formulas

[Michael Kent]

While this may not have to do directly with EFI, it has to do with the 
intake manifold that I will mount my EFI stuff on so...

I have been able to find a few equations dealing with the design of tuned 
intake manifolds. They seem quite generic and I was wondering if any of 
you know of other formulas that might be more appropriate. My application 
is a 2.6L 4, turbocharged and intercooled running pump gas. I will be 
fabricating the intake manifold but first need to finalize the design.

Helmholtz Tuned Induction system

	F = ( C / 2pi ) * ( A / LV )^.5

	F = resonant frequency
	C = sonic gas velocity
	A = cross sectional area of tuning pipe
	L = length of tuning pipe
	V = resonating volume

The SAE article I got this from made no mention of the units nor how F 
relates to RPM. Would it be directly proportional? (F->RPM)

Super Generic RPM based harmonic formulas

	2nd harmonic	132000 / RPM	= tuned length in inches
	3rd harmonic	97000  / RPM
	4th harmonic	74000  / RPM

For these it seems that the earlier the harmonic, the broader and more 
powerful the tuning effect is. Unfortunately a 22 inch runner is kind of 
hard to package.

Lastly, does anyone have the formula for calculating mechanical 
efficiency of an engine relating to compression ratio?

Thanx much in advance, Mike Kent
another poor engineer in training...