Dave Lemon owner of Mazdatrix discovered a strange phenomenon.
Apparently a Weber carb on the end of tuned p-port manifold
can enter a unstable condition where the mixture obviously
is changing rapidly from way too lean to way too rich.
The engine goes maximum rough and a ton of fuel air mist
eight feet high appears over the carb intakes. We are
not sure what causes this. It could be a mechanical resonant
condition of the carb intake system shaking the float bowl
or it could be something to do with rapidly reversing airflow
confusing the venturi sensor. It happens about the tuned
RPM or peak torque RPM. One can pass through it. It seems to
be a function of the jetting. This is a new one on me.

We will know more in a couple of days.

I was pleasantly surprised to find out the 2nd gen front cover
water pump and ignition distributor fits the RX8 engine with a change
to a 2nd gen drive gear on the nose of the RX8 e-shaft.
That makes for a very simple stand alone ignition system.

Hi Paul;

Sounds like a phenomenal resonant condition in the wrong direction!
I think Gary is right - smoking can be bad for your health :)
The fuel draw at 6000 rpm is HUGE!
Without knowing the RX8 exhaust port timing - it sounds like you are
getting a combination of:
1. the resonant intake pulse reflecting off the rotor face as the intake
closes
(until exhaust TDC plus a bit); +
2. the reversion pumping from the leftover exhaust going back out
through the intake,
as the intake opens until after exhaust TDC due to momentum; +
3. possible reversion on the intake (due to late Pport intake close
timing and reduction of
momentum due to reversion); +
4. other possible pressure wave reflections

You might try joining the individual runners with a U-bend and a single
larger carb in the
middle to try to capture the momentum and pulses and reduce the 8' spit
back.

OR
RX8/Renesis with 3rd gen Pport housings?

Cheers
Cary



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