sizes richer than stock, producing a safe 110+ HP while reducing weight
by another 5 pounds, for an 11 pound total weight reduction.
Next, a thicker base gasket was installed to raise the port timing and the head
was machined to get back to stock compression. This produced 112.5 HP with similar
fuel consumption. The next step was to perform some slight trail porting to the
cylinders to provide a wider power band and bring the rpm back down. Being able
to make more HP at a lower rpm with greater torque increases acceleration. This
provided for a significant increase in power, resulting in nearly 116 HP at 8100
RPM, and a power increase at every rpm above 7000. Notice the fuel consumption,
it was a bit richer than the stocker, and Rich felt that if the jetting had been
reduced one more size that this package would have pulled 118 HP with fuel
consumption numbers in the 5's like the stocker.
The new type 593 Rotax engine is clearly stronger than the rotary valve 583 across
the entire power band, but surprisingly Rotax has left some power on the table for
the aftermarket to deliver. This may be
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caused by the choice to abandon the center outlet pipe design, or possibly due to the
fact that tighter noise level targets were desired with this next generation engine.
The fuel consumption numbers indicate that this engine will operate safely with less
fuel than most every engine
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previously tested, but we want to verify this on the snow during the course of the Winter. A
new engine out of the box will be down slightly on power due to the electronically controlled
ignition that switches to full advance after a four-hour break-in period. This feature should
result in improved reliability and reduced warranty claims for Ski-Doo. While some buyers may
be slightly disappointed that the engine does not produce closer to 110 horsepower, it will be
very competitive and time will tell if it is the fastest single pipe 600 on the snow. For those
who want even more, the engine responds very well to trail porting and can deliver close to 118
horsepower with a quiet single pipe. What about twin pipes? As with any brand new engine design,
give the aftermarket some time to digest and understand this new engine, and they'll likely find
out what options work best as the season progresses.
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