Community Forums

Ray,IN · 09-22-2014, 08:37 PM

Quote:

Originally Posted by 450Donn

Another lesson, leave the EB on ALL the time!

That is inconsiderate to following vehicles. Every time the exhaust brake activates the brake lights activate, even if you just let off the go-pedal a bit too much. Very aggravating to others following, who must respect your brake lights and hit their brakes too.
On another note, a Cummins repair center, when asked, told me they believed the main reason for cracked exhaust manifolds on the ISC engine was due to excess heat from constantly using the exhaust brake.
We just finished a 4,000 mile caravan. A few constantly ran with their exhaust brake on. It was difficult to follow those drivers.

brunsje · 09-22-2014, 08:55 PM

Folks,

1. RV's are frequently overloaded beyond their design specs. Then when a problem arises, there is no margin left. Please have your rigs weighed and be certain your safe! Just for the case mentioned above.

2. Modern exhaust brakes do not add much engine noise. Turning off the engine brake greatly increases stopping distances. Take your choice between an accident and the risk of a ticket!

JohnnyB

Jupiter · 09-22-2014, 09:08 PM

Yet a differing opinion... I never leave the exhaust brake constantly activated because to me it doesn't seem like a very efficient mode of operation. Meaning that when slowing down slightly the brake often activates causing a loss of speed beyond my intended speed reduction. Then, it often takes more throttle to regain the lost speed. May seem insignificant to many, but it's how I choose to... umm roll.

Again, it seems so easy to simply flip a switch when needed without as much as a glance. And, ditto on the brake lights.

cheers,
Joopy

1ciderdog · 09-22-2014, 09:53 PM

I added this to my exhaust brake system. http://www.brakeswitch.com/ I think you can do similar with an Allison program modification. My exhaust brake switch is always in the on position but the exhaust brake does not activate unless I push the brake pedal and then the exhaust brake stays on until I push the fuel pedal or the RV gets under 15 mph. So when driving when I left off the fuel pedal it coasts (so to speak) but the exhaust brake does not engage until I push the brake pedal. Works for me.

Dr4Film · 09-22-2014, 10:38 PM

For those drivers not interested in following my vehicle with the brake lights on when I am using my Exhaust Brake to slowdown while descending a grade or for that matter anywhere, you have every right to go around me if you choose to drive faster than me. Hell, since I am slowing down and in the right-hand lane anyway you are welcome to pass me on the left and go as fast as you heart desires.

Dr4Film ----- Richard

ImagineIF · 09-23-2014, 06:12 AM

It seems all not brake pad systems are being grouped together. There are at least 3 exhaust related braking systems. Two are Jakes, one incorporated in the head and one in the exhaust pipe. In newer engines you will find turbos that create drag by changing the pitch of vanes. This one is often coupled with an automatic down shift to 4th. Finally, newer coached may have transmission retarders. All of these systems increase heat. That's not too suggest excessive heat, but they may. I leave my in head Jake on low when ever I'm out of town and use it in high only in hilly areas.

I have disconnected my Jake activation of the brake lights, as many have. I'm not braking, but rather slowing down. Sometimes, like when I have the cruise control set I'm not even slowing down but rather maintaining a set speed.

Ray,IN · 09-23-2014, 06:26 AM

Climbon69, I apologize for hijacking your thread. Apparently I angered some members and jumped your thread off the track.
I have been guilty of doing the same as you, bypassing the safety brake check pullout for HD vehicles. I've learned from your experience. Thanks for posting.

MSHappyCampers · 09-23-2014, 07:42 AM

Glad you're OK Al!

slemnah · 09-23-2014, 08:25 AM

I never leave mine on, I have the switch next to me and as I am going down a steep hill I modulate between low and hi depending on how much speed I am gaining or losing. I use the brakes very little just using them to quickly drop a few mph and then off the brakes again. I can go down the steepest part of the grapevine at 35mph using this method on a 47k lbs motorhome with toad. I also turn it on if I have to come to a quick stop in town such as a traffic light changing to red. I use it when coming to a slow stop until I hit around 10mph and it shuts off then I hit the brake. I have a Jake brake on my C-13 CAT but I did the same thing with my exhaust brake on my 8.3l cummins in my 97 Imperial.
Steve

Climbon69 · 09-23-2014, 08:56 AM

No problem on "thread jumping" Ray. The discussion was interesting. It's obvious that there are a variety of EB/transmission/air brake combinations. My EB is not linked mechanically or electronically to any other component. It is either on or off. Leaving it on for long distances does increase engine and transmission temps on my coach. I don't have a pyrometers in the exhaust manifold yet, but I suspect temps go up dramatically in the manifold when my EB is on.

