Intake Runner?

[Edward Hernandez R]

Snipped from a private post:

"You stated that the "runner" formula quoted will only work on 4 
cylinders or less .  Could you explain why ?Surely if the the lenght 
is measured from the plenim to the cylinder it would not matter how 
many cylinders their are , as the sonic waves would only see the one 
cylinder from the plenim down , or does all this "ram effect" take 
place in the plenim itself ?

Taking a close look at the formula, you will find a volume that is 
represented by, in the case of a four cylinder, the other three 
cylinders that are not breathing. The more cylinders you have, the 
more volume you have, and this volume affects the output of the 
formula.

I have personally tested this formula on V6s and compared the results
 against more sophisticated modelling software and dynamometer data. For V6s, the formula is very inaccurate. Furthermore, modern V6s have
 a variety of tuning devices in the plenum with valves and tubes. The 
one I am working on has two of each. This represents additional volume
and even if you include this in the formula, the results have turned 
out inaccurate.

The ASME paper warns against applying the formula to engines of more 
than four cylinders, and my work confirms this.