Spark plugs/injectors

[Danny Barrett]

Does anyone know if it is possible to get spark plugs with fuel injectors
built in? I have seen one of the list members write about keeping the intake
pressure as close to atmospherice as possible (and varying the power/speed
by the amount of fuel pumped in). There is one problem with this - It is
very hard to get a reliable combustion from mixtures leaner than 18:1. There
is a solution to this problem (from what my Thermodynamics textbook says).
This is by charging the cylinder with a non-uniform mixture. ie: around
14.5:1 around the spark plug, and virtually nothiing elsewhere (where
required). This, it has called "stratified charging." Apparently, engines
have been successfully developed and run in the laboratory, but not in
production cars (or at least, we've not seen them...). The book was first
published in 1957, with the third edition (the edition that I have)
published in 1980. I think it is fair to say that our EFI technology has
advanced quite a long way since 1980. So... Why can't we build direct
injection petrol engines that vary the mixture instead of the amount of air
going in? Since we now have sequential fuel injection, knock sensors (even
the Trionic one that we seem to hear so much about on this list - go for it
gentlemen...), etc... Why can't we make a direct injection petrol engine
that uses a combined spark plug/fuel injector, so that we can use stratified
charging to our advantage? I reallise that there are problems associated
with NOx gases produced in excess when lean mixtures are used, but isn't
that what the catalytic converter is for? Also, wouldn't it be worth just a
little bit more NOx in the air (yes, I know NO2 is a poison), for the sake
of using far less fuel, and having less benzine rings (which can cause
cancer) floating around in the air??? Or is there something I've missed?

Danny Barrett.