volumetric efficiency and math

[bgd73]

As today it is crazier than ever, and yesterday, the carbs that did get proper venturi are in a museum worth a million dollars...
I am trying to build an air intake to put on top of my 1781cc boxer...and realized dimensions are endless.

1. materials: plastic equals warm. aluminum is electrically conductive, and carbon fiber is a 1960s boat recycled. I would just assume use aluminized exhaust pipe and thorough paint external..WELDED venturi.
2. temperatures along the route. Venturis can cheat this..but it must win. It is easier to make a loser. the carb is in the center of the engine, the inlet a cold outside source...indirectly, where a modern cone filter will go.
3. cam timing. A delay like injection needs a gigantic air plenum. Carbs do not...but what math to apply exactly? My cams are the classic 3 degrees snapper.
here is some math I apply free from the net:
this number is "air capacity"
below is max hp rpm. it is 90hp at 5200 on a 109 cubic inch engine.
5200X109 /3456 = 164 cfm at 5200 rpm. That would need hardly anything.
but the engine does climb to 7000 easy enough:
7000 x 109 /3456 = 220 max cfm, the rest is a legendary whistle.

here is max torque figures for "air capacity"
2800 x 109 /3456 == 88 cfm. and that could breathe through a one inch straw.

with above figures, no engine uses all of it. that is where volumetric efficiency equations comes in. again cam timing/lift and temperatures, compression, thermal dissipation (I love to mention this when speaking of a liquid cooled boxer) etc.

Now I am stumped. What size pipe do I need, and what perfect strain of venturi, given what I have written....from one end to the other, about 18inches...
At what speed is the cold air at the end of a 3 inch venturi, and at what speed makes it equal towards the middle of the hotter engine... before trial and error, I am welding this custom plenum, and need a roundabout math to get started...and it is certainly not subarus by oem plenum (it was as ridiculous today as 22 years ago when it was new). Anyway, thanks for ideas. My goal is not to allow a heated intake at the center of carb..therefore venturi is a helper. It would be easy to reply with "a pipe big enough" but that is like saying fual injection was a winner.

[aerohead]

I don't think I understand the premise for your project.Are you converting from carburetion to fuel injection? That conversion in an of it's self,will not "solve" your volumetric efficiency challenge.The throttle is your nemesis on this one.And your engine must have a throttle.And at "normal" driving rpms,the existing induction system has many millions of design dollars behind it for the mixed-load driving,between idle,and W.O.T. conditions encountered in the real world.------------- Without a flow-bench and engine dynamometer you have no tools with which to develop a manifold.Also,any modifications to the induction system must be balanced with changes to the exhaust tract.------------------ You can develop a set of equal-length exhaust headers with rubber hose.An intake manifold would be a daunting task even if you had unlimited underhood space,which you don't.----------- Reducing pumping losses is a noble undertaking,however,you're picking one of the most complicated projects of questionable outcome.I recommend you inspect some modern systems on new cars and see where they've gone since your car was manufactured.