Paul,
 I believe you are correct about Mazda trying some of these things.

Some of the injection techniques probably worked great "but" aren't
economical in street car production. Direct injection is one of the ideas
that is more expensive than port injection so if you can get port injection
to work the cost of direct injection isn't justified.

 I like the direct injection idea for two reasons. First; there is no

probability of manifold icing. In the design the car people have come to
call the shower head, (into the bellmouth), there is still a real
possibility of loss of power due to icing. Not failure like a carburator but
signifigant restriction could occur. Second; Direct injection has always
been good for power, as far back as the 30's Grand Prix cars. The original
racing MB 300 gullwing 6 cylinders as well.

Bill Jepson

I think if it gave a significant increase in MPG they would use it. Say

5%.

Paul Lamar

Paul, One thing that will improve the efficiency is to use the technique

used on diesels and relates to what Francois was saying about tuning
methods. Use direct injection and no throttle plate at all. This hasn't been
done in cars in the past since the throttle controlled injection is much
easier. The fuel controlled "power lever" was used by Mecury on some of
their direct injection 2 cycles. Works very well and obviously reduces
throttling losses. Since a system without a throttle plate requires a full
engine management system, it hasn't been used that much in spark ignition
engines. The Mercury 2 cycles sound "wierd" in that thy don't 4 cycle at
idle, but rather hit on every stroke. They sound like they are idling twice
as fast.

Bill Jepson

This sounds very much like "stratified charge" which can reduce pumping
losses much like
a "Diesel" . However, direct injection runs into the same mixing limits as a
"Diesel"
which can limit full power output levels. I think the last time I looked at
Mercury
data the direct injection engines were rated lower HP than the port injected
same
model. Direct injection can be a double edged sword in this way - it
improves effective
volumetric air efficiency - particularly when compared to vaporized fuel
mixtures,
but makes uniform distribution for high power output more difficult. - Vance

 
The Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2004 All world wide rights reserved.