LPG injection

[Mike Klopfer]

I was looking at a SAE book on the Natural Gas Vehicle Challenge and
several of the entries used Bosch injectors which I'm guessing are standard
pintle type injectors used in gasoline vehicles. I took a quick glance
at the paper from some Nebraska university and it talked about having
two levels of pressure regulation the final one supplying the injectors at
100psi (as I remember). It also seemed that they used two injectors per
cylinder to get enough flow. This lead me to wonder what are the reasons
for wanting to inject liquid propane instead of propane vapor. From the
various threads on the subject I gather that there might be some problem
getting the liquid to a vapor at low temperatures. I'd guess that it takes
less injection time to inject a given mass of fuel as a liquid. Wouldn't
you need some pressure regulator in either case? I suppose the density of 
propane vapor would vary considerably with the temperature but as long as
it followed the ideal gas law it should be easy to compensate for.

mike