Al Gietzen wrote:

POWER AND TORQUE

Wide open throttle power and torque curves were run after adjusting the
mixture correction table and the timing.  Mixture setting was
approximately for maximum power.  Data was initially gathered up to
about 6000 RPM, but looking at the data showed that the torque curve was
still flat, and hp increasing, so subsequent runs were made to 7000 RPM.
Still no break in the hp curve.  Given that the 2.17 redrive ratio
limits engine RPM to about 6300 (Prop @ 2900), there was no point in
pushing things further.

The torque curve is distinguished by it's flatness; varying only by 10
ft-lbs from 210 ft-lbs at 4000 rpm to a peak of 220 ft-lbs at 5000 -
nearly constant from 4800 to 6800.  The 220 ft-lbs is not extraordinary,
and could be improved by 9.7 compression rotors vs the stock 9.0 rotors
that are in the engine.  Mazda's data indicates about a 4% increase in
power with 9.7 vs 9.0 at 5000 rpm.  It may also improve some as the
engine wears in - this is an engine with only a couple of hours of
running since overhaul.

I won't argue the case for/against the longer so-called 'tuned'
induction runners, but I conclude that performance benefits are minimal.
Tuning for a given range may give slightly higher power in that range,
but I'll have to see the dyno results to believe it.  If you're looking
for a flat torque curve (great for a car) this setup achieves it.  The
manifold is 4 ½" flange to flange, engine to throttle body, and the
throttle body barrels are about 5".

Al

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