Exhaust Brake ???

MrWizard wrote:
My situation is a little different than most
My exhaust brake is the "D-Celerator" it has electric Solenoid operation
If the EB switch is on, it will engage when I lift my foot from the throttle, in any gear at any speed
There is a switch mounted in the pedal
But it does not control the down shift
Going down hill it will not shift down unless I do it manually
And the effectiveness depends on the gear, it don't do much when in 5th or 6th gear

Ditto. Mine was fully exercised & proven on the long western hills of the Mass Pike. The exhaust brake controlled the downhill speed quite nicely when going east. While westbound, The exhaust brake was on, I downshifted into 5th & felt perfectly safe with the controlled speed.

Later today, I'll be doing it again in the western Maine mountains - up & over the beautiful Height of the Land.

My exhaust brake will not work over 65 mph, as said in the manual.

I was just on a long trip with my first encounter with lots of steep hills.
My exhaust brake (made by the same company that makes what some call a true Jake brake) will engage when on cruise. I would watch the speed build up going down hill and just right at the limit of my own comfort level the exhaust brake would cut in and slow things down. On steeper hills I would still use the service brake quickly to slow down a bit more. Then if I did not engage the cruise the exhaust brake would would turn on whenever I took my foot of the accelerator.

Based on previous discussions on this forum, not all exhaust brakes work the same way - some fight with the cruise control (my 99 DSDP did) and some have no issues. Some are called exhaust brakes, some engine brakes and some are Jake brakes but they are all generally meant to do the same thing - slow you down within the parameters specified by the manufactures.


Chris

J-Rooster wrote:
Maybe a weak spool valve in the Jake head?

OP said he has the Cummins 8.3 ISC.

No jake brake on the C engine, just exhaust brake or variable vane turbo on later ISC's.

Maybe a weak spool valve in the Jake head?

What year is your cummins 8.3?

Modern cummins engines don't actually even have an exhaust brake. They have a variable vane turbo that controls boost (they don't have a wastegate either) and engine braking.

And all this talk about air compressors in pickup trucks adds nothing to this thread.

Our engine brake (2008 cummins 8.3) has little effect over 60 mph. As was said by others, letting the throttle (sic) off with the engine brake on will almost immediately show a 2 in the desired gear (left digit) on the allison display.
The system will downshift to 5th at 65ish, but little braking is felt. Under 60 it will go into 4rth, at this point the coach slows like it hit a wall.

And no, I don't leave it on all the time, especially on a highway. There will be many times you'd rather the coast just coach when you let off.

I used to think the same way as the original poster, but in fact it does shift down to fifth gear and it is not noticeable that it has down shifted. But if you look at the RPM's on the tachometer you will see that in fact the RPM's have jumped up but not enough to over rev the engine. Then as you slow down it will shift to a lower gear.

Probably off topic, but I wonder how many coaches have pac-brake that are not working? I am ready to give up on mine, I had it off twice and freed it up and lubricated it with the pac-brake lube and it will work for a few trips, but after the coach is not used for a month it hangs up again.:D

Ok did you have the cruise on? If you had the cruise on not nesacarely engaged it won't turn on the exhaust brake until you tap the brakes and disengage the cruise.
Bill

Old-Biscuit wrote:
As a flight instructor and aircraft mechanic I would imagine you have read the manual ?

There's a manual?? LOL Just kidding. The manual says, turn the exhaust brake on to aid in slowing the vehicle..........Not much help.
I'm thinking that the computer is keeping the transmission from shifting down due to exceeding the max rpm's.
I rationalize this due to the fact that if I apply the air brakes momentarily, to down, then it will downshift and began to slow. The exhaust brake works fine at speeds below 60mph or so.