<Big Snip>

Tom Kendall responded:

I'm lugging the stock 3 rotor manifold with me to the foundry for

them

to

eye-ball.  I don't think they (or 99.9999% of anybody in this

country)

knows

3 rotor engines exist.

I was looking it (the 20B manifold) over tonight, and noticed that

although

the ports on the block are different sizes (the same as the various

13B

ports), the runners all transition to identically sized diameters.

Is

this

the case with the 13B stock manifold?  On our version, the smaller

ports

will have proportionally smaller runners.  This should keep intake
velocities uniform throughout the runner length.  Just a curious

deviation.

I doubt it will make any difference whatsoever.

Due to the nature of the three rotor it is not possible to do a

dynamic

chamber manifold so a simple tuned manifold was used. Same goes for

the

new RX8.

Paul Lamar

OK, that makes sense.  The total stock intake tract length on the 20B

seemed

very long.  Made for a very tall engine too.  Using the "wraparound"
philosophy of putting the intake plenum over on the plug side of the

engine

instead of on top, I should be able to reduce the assembly height by

several

inches.

The Casting:  Got a first hand look at it today.  Chunky little bugger,

but

even unmachined, it weighed in at only 5 lbs.   The cast surface finish
isn't nearly as nice as the stock ones, but certainly serviceable.  All
major dimensional checks came out fine, and the machine shop should have

it

skim cut & drilled some time next week.  I was also pleased to find that

the

as-cast "sockets" for stubbing in tubing bends came out 0.010 - 0.030
undersized (Yeah!  How's *that* for accuracy in a casting!).  Depending

on

the quote, I'll see if the machine shop is willing to clean out these
counterbores.

The only disappointment is that the runner openings on the flange face

are a

little oversized.  Looks like I was a little too aggressive with the

gouge

when I made the core boxes.  But the geometry is good, and for the

purist,

the surface finish should hold some JB weld real well for fairing in and
exactly matching the engine port openings.

I plan on mailing this first piece to Paul to be mated up with tubing

bends

to see how it all fits up on a Real Engine.

I'll probably port the cast iron a bit to fit the manifold.
I got the tubing for the rest of it right here.

Paul Lamar

Is it just the camera angle, or is that top bend something less than 90
degrees?  I haven't seen the "big picture", but I always envisioned all 4
bends being right angles and the runners ending up parallell in a horizontal
plane across the top of the engine.  Can't do that with anything other than
a 90 elbow.

Tom Kendall

Yes it is. 45 degrees.  I am playing some tricks on the other end to get the
fuel rail on top of the runners.

Paul Lamar
 
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