I have been curious about this, since there are injectors and pumps
out there that can support lots of fuel and power, would it be better to
place the injectors at or near the point of peak compression in the
housing or at the intake portion of the housing like the newest Mazda
rotary concept? What about angle? My thought is to do a combination
direct and port EFI system for my next project.

    Steve Ross


The problem is getting the fuel  thoroughly mixed with the air.

Injectors at the beginning of the runners gives the lowest fuel burn
for the HP generated.

Not used in racing cars because the throttle response suffers.

Paul Lamar

Ok, so the motion generated by the rotor is not sufficient to help
atomize the fuel? My thought was that with the high pressures generated
by the gasoline direct injectors and the modern nozzle designs that the
atomization characteristics would be better.

I guess along this line, are there combustion chamber shapes that would
be more ideal for direct injection?

Steve Ross


I suspect it has more to do with the time the fuel stays in contact with
the air.
I could be wrong.

CW, John Deere and RPI spent millions investigating this sort of thing
and they
never bettered the Mazda BSFC. Mazda has tried several chamber shapes
and the
latest RX8 is a simple  rectangular bath tub of uniform depth relative
to the face of
the rotor.

http://www.rotaryeng.net/Stratfied-charge-rotary.pdf

http://www.rotaryeng.net/Direct-inj-strat-charge.pdf

The answer to better efficiency is turbo compound F1 style. We should
see that
in 2017 or 2018 with the new RX9 or what ever they call it.


Paul Lamar

Hi all, In the pictures of the experimental direct injection Mazda engines
the injector was at the 12 o'clock position. DI is most beneficial for smog
and low power efficiency. It may not be worth the trouble for aircraft use.
A dual DI and port system might work especially if the engine will run on
either system if the other fails.

Murry Rozanzky

What is remarkable about these R16 pictures is the simplicity of the intake
system compared to the current RX8 engines.

Obviously Mazda is counting  on the 3.2 L displacement verses
the current RX8 engine's 2.6 L for the additional low rpm torque.
It will greatly widen the choices for transmissions.

If it is a turbo compound hybrid, as rumoured, the electric motor will supply
a lot of low RPM torque as DC motors have maximum torque
at zero RPM. AKA stall.

Stripping all that stuff off and putting a TTC style turbo on it we are looking
at close to 1000 HP for a under 200 pound 2 rotor  rotary as aluminium
end housings are standard on the R16. Imagine a Lancair rotary powered
Reno racer with 1000 HP.

Paul Lamar

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