Fuel injector optimum location

[CHarris233 at aol.com]

Mike-

Placement of the fuel injector always seems to generate a lot of
"discussion".  Unfortunately, there isn't always an easy answer, even in
similar conditions.  As an example, I'd like to point out the difference in
injector location on two Indy car engines.  The Ford-Cosworth variety places
the injector low in the port, just above the inlet valve.  This should enable
more precise distribution between cylinders, though at some loss in  fuel
evaporation due to the slightly shorter travel.  The Mercedes Benz-Ilmor (my
job, BTW) places the injectors high above the trumpets.  This gives slightly
more time for fuel vaporization, but gives slightly less control over where
the fuel ends up.

In the end, it alls seems to be a toss-up for WOT running.  If you run into
problems with fuel distribution, moving the injectors downstream tends to
help.  If you want to try for a *minor* decrease in fuel consumption, move
the injector upstream.  At low rpms, placing the injector near the inlet
valve can still give good fuel vaporization by timing the fuel delivery to
strike the valve when closed.  At WOT, pulse width and duty cycle conspire to
reduce the usefuleness of worrying about when the injector opens.

I wish there was a pre-packaged answer to your question.  It would make life
easier for a lot of us.  As all the above tends to lead toward the dreaded
cut-and-try method of development, could you consider molding you intake
system with two injector locations?  The unused locations could be plugged.
 This would give you the opportunity to try different locations without
starting over.  Good luck, and let us know how it goes.

                                                  Charlie Harris