As newcomers to the personal watercraft industry in 2002, Honda's product engineers set out to forge innovations that would advance the state of the art for the entire sport. In order to create a trend-setting PWC, Honda brought to bear the full scope of its world-renown engineering prowess to create truly innovative four-stroke watercraft.
By all accounts, Honda reached that goal last year with its first efforts in the popular three-passenger arena with the AquaTrax F-12 and turbocharged F-12X. But this year, Honda is stretching the PWC envelope even further with a new sport-oriented craft, the AquaTrax R-12X. And the two-seater class will never be the same.
Free to create a powerful, lightweight and compact engine from scratch, Honda's development team dreamed up an engineering tour de force: a liquid-cooled, DOHC 16-valve 1235cc four-cylinder four-stroke engine, complete with fuel injection and a water-cooled turbocharger with intercooler. Purpose-built for marine duty, this rugged, high-tech engine churns out abundant power down low before it really hits its stride and tops out at 165 horsepower--what one magazine called "enough muscle to light up the eyes of even the most jaded PWC rider." And now this same engine powers the smaller, more nimble and decidedly sportier 2003 R-12X.
Racing-Style Adjustable Quick Trim System
In addition to this abundance of power, the R-12X also features racing-inspired technology that uses the AquaTrax drive system to enhance its handling. An ingenious adjustable quick trim system redirects the angle of the drive system's jet nozzle to control the attitude of the R-12X's bow. By dialing in trim during take-off, the rider can bring the R-12X to planing speed from a standing start double quick--can you say Holeshot with a capital H? In addition, the quick trim system also allows the hull to grab the water and change direction much more quickly while turning aggressively--many racers have proven the performance of this type of system over the years.
With the Honda R-12X, the rider actuates the quick trim via a lever mounted on the left handlebar. It's an easily accessible location, and the pull-to-activate style of operation is extremely intuitive. The leverage advantage built into the quick trim linkage system allows the rider to dial in just the right amount of trim easily and instantly, without fighting the considerable pressures needed to redirect the jet drive nozzle. Thanks to this new quick trim system, AquaTrax R-12X owners now have another option to further enhance what will be one of the most sporting packages afloat.
A Narrower and Shorter Hull for High-Performance Handling
As one development engineer explained, "We had a great powertrain as a starting point, our liquid-cooled DOHC turbo four-stroke. This engine is light, compact, powerful, and environmentally friendly, earning a 2-Star emissions rating from the California Air Resources Board. To create an agile, high-performance package, we created a hull that is 3.3 inches narrower and 5.4 inches shorter than the F-12 hull, and it's a single chine design rather than a double chine. The F-12's double chine produces a softer, cushier ride in keeping with its intended three-person, family-use aspects, but we wanted the R-12X to be especially aggressive in its turning traits and have more grip in turns. Together, all of these changes make the R-12X amazingly athletic in motion. Add to that the effects of the new quick trim system, and you'll find this new two-seat AquaTrax sets entirely new and higher standards for sport handling in the class."
Honda discovered from the very beginning there was no magic formula for hull design. Computer Aided Design (CAD) programs helped at the start, but it was only through a long and complicated process of hands-on testing, testing and more testing that real-world results could be accomplished. Minute alterations in angle, size and length of the hull's chines or sponsons often yield huge changes in turning characteristics and stability.
A hull's dynamic characteristics are also intertwined, so even small changes in one area can affect performance in another. Consequently, literally hundreds of variations were tested in the initial quest to find Honda's desired blend of turning, acceleration, comfort and stability.
As one development team member explained, "It took a tremendous amount of time and effort to develop the F-series AquaTrax, but this extensive testing process allowed us to shape the R-12X hull much more quickly. We were looking for a very different set of performance parameters for a very different kind of audience, one that emphasized sporty, aggressive performance. But thanks to what we had learned with the F-12 and F-12X, we were able to shorten our development time while working with the R-12X. What's more, the new R-12X not only sets new standards for its sporting ability, it also establishes higher class standards for comfort and convenience."
