engine braking good or bad ?

[digitaldust]

So I have been told by a few others that engine braking a deuce is a bad idea both the trans and the engine. do not like it ?

is this fact or fiction .

is there a correct way to engine brake?

 

[USAFSS-ColdWarrior]

Good question...

Has anyone got an INFORMED answer?

 

[Westech]

well you don't want to be down shifting. if you go up a hill in 4th go down it in 4th... the main problem with "engine braking" in a multi is that you can over Rev the engine fast. The multi fuel really has no engine braking due to how the injection system works. You are not able to shut off the fuel unless you pull the handle and I don't think the pump head will like that too much spinning and not getting and lube from the fuel.
There is a PM (connie cartoon) on this. I think Crane Truck has a copy of it.

 

[gimpyrobb]

Exhaust braking is what you want, Bjorn(cranetruck) has a great thread or two on the system he installed.

 

[k4vem4n]

I think one of the TM's actually explain the correct procedure, I can remember reading something about it under "startup and operating procedures"

It did say engine braking was a no-no, but can't recall the specifics

 

[gimpyrobb]

The diesel has no throttle plate(like a gasser) to restrict airflow so it doesn't work. The only thing to restrict rpms is friction in the motor.

 

[Akicita]

The TMs warn against engine braking. The gears on the Deuce aren't really designed for that.

If you ask because you haul heavy loads downhill and the weight causes the engine to rev over the max permitted RPMs when you're in the best gear for the load and safe speed, think about installing an exhaust brake, or take less of a load downhill if that is an option.

Controlling the descent and RPMs with the regular brakes should be possible as long as you don't ride the brakes. "Riding the brakes" means keeping your foot on the pedal without releasing it every few seconds. This makes the brakes very hot and can boil your brake fluid. When that happens, the brakes fade quickly and it's time for you to ditch the truck to keep it from becoming a run-away.

The trick is to apply the brakes until your engine has slowed down enough for you to release the brakes again. You have to do this repeatedly, of course. This is not the same as "pumping the brakes". Pumping causes your air tanks to empty which could become a problem if your compressor can't keep up. I'm talking about braking hard enough to slow down the truck without locking up the wheels, then releasing the brakes to let them cool off for a few seconds, then applying them again to slow down again, releasing them to let them cool, and so on.

When the Jake brake on my Detroit Diesel quit due to an electrical malfunction on the descent from Skyline Drive in Virginia, I had to slow it down by braking, releasing, braking, releasing and so on. There are no Jake brakes for the multifuel engine in a Deuce but exhaust brakes do a great job and cost far less than a Jake would.

I had a butterfly valve brake (exhaust brake) on a Cummins several years ago. I really liked it once I had gotten used to turning it on. I didn't have an electric switch and had to turn it on with a foot activator every time I wanted to use it. That was not the ideal set up if you ask me, but that's how it had been installed. If I wanted to install one a Deuce, I'd install an electric on/off switch. That would have been helpful on that long descent on the Northern end of Skyline drive.

I hope this long explanation helps.

 

[cattlerepairman]

I had a butterfly valve brake (exhaust brake) on a Cummins several years ago. I really liked it once I had gotten used to turning it on. I didn't have an electric switch and had to turn it on with a foot activator every time I wanted to use it. That was not the ideal set up if you ask me, but that's how it had been installed. If I wanted to install one a Deuce, I'd install an electric on/off switch. That would have been helpful on that long descent on the Northern end of Skyline drive.

I hope this long explanation helps.

You know, the setup you describe is the standard setup in Euro trucks, including military. I learned on it, so I am used to it and for me the automatic exhaust brakes are still disconcerting. I would much prefer the foot valve for the butterfly valve in my truck.

To get back on topic, I do not see anything bad in "engine braking" (i.e. using the energy delivered by the wheels spinning the tranny spinning clutch and pistons) to slow the truck, as long as you keep a close eye on the tach and do not exceed the 2600 max rpm threshold. Downshifting before an intersection or a stop sign is "engine braking". I usually do that, rather than clutch and brake only.

I agree fully with the danger of overreving due to improper downshifts or wrong gear for the slope. This is not, however, Deuce-specific but an issue with all manual transmission trucks.

 

[Floridianson]

I don't think I need a Jake or exhaust brake for the speeds I drive. (45-50)
I do down shift if I get caught at a light but I do watch my tac and down shift hopefuly at the right rpm. ( most of the time I'm good) The thing the with over reveing is watch the tac when you start letting out the clutch. If you played it wrong then before it goes over what the rpm you might feel safe at push the clutch back in. Then brake a little more then try letting out the clutch again. I also don't have hills to worrie about which makes it a lot easer.

 

[jesusgatos]

Exhaust braking is what you want, Bjorn(cranetruck) has a great thread or two on the system he installed.

Deuce exhaust brake details
Deuce exhaust brake?
Exhaust Brake?
Exhaust brake

 

[11Echo]

From the deuce operators manual.

 

[cattlerepairman]

I know the part of the -20 manual regarding downshifting and engine braking. I also respectfully submit that the context of (maybe inexperienced, maybe careless) eighteen year old conscripts operating the trucks is important when reading SOME of the passages in the TM.

Even the girl with the santa hat says...team up both your brakes and the gearbox.

I do not believe for a second that normal, careful downshifting, i.e. using the service brakes or resistance/drag to slow down to a speed compatible with the next lower gear (look at the dash plate for guidance) and engaging said lower gear, is "harmful".