On 11 Dec 2003 03:04:00 GMT, (Karl Denninger)
wrote:


In article . net,
Rick wrote:
Karl Denninger wrote:

(It will pull a near-zero-zero vacuum..... as will the fuel pump, in fact.
I've seen the fuel restriction gauge showing effectively a zero vacuum when
I foolishly started the engine without remembering to turn on the fuel
valves first....)

Cringe ... zero vacuum is one atmosphere, one Bar, or around 14.7 pounds
per square inch absolute, it is no vacuum at all.

The most complete vacuum you can produce will still only create a
pressure differential of 14.7 pounds per square inch at sea level, or
one atmoshphere.

Rick

"zero-zero" in my view means "absolute vacuum", or -14.7 psig.....

It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig. Your way depends on your altitude, the
barometric pressure.

Steve

Steven Shelikoff wrote:


It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig.

It is far better to describe it as it really is. An absolute vacuum (or
as close as we can get to one) is about .0049 psi.

There is no such thing as -X.X pounds per square inch.

Rick

Ummmm...the normal shutdown of a diesel (like my Cummins equipped Dodge) IS to
kill the electrical supply. Thereby closing the fuel shut off valve. Had a
problem once with the starter bypass ckt once that required pulling the
electrical plug off the fuel valve to kill the motor. My owners manual does
say that the engine will run away if there is enough fuel vapor available in
the area and to remove the supply of air to stop things. Same with a bad turbo
seal that allows the motor to consume its own lube oil.
Mike

Ummmm...the normal shutdown of a diesel (like my Cummins equipped Dodge) IS
to
kill the electrical supply. Thereby closing the fuel shut off valve.

Most diesels, particularly older models, do not require electricity to supply
fuel to the engine.

Well, that's as may be, but, my truck has an electric fuel shutoff valve. Most
modern diesels in truck (and I would think also boats) applications do.
Or how does turning the key to off stop the engine? A vastly complicated
mechanical linkage to a manual fuel shut off lever?
The fuel pumps that supply the engine are engine driven of course and require
no electrical power to operate.
The point I was tring to make is that though the engine may run with out
electrical power it requires it to start and stop.
Mike


Gould0738 said:
Most diesels, particularly older models, do not require electricity to supply
fuel to the engine.

In response to a previous post that went (in part):
Ummmm...the normal shutdown of a diesel (like my Cummins equipped Dodge) IS
to
kill the electrical supply. Thereby closing the fuel shut off valve.

Well, that's as may be, but, my truck has an electric fuel shutoff valve.
Most
modern diesels in truck (and I would think also boats) applications do.
Or how does turning the key to off stop the engine?

Your truck is designed to be started in the same fashion that people are
accustomed to use when starting a car.

A lot of diesel boats don't use the key to start or stop the engine. The key is
turned on to activate the electrical panel and the alternator, but a separate
push button is used to crank the engine. When the engine is shut down, another
push button
activates a solenoid that, yes, does actuate a mechanical fuel shut off
mechanism. Only after the engine comes to a complete halt is the key turned to
"off."

Depriving a gasoline engine of the electricity reuired for the ignition system
would shut down the engine. Unless your diesel needs a constant supply of
electricity to keep the fuel supply flowing,
cutting off electricity will have no effect. As the question was generic in
nature, a choice that applied only in very unique circumstances would not be
the best choice among the answers- even though in those unique circumstances it
would be entirely correct.

My new engine (going in next week, yeah!)
won't even have a key, just a switch. :-)

On Thu, 11 Dec 2003 04:52:17 GMT, Rick wrote:

Steven Shelikoff wrote:


It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig.

It is far better to describe it as it really is. An absolute vacuum (or
as close as we can get to one) is about .0049 psi.

No, an absolute vacuum is 0 psi. It doesn't matter how close we can get
to one. If 0.0049 psi is as close we can get to one, that only means we
can't generate an absolute vacuum.

There is no such thing as -X.X pounds per square inch.

There may not be an absolute -X.X psi, but there certainly is such a
thing as -X.X psig.

Steve

(Steven Shelikoff) wrote in message ...
On Thu, 11 Dec 2003 04:52:17 GMT, Rick wrote:

Steven Shelikoff wrote:


It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig.

It is far better to describe it as it really is. An absolute vacuum (or
as close as we can get to one) is about .0049 psi.

No, an absolute vacuum is 0 psi. It doesn't matter how close we can get
to one. If 0.0049 psi is as close we can get to one, that only means we
can't generate an absolute vacuum.

There is no such thing as -X.X pounds per square inch.

There may not be an absolute -X.X psi, but there certainly is such a
thing as -X.X psig.

Steve

Got to agree with Steve on this one. Just because we can only get to
ABOUT 0.0049 doesn't mean that is absolute. An absolute vacuum,
is......0psi

Rick wrote in message link.net...
Steven Shelikoff wrote:


It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig.

It is far better to describe it as it really is. An absolute vacuum (or
as close as we can get to one) is about .0049 psi.

There is no such thing as -X.X pounds per square inch.

All depends on the reference. If you are measuring with a gauge where
"zero" is atmospheric pressure then you would see it go below zero
PSIg when suction (vacuum) is applied. If your reference is actually
zero, then yes, there is nothing below zero PSIa.

But then again we are talking about the vacuum (or low pressure) in
the intake of an engine. Intake pressure is normally measured in
inches (Hg) --- perhaps to avoid this arguement altogether.

Steven Shelikoff wrote:
It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig.

For extremely low pressures there is a measurement called a Torr. Much more
useful and it also shows (as with all properly used technical jargon) that
you know what you're talking about.



Rick wrote:
It is far better to describe it as it really is. An absolute vacuum (or
as close as we can get to one) is about .0049 psi.

Huh? 1 Pascal is .000145psi. There is off-the-shelf industrial equipment
that goes this low.

http://www.npl.co.uk/pressure/vacuum.html

By my figures, the evacuation pressure they are talking about here is
approximately
0.000000000725psi which is a LOT lower. You could probably could the air
molecules floating by....




There is no such thing as -X.X pounds per square inch.

Great. Next you'll be telling us that vacuum don't suck.

Regards
Doug Kng