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Old 02-14-2009, 01:40 AM   #21
encantotom
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here is the installation manual for 8v92 jacobs brake.

http://www.jakebrake.com/service/pdf2/003879.pdf

it shows for ddec2, which i have has a connection that goes into the ddec...however i am sure that is not the way that i have it hooked up.

it also shows a high low switch.

so in the non ddec hookup, i dont quite get the connections.

is it one wire for each bank or two wires for each bank? one wire for low and one for high?

tom
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Old 02-14-2009, 02:08 AM   #22
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Its one wire for each bank low is one side high is both......
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Old 02-14-2009, 04:27 AM   #23
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Hi guys,
Back to my discussion with my bus garage friend. He informed me that a jake brake and and exhaust brake are two different systems.
The jake is an internal system that does not cause any damage to the engine with it on all of the time.
The exhaust brake is a system in the exhaust system itself and can cause damage to the turbo and engine if on all of the time. He said that there are not many detroits that he is aware of that have an exhaust system but it something that you should be aware of if you do have one.

This topic sure has generated a lot of interest.

Happy travels, Wally Arntzen
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Old 02-14-2009, 05:29 AM   #24
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Although Jacobs now makes an exhaust brake, a true Jake Brake works by forcing the exhaust valves closed rather than by closing off the exhaust pipe to create back pressure. I have had a coach with an exhaust brake and it would not activate with the cruise control on or anytime the throttle was partially open. The exhaust brake has the advantage of being silent but doesn't have nearly the braking force of an engine brake.

I do find that my Jake Brake and my cruise control do not play well together with my 4 speed non-electronic controlled Allison transmission. I get some bucking when the jake tries to kick in as the cruise control closes the throttle. I may leave the jake on when driving without the cruise control but don't leave it on with the cruise control.
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Old 05-02-2009, 09:22 PM   #25
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anyone know if there is a fuse for the jacobs brake? mine just stoped working and I sure miss it.learning to down shift all over again.
the jack switch lights but no "bark" and no decell.
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Old 05-03-2009, 01:59 AM   #26
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I believe mine is in the passenger kick panel.
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Old 05-03-2009, 02:24 AM   #27
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Yep on my 1992, the fuse is number 16 in the panel in front of the passenger's seat.
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Old 05-03-2009, 03:18 AM   #28
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thanks mine was #16 also and it checks good guess more troubleshooting tomarrow.
warren
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Old 05-03-2009, 05:05 AM   #29
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I suspected that when you indicated that the light was working. If I understand that your coach is a 1985, the Jake is manually controlled rather than being controlled through the DDEC (Detroit Diesel Electronic Control) that was introduced after your engine was built.

There are a couple of possibilities: 1) the wiring from the switch to the Jake has broken or 2) the wiring within the engine has disabled several of the cylinders when the Jake is on. Since you no longer hear the sound of the Jake, I suspect #1. I would first troubleshoot after the switch and light which are obvious getting current and the engine for a short.
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Old 05-06-2009, 05:49 PM   #30
Stick Miller
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Default More questions about Jake Brake

What is the difference between a Jake Brake and a transmission retarder? I've seen a few of these listed, especially on the Barth site and wondered how, and if they work.
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Old 05-06-2009, 06:14 PM   #31
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My 91 has a "brake" pedal on the left side. I don't hear it when it's in use so I'm pretty sure its not a Jake. It feels more like it downshifts and pulls back.
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Old 05-06-2009, 07:29 PM   #32
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There are three types of retarding devices used on diesel power motorhomes; exhaust brakes, Jacobs (Jake) engine brakes, and transmission retarders (there are also electric drive line retarders but I don't know of any motorhome manufacturer installing them).

Exhaust brakes, typically used on coaches with diesel engines less than 10 liters, close off the exhaust pipe when activated to apply back pressure to the engine which helps slow the vehicle. These are typically the least effective of the three types but are the less expensive and can be installed on virtually any diesel engine.

Jacobs (Jake) brakes close down the exhaust valves in the engine and literally turn the engine into a giant air compressor. A lot of restraining horsepower is generated by a Jake brake, enough that in 4 stroke diesel engines, typically a switch is provided to reduce the engine braking from working on all 6 cylinders to working on only 3 cylinders to keep you from slowing down too quickly going downhill. Click Here for drawings of how a Jake works.

A transmission retarder works not on the engine but on the transmission. It reroutes the flow of transmission fluid to a retarder vane provide braking within the transmission itself. These are extremely effective and can generate enormous amounts of retarding horsepower BUT they are VERY expensive and can overheat the transmission quickly under heavy usage so an inexperienced driver can cause damage not possible with either a Jake brake or an exhaust brake as well as potentially lose retarding just as it is needed the most. Transmission retarders are great as long as they are used with a careful eye on the transmission temperature gauge and retarding reduced before tranny temps get out of hand. Foretravel has used Allison transmission retarders for years. Only a few Newells have been built with them and Jimmy and Debbie own one (notice that it was a show coach which frequently incorporate new and interesting features to gauge customer demand).

