absurd pressures figures was: atomization enhancement

[Jennifer and Brock Fraser]

> do however find it highly improbable that a fuel injection system
> could have a pressure range of 1600bar with a breaking pressure of a
> small fraction of that number..... I have yet to see any injector
> breaking pressures listed which suggest line pressures of this
> magnitude.  That such pressures could be associated with a common rail
> system is simply beyond belief.......

What you are failing to realize is that (unit pump, HEUI, EUI, or common
rail) electronic Diesel injectors are much more than just poppet valves.
There's no such thing as a popping pressure on an electronic injector, so
the very fact the "local pump shop" that was mentioned went looking for
maximum popping pressures shows that they had a feeble grasp on what the
current state of injection technology was.  It's likely that they might not
even be servicing any of these systems yet.  Good 'ole electrons control
when the injector opens and closes, not a mechanical pop pressure.

There's no mistake, no decimal place error, no magazine mix-ups, or anything
like that.  The more pressure you have, the shorter you can make the
ignition event, and the better mixture quality you can achieve.  You can run
more holes in the nozzle tip, allowing a lower swirl ratio.  It's a systems
approach.  With electronic control of the injector, you can rate shape and
do pilot injection... mostly for the sake of noise but also to help NOx
formation and cold starting.

Somebody related the tensile strength of aluminum to the pressures present
in these types of systems.  That's why the rail on a common rail system is
usually made of forged steel!  Cast materials typically won't work because
the porosity is too high.  Lines don't have to be that exotic, because the
ID is so small that even though the pressure is very high, the area being
acted upon is not.  The line OD is very big compared to the ID.  Ratios of
4:1 or 5:1 are typical.

The Cummins ISB and ISC engines (at least most of their applications) use
Bosch VP44 pumps, which is basically a warmed over version of the good ole
rotary pump, but will full electronic authority over timing and delivery.
They are headed for common rail.  You have to understand that emissions regs
drive these changes, and Tier 2 isn't being phased in for "off-road" until
2002 for the most popular of rated power ranges.  VP44's still use poppet
valves, and are NOT particularly high pressure systems (1000-1100 BAR),
although they do a better job than something like a Stanadyne or Lucas
rotary pump.  Stanadyne or Lucas rotary pumps, as I mentioned before, are
only good for about 600-700 BAR.  We fondly call these "drip pumps" or even
"gravity injection".  Possibly this will help illustrate the frame of
reference.

Most high pressure systems (common rail is the most popular) are being made
by Lucas, Bosch, or Denso.  They are cost competitive with full-authroity
rotary distributor pumps, because distributor pumps still cost WAY more to
manufacture than a simple high pressure supply pump.  The rail isn't too
bad, and the injectors still aren't expensive enough to eat up the pump cost
advantage.  EUI's are "high-dollar", not only for the injectors but also the
massive cam that's required.  They do have an advantage over common rail as
far as rate shaping, however.

Greg's spot-on about the relative danger of split injection lines.  You
can't build high hydraulic pressure with a leaky line.  Our R&D lines that
have been instrumented with pressure transducers routinely develop leaks,
and believe me, nobody is getting their arms and legs cut off... at least
not on a daily basis.    :>)

Nobody likes a good debate better than me, but I just couldn't take the
disbelief any longer.

Nobody postulated on what would happen if you tried to inject GASOLINE at
1800 BAR!!!!!!!!!!!!!!!!!!!

-Brock