Pay attention to this as all you people with
 side 4 port RX8 engines are going to need something
 like this to get more than about 150 HP.
 Make a folder on your hard disk and save it.

 The plenum should be made real strong as when the
 throttle is closed there is high vacuum in the plenum
 and it will collapse. My suggestion is 1/8 thick door skin
 mahogany ply covered on both sides with one or two layers
 of carbon fiber.

 Of course this will work with a carb or fuel injection.
 The mass airflow sensor goes up stream of the butterfly
 throttle. A 3" (76 mm) inch ID throttle and mass airflow
 sensor is shown. My guess is you will get about 200 HP
 at 7500 RPM with this configuration. A 2.75" (70 mm) version
 may also work. You can get more HP with a side port engine
 but you must take it apart and port it. If you are going to
 do that you may as well convert it to a p-port.

 The difficult part is the transition from the two oval ports
 on the center housing to the 1.5 inch round tubes.
 The ports are only 40 mm high and 20 mm wide. They are separated
 from each other by only 5 mm. This transition needs
 to be hand made with a die grinder out of a block of aluminum
 an NC mill or a casting. Squashing the round tubes to ovals
 in a press does not get it as the area changes. You want to
 keep the runner area  constant. Besides that approach is very
 difficult to weld. The devil is in the details. The front
 and back RX8 housings have round holes unlike the 13B with
 ovals in those locations. In that regard the RX8 is a bit
 easier. At least the low power RX8 version is. The six port high
 power RX8 engine is another matter. The side 6 port manifold becomes
 a real nightmare.

 It is not practical to make a slide throttle with a side port
 engine. Taking your engine apart and installing p-ports and
 a slide throttle would result in about 250 HP.


 Paul Lamar

This is how we did it for the ground test article. Inlet runner lengths
 all
 came in at 16". The inside of the cowl could accommodate runners @ 20" for
 the RV-8. The exhaust manifold was just for testing, otherwise everything
 fit within the RV-8 cowl. Milo

Nice workmanship but why only 16 or 20 inch runners. Mazda says they need to be
a bit longer for low BSFC at 5500 to 6000 cruise RPMs and max takeoff power
at 7500 RPM. Are all runners the same length? Interesting looking bell mouths.
How did you do the transitions from oval to round for the center housing?
The oil pan needs to be a bit deeper as RX8s have oil breathing problems.
That six bladed prop looks like you are expecting a lot more than 200 HP :)

Paul Lamar