Exhaust Brake ???

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

kalsbeek wrote:
Nothing wrong.
What happened was you were going too fast for it to kick in.
The engine would have gone past the 2800 RPM governor speed and caused damage. It self protects. At that speed it will not engage until you slow it down to 60 MPH or so. If you are in hilly country at highway speeds.....leave it on.
Hope this helps

HUH????????
I think something's amiss here. His RPM hovers around maybe, MAYBE 1600-1650 @ 60 MPH based on his report of 1500 @ 57 mph. That's really close to the same RPMs that mine does in our '04 Horizon 36GD with the C-7 330HP CAT. So, that would mean that, his RPM SHOULD be around 1700-1750 @ 65 mph. With that being said, his coach SHOULD have applied the Exhaust brake at the requested 65 mph.

And at that speed, the engine RPMs would jump to around 2200, plus or minus, BECAUSE, it will only drop to 5th. That's WELL WITHIN OPERATION GUIDELINES of the engine ECM. But, depending on just how his ECM and trans TCM are setup, as soon as he slows to around 63 mph, the trans will downshift again to 4th and that will jump engine RPMs to around 2500. AGAIN, it's still in operational guidelines.

Now, what CAN make a difference here is, whether or not the CRUISE CONTROL was on and set. On our coach, it it's SET, the E/B will not activate. But, if it's NOT SET, but in the ON position, the E/B will work when called for. And ours is not presently activated by touching the service brakes. It activates the micro-second I let off the throttle pedal. And that includes speeds up to and beyond, 70 mph.

But, again, depending on setup parameters, above around 63 mph, the trans will only downshift to 5th. And, at that speed, downshifting to 5th will only present a SLIGHT decrease in speed. Most of the time, on a heavy coach with a toad, you PROBABLY won't feel any actual downshift and or decrease in speed unless you're looking at the tach. If the decent is too steep for 5th to handle, the speed and engine RPMs will both increase. That's when assistance from the service brake pedal will be needed to bring things down to desired down hill speeds.
Scott

As a flight instructor and aircraft mechanic I would imagine you have read the manual ?

Brian, you need to confirm what happens to the gear selected window when this happens at 65. You can do this on flat ground and if it does not change from 6 to 4 or 2 THEN you have a problem. Also what are your RPMs?

I have a Cummins 8.3 350hp. I seldom drive at 65mph so I don't know what the rpm's. at around 57mph it's around 1500rpms. I don't know when it downshifts, I know it upshifts from 5th to 6th around 60 mph.
Brian

Clearly, without knowing your engine, rear axle ratio and tire size we are all speculating on max safe speed in each gear.

So, please post what engine you have and engine RPM at 65 MPH in 6th gear and if it will "down arrow" to 5th gear what that RPM is.

Nothing wrong.
What happened was you were going too fast for it to kick in.
The engine would have gone past the 2800 RPM governor speed and caused damage. It self protects. At that speed it will not engage until you slow it down to 60 MPH or so. If you are in hilly country at highway speeds.....leave it on.
Hope this helps

Brian can confirm this, but with his coach/drivetrain, 65 MPH should easily allow a downshift to 5th gear and exhaust brake engagement (i.e. 65 MPH in 5th gear would not overspeed the engine).

Mose exhaust brakes also down shift, and will be locked out if that down shift will exceed the max RPM of the engine.

At least mine is.

lc0338 wrote:
Don't believe I would want to run all the time just to keep air tank full, if a tank was added.

No, the pump/compressor should NOT run all the time. It should run long enough to pressurize the system and then the pressure switch should turn it off. Unless there is a leak, the pump/compressor should not run again until you use air.