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Author Topic: Jake Brake combinations on 8V71  (Read 6647 times)
NCbob
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« on: June 22, 2006, 06:37:29 AM »

Since I have never had or used Jake Brakes before and a set is being installed on my engine I'd like to get some advice on the best way to switch them from you more experienced users, please.  Smiley

I probably will used 12V cube relays to operate them and use whatever switch combinations simply to apply the ground up front.
Is a 2-2 the best combination or 1-3 here in the mountains of NC?  I know a lot of you run the mountain west so your advice will be appreciated as well.

Do you use double switches or an On-Off-On combination in one switch?  And where do you put that Big Red Panic Button in the event they don't work?  Shocked

Thanks,

NCbob
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« Reply #1 on: June 22, 2006, 06:53:17 AM »

Hi NCbob,

There is really no need to use cube relays, since the Jake solenoids draw less than an amp each anyway.  My take is that relays, as reliable as they are, should not be added into a system that is a safety kinda thing, if they're not really necessary.

I'm not understanding exactly what you're meaning by 2-2 or 1-3, but here's what I know:

If you have three banks avaliable, I'd hook two banks to one switch and the last bank to another switch.  That way you can have a choice of 1, 2, or all 3 banks with just two switches.  Of course don't forget to also include switches on your clutch and throttle pedals to disable them when pressed, and if you have  a way to disable them at engine idle, do that too.

I like to put 3 dash lights in- one that signals when the system is "armed" and two more for the jake solenoid circuits themselves.
 The big red panic button gets painted right in the middle of the brake pedal in case they quit on you..  Smiley
« Last Edit: June 22, 2006, 06:55:23 AM by boogiethecat » Logged

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« Reply #2 on: June 22, 2006, 06:55:39 AM »

Hi Bob ...I have 2 switches, one is on/off, the 2nd is high/low (right bank / both banks) they are 2 position switches.
Ron
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DrivingMissLazy
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« Reply #3 on: June 22, 2006, 07:02:50 AM »

I used one, three position, double pole, center off switch. Up, both banks, down, one bank, center all off. I used cube relays also, although it really may not be necessary.
Richard


Since I have never had or used Jake Brakes before and a set is being installed on my engine I'd like to get some advice on the best way to switch them from you more experienced users, please.  Smiley

I probably will used 12V cube relays to operate them and use whatever switch combinations simply to apply the ground up front.
Is a 2-2 the best combination or 1-3 here in the mountains of NC?  I know a lot of you run the mountain west so your advice will be appreciated as well.

Do you use double switches or an On-Off-On combination in one switch?  And where do you put that Big Red Panic Button in the event they don't work?  Shocked

Thanks,

NCbob
« Last Edit: June 22, 2006, 07:05:37 AM by DrivingMissLazy » Logged

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NCbob
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« Reply #4 on: June 22, 2006, 07:41:11 AM »

Perhaps, for the guys who run inline 6's, I should have mentioned that on the 8 we use a total of 4 jakes.  That was the question about the 2- and the 1-3 combination.

Hope that clarifies things.

NCbob
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DrivingMissLazy
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« Reply #5 on: June 22, 2006, 07:47:04 AM »

I was not aware there were four Jake units on a V8. Therefore, if I were doing it again I would follow Boogie's direction and use two switches so that I could have four position Jakes.

Perhaps, for the guys who run inline 6's, I should have mentioned that on the 8 we use a total of 4 jakes.  That was the question about the 2- and the 1-3 combination.

Hope that clarifies things.

