Fuel Injector Valve Phasing...

[Timothy Coste]

To Fred's question about improving spray...

All I can say is that we use specially prepared injectors.  Pneumatic
assist injectors have been around for a long time.  From what I've
seen so far however, their spray angles are too huge even given the
very small (< 10 micron) droplets.  Maybe if you were certain air flow
was high during injection, they could work.  Easy concept and 
assembly, but you need pressurized air.  We also work with some
proprietary injectors here which are still undergoing development.
These produce relatively fine (about 30 micron I believe) sprays in
excelently controlable patterns.  I read (in SAE?) that Ford is
building a new injector facility...maybe they have something cool 
about to go into production???  Other than that...  I believe I've
seen very high pressures (which I guess would require shorter
duty cycle times) causing more turbulence at the nozzle and 
therefore better atomization.  This is something one could tinker
with at the home level.  I don't know for sure the effect of
boosting pressure on angles though.  I think that next time I run
my test engine (a SEFI 4 cylinder) maybe I'll try fine spray
injectors and switch the leads between injectors to get them to
fire on an open rather than closed valve.  Hmmmm, what was that
firing order...

As to real duty cycles...  I guess I didn't consider full load-lower
speed.  I'm not really sure what they are (duty cycle that is) at
those conditions.  I baby my engine (head is swiss-cheesed with
sensors) and rarely see over half of max torque.  If the thing
grenades now...no Ph.D.! :(  In general, I've seen increased load-
speed reduces the effects of fuel prep.  Engines hotter, more
turbulence, etc. so I still think it's less important as power
output increases.

   I'll stop rambling now...need to actually get some work done.
BTW...sorry, but our Unix mail program has no spell checker...try
editing your already typed mail in vi!

   Tim Coste
   tlcoste at mtu.edu