We have two RX-8 engines the rev ranges used will be exactly the same
One is a six port and the other a four port

The typical rev ranges will typically not exceed approx 6200-RPM and
definitely not more than 6800-RPM. Use Tandem Gyro lengths 4.8/4.9 &
4.5/4.6 metres long, PSRU = 2.47 : 1, props 76" / 74"

Seeing as Gyros are typically fairly slow flying aircraft it is more
applicable to keep to a REV range that is suitable to the flight speeds
the machines do. There is really no point is making the engine spin any
harder as we will simply develop more HP that we can't use. we believe
that the engine will only be around 5500-RPM. Easy cruise = about 65
Knots, Fast cruise up to 80 knots  but not faster than this and there
are good technical reasons why no faster. However they are not relevant
to the question.

How long should we be making the intake runners for our RX-8 engines.
Tracy's computers will be used on both engines so there will only be 4
injectors. How do you think the 6 port engine runners should done.
Height is not really any issue although I would prefer to keep them
fairly close  but things like the alternator etc will be left where they
are by default as they definitely do not interfere with anything and we
have more than enough space for them to stay there.

So your recommendations  that would provide the most efficient
performance both in length and diameter of the runners. I would like to
use the original RX-8 throttle body as well, why you may ask, well
because  amongst other things I have finally got hold a CCT to use it
and have a electronic throttle  rather than a cable one. (I can do a lot
more with that than a cable controlled one, also I'm being slack I don't
have to make it.

Anyway suggestion and maybe a suggested config would be really great, I
have to get on to this pretty shortly one of the machines I have to
start putting the engine in and making the mount etc.
Oh and yes we will be using some ram charging, while it may not have a
great effect it will have an effect to fuel use and performance.

Thanks in advance

Regards David

I have no idea David. Most of the dyno data we have is for a 2 inch diameter
.065" wall tube 23 to 25 inches long connected to a RX8 P-port engine. That gives
240 peak HP at 7500 RPM . That will not necessarily work for a side port
RX8 engine or be what you need.

Check out key word "RX7 Airplane" on Youtube for a How-To do an RX8 p-port
engine.