Paul,
Okay, I can't stand it! I have a beautiful airplane almost ready to fly
and I don't want to skimp on the power plant. I ordered what I think I
need to build the runners and dynamic chamber, but now I'm not sure it
will all fit under the cowl. How important are size and shape of the
chamber? and I am shooting for 28inches on the runners right? How about
the significance of where I install the injectors?

Sorry I'm a pest!

Steve Denny

No problem Steve. I'll work with you until you have something you like.
Thats is why I am here.
Forget the dynamic chamber. The runners would have to be only 12 inches
long
as that is probably very difficult to convert to actual hard ware.
The Mazda versions are designed for torque at 3000 RPM which is useless
in an aircraft.  Use some 2 inch OD tubes on the outer ports
and 1-3/4 OD or 1-7/8 OD on the two center housing ports. Make
them about 28 inches long but design it so you can change the length
a few inches one way or the other. Put a plenum on the end.
If you use a 4 inch round tube plenum and weld the runners in you get
a fair transition so you may not need trumpet mouths on the
ends of tubes where they enter the plenum. Your throttle body
looks fine. Cold ram air is very important. However if you
have a dusty runway you will need a filter some place.

The injectors can go anywhere. There has been reported a slight
BSFC advantage if the injectors are mounted out near the plenum.
Others say no.... mount them close to the engine.
This Ford Escort manifold is the right idea but the runners
are too small.

Put a power bulge on the cowl if necessary :)

Paul Lamar ...No rotor no motor.


Paul,
Oops! Sorry I fat fingered the keys and sent that last one by mistake.
Thanks for the info. It sounds easy enough. I plan to use thin wall 4130
so I can weld it. I'm not sure what to use or where to look for the 4".
Should the pressure taps and temp sensor for the controller be mounted
in the plenum then?

Steve

Yes on mounting the pressure tap and temp sensor on the plenum.

BTW you might want to run it the way it is. I am sure you will
get at least 150 HP. Later on after you fly it you can make
some improvements in engine HP.