My '72 Mercedes diesel had a throttle plate, not sure of its purpose.

 

I am just learning about my new truck. I am pretty sure the throttle plate is more related to using exhaust gas recirculation. When you close throttle plate from the intake, and openi EGR valve, then the dirty exhaust is sucked into the cylinders to be reburned.

The original thing, if you are in auto D, and tow haul and use the minus button on the shifter you can force a gear drop, when the auto engine braking is on, as it shifts down, then as RPMs go up, then you get more engine hold back. If you manually drop it down another gear, then more RPM, more engine braking. When towing, or loaded with tow haul and engine braking, and you take foot off throttle, it will hold a gear, hit the brake once, it will downshift, depending on push from the load on the truck. Same effect, hold back. If your not in tow haul, the hold back is less noticeable or aggressive. I would caution not good to use in manual mode on slippery roads either.

Or, you can do auto engine brake, tow haul, AND do the same with cruise. Going downhill, load sensing will use the tow haul and engine brake to hold the set speed. If you minus the cruise by using the cruise minus button, it will start holding back, and shifting down, decreasing gears, holding back, more RPM, more hold back. The bigger the load, more aggressive.

More hold back is enabled with manual engine brake then auto like explained above. Manual will hold the lowest gear it can and bring you to a stop. Where auto is smoother, but in the lower gears it will let off a bit as you come to a stop.

I am really looking forward to using this new truck with a heavy load to see how effective this engine brake really is. Have fun experimenting with yours. I have had to read through the manual a few times, but for the most part, much like my older diesel, just the new transmission and the button on the dash are better and the engine braking is more effective because you can get it to do the changes of gears manually or with the cruise. The manual transmission control is way better in M mode.

 

So why not just leave it in Automatic all the time? worse fuel mileage? If you put it in Auto, will it still be there next time you drive?

 

According to troverman's post on page one, it defaults back to off every time you start the truck.

 

When going to the Eastern Sierras I first set the CC and then set the auto brake. Keeps the truck within 4 mph wether climbing or going downhill and that's with a 31' 5er.

 

Indeed they do, but it is not to control air flow like with a gasoline engine.

 

Well...it does actually control the flow of air, what else would it be used for? Yes, I understand it is used to slow down incoming fresh air and reduce pressure to allow more EGR into the system. But I'd bet it is shut during engine braking operations...why not take advantage of this?

 

EGR and vacuum control
Turbo vane control is what is allowing engine braking.
Diesel engines by basic design do not need throttle bodies. Want more RPM, dump more fuel.

Intake Throttle Body
The intake throttle body is mounted on the lower intake manifold.
The intake throttle body promotes flow of EGR gases to the intake manifold by creating a differential between exhaust pressure and intake pressure.

 

It's not a throttle plate....it's an emergency shut-off plate for diesel run-away situations.


You turn the key off and the plate closes to prevent any air from entering the engine just incase the engine is in a run-away situation. With out this device, your truck would continue to run even with the key off. Remember, in a diesel you only need fuel to run (no spark), so there's no turning off the ignition (spark plugs) so to speak. You blow a turbo seal and all your crankcase oil gets pumped into your intake providing fuel to keep running at full throttle! This shut-off plate prevents a scary situation.

 

Where did you get this from?

 

It could serve that function, but that is not the primary purpose of that throttle plate...the coffee table book is clear that the purpose is to help introduce EGR gasses into the intake stream. We also don't know if that plate fully shuts when the engine is off or not.

I'm curious to see if its even possible for a modern diesel like this to run away on engine oil. There are no pre-combustion chambers like an IDI and compression ratios are lower. If it did run, it probably wouldn't run well. The turbo oil line doesn't exactly supply the volume and pressure of fuel needed to make full power, and it does have to pass through the CAC which would certainly slow down the amount of oil coming through...

 

Oh yes, it's possible. This has been known to happen with 6.4L engines that have issues with fuel dilution causing an overfull crankcase. Crankshaft froths up the oil, forcing it out the breather tube into the intake, which feeds it back into the engine causing a runaway.

 

The throttle blade (butterfly) is on a shaft, allowing it rotate in the throttle body - from parallel to almost perpendicular to the body.
An engine running on it's own would still pull air past the throttle blade, maybe even overcome the applied closing force (spring, drive motor etc).

Diesel engine air intake shutdown comes from a "door" that closes over the intake, completing covering the opening.
2 stroke Detroits have had them for a very long time. They were to be used only for an emergency shutdown and doing so at high RPM's could very well damage the blower seals.

 

I know this is an older thread but being fairly new to towing I wanted to ask, do you keep the engine brake turned on the whole time while towing?
I’m always in tow/haul mode while pulling my TT but only turn on the EB when going down steep hills. I always tap the brakes going downhill and love how the trans slows us down. Is the EB being engaged anyway on account of me being in T/H?
I’ve read the manual and it only explained what the EBs function was.
2015 F250 PS, 9700# TT
Thanks.

 

Just in the mountains (I-70) for me. Set Tow/Haul, Engine Brake Auto and Cruise Control and the truck takes care of the rest. It will hold you're set speed within a couple MPH either way and works great. 10k trailer and going down IKE you won't touch the brakes once.