In a message dated 5/13/2007 2:13:30 A.M. Eastern Daylight Time,
lendich@optusnet.com.au writes:
Lynn
Your
saying what I want to hear P-port, high intake velocity (smaller diameter
tubes - I thinking about 1.6") and a after considering Tracy's set-up
and Talking to Ian Beadle ( Western Australia) I'm also leaning toward the
shorter inlet tube length.
Of course nothing beats proof of testing.
Well, there are some things to think about here. The shortest length that
gives you one complete cycle of inlet reversion at the peak power RPM is all
that is required. The idea that the inlet tract length has a big affect on power
output has been proven time and again. For the math impaired, like me, it is
quicker to build the example and make the changes to peak it up on a dyno. But
others have gone before to break this ground, so copy from them, or from a known
good performer.
How is it that different lengths could work for the same situation? The
exact length may not be as long as you would think. But it may present other
difficulties that occur at lower RPM than peak power. So, at a peak of say,
6,000 RPM a standing wave of fuel mist may be just inside the bell at the inlet
end of the runner. Where would that ball of fuel mist be at 5,500 RPM where we
want to cruise the engine? Well, it would be just outside the bell shape in the
air filter or in the log manifold. In the event of a misfire, at top speed, this
would be ingested with no problem, but at cruise there might be 4 such balls
floating in the air filter, and a misfire would be a life altering experience. .
Another vote for both injectors closer to the engine. The fuel mist balls are a
physical manifestation of the reversion wave rarifying. Marking how long the
completed reversion column is at that RPM. Often seen on the dyno when running
with no air filter
So maybe, doubling the ideal inlet length would be a good idea. The first,
fourth and sixteenth harmonic of any frequency should work nearly as well so
twice the length should be fine. Plus the more mass in the air column should
make the mid range come up a bit stronger. The effect on top power will be to
reduce it somewhat. So the best performance for doubled the length would be at
3,000 RPM where it adds to the mid range and does not seem to fit the bill
at all. But the anything will work rules apply and the loss at the top may not
affect 5,500 RPM and now may help it.
Another gag to shorten a system without much of a penalty is use a tapered
runner. Bigger carb or TB on the end and increasing velocity as the flow enters
the engine. About the same mass, same or better velocity at the port face, less
dependant on harmonics, less drag from a smaller diameter it's whole length.
Speaking to Ian (he's into electronics) he suggested ( If I understood
him correctly) that the sine wave of the exhaust pulses are shorter as the RPM
goes higher (makes sense), so the intake length needs to be shorter.
I was always under the impression that the shorter manifold was for
torque and the longer for HP - but as they are inextricably linked
(HP=TxRPM/5252), what real difference is there, if any, in relation to
aviation needs. Perhaps pulling a few more RPM??
Mind you I'm still working on the single and to get a healthy HP out of
it. I'm hoping to achieve 125HP and maybe as much as 150
hp.
You should get at least 110 HP at 6,000 RPM without much strain. More for a
Pport. A bit of boost and the sky is the limit. The single rotor with no rocking
couple should do just fine, and be very smooth at higher RPM.
I'm still debating the simplicity of a carby V fuel injection, after
riding the new bike around Australia I now understand the benefits of FI in
relation to economy.
The injection wins both ends of the argument, if you don't count
cost.
BTW I was hoping you would take a stab in the dark and say 6" to 8" would
be sufficient for the intake tube.
Guessing 20" of constant diameter tube. Or, with a nice taper maybe 12" to
16".
After thinking about two TB's (as you suggested), it adds another
variable to the equation, I've got all sorts of things to consider.
On another point, have you used the steel Bellhousings on the rotary and
are they very heavy!?
I have never heard of or seen a steel bellhousing for a rotary?
George ( down under)
Lynn E. Hanover