They wouldn't......for some reason my brain assoiated shutting off the injectors with shutting off the pump. Just a good old fashioned brain fart.....unless I'm old enough for it to be a senior moment!!!

 

it won't work. you need the kind of exhast brake butterfly isuzu uses. very simple and works well. butterfly closes off exhaust and allows about 40 psi pressure to build

ken

 

Any thoughts on this?

 

cutting out cylinders won't work because the cylindersare still pumping. you can do this but you must disable both injector and valve action in that cyliner. that is how vd engines work. every other cylinder in the firing order for balance in a v8

 

Interesting. I think I have felt this on the '96, kind of a lil jerk when getting back on the throttle. I will be playing around later today, after the rain stops. have to listen for that, but its kinda hard over the turbo whistle.

On edit, the Variable displacement thing. IH did it in the 70's with the 550 C.I.D. V-8 in the tractors. 1468 and 1568's had them as an option. they would only run on 4 cyclinders under a light load, 8 on heavier loads. a fuek conservation thing. I dont remember exactly how they did it, but it sucked, and most were switched over to run all 8. I am assuming something in the pump was diferent. that and a twin turbo kit and they ripped pretty good.

thanks all.

Diesel Rod

 

A diesel engine works with a governor to control how much fuel is injected.
The throttle sets the RPM of the engine on the governor.
The governor then takes appropriate action with the fuel control to reach the RPM the throttle is asking for.

Say idle is 650 and the engine is turning at 2100 as you drive down the road. When you take your foot off the throttle the governor shuts the fuel off till the engine reaches 650 RPM. At that point the governor gives the engine the correct amount of fuel to maintain 650 RPM.

Some governors work better than others, Caterpillar probably is the best on the market. The bigger Cat engines are almost impossible to stall with a manual transmission, reason is when the RPM starts to drop below idle the governor starts feeding more fuel to the engine to maintain idle speed. It will go wide open fuel at idle RPM if you give it enough time and the RPM is less than idle speed.

The engine in your truck will do the same thing on a smaller scale, with a manual tranny put it in a lower gear at idle and let of the clutch a little fast. See the small black cloud out the exhaust? That is the governor opening up the fuel to the engine to maintain idle speed even though you did not touch the throttle.

It takes X amount of power to maintain speed when going down the highway. If you shut off the cylinders, the only thing that has changed is the number of cylinders you are using to produce the required amount of power. Due to parasitic loss of the dead cylinders that are producing no power, the total fuel consumption will increase when you turn the cylinders off. The only way around this would be to hold the intake and exhaust valves open on the cylinders you cut the fuel off to. Also the error codes the computer kicked out when you cut the injectors off would probably make a service tech have a heart attack or worse if it did not damage the computer.

 

No actualy "governor" on these though, Dave. all electronic. not even an injection pump. But i know what your saying. Done the string on the gov. thing before in the fields.

Diesel Rod

 

Just because it is electronic instead of mechanical does not mean it is not a governor.
The principle is still the same.
The big Cats are electronic now as well.

 

As I am sure you all are aware of, I am new to the PS world and I love it.

I have noticed that sound change and was wondering what it was and the cause. Acutally it was starting to worry me a little. NOT ANY MORE -- Thanks for the info.

I can change the downhill sound (coasting) just by slightly pushing on the accelerator. It shuts off the sound like Kwikkordead said.

Just another Diesel dummy learing the ropes.