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Dennis is correct, the Renesis and the older N/A RX-7 13B used different
aspects of the Finite Amplitude Wave effect (FAW) caused by the opening and
closing of intakes - Mazda refers to it as the Dynamic Effect Intake.
As Dennis indicated, the ideal was to use these pulses created in the intake
to generate localized pressure increases at particular time relative to
intakes opening and closing to generate more torque/power.
The older 13B retain considerable pressure in the combustion chamber when
the intake opened. This pressure generated a pulse/shock wave as the port
opened and it then traveled down the intake to (assuming rpm and runner
length was appropriate) pressure the second rotor's intake just as its port
was closing. This localized pressure increase next to the closing port help
prevent "reversion" of the charge already ingested by the chamber. Mazda
found this increase power at 6000 rpm by around 15% on the older 13B. This
was the N/A block, however, it will work on the Turbo block as well.
However, port time is a crucial factor in this effect and will effect at
what rpm this effect takes place.
Because the Renesis no longer has this overlap between exhaust and intake
and have moved the exhaust port to the side housing it can no longer use the
exhaust generated pulse. Instead they make use of several FAW effects
including the inertia rebound off of a closed port to generate this
additional power.
Dennis took the effort to determine what the relationships were for the
Renesis and his power increase (and associated cooling problem) are the
results.
But as I have said - having a cooling problem because you are now producing
more power is not the worst of all possible worlds.
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Dennis Haverlah
Sent: Wednesday, July 22, 2009 2:23 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Intake velocity stack lengths
Ben,
I must remind the group you are using a Renesis engine. information on
intake lenghts for the RX-7 probably are't applicable to the Renesis.
It is my understanding that the RX-7 intake uses a pulse coming out of
the intake valve created by the overlap of the exhaust and intake valves
on the rotors. The overlap has been eliminated on the Renesis and a
seal incorporated on the side of the rotor to cut-off any exhaust flow
into the intake opening. When I designed my new intake I adjusted the
intake tube lengths so that when the flow into rotor #1 is stopped by
the closing of the valve the reflected wave or pulse would travel to
rotor #2's intake and arrive near the end of the intake cycle.
I have seen better take-off performance and improved high altitude
performance. The higher horsepower has exacerbated my marginal oil
cooling!!
Attached is a picture of my intake.
Dennis H.
P.S. I probably will not make Oskhosh this year. I went last year and
enjoyed it but my tennis team plays in the Texas Sectionals in Dallas
during Oskhosh.
Ben Schneider wrote:
>Fellows,
>
> I have been thinking up this crazy idea of trying to make intake runner
tubes out of carbon fiber. My question is regarding length of the velocity
stack. Does the length make a difference? Could a velocity stack be more or
less the entire length of the tube? Meaning, if I have a 12" intake tube,
could the entire length of the tube be a gradual taper to the diameter of
the block opening? Would that mess with the speed the air is traveling in
the tube? Aerodynamics is not something I have a very good handle on, and am
hoping someone out there in Fly Rotary land can shed some light.
>
>Toughts???
>
>BTW, Any reasons why carbon fiber should not be used for intake tubes? May
make the velocity tubes a mute point.
>
>Thanks for any thoughts.
>
>Ben Schneider
>
>P.S. Any Fly Rotary fellows going to OSH??? Perhaps a lunch one day or
something.
>
>
>
>
>--
>Homepage: http://www.flyrotary.com/
>Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html
>
>
>
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