Paul,

Published in the October 2009 issue of Automobile.

Two engine technologies- turbocharging and fuel injection- have recently
joined forces in mechanical matromony.  Spraying the fuel directly
into the combustion chambers achieves more precise mixture control,
since no droplets are left behind on the intake port walls, injecting
the fuel at 2000 or so psi versus the 50 psi common with port injection
facilitates finer atomization and more complete vaporization.  Also
the cooling effect from the fuel's change of state from liquid to vapor
enables significantly higher compression and expansion ratios.  According
to the EPA, the net improvement in efficiency attributable to direct
injection with turbocharging is a substantial 12 %.

Who has it:   BMW,Bugatti, Chevrolet,Ford, Lincoln, Mazda, Mini,
Porsche,Volkswagen.



I checked with Mazda in Missoula, MT and they never heard of it.

Gene Sandburg

I'll believe it when I see it/ Direct injection in a gasoline engine is not
easy. They have talked about it for years. Mercedes had direct injector
50 years ago in their race cars. Formula 1 engines would have direct
injection if it did anything and they don't.

Porsche spent big bucks on R&D and the improvement was barely noticeable.
It is also very expensive.

Paul Lamar


Paul, reguarding direct injection on aircraft engines. It would have the
same $2500 fuel pump as a diesel and likely need a mechanical volume
metering system to fire at 6000RPM. I could see it working on a piston
engine although mixture control would be tedious. From what I have read it
is necessary to mist the fuel near the ignition source to produce a
stratified charge. This allows a leaner mixture overall for the entire
charge and a faser burn with much of it occuring near the plug in the
enriched area of the stratified charge, The rest of the volume provides
additional mass of air to heat for expansion pressure.


In the case of a
rotary running at near maximum power we need the oil mixed in the fuel for
lubrication. If the direct injection is a stratified charge system there is
almost no exposure of the side and apex seals to the oil and without
lubrication even ceramic seals  will not IMHO survive. I know that Mazda is
working on a direct injection follow on to the RX8 series with the 3
injector oil metering system they now use. The metering pump seems reliable
to run along at 65 MPH at reduced power with only short seconds of
acceleration power  but this is a car engine.

I would be surprised  if Mazda
ever  raced anyhing that didn't have oil mixed fuel. If the goal is not the
fuel efficiency of stratifierd charge what possible benefit is there to
direct injection.. Introducing the fuel in the  intake runner gives a lot
more time for the fule to vaporize and cool the intake charge. I am not sure
what fuel pressures are these days in multipoint car injection, but I think
70 PSI should be close. In out sprint car we has 220PSI at  the inlet of the
barrel valve and more than that at the injectors when the valve was turned
open. These were constant flow systems running methanol as fuel and we
thought fuel burn was good for a 750 HP engine.


We used a high system
pressure relief valve and two drip in orfices "pills" before and after the
barrel valve for idel and max power fuel metering. the barrel valve linked
to the throttle plates  controled the fuel after idle to full power. This
was by todays standards crude as a club, but fairbanks wasn't making
integrated circuits at that time and aircraft radios used tubes and crystals
for tuning.

Now we have EFI with the possibility of changing charge density
by  timing the beginning of the pulse so that an enriched mixture is around
the plug when it fires. It would appear that a p-port rotary with an
optimized port shape and the fuel sprayed by two injectors near the top and
bottom of the port could produce a sratified charge  for a rotary . engine
running at a near constant RPM. The goals would be to reduce swirl mixing
and introduce the fuel during the most laminar flow into the rotor chamber
by adjusting the beginning point of the fuel pulse timing.

george grimes