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


Paul.
Since we are looking for only 200-230hp 16-20" ought to get us in the
ballpark. Got the numbers from Tracy several years ago! By the way nothing
on the ground test stand is airworthy, it is just a vehicle for fabrication
and design, if it works as planned a whole new package will be done, and if
not of course the project will be scrapped.
All runners are exactly 16" long.
We did the transitions by carving a male form out of hardwood that was
tapered on the end to go inside the tubing and then tapping the end of the
tubing with a soft wooden hammer forcing it over the hardwood form, perfect
fit.
The oil pan is an after market item that holds an additional 1.5 qts, just
for testing.
The prop was an item we had in the shop for other tests and is not
airworthy. milo


Don't forget Tracy's engine was a four port RX8 engine that had been ported
and it barely makes 200 HP. It would do better with longer runners. To port
and engine you have to take it apart. You might as well p-port it and get
an easy 250 HP.


Paul Lamar