(snipped)

Manifolds:  I've been working on a layout for the 20B

intake manifold

and am thinking of a radical departure.  If I join the two runners
from each rotor right at the manifold it will simplify the tubing
(half the runners), the casting (avoids all the bolts in or

near the

runners), and makes for a generally cleaner layout.  It will also
require larger diameter runners to port the air.  BUT.... are there
any compelling reasons to keep the runners separate all the

way back

to the plenum?  I asked a couple of folks about this when

the list was

down and the speculation was that the separate runners probably had
more to do with tuning the engine to run well through a broad RPM
range (especially with the twin sequentially staged turbos) than
anything else, and that combining them for an aircraft

engine should

be no problem.  Getting large enough injectors may be,

though ganging

up two injectors per runner could be done with little

problem and may

provide some redundancy.  Thoughts all?

Tom Kendall

Its worth a try Tom. So far nobody has used a high speed
pressure sensor to map the intake manifold pressure pulses
except Mazda. Chuck Dunlap and I
were talking about that when we stopped at his place in
Thatcher AZ. He has a high speed pressure sensor but he was
not sure what the speed actually was.

Did you get a number on the pressure sensor speed Chuck?
Also make and
part number please?

Paul Lamar

I have a Sen-Sym ASCX30AN I was going to try measure intake pressure
pulses. The response time is 100 Microseconds, the time it takes to go
from 10 to 90% of full scale. It?s a 0 to 30 PSI absolute, signal
conditioned pressure sensor. I tried it hooked to the manifold pressure
line in the cockpit, with the sensor connected to a Pico 8 bit PC
oscilloscope adapter. I was able to see pulses, but the resolution and
triggering was not adequate to get any meaningful info. I need to try it
again connected to a real scope, but I don?t have one that I can capture
a screen shot with. I think the sensor will have to be mounted very
close to the manifold as the long tubing probably damps the pulses.

About combining the runners, I think the ports open at different times
and you would loose some of the "punch" of reflecting the pulse back at
just the right time that separate runners provide. No problem if you
have a turbo, just crank up the boost.

Chuck Dunlap

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