To make things more confusing Jacobs now markets an exhaust brake but it is not an engine brake.
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Old 05-06-2009, 07:49 PM   #33
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The jake brake uses the high compression of a diesel engine to provide resistance. The way it does that is that the jake actually opens the exhaust valve as the piston reaches the top of the compression stroke and lets the compressed air escape through the exhaust manifold. That is the noise you hear when on the jakes.

A transmission retarder actually has a fluid circulation loop in the transmission that is restricted and acts as a brake. Most transmission retarders have multiple settings depending on how much braking help you want. Almost all of them have a cooling loop for the tranny fluid because it does get very hot. They work very well, and with more adjustability than jakes, but you do have to keep an eye on the transmission temperature.
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Old 05-11-2009, 04:32 PM   #34
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I have begun to use mine in the last 6 months since I now know what it is. We don't have a lot of hills in Alabama but when I pull my racecar trailer I can tell a big difference. I have never noticed my trans temp climbing but again, I'm not coming down steep grades like some of you guys out west.
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Old 05-12-2009, 12:45 AM   #35
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We live in CO and climb and descend 6% grades regularly. The guy that I purchased our coach from said what you go up in, transmission gear, go down in. Seemed pretty simple advice and it has held true for us. We typically climb at 32 mile per hour on 6% grades and descend at the same speed, all in second gear on our Allison tranny. We run with an 8V92 500hp 42'9", towing 3,500 lbs. I keep the Jake Brake on except when on cruise control. It doesn't work when the cruise is on. I simply put my flashers on and don't look in the mirrors when going on these grades, that way I don't see anyone giving me a salute. lol. So far, so good on the hills.

David
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Old 06-08-2009, 10:59 PM   #36
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Page 9.2 of my Owners Manual in the section on the Jacobs Engine Brake is the following:

Quote:
Your Newell is equipped with a Jacobs engine brake which uses engine compression to retard road speed. The Jake brake is activated with a switch labed "Jake" located on the shift console of the dash. When activated, the Jake will function any time the throttle is released while the vehicle is moving unless the cruise control is engaged. The Jake brake is an effective and important safety feature, especially while descending long grades. It reduces the use, and consequently the heat buildup and fading, of the vehicle service brakes.
So the manual for my coach SPECIFICALLY indicates that the Jake does NOT work when the cruise control is in operation.
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Old 06-09-2009, 02:47 AM   #37
Wally Arntzen
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Hi guys, I never turn my jake off and it does work with the cruise control on. When I'm driving on cruise with the jake on and touch the brake the jake activates and I tap the cruise when i'm ready and it reactivates in the cruise mode.
If i'm running in cruise mode and go down a hill the jake activates on its own and the curise reactivates on its own when the speed reaches the running speed that was set prior to entering the hill.
I do not know why mine is different from some of you guy's but maybee yours is electronic and works in a different fashion.
I rember the discussion at Austion where most of the coaches did not work while on cruise.

Thats my story and I am not hallucinating.

Wally
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Old 06-09-2009, 02:56 AM   #38
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as for wally not hallucinating, i cannot confirm that and in fact i think have witnessed it a few times.....

, but the part about the jake brake differences is accurate. mine and michaels didnt work with the cruise on and wallys and clarkes did.

tom
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Old 06-09-2009, 04:06 AM   #39
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The difference is the mechanical engines versus the electronic controlled engines. With the electronic controlled engines, the Jake can be programmed either way but apparently all the DDEC II engines that Newell used were programmed with the cruise overriding the Jake. With DDEC III and above, at least some, if not most, were programmed to have the Jake work with the cruise control engaged.

With the mechanical engines, the cruise and the Jake didn't have a clue what the other system was doing so the Jake is still operational even with the cruise control actually engaged.

Pros and cons either way. Good to have the Jake help slow you down on a short downgrade with the cruise control on but they can fight each other under some conditions.
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Old 06-09-2009, 05:19 AM   #40
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Tom, I spoke to my friend at the bus garage and he informed me that something can be done to make the jake work with the cruise on any of the 8v92's wether its electronic or not. If you check with Leo I bet he will have a way to get it done.
My friend said he thinks that its possible that Newell did that for several years for reasons unknown due to the fact that coaches for some years have it one way and other years a different way.
This has been an extended discussion and maybe we can get cleared up. Michael, maybe if you talk to someone at Newell they can help.
I'm not passing the buck, just that you are an engineer and I would not understand the solution if they gave it to me.
Many things on these coaches I can take on and fix or replace and others, like electronic stuff I leave to guys like you that get it. I am not an electronic guy and doubt that I ever will be, but I can assure you that there is nothing on my coach that does not work and I'm a fanatic about having stuff that does not work.
I hope I did not add any confusion to the discussion.

Wally
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