Engine brake

Topic: Engine brake (Read 732 times) previous topic - next topic

Engine brake

October 25, 2015, 03:05:02 pm

Has anyone had any experience in using a Jacobs engine brake on a M11?

Future project to maybe add one on our coach.

Three coach bucks or so.

I have has my warning buzzer come on twice in major hills. Went off in two miles so no big deal.

If on max I think it would be around the third position on the joystick.

Like it to run on cruise like my retarder

I have heard there were a few dual installs done

Retarder is fairly abrupt at low speeds. I wonder if the jake would be less aggressive?

Re: Engine brake

Reply #1 – October 25, 2015, 03:34:17 pm

I've got a Jake on my M11, Bob. It's a two speed (originally a one speed) and preselects 5th gear (originally 4th). Works very well. I have also had a retarder on an M11. I drove it down some pretty steep western grades but did not experience any transmission overheating. I was always careful to keep the revs up though. I wonder if you have something else going on.

Regarding the abruptness, that's why I changed my pre-select from 4th to 5th. I drive with "mode" on and do the shifting manually.

Oh, here's what the Jake looks like on my M11. Took this photo when the German was adjusting my valves and injectors. The other photo shows my Jake switch with is not the original.
jor

Re: Engine brake

Reply #2 – October 25, 2015, 03:46:31 pm

Quote from: jor – October 25, 2015, 03:34:17 pm

I've got a Jake on my M11, Bob. It's a two speed (originally a one speed) and preselects 5th gear (originally 4th). Works very well. I have also had a retarder on an M11. I drove it down some pretty steep western grades but did not experience any transmission overheating. I was always careful to keep the revs up though. I wonder if you have something else going on.

Regarding the abruptness, that's why I changed my pre-select from 4th to 5th. I drive with "mode" on and do the shifting manually.

Oh, here's what the Jake looks like on my M11. Took this photo when the German was adjusting my valves and injectors. The other photo shows my Jake switch with is not the original.
jor

Jake only on this coach?

Re: Engine brake

Reply #3 – October 25, 2015, 11:16:38 pm

Mine is wired as a one speed too. Jake only (trans retarder was still optional in 95). I bought the same hi lo switch. Some day I'll have mine rewired too.
Jake does a great job in the mountains

Re: Engine brake

Reply #4 – October 25, 2015, 11:38:08 pm

Quote

Jake only on this coach?

Just like Dave's - only the Jake. For descents it is very effective with no transmission heating of course. Other than being smoother and incremental I don't think the retarder is any better at holding us back while descending. Where the retarder really shines though is in emergency braking. The Jake is little help but that retarder full on is something else!
jor

Re: Engine brake

Reply #5 – October 26, 2015, 01:35:34 am

JAKE only on mine, works very well.

Re: Engine brake

Reply #6 – October 26, 2015, 02:25:04 am

Our coach has side by side RETARD switches as well. Is this the same config as yours? Center (right) switch pre-selects 4th gear when depressed. Can you direct me to info on proper use and how to try the option of going to 5th gear when selected? Thanks. Paul

Re: Engine brake

Reply #7 – October 26, 2015, 09:41:27 am

Quote

Our coach has side by side RETARD switches as well. Is this the same config as yours?

Sounds like the same setup as my 95. The left switch enables the system and the right allows you to select high or low braking. You can leave the left one on if you like.

I don't know about a single source tutorial but there is lots of discussion on proper engine and exhaust braking technique over at rv.net and elsewhere. I changed from a one speed to a two speed and from 4th to 5th pre-select to give me more versatility. For example, on a long and easy hill I am in 5th with the Jake on low (3 cylinders). When the hill gets steep I can manually shift into 4th and leave the Jake on low or maybe leave it in 5th and select high on the Jake. Another example: Coming off the freeway into a rest area, I use high and manually downshift for max braking. I think the two speed setup along with the 5th pre-select and using the "mode" on the Allison gives you performance that comes close to what you get with the Allison retarder. Of course, like I said above, no comparison in emergency stops.
jor

Re: Engine brake

Reply #8 – October 26, 2015, 10:02:18 am

Hey, jor.

I tried to send you a PM but your inbox is full.

best, paul

Re: Engine brake

Reply #9 – October 26, 2015, 10:49:25 am

Quote from: jor – October 26, 2015, 09:41:27 am

Of course, like I said above, no comparison in emergency stops.

Unless the air brakes need maintenance, you should be able to lock up all six with a max pedal effort in an emergency. In this case, all attention should be on the road and any possible evasive options you may have.

The use of a transmission retarder in wet or icy conditions along with maximum service brake application can have unintended consequences. Especially true downhill. Not much stopping the rear when it starts to come around and with a push from the toad...

Bob,

The Jake gives a mild braking effort in the higher gears. Much more at lower speed/gears along with high RPM. Don't think I would ever say it is abrupt. Works a little better with four cycles than two cycles.

Pierce

Re: Engine brake

Reply #10 – October 26, 2015, 11:08:22 am

Quote

Unless the air brakes need maintenance, you should be able to lock up all six with a max pedal effort in an emergency.

ABS on both rigs. No lockup.

I speak from personal experience re the emergency stops as I had one in my present coach that has a Jake and one in my previous coach that had the Allison retarder. The brakes were in excellent condition on both coaches. In the Jake coach, I slowed quickly but would not have stopped; the ABS allowed me to steer around (stalled vehicle in the middle of the freeway). In the retarder equipped coach, that baby stopped.
jor

Re: Engine brake

Reply #11 – October 26, 2015, 11:15:38 am

I've had the same experience.

