On 04/15/2011 10:17 AM, GRAHAM SINGLETON wrote:
> To a certain extent the same thing happens with Rotax so the front
> cylinders get more fuel than the rear at some throttle settings, drops
> of fuel don't turn corners the same as air molecules!
I believe the "problem" with the Rotax is of a different nature. There
are two carbs, and the inlet pulses are not equally distributed. Each
carb will see two inlet pulses in sequence, then followed by a long
pause when the cylinders on the other side (fed by the other carb) have
their respective inlet pulses.
After the pause, the flow of fuel inside the nozzles is stalled. With
the first cylinder breathing, the fuel has to start moving again, and
the second cylinder has the benefit that the fuel is already up to
speed. So the second cylinder in the sequence receives a slightly richer
mixture.
A solution can be to use a bigger bore balance tube. Some Italian
company is selling a pair of manifolds and balance tube for this
purpose, and the manifolds have already the bosses in them to mount fuel
injectors for future upgrades (and using the carbs as fuelless throttle
bodies and backup in case the EFI fails).
Ok,the subject was "Jabiru". To keep it in the subject: After the long
list of problems and disadvantages, can anybody enlighten me what the
benefit is of the Jab over the Rotax? (I assume there must be one, why
else would anyone bother to install one?)
Frans
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