PO must have thought he was doing right thing by leaving it on all the time as I ended up replacing the exhaust manifold. The original EB butterfly leaf inside the manifold was completely gone. Presumably, cooked.

I had this same discussion with a friend who has a much newer coach. His operation manual recommends the EB be turned on for city driving and mountain driving, but his EB is electronically linked to his transmission and air brakes. The EB butterfly leaf activates only when his air brakes are applied or when his "smart" transmission thinks it needs to engage. That would be cool, but it ain't happening on my old coach.

The input on the proper application of air brakes was also excellent. My son is a truck driver and works for CAT. He also drove a platoon of Marines into Bagdad. Both the Marine Corps and CAT taught him that method of using your air brakes and he beat it into me when I got my RV. He also rants that I should have a CDL to drive this heavy bus!!

spritz · 09-23-2014, 09:24 AM

I only have a pedal break in my MH, Soooo slow, still start in first. When I drove OTR in a 83 Peterbuilt towing a 45 foot trailer and weight ins around 80,000 lbs and with the 4 way's flashing, I never came off the top of a pass but in first gear Never, I shifted and braked and used the Jake break. I have seen the guy that went flying by me only too see him in the Run Away Lane while I was still going 35-40 MPG. and under control going by him or the guy that's trailer breaks are Just smoking. I'm sure you have seen it.
Whats the Hurry I just will never get it, SLOW DOWN The CG will still be there.
I wish I still had that 83 Pete, What a life, but now I can stop as those places I wanted too.
The RV Life
Tim

Dr4Film · 09-23-2014, 09:31 AM

Exhaust manifold temps will only go up significantly when you have your foot fully into the fuel treadle. That happens when you are ascending a grade.

If they go up significantly when descending a grade then you have something drastically wrong with your engine. There is very little fuel entering the cylinders when your foot is off the treadle and your Exhaust Brake is activated. To produce heat you need to have lots of fuel entering the cylinders.

If climbing a grade using your turbo and your foot all the way into the treadle then yes your exhaust manifold temps will increase. Keep the temp under 1200F -1300F and you will be OK. The engine will de-rate at 1300F to protect itself if it's one of the electronic engines. If it's an older mechanical engine then you need to get off of the treadle before it reaches 1300F or you will damage the engine.

EGT gauges are very useful devices.

Dr4Film ----- Richard

TexasSprinter · 09-23-2014, 01:04 PM

This is an interesting thread with all this information. Our coach is newer and it has an engine break associated with the turbo and connected into the transmission. I do leave it on most of the time, but with a light on the dash showing me when it is engaged, I've discovered that it is surprisingly easy to modulate. The slightest pressure on the fuel pedal and it goes off, and it doesn't work at all with the cruise control on. On downhills, I've found that if you start downhill slow enough and press the downshift button on the tranny control a couple of times, it pretty much handles the grades w/o ever pressing the brake treadle, even pulling over 4K of car. And the car brake almost never comes on.

When I do need the brakes, I do as suggested here and pull it down to 5-10MPH below the max speed I want, then let it go. If it gets much over 5MPH above what I want, I repeat. But that doesn't happen all that often.

I sure don't want hot brakes coming down hill and so far, despite driving a fair amount around Colorado, I've not had any.

GraciesDaddy · 09-23-2014, 02:17 PM

Quote:

Originally Posted by ImagineIF

Just remember you can get an expensive ticket in a lot of cities that don't allow exhaust brakes.

There is a sign on I-459, which skirts the eastern side of Birmingham, at the top of a long hill in Hoover/Vestavia Hills which says "No Jake Brakes". At the bottom of that hill is a sharp right curve. MY stance is this: If the good people of Hoover/Vestavia Hills want to buy me a new rig because they wouldn't let me use the Jake, they're welcome to do that. But until then, I'm using the Jake!

I'll tell a cop and a judge the same thing!