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)
----------------------------------------------------------------------------
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.
Paul and Dave,
Way to go. Incredible. I'm impressed. The BSFC numbers are high but that
can be attributed to any number of inefficiencies at this stage in
development and doesn't bother me a bit. The main point is that you are
still just STARTING to tweak the engine. Great. The 19 inch manifold length
is a good thing and gives us more options in manifold make-up in crowded
aircraft cowls. So the next logical question is at 16.5" length and 8,000
rpms., with EFI injection can you beat the Lemans engine? Now we have an
engine with cooler exhausts, able to withstand more back pressure and a even
perhaps a few pounds of boost. Watch out Lemans.
Challenges remain to see if the side exhaust ports flow choke at any rpms.
I like to point out to the new guys that speculation about the merits and
demerits of a P-port Renesis engine have been talked about and debated for
years on the different discussion groups but I found none that actually did
it.
A great Christmas present. Paul thanks for having the wherewithal to 'Just
do it'.
Doug in Japan
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Copyright 1998-2007 All world wide rights reserved.