NCbob
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« Reply #6 on: June 22, 2006, 07:49:32 AM »

Whether it be a 6V or 8V, the regular way (at least what was done in trucks) is to have them hooked up by cylinder head.  The easiest is to use a two position toggle switch (on a PacBrake, it is the standard switch) that has off on the bottom, then first up position is one cylinder head and the upper position is both cylinder heads.  That way when going down a not to steep hill you can toggle between 1 and both heads without having to go through the off position-although it isn't wrong to use a on-off-on switch.  Relays are not necessary-do don't complicate it. If you have a 6-71N you can choose either 3 or 6 cylinders.  On a Series 60, you have 3 Jake units for the 6 cylinders, so a separate off switch with another three position switch will cover the bases of 2-4-6 cylinder operation.  Also have a micro switch on the accelerator pedal to kill operation when accelerating and if you have a clutch, also on the clutch to kill operation when you push down.  As far as the no Jake at idle, some don't like to give up the fast idle solenoid, since this is where the sensor goes.  If you don't like it, you could keep the fast idle solenoid and just not have the idle position cut off since most 2 strokers don't put out enough oil pressure at idle to activate the Jakes anyway (they work off the oil pressure).  But one of the nice features of the idle cut off solenoid is if you have the Jake on and are at top governed engine speed, if you go down a hill and the engine gets going to fast, the no fuel will activate the Jake telling you that the engine is going to fast.
A basic lesson on how the Jake works.  Each Jake unit sits above the rocker arms-this is why you have to get higher valve covers.  The Jake is hooked into the oil system of the bus.  When activated the solenoid opens the oil pressure side causing the injector plunger to fill up and come down in contact with the unit injector rocker arm.  The exhaust valves still work the same way except now when the injector rocker arm moves, it pumps the oil over to the exhaust valve plunger that opens the exhaust valve at the same time that the injector would normally be firing, so it releases the compressed air of the cylinder at the maximum compression causing a sudden loss in pressure and energy-hence your braking power.
If you have an engine that doesn't have unit injectors (Caterpillar, Mack) what would be the injection plunger will work off the associated exhaust valve of another cylinder, but timed with the exhaust valve of the cylinder that is being exhausted. 
There are other retarders that are more powerful than the Jake brake.  If you have a Caterpillar, they have the BrakeSaver that is between the engine and clutch-it is basically a torque converter in reverse-works well except you have to "dump" it periodically to keep from burning the fluid.  This is similar to the Allison transmission retarder.  Both of these hydraulic retarders are best for stop and go-not for long down grades.  You also have the Telma electric retarder which is mounted on the driveshaft and looks like a disc brake with electro magnetic coils on the outside.  It works like an electric motor in reverse.  Works well-puts out up to 800hp of braking, but is heavy, expensive and requires a couple extra batteries with a big alternator (that most buses already have).  The last is the Mercedes-Benz Series 4000 (12.8 liter up to 450hp and 1550lb/ft torque) system.  It has an extra small valve in the head that is operated by hydraulic (say oil system) power to create a Jake brake type response.  What is unique is the  turbo brake which is a sliding sheeth the slides over the exhaust wheel making the exhaust gases increase in speed to get around the restriction which spools up the turbo with no power to it.  Hence it pumps alot of air into the engine that makes the compression brake pump more-to the tune of close to 600hp worth of braking.
Sorry for the long post-got carried away.  Good Luck, TomC
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« Reply #7 on: June 22, 2006, 08:12:58 AM »

Thanks for a great response, Tom. I learned some things today!
Richard
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NCbob
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« Reply #8 on: June 22, 2006, 09:47:39 AM »

Is there an acho in here, Richard.  I was about to say almost the same.  I'll copy and paste that article for the future.

NCbob
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NCbob
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« Reply #9 on: June 22, 2006, 03:14:15 PM »

Question....If I used a 3 way switch...Off/on/on with the third position to bring in the second bank....in other words, 1st position OFF.
Second position 2 cylinders, 3rd position 4 cylinders...wouldn't I have to bridge the terminals on the back of the switch to keep the first two in there while bringing in the last two banks and might the changing of the switch cause the solenoids to release and have to close again?   Sounds a bit touchy to me.  Might I not be better off to use a second switch to pull in the second bank?

