flyrotary@lancaironline.net Mailing List Archive

I understand, Tom. I have built 4 intake manifolds trying out various ideas/theories of tuning and it is terrible complicated in that you have two basic phenomena occurring in any intake. The is the inertia or momentum action of the macroscopic movement of the air mass being pulsated by the opening and closing of the rotor intakes. This air mass may hit Mach 0.6 but the average is closer to 150- 200mph. Then there is the Finite Amplitude Waves (FAW) which travel at the speed of sound and which may be pushing molecules in the same (helps) or opposite direction of the main air mass. At different rpms these two phenomena may work either together or against each other. When they are working together you can get close a 15% increase in power according to the results the Mazda engineers reported in SAE papers.

The FAW is the principal on which the 13B NA Dynamic Intake effect (self supercharging ) is based on. Fascinating but complex topic - these two phenomena is probably the reason that frequently what on the surface appears to be a good intake design is mediocre and a apparently poor design does better than expected.

There are of course the numerous other factors of which you have mentioned, cooling the air increasing the density, sequential injection rather than batch, no throttle plates in the intake just one that slides completely out of the way, etc, etc. I must warn you though, if you start messing with intakes - make certain your aircraft project is finished otherwise you may never find time for it.

I am most interested in any intake experimentation you undertake, so please keep me apprised (off line if you prefer)

Ed A

----- Original Message -----

From: Tom

To: Rotary motors in aircraft

Sent: Saturday, March 19, 2005 12:35 PM

Subject: [FlyRotary] Re: Intake Ideas....

Saturday morning, coffee in hand.

That's it Ed, I meant to say I would primarily run at or above 7000rpm. ;)       For reference I'll have to dig out my copy of Tracy's papers to see what his Dynamic Manifold looked like.

I can't ignore results various guys got but I wish I could see pics of all the installations and the results they got them.     I can see other things that would be involved, such as specific shape of the plenum, location of the throttle-plate in the system, and smoothness of the manifold baseplate --> gasket --> intake-port interface.   Another factor would have to be the change in location of fuel-injectors and when they were timed to squirt. This was probably entirely overlooked when declaring the primary reason manifold changes effected performance.    I'm not saying they're wrong, only that I'm not entirely on board with the conclusions, yet.

I undertand another factor, especially for carburetors and throttle-body-injectors (Ellison), would be the increasing air-density after having applied a fuel mist to it and causing some cooling.    I understand some power enhancing fuel additives primarily work on this principle.    So extending runners would help this concept.

Here's a little perspective of runners and airstream momentums, chaos, from my strange universe.   As for airstream momentum, I would think it would still be dependent on what's happening at both ends, at least in the distances we're talking.  With runners there's still chaos/confusion in the plenum that feeds them and you would still have negative effects from that (maximized when you're switching between the ports you're feeding and minimized near the end of port feeding when airflow is established and moving along but still with some residual chaos).    So plenum+runners or plenum-only you still have this issue.    Runners themselves, with or without plenums, add another level of airstream momentum issues, as you already mentioned with DIE.

Airstream momentum in runner-only designs where each has a throttle-plate, ....well...some other time.

Also I was thinking of what must be happening inside these plenums several guys have where it's essentially a tube with a throttle-plate on one end and runners attached along the sides.   They seem to work but to me the changing air-pressures in the two halves and changing airstream momentums during port changes are totally negative.

Now if only I can convince laws of nature to swing my way...

Tom, speculation galore

Ed Anderson <eanderson@carolina.rr.com> wrote:

It all depends, Tom. ..... Now if your engine is going to turn 7000+ rpm then I would agree larger dia shorter tubes are called for......

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