On Tue, 22 Jun 2004 08:56:08 -0400, Steve Robertson
wrote:

Also FWIW, I really don't like fuel injection on airplane engines. Sure it's
great not to have to worry about carb heat. But instead I worry about hot
starts and plugged injectors. As far as the "advantage" of quicker throttle
response for FI, I say big deal. Your supposed to throttle up gently on all
engines, so I just don't see FI as an advantage here. Still, the Lyc IO-360
seems to be a pretty good engine and it and I have come to an understanding
about hot starts.

I doubt that the throttle response from carburator to fuel injection
would be discernable. Carburators have a system called the
accelerator pump which literally injects fuel directly into the
venturi when the throttle is snapped open. It's a one time shot to
prevent stumble when you stamp on the accelerator pedal. After that,
the full throttle fuel enrichment system takes over, as long as you
are demanding full throttle, or above normal throttle.

Fuel injection, the type that has individual injectors for each
cylinder, can't do that. The amount of fuel injected has to respond
according to how it's been designed to operate. In todays cars, the
injectors are designed to be able to inject the proper amount of fuel
according to a number of parameters and sensors, all controlled by a
computer. But unless you're flying behind a FADEC system, the fuel
injection systems for Lycoming and Continental are not that
sophisticated.

With the non computer controlled injection systems being used in
aviation right now, the only advantage you get over carburators is not
much worry about carb ice and somewhat better fuel distribution per
cylinder which may permit you to use mixture settings on the lean side
of peak.

Hot starting is not one of the advantages.

Getting a much better fuel burn is not really going to happen until
computers get involved with controlling the injectors.

When you consider that most of the life of the engine is spent
cruising at the leanest safe settings, both carburated engines and
fuel injected engines end up being fairly close together in fuel burn
because both are optimized for that operation.

That's as I understand things.

I did not know that Lycoming counted on a certain amount of post
engine shut down bleed through from the injectors to allow a hot non
primed restart. With a carburator, hot starts are (or should be) non
events as the moment the engine is turning it's sucking fuel from the
carburator.

Corky Scott