When I said STOP!

It stopped.

best, paul

Quote

I speak from personal experience re the emergency stops as I had one in my present coach that has a Jake and one in my previous coach that had the Allison retarder. The brakes were in excellent condition on both coaches.
In the Jake coach, I slowed quickly but would not have stopped; the ABS allowed me to steer around (stalled vehicle in the middle of the freeway).
In the retarder equipped coach, that baby stopped.

Re: Engine brake

Reply #12 – October 26, 2015, 11:35:26 am

A lot of us don't have ABS. Sure is nice. In Yellowstone, several elk suddenly came out from the trees. I hit the brakes (Jake switched off), threw Gaylie from the stove to the front seat and smoked all six. Missed the elk. Might have stopped a bit shorter with ABS but like I said, 1994 and earlier don't have it.

I do remember giving ABS demonstrations with a MBZ back in the mid 1970's in Germany. ABS was not allowed in the U.S. for several years because of some fear it would set off construction site explosives. Anyway, I would do a panic stop on wet cobblestones while turning the steering wheel at the same time. Even more impressive was putting one side of the car on wet street car rails while making a panic stop. Great safety addition to any vehicle.

Pierce

Re: Engine brake

Reply #13 – October 26, 2015, 11:45:56 am

Bob, you might give some thought to the Pacbrake. It's installed in the exhaust system and might be cheaper but still do what you want. It's a pretty subtle braking but effective. Ours is an older model and a passenger cannot detect anything when I engage it (simple rocker switch rewired on the dash) but I have found that it keeps the coach and toad at a safe speed even on mountain passes.

It's so subtle that I was surprised at how much I missed it when it quit working last year. Our most traveled mountain pass descent is Snoqualmie Pass via I-90 westbound. This is not an especially steep grade but the first few miles are the steepest; this route gets a lot of traffic which affects how often I have to brake. The difference between having it and not having it was significant. With it I hit the service brakes maybe 2 or 3 times from the summit down (usually only because of traffic situations). Without it I was on the brakes often.

On I-5 through the windy sections of southern Oregon and N. California it made my job a lot easier. Worth a look.

Craig

Re: Engine brake

Reply #14 – October 26, 2015, 12:13:27 pm

If rear tires skid or hydroplane, the heavy end (engine/tranny) will try very hard to become the front of the vehicle!!

Re: Engine brake

Reply #15 – October 26, 2015, 12:52:55 pm

Really appreciate the input. Lots of experience out there.

I have driven a lot of different jake breaks, exhaust brakes and retarder equipped coaches since 1984.

Your posts match my experiences and what I expected to read.

Having the jake on normally might be needed/helpful coming up next week as the shop manager is going to reprogram the ECM in my coach.

Seems to have been ordered with its brain set for 420/1050 instead of the advertised 450/1450.

If so the cooling system might benefit from any reduced loads. I doubt if it's needed but my first thoughts were to have the Jake do the nominal slowing and have the retarder for the emergency stops which I also had use of once. Your sweat will pass you.

Plus something more to play with.

Cat 3176 in a Marquis had a three position Jake with a sidewall mounted panel next to the drivers elbow to operate it.

I think the n14 signature also had three positions.

Seen the Jake m11 parts recently as my local cummins shop had one apart. Big steel parts.

Need to talk with the foreman. Love to be able to switch back and forth or run both as stated.

Re: Engine brake

Reply #16 – October 26, 2015, 01:52:15 pm

The Meritor disk brakes we have on our coaches are excellent. They are the standard for most fire trucks. We absolutely tortured them, making max application intersection after intersection. The drum brakes stopped as quickly but did fade noticeably more coming down steep canyon roads on campaign fires. The fellow who wrote the specifications tried to save money by leaving the Jake out on all trucks so we had to depend on the service brakes alone. A big mistake as we lost brakes several times on the drum brake equipped rigs. When the brakes have faded, hitting the parking brake button does absolutely nothing for those who might wonder.

One apparatus had an Allison with a retarder. Since it had 1000 gallons of water and 150 gallons of diesel, the liquid weight was over 9000 lbs. The retarder did a great job with the six speed but did have to watch the big yellow dash light for overheating. Dropping a couple of gears and using both the brake and retarder pedal gave a lot of confidence when we had to slow in a hurry.

Pierce

Re: Engine brake

Reply #17 – October 26, 2015, 04:28:46 pm

Retarder/jake are usually connected to the ABS system. Do the research, but I'd reckn' that when ABS kicks on, the retarder/jake is disengaged.

Re: Engine brake

Reply #18 – October 26, 2015, 04:53:26 pm

Anybody ever come down the "Cabbage Patch" on Oregon I-84 into Pendleton from the Meacham summit? Talk about a hill that needs every retarder one could get their hands on!

By the way, the cops sit at the bottom and do very well with the rigs that have lost their brakes.

Re: Engine brake

Reply #19 – October 27, 2015, 11:03:19 am

Quote

I'd reckn' that when ABS kicks on, the retarder/jake is disengaged.

This is an interesting supposition by Krush. Sounds reasonable to me but does anyone have a definitive answer? In my own experience with Jake and retarder, the wheels didn't lock up. Anyone else have any experience with full on emergency braking with retarder or engine brake engaged? Thanks.
jor

Re: Engine brake

Reply #20 – October 27, 2015, 11:10:23 am

I seem to recall people on here saying their retarder wouldn't work when the ABS light was on.

I also seem to recall seeing an input to the allison computer (which controls retarder) for an ABS fault signal. But I could be imagining stuff!

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