Lehanover@aol.com wrote:

http://www.newcovenant.com/speedcrafter/calculators/intake.htm

Here is an interesting Spreadsheet for calculating Torque peak.

Lynn E. Hanover.

Thats pretty amazing Lynn. Thanks for finding that.

Paul Lamar

I went in to that site and put in 160 cubic inches which is
about what the 13B is equivalent to in a four cylinder four cycle engine
and 6000 RPM for max torque. For whatever this is worth comparing
such widely different types of engines. 

Here is their formula.

"Intake Runner Area = (Cylinder Volume  X  Peak Torque RPM)/88200"

As you can see and as I have been maintaining runner area is directly
proportional to RPM for peak torque/HP. 

It came back with a runner area of 2.72 square inches.

A = pi R^2 

A/pi = R^2

R = square root of A/pi  = .93

That would be four runners of course for a four cylinder engine.
2.72 square inches is equivalent to a .930 radius round
pipe or 1.86 inches ID.  The large runner size ID for the ACRE NL injector 
holders and intake manifold is 1.625". According to this calculation 
TOO SMALL for max power at 6000 RPM.  So you will need to polish them 
out to 1.86 if you are looking for max HP at 6000 RPM. At least to the tubing 
bend ID size of 1.75 inches.

The small runners are WAY TOO SMALL at 1.375 inches. Not
a heck of a lot you can do about that as the center housing ports
are rather restricted on the current engine. You can polish them out to 1.5 
inches the same as the small tubing bends. 

By this calculation the ACRE NL manifold should have pretty good
BSFC at about 5000 RPM as the 17" runners are too long anyway for 6000 RPM.
A good compromise between peak power and good cruise fuel burn.
All bets are off if you use a dynamic chamber on the ends of the
runners.

We will have to do another manifold for the RX8 engine with yet larger
runners for peak torque/HP at 7800 RPM assuming the use of a 2.85:1 psru.
 
Paul Lamar
 
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