I'm just concerned of asking the solenoids to cycle that many times in a short period of time and end up with a big nothing as a result of my efforts and have to hit that "Big Red Panic Button" on the brake treadle!
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RJ
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« Reply #10 on: June 22, 2006, 11:36:55 PM »

Or, you could follow the factory, like MCI used to do on the MC-8s and 9s when ordered new w/ a Jake:

Click Up = on
Click Down = off

Single toggle, installed at the rear of the LH switch panel.  No relays. 

Virtually idiot-proof for dependability. 

It's either on or it's off.

Simple. . .

KISS!! Shocked
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« Reply #11 on: June 23, 2006, 04:06:17 AM »

First, let me say "we do not have our Jakes installed yet (syill lookin for a deal on fuel lines)". I havge been told by some that have Jakes that they are not as efficient on 2 cycle engines and they always use them all or none. They do not run 1/2 or 1 bank. Perhaps those that have Jakes installed can reply to this post.  Jack
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« Reply #12 on: June 23, 2006, 05:26:16 AM »

Jack, my understanding is directly opposite yours! LOL

I have always heard that the Jake works better on the two stroke than on the four stroke. They get to provide     deceleration on each turn of the crankshaft for each piston, as opposed to every other turn on a four stroke.
 
In my specific case, and based on actual experience, They worked great on my 8V92. I had a three position switch. LO-OFF-HI.

If I were installing one now, on a V-8 I would make it a four selection operation. It would then be easy to keep the engine in the 1800-2200 RPM range. Many, many times I could have used the four different selections as to how much braking I wanted.

Boogie or I ether one, among many on the board, can show you how to wire it up, but since I do not know how to put a drawing on here, I will delegate that task to him. LOL

Based again on actual experience, I totally disagree with Russ's suggestion to just use an ON-OFF switch.

Again, based on actual experience, I would use a set of cube relays in the rear for control. Really makes it easy to troubleshoot problems.
Richard


First, let me say "we do not have our Jakes installed yet (syill lookin for a deal on fuel lines)". I havge been told by some that have Jakes that they are not as efficient on 2 cycle engines and they always use them all or none. They do not run 1/2 or 1 bank. Perhaps those that have Jakes installed can reply to this post.  Jack
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« Reply #13 on: June 23, 2006, 06:35:01 AM »

Richard- also- the 92 series, especially the 8V-92, has very effective jakes.  On my first truck, I could go down the north bound side of the Grape Vine with 80,000lb and maybe tickle just the trailer brakes two or three times.  That was with Delaney and Ahlf in Bakersfield doing a truly precision valve and jake adjustment (I used to drive from L.A. to Bakersfield just to get the tune up done).  On the 71 series it is less effective (function of smaller displacement) and then compound that with mechanics that are maybe scared or just plainly don't know how to adjust the jake right, and you have a not to effective jake.  So in that instance, that's where some get the on-off only idea.  Personally, with my 8V-71, I do use the 1 head position at times, but mostly the 2 head position.  Good Luck, TomC
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« Reply #14 on: June 23, 2006, 08:31:34 AM »

OK. That all makes good sense. One thing I found that a clearance setting the Jakes at 0.055 instead of 0.059 really made a significant difference. BTW, I made this adjustment with the engine hot. I had never really thought about the smaller displacement of the 71 series. I do know that the higher RPM you run it, the better it works. I always tried to keep mine in the 2300+ range, but many are scared to run the engine this fast.
Richard

Richard- also- the 92 series, especially the 8V-92, has very effective jakes.  On my first truck, I could go down the north bound side of the Grape Vine with 80,000lb and maybe tickle just the trailer brakes two or three times.  That was with Delaney and Ahlf in Bakersfield doing a truly precision valve and jake adjustment (I used to drive from L.A. to Bakersfield just to get the tune up done).  On the 71 series it is less effective (function of smaller displacement) and then compound that with mechanics that are maybe scared or just plainly don't know how to adjust the jake right, and you have a not to effective jake.  So in that instance, that's where some get the on-off only idea.  Personally, with my 8V-71, I do use the 1 head position at times, but mostly the 2 head position.  Good Luck, TomC
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