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Thanks for the contribution, Bill, point well made.
Clearly there are many aspects to induction (libraries written on the
reciprocating engine ) and the complex interaction of different forces in
induction systems makes any discussion which promotes understanding of the
rotary useful. I have tried short intakes and long intakes on my turbo 4
port (no turbo) and there is no question in my mind that at least in the
4500 - 6500 range longer is better. Now clearly as you go up in rpm
shorter tubes provide all the attributes you describe. Sure wish my engine
would respond to 3-5 inch inlet tracks {:>).
Ed
----- Original Message -----
Sent: Thursday, February 10, 2005 12:56
AM
Subject: [FlyRotary] Re: Same HP = Same
Air Mass <> same air Velocity [FlyRotary] Re: ...
So if the rotary has less displacement of the
sucking component and must take 25% longer for each revolution.
Therefore the only way it can obtain an equal amount of air is for the
intake air to have a higher velocity than the Lycoming
does.
The air velocity of the area in the intake for
the rotary would appear to have to be much higher than the Lycoming.
If my assumptions and calculations are correct that would imply (at least to
me) that to minimize air flow restriction a larger opening would be
required on the rotary compared to the same HP Lycoming. Its not
that one is taken in more air its that the rotary has less time and smaller
displacement pump so must take in the air at a higher
velocity
Ed, you have a good cut on the discussion, with one other variant to add
in. There is flow stopage in the rotary in the overlap phase so the easiest
way for the tuning to work is low restriction. You can use a single throttle
body but it better be a big one. Air has mass which is why tuning works at
all. The correct length inlet tube keeps the air moving toward the chamber
durring the overlap phase. You are right on about the timing which is why a
no-compromise intake like the Le Mans engine uses the variable length inlets
that get shorter at high RPMs. The shorter time to cram in the air, (higher
RPM), the less restriction you must have to extract the most out of the
engine. On the latest F1 engines 18K RPM is common, that's why they have an
intake tract about 3-5 inches long. They started the showerhead style
injection because the length is so short that shooting across the plenum
allowed milliseconds longer for the fuel to vaporize. Pretty extreem stuff.
Your comments about rotor speed also indicated why we need longer intakes than
piston engines for the same shaft RPM. The rotor turns slower than the E-shaft
so our intake event is like a piston engine turnig over slower.
Bill Jepson
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