A New Engine for a New Generation of Watercraft
The turbocharged 1235cc four-cylinder four-stroke AquaTrax engine boasts a compact, dry-sump configuration with the crankshaft centered a mere 180mm above the bottom surface of the hull. This creates an incredibly low center of gravity. The crankshaft directly drives the jet pump shaft to avoid any power loss in the drivetrain. A rubber damper is placed between the drive coupler and driven coupler to reduce shock loads and smooth out the power delivery.
Honda has applied its proven, cutting-edge motorcycle design technology by incorporating dual overhead camshafts to actuate four valves per cylinder via a direct cam-over-bucket system. The upper half of the engine case is a sturdy one-piece cylinder block engineered to withstand the added rigors of heavy-duty marine use. A side-mounted, silent-type camshaft drive chain and ultra-narrow cylinder sleeve spacing reduce engine size and weight.
The AquaTrax's high-pressure fuel injection system incorporates new-generation injectors. This design provides the most accurate air/fuel atomization to yield maximum combustion efficiency and power. An ultra-sophisticated electronic control unit provides two digital 3-D fuel injection maps for each cylinder and one digital 3-D ignition map for pairs of cylinders to deliver the ideal fuel mixture and precise spark advance settings.
Four waterproof transistorized direct-ignition coils are integrated into the spark plug caps and high-tension leads to produce a long-duration, high-voltage spark for sure ignition. Iridium-tip spark plugs placed under the direct-ignition coils produce maximum spark performance, maximum spark-plug life, and minimal carbon build-up.
One secret of Honda's competitive edge is the elimination of high-tension spark-plug wires. High-tension wires tend to look for ignition system low-resistance paths in wet environments, such as in a watercraft bilge area. The resultant ignition "leakage" occurs in other PWCs when the humidity of the bilge area increases, giving the high-tension leads an opportunity to short-circuit or create an ignition misfire. This phenomenon is increased by 1000 percent in a salt water environment.
A Turbocharged Path to Extra Power
Honda graced the X series AquaTrax engines with a forced induction system to boost power output--substantially--while keeping the engine package as light and compact as possible. Turbocharging was the natural method of choice; a turbo makes use of power in the exhaust system that merely goes to waste in normally aspirated systems, and its power-boosting characteristics are well suited to waterjet pumps. In addition, turbochargers don't exact a parasitic power loss as superchargers do, and there is no need to devise a complicated and fragile crankshaft-driven mechanical power take-off system from the engine, as is necessary when driving a supercharger.
The R-12X turbo system incorporates a water-cooled IHI® turbocharger plus a water-cooled intercooler to produce a maximum boost of 13 psi. This pressurization generates 32 percent more power than a normally aspirated design, for an incredible 165 bhp. Thanks to the intercooler, an ongoing supply of cool, dense air/fuel mixture is fed to the engine for maximum power and combustion efficiency. An electronic control unit (ECU) monitors atmospheric pressure, boost pressure, engine speed, engine temperature and an engine knock sensor to manage an electronic waste gate valve that controls turbocharger boost, thereby protecting vital engine components and maintaining long engine life.
The turbo's turbine bearing is an enclosed, ceramic-ball design that withstands sustained high-rpm compressor operation while providing nearly vibration- and friction-free performance. Forged pistons and connecting rods help the R-12X engine handle the additional horsepower created by the turbocharger.
A specific impeller design matches the engine's power characteristics, and Honda's engineers selected pump designs that optimized acceleration and top speed. Pressurized water from the jet pump circulates through two separate circuits to cool the engine and exhaust manifold, ensuring consistent operating temperatures for both systems.
Environmental factors have become major considerations in the PWC world, and Honda is leading the way in this area of the industry as well. The four-stroke engine is already an inherently quiet powerplant, and Honda's engineers designed the AquaTrax pumps specifically to produce less cavitation noise than conventional designs. Since the R-12X also has a waste gate in the exhaust loop, it is especially quiet, almost uncannily so for such an impressively potent machine. All of which make noise virtually a non-issue with the R-12X.
Just imagine: an eco-friendly, ultra-high-performance two-seat watercraft that's so easy to live with you'll want to stay in the saddle all day long. But it's no dream. It's the Honda AquaTrax R-12X. And it's here now.