Dave Lemon <dave@mazdatrix.com>

Paul,
I'm making my own slide carb (see attached) and the information from some
Aviation carb web site would indicate that a venturi isn't needed - so I
haven't included one. It probably be difficult with this design anyway. I've
made it from a couple of slabs of aluminum and as such you may see some
resemblance to the Aero Carb - for that reason.

From memory the carb your using is a 52mm but the restriction( Venturi) is

46mm. This may be acting as more of a restrictor than you might believe,
although to my mind 46mm should be enough for your needs. I have in my mind
that the venturi will increase the signal ( velocity/ response) but produce
a low pressure area which reduces the air density. If this is correct it
will be adversely affecting the VE.

I was hoping for more HP from your  trials, especially with the Rx8 and it's
higher compression ratio, I was expecting at least 250hp at 7,000 to 7,500
RPM. The larger carb may or may not work as anticipated because of the
venturi factor. Most carb sites suggest an oversized carb don't provide
improvements and in many case give worse results, but may be worth the trail
for confirmation of that theory.
George ( down under)

Well the venturi must be smaller than the runners to work as a mixture sensor
for carburetors. EFI systems use MAP, throttle position, mass air flow sensors
and air temp sensor to controll the mixture. Therefore the restriction of the
venturi is not needed. In our RPM range the bigger the hole the more the air.
The more the air the more the HP. Also I might add the better the BSFC assuming
the mixture is closely controlled and leaned properly. You won't get that
with a carb.

For power check out the latest down load from Dave Lemon at Mazdatrix.

Paul Lamar

Paul,
That's more like it - excellent results, so was it just the intake length or
was there some jetting adjustments?
Those results confirm the possibility for a single rotor to achieve 125hp,
which puts my mind to rest. I didn't want to go to all the time expense only
to achieve 100hp.

I figure it will only be a matter of time before your up to your armpits in
the 16X developments. By the look at those Bridgeport inlet and outlets,
there will be some serious breathing going on without the need for a PP -
always the way isn't it!?
George (down under)

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It all depends on what RPM you want the peak HP. The 22 inch length runner would be fine
on the RX8 p-port  for a 2.17:1 gear box. It is also as good as your going to get at
only 6600 RPM or so. A bridge port is impractical for a street or aircraft engine.
It will never breathe as well as a p-port. Air does not like to turn corners
and is does not like to flow through a bunch of small tubes or holes. That
may be necessary for a street car but not for an aircraft or out and out
race car engine.

It will be a long time before the 16X happens. Also from a p-port point of view
the 16X is not as good as an RX8 engine due to the 5 mm narrower rotors.
It will also have a lower RPM limit due to heaver rotors and higher
rotor bearing loads. What Mazda needs to do soon is put a high speed
paddle shifter in a six or seven speed RX8 transmission. Only a highly
skilled driver can get the most out of an RX8 as it is now.

Direct injection to evaporate the fuel and cool the rotors would
also work on an RX8 engine.

Paul Lamar ...No rotor no motor.

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