Blower Drive!

BLOWER DRIVE!

ROUNDUP

I’VE BEEN WAITING FOR rational supercharging to hit mass-production, and the builders of personal watercraft have done it first.

Yes, yes, the Big Four built factory turbo bikes in the 1980s, but the tricky torque curve that comes with exhaust-driven turbo systems is no gift to street motorcycling. I’m talking about crank-driven supercharging that magnifies engine power at all rpm, not suddenly, just near peak as is with turbos.

Think about it. Think about a light, handy 600cc sportbike supercharged to make a smooth 1200cc of power. Why lug around a heavy car-size engine for the 1 percent of the time when you might use its big-displacement power?

Kawasaki has for a couple of years put a naturally aspirated 1498cc, 160-horsepower version of the big ZX-12R engine into its 15X watercraft. Reviewers love it because its big engine delivers instant torque-no waiting. So when Kawasaki wanted to power up this model, it added a positivedisplacement blower-a type that feeds the engine a con-

stant volume of air per revolution. Because the chosen roots-type blower adds just as much boost at 2000 rpm as it does at 7500, the result is an engine that acts like it has 50 percent more displacement than it actually does. Throttle response remains instant, unlike it would be with a turbo. Called the Ultra 250X, this watercraft makes 250 hp and more than 1500 pounds of thrust at the nozzle,

enough to shoot the craft straight up in the air if water could be delivered to the pump intake!

Positive-displacement supercharging is just what motorcycling needs to shed the blubber that normally comes with power. A razorsharp-handling ZX-6R with an easy 180 horsepower?

It’s time to think about this. Over to you, Kawasaki...

Kevin Cameron