Injector Sizing: not dumb questions at all

[Gary Derian]

Thanks for your comments Greg,

The Hilborn and Enderle injection systems had very poor metering at anything
other than full throttle, they went way rich.  They were replaced not
because they had constant flow but because they had poor metering.  Both
Rochester and Bosch had very good constant flow FI systems.  Earlier this
year in "Automotive Engineering", SAE's magazine, there was an article
examining fuel droplet size vs. injection timing.  The researchers found
that droplet size was smaller when the fuel was injected onto a closed valve
and the exhaust backflow hit it than it was when injected during the intake
stroke.  Backflow is a fact of life and can be useful to atomize fuel.

The Lucas timed injection was indeed mechanical but at high rpm it was
practically constant flow, similar to an EFI.

Your comment about using cylinder turbulence to cover sins is a bit strong.
I'm not bent on committing sins, I just want to have an effective FI system
that works and that I can afford.  Do you have any real evidence that
injection timed to inject only during intake flow provides better torque and
fuel consumption at anything other that light throttle and low rpm?  As
intake dynamics change with rpm and intake pressure, how do you vary the
injection stroke start and stop time to inject only while air is flowing
into the cylinder?  You must vary fuel flow rate quite a lot, either with
pressure, a variable flow injector or multiple injectors.  If air is allowed
to enter the cylinder without fuel, you still need to use cylinder
turbulence to mix it up, the same sin you accuse me of.

I agree with low compression/hot exhaust.  Its basic thermodynamics.

Gary Derian <gderian at cybergate.net>