pre-heating a diesel for MPG?
 

I have a Dodge 3500 CUmmins and I have been reading some of the extreme success from Diesel Dave. I would not be willing to apply a lot of his methids (running without AC or modifiying emissions) But one thing he mentions is using the trucks block heater.

I'm curious how siginificant that might be? My commute is 23 miles and the truck comes up to temp in the forst 3 (when it's warm)

Thanks

Dave

Anything that helps get the engine get into closed loop faster should help the MPG of the truck. Running rich while warming up consumes a lot of fuel which is part of the reason why most cars' MPG take a dive in the winter.

Do diesels have open/closed loops?

I run my block heater in the winter mostly because my batteries are failing and can't start a cold engine. My Cummins also takes 10 miles to come up to temperature, so this helps in that regard too.

The grid heaters frequently come on when the engine and intake air is cold, so plugging in helps in this regard too.

I wouldn't bother plugging in if it's above freezing.

They don't have open loop like a gas engine.
Expect the intake heater to stay on a lot more which can eat up alternator and battery life.
Its basic thermo too, heat does the work, while trying to flow from hot to cold, if your block and cylinder head is cold energy that could have been used to push the piston down trying to reach a colder state is instead being absorbed by cold metal parts.
Cold starting them is not doing them any favors.

Thanks for clarifying. I'm not very familiar with diesels but knowing how combustion happens I figured that being cold would hurt MPG and that anything that gets the engine up to temp faster is a good idea. Since I'm more familiar with gas engines it was easy for me to think of open and closed loops.

If you have some way of heating up the gas tank it would probably increase mpg, from my understanding diesel gets thicker the colder it is, which is why in the sub-zero temperatures truckers have to keep their engine running. I could be wrong guy, and probably am.

Some diesels have fuel heaters, some are electric some are coolant warmed.
I am going to tie the cooling system into the fuel system via a heat exchanger and that will keep from having to heat the entire fuel tank.
Mainly so filters don't ice and wax up. Diesels seem to get the best fuel economy with their fuel heated from around normal temperature up to 120'F.

You can feel this energy redirecting by the great reduction in engine power produced when pressing down on the accelerator of a recently started cold diesel engine on a cold day. Although the fuel flow rates are normal, the power coming out of the engine is way down until the engine gets up to operating tem since part of the fuel energy is going to heat up the engine block than moving the pistons. You are literally burning fuel to heat up the engine block.

As an aside, internal combustion engine cylinders are designed to get rid of heat, but steam engine cylinders are designed to retain heat since any heat energy lost to the cylinder walls is lost engine efficiency.