is a good explanation I found on the Internet which I have taken the liberty to copy and paste here.

There are three different "auxiliary" braking systems used on different diesel engines.: Exhaust Brakes, Engine Compression Brakes and Variable Geometry Turbo Brakes.

Exhaust brake: literally a "flap" which closes off exhaust flow just downstream of the turbo in the exhaust system. This causes back pressure (55 PSI on ours) which generates braking power. With the Allison transmission, it is usually tied with downshifting of the transmission to the "pre-selected" gear (usually 2nd or 4th). Think of it as a potato stuffed in the tail pipe.

Engine Compression Brake (aka: Jake brake) The exhaust valves are opened as the pistons reaches TDC (Top Dead Center) on the compression stroke after the engine has done the "work" of compressing about 18 volumes of intake air to 1 volume . If the exhaust were not let escape by the compression brake's opening the exhaust valves (i.e. coasting with brake off), the "compressed air" would mostly be returned as power to the engine forcing the piston back down. With the Jake brake on, the engine works to compress air in the cylinder, then the air is let out. This generates quite a lot more braking force than an exhaust brake. The smallest engines to offer an engine compression brake are the Caterpillar C9 and Cummins ISL.

Variable Geometry Turbo: The vanes reverse or aperture closes (depends on engine manufacturer) to create back pressure with much the same effect as an exhaust brake.

Another alternative used by Foretravel and some over the road busses us TRANSMISSION RETARDERS (see Wayne's link) on their Allison transmissions. Transmissions with retarders will have an "R" suffix such as 4060R. They generate even more braking HP than exhaust or compression brakes, but are more expensive.

Brett Wolfe


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Old 09-05-2014, 09:16 PM   #22
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Originally Posted by Dr4Film View Post
AFAIK only the most expensive RV's may have a retarder. BUT then there are RV companies that will use the term Retarder in place of Engine Brake or Exhaust Brake when it reality they are not TRUE retarders.

Most RV's have only one of three different type of auxiliary braking systems.

Exhaust Brake, Engine Brake and Variable Geometry Turbo/Exhaust Combo Brake.

Here is a good explanation I found on the Internet which I have taken the liberty to copy and paste here.

There are three different "auxiliary" braking systems used on different diesel engines.: Exhaust Brakes, Engine Compression Brakes and Variable Geometry Turbo Brakes.

Exhaust brake: literally a "flap" which closes off exhaust flow just downstream of the turbo in the exhaust system. This causes back pressure (55 PSI on ours) which generates braking power. With the Allison transmission, it is usually tied with downshifting of the transmission to the "pre-selected" gear (usually 2nd or 4th). Think of it as a potato stuffed in the tail pipe.

Engine Compression Brake (aka: Jake brake) The exhaust valves are opened as the pistons reaches TDC (Top Dead Center) on the compression stroke after the engine has done the "work" of compressing about 18 volumes of intake air to 1 volume . If the exhaust were not let escape by the compression brake's opening the exhaust valves (i.e. coasting with brake off), the "compressed air" would mostly be returned as power to the engine forcing the piston back down. With the Jake brake on, the engine works to compress air in the cylinder, then the air is let out. This generates quite a lot more braking force than an exhaust brake. The smallest engines to offer an engine compression brake are the Caterpillar C9 and Cummins ISL.

Variable Geometry Turbo: The vanes reverse or aperture closes (depends on engine manufacturer) to create back pressure with much the same effect as an exhaust brake.

Another alternative used by Foretravel and some over the road busses us TRANSMISSION RETARDERS (see Wayne's link) on their Allison transmissions. Transmissions with retarders will have an "R" suffix such as 4060R. They generate even more braking HP than exhaust or compression brakes, but are more expensive.

Brett Wolfe

Dr4Film ----- Richard
I have both the Retarder and Engine (3 position Jake) on my Truck, use it ALL the time..470,000 on the original service brakes before new linings, service brakes are for stopping, Retarder/Engine brakes are for slowing, holding back weight on a grade etc. In my Coach the Exhaust Brake is left on no matter where I am driving, that's what it's for.
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Old 09-05-2014, 10:11 PM   #23
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I was using the more common term, sorry. The engine braking systems for Cummins M11, M11 Plus, ISM and all N14 engines are branded the C Brake by Jacobs. Earlier production models carry the Jake Brake engine retarder brand name. In addition, the Cummins E Brake by Jacobs is the exhaust brake model for all Cummins 5.9 and 8.3 engines. The new ISL engine is available with either a compression or an exhaust brake. So, yes to be specific our coach has a Freightliner Maxum chassis and an ISL 8.9L 450-hp turbo charged diesel with 2 stage engine compression brake. That said, the primary point was to share an issue related to a bum throttle assembly despite using an engine or exhaust brake. Thanks.
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Old 09-06-2014, 07:59 AM   #24
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Quote:
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I was using the more common term, sorry. The engine braking systems for Cummins M11, M11 Plus, ISM and all N14 engines are branded the C Brake by Jacobs. Earlier production models carry the Jake Brake engine retarder brand name. In addition, the Cummins E Brake by Jacobs is the exhaust brake model for all Cummins 5.9 and 8.3 engines. The new ISL engine is available with either a compression or an exhaust brake. So, yes to be specific our coach has a Freightliner Maxum chassis and an ISL 8.9L 450-hp turbo charged diesel with 2 stage engine compression brake. That said, the primary point was to share an issue related to a bum throttle assembly despite using an engine or exhaust brake. Thanks.
You are right, they do call the Jake a retarder now and the retarder a Brake Saver, when the others started using the term retarder Caterpillar went to the term Brake Saver witch is a true Retarder, the older Cummins (small cam 350 era) had a 3 stage Jake brake (3 different valve boxes) don't understand why they only use a 2 stage now, the single stage works great on ice and snow!
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