Intake runner sizing..

[Corey Cole]

On Wed, 21 Feb 1996, Kenneth C. King wrote:

> On Wed, 21 Feb 1996, Corey Cole wrote:
>  [ munch ]
> > I have a QuattroPro spreadsheet that calculates at what RPM the peak will 
> greetings:
>   could you post the equations (or make the file available on ftp)?
> 
> later,
> kc
> 
Looked up the basic equation, and it should work for Rotary engines.  One 
question, however.  I've heard mentioned that the airflow through a 
rotary is essentially twice its "displacement".  I've pretty much ignored 
rotaries, so I'm not sure how technically sound this is...

Anyways, here is the equation:

   _c_ {_(ab+a+1)+-(((ab+a+1)^2 - 4ab))^.5_}
f= 2pi {         2ab(L/A)sub 1 * V sub 1   }

where:  a=(L sub 2 A sub 1)/(L sub 1 A sub 2)
	b=(V sub 2)/(V sub 1) 
	V sub 1= Vswept/2*((CR + 1)/(CR - 1))
	c=speed of sound

CR:  Volumetric Compression Ratio
L sub 1:  Inlet pipe length
A sub 1:  Inlet pipe area (cross sectional)
L sub 2:  Air duct length
A sub 2:  Air duct area (cross sectional)

Some notes about the above equation:  The brackets ({) indicate a square 
root.  The underline characters indicate that the upper set is the 
numerator, and the lower set is the denominator.  The +- is ascii for 
plus or minus (I didn't want to throw another slash in there and possibly 
throw everyone off).

Check out this crude ascii picture for clarification (hey, I'm trying):

	     v Throttle
=============|[[[[[[[[[[[[[ < Intake Chamber (a.k.a. Plenum)
^Air Duct     || || || ||
	      || || || ||< Inlet pipe
	      || || || ||
      	      1  2  3  4

1,2,3, and 4 are the cylinders.  For rotaries, V sub 1 corresponds to 
mean cylinder volume, so I would assume that you would put "displacement" 
in there, but I'm not sure.

If none of this helps, the equation and figure come from Richard Stone's 
"Introduction to Internal Combustion 2nd Ed."

 Corey Cole					colec at pr.erau.edu
 '65 Skylark
"Knowledge is power...but cubic inches help."		Go #24!!!!!
 
I was drunk the day my mom got out of prison
and I went to pick her up in the rain.
But before I could get to the station in my pick up truck,
she got runned over by the darned old train...
						David Allen Coe
						Steve Goodman