[Vwdiesel] negative aspects of burning water

James Hansen jhsg at sasktel.net
Mon Sep 17 23:54:21 PDT 2007

Terry Briggs wrote:
 > the advantage of a diesel-electric hybrid, thats an easy one, you can
 > use a much less powerful diesel engine and still have the torque of an
 > engine 3 times the size of what you are using and still get great
 > mileage {comparatively}. It's being used now for that very reason

Is it really an easy one?

Have you considered the efficiency losses Terry?  If you can't do 100mpg 
with a hybrid, it really isn't worth the extra energy footprint to make 
assemble and carry around all the stuff to have the hybrid.  A lupo does 
in the 90's with a simple 3 cylinder tdi, so a diesel hybrid better do 
more than that, or you're just chasing your tail.

Diesels only use as much fuel as needed to make the power required at 
the time, unlike a gas engine.  To expound on that, cause it seems to be 
falling on deaf ears at present... all the air going through a gas 
engine has to be at stoich mix fuel to air ratio, or the motor grenades 
eventually.  Diesels have no such constraint, so they will run very 
efficiently throughout the range of power requirements and rpm.  If you 
run a diesel at low power requirements, you essentially HAVE a much less 
powerful motor, until you stomp on it- if you design a car to need 10hp 
at 60mph, your diesel motor will be making 10hp, and using a 
corresponding amount of fuel. The only loss in a diesel over a gas is 
the pumping losses of moving the unthrottled air through the motor.
   A gas motor cannot run at much less than stoich mix, hence the 
tremendous gains in efficiency in running it at a constant speed at max 
efficiency to generate power a la hybrid.

Trick is, each step in the hybrid train has efficiency losses. 
Generation, storage, regulation, transmission, usage, do not have 100% 

I'm curious if anyone has run the numbers in this.  Roger, you're a 
clever fellow.  If you're following along, do you have any top of the 
head guestimates on losses in each of the steps a hybrid goes through 
with it's energy production, regulation, storage, sharge control, etc?


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