Paul
Fuel Injectors have been greatly improved in
the last few years. Â How good are the Mazda
Wankel engine fuel injectors/ Â ~ 10 microns?
What is the BSFC of the RX7 and the RX8
engines for normally aspirated as well as
Turboed?
The rotor has a symmetrical shape between the
apex seals with a dished elongated volume in
the center. Â This is I assume to try to
'sphere -alize' as much as possible to help
volume to surface area ratio, optimized for
exhaust/intake flow rates? Â But, is this the
best configuration or has rotor inter-apex
seal configurations ( especially in the side
port engines) been investigated by other than
MAZDA in the Mazda Wankel engines?
Can the RX7 or RX8 be turboed to 150HP/rotor
@ say 7500RPM? Â To be used for take off and
climb performance with 105 hp/rotor for
cruise.
Or  could this be more easily accomplished
with N2O?
The  engine is certainly a rugged design
except perhaps the various rotor seals?
Norm
That is a good question. I don't know.
BSFC normally aspirated is down around .47. We
don't have much data on the turbo but I suspect
the fuel burn is higher. The main improvement
in the RX8 engine has been at low power low RPM
rangers. Particularly at idle.
Mazda did a lot of experimenting with the
combustion chamber shape. Some of the
considerations were emission so it is not
necessarily optimized for HP or BSFC.
Midwest/Diamond uses a different shape.
Yes 300 HP is no problem at all for a 13B turbo
engine as long as you can choose a turbo that
will live. Several people are still using a
modified stock turbo because it is small, has a
built in waste gate, is water cooled and is
very much easier to install than say an after
market TO4.
Ken Welter used NOS for years to help him get
 off the water with his NA 13B powered 2900
pound Coot. Did not seem to hurt the engine.
Allan Tolle used NOS to set the all time record
time to climb to 3000 feet at Sun & Fun. His
competition Pushy Galore (Cat?) was also using
NOS however. He also used it for take off with
a top speed prop in the Sun 100 cross country
race. Something in the neighborhood hood of 300
to 350 HP I suspect. Of course he also had a
p-port engine which helped.
Yes the stock 2 mm seals tend to fracture if
you allow the turbo engine to detonate. I
highly recommend 3 mm seals if you are going
with a turbo. Detonation is almost unheard of
with an NA engine.
As long as you keep the foreign objects out of
the NA engine, keep it cool and mix 2 cycle oil
in the fuel it seems to last forever.
Paul Lamar
norm wrote:
Paul:
Do the injectors for the RX8 have different
part numbers than for a RX7 and are injector
pressure similar?
Norm
I am sure the part numbers are different as the
injectors look entirely different. There are
six injectors on the high power RX8 engine. Two
different spray patterns. 19 and 30 degrees.
Primary 1 front and rear is 30 degrees.
Primary 2 and secondary front and rear are 19
degrees.
Max pressure on the pump is 56.6 psi. It is a
return less system so pump speed is controlled
by the computer I think.
Paul Lamar
Paul:
Since the particle size distribution varies with
angle within each nozzle I would say it is most
likely that at least the 19 Deg angle nozzle has
~10 microns min size in the middle of the spray.
Interesting that there are two nozzles and each at
a different cone angle. Is the 30 degree angle
spray further from the intake port than the 19
degree angle nozzle? Difference in volume
sprayed? Are both on with the same delta time
and timed simultaneously?
The combustion rate and combustion completion
extent seems to be greater for the RX8 Rennie
especially with the drop of >200 F EGT.
This could be an advantage to use in a RX7 13B to
get that very high EGT down as well as the BSFC.
Norm--
The 30 degree nozzles are used closest to the port.
Primary 1 front and rear rotors.
The injectors are staged. Primary 1 first. Then secondary. Then secondary.
Then primary 1 and primary.
The lower EGT is mainly due to the delayed exhaust port timing IMHO.
The side exhaust opens around BTC while the peripheral exhaust opens
well before BTC. The side exhaust also closes sooner but the total
area is almost double the peripheral exhaust port area. That should make
up for the worse flow coefficient of the side exhaust port.
Peripheral ports always flow more for a given area than side ports.
This applies to the exhaust as well as the intake.
IMHO what will eventually work the best as far as power is concerned
is both peripheral and side on both exhaust and intake. The RX8 engine
is still not as powerful as the Le Mans all peripheral port engine by
a long shot. In two rotor form the Le Mans engine would be 350 HP at
8500 to 9000 RPM. When it comes to power breathing is the name of
the game.
Paul Lamar
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