As newcomers to the personal watercraft industry in 2002, Honda'sproduct engineers set out to forge innovations that would advance thestate of the art for the entire sport. In order to create atrend-setting PWC, Honda brought to bear the full scope of itsworld-renown engineering prowess to create truly innovativefour-stroke watercraft.
By all accounts, Honda reached that goal last year with its firstefforts in the popular three-passenger arena with the AquaTrax F-12and turbocharged F-12X. But this year, Honda is stretching the PWCenvelope even further with a new sport-oriented craft, the AquaTraxR-12X. And the two-seater class will never be the same.
Free to create a powerful, lightweight and compact engine fromscratch, Honda's development team dreamed up an engineering tour deforce: a liquid-cooled, DOHC 16-valve 1235cc four-cylinderfour-stroke engine, complete with fuel injection and a water-cooledturbocharger with intercooler. Purpose-built for marine duty, thisrugged, high-tech engine churns out abundant power down low before itreally hits its stride and tops out at 165 horsepower--what onemagazine called "enough muscle to light up the eyes of even the mostjaded PWC rider." And now this same engine powers the smaller, morenimble and decidedly sportier 2003 R-12X.
Racing-Style Adjustable Quick Trim System
In addition to this abundance of power, the R-12X also featuresracing-inspired technology that uses the AquaTrax drive system toenhance its handling. An ingenious adjustable quick trim systemredirects the angle of the drive system's jet nozzle to control theattitude of the R-12X's bow. By dialing in trim during take-off, therider can bring the R-12X to planing speed from a standing startdouble quick--can you say Holeshot with a capital H? In addition, thequick trim system also allows the hull to grab the water and changedirection much more quickly while turning aggressively--many racershave proven the performance of this type of system over the years.
With the Honda R-12X, the rider actuates the quick trim via alever mounted on the left handlebar. It's an easily accessiblelocation, and the pull-to-activate style of operation is extremelyintuitive. The leverage advantage built into the quick trim linkagesystem allows the rider to dial in just the right amount of trimeasily and instantly, without fighting the considerable pressuresneeded to redirect the jet drive nozzle. Thanks to this new quicktrim system, AquaTrax R-12X owners now have another option to furtherenhance 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 powertrainas a starting point, our liquid-cooled DOHC turbo four-stroke. Thisengine is light, compact, powerful, and environmentally friendly,earning a 2-Star emissions rating from the California Air ResourcesBoard. To create an agile, high-performance package, we created ahull that is 3.3 inches narrower and 5.4 inches shorter than the F-12hull, and it's a single chine design rather than a double chine. TheF-12's double chine produces a softer, cushier ride in keeping withits intended three-person, family-use aspects, but we wanted theR-12X to be especially aggressive in its turning traits and have moregrip in turns. Together, all of these changes make the R-12Xamazingly athletic in motion. Add to that the effects of the newquick trim system, and you'll find this new two-seat AquaTrax setsentirely new and higher standards for sport handling in the class."
Honda discovered from the very beginning there was no magicformula for hull design. Computer Aided Design (CAD) programs helpedat the start, but it was only through a long and complicated processof hands-on testing, testing and more testing that real-world resultscould be accomplished. Minute alterations in angle, size and lengthof the hull's chines or sponsons often yield huge changes in turningcharacteristics and stability.
A hull's dynamic characteristics are also intertwined, so evensmall changes in one area can affect performance in another.Consequently, literally hundreds of variations were tested in theinitial quest to find Honda's desired blend of turning, acceleration,comfort and stability.
As one development team member explained, "It took a tremendousamount of time and effort to develop the F-series AquaTrax, but thisextensive testing process allowed us to shape the R-12X hull muchmore quickly. We were looking for a very different set of performanceparameters for a very different kind of audience, one that emphasizedsporty, aggressive performance. But thanks to what we had learnedwith the F-12 and F-12X, we were able to shorten our development timewhile working with the R-12X. What's more, the new R-12X not onlysets new standards for its sporting ability, it also establisheshigher class standards for comfort and convenience."
A New Engine for a New Generation of Watercraft
The turbocharged 1235cc four-cylinder four-stroke AquaTrax engineboasts a compact, dry-sump configuration with the crankshaft centereda mere 180mm above the bottom surface of the hull. This creates anincredibly low center of gravity. The crankshaft directly drives thejet pump shaft to avoid any power loss in the drivetrain. A rubberdamper is placed between the drive coupler and driven coupler toreduce shock loads and smooth out the power delivery.
Honda has applied its proven, cutting-edge motorcycle designtechnology by incorporating dual overhead camshafts to actuate fourvalves per cylinder via a direct cam-over-bucket system. The upperhalf of the engine case is a sturdy one-piece cylinder blockengineered to withstand the added rigors of heavy-duty marine use. Aside-mounted, silent-type camshaft drive chain and ultra-narrowcylinder sleeve spacing reduce engine size and weight.
The AquaTrax's high-pressure fuel injection system incorporatesnew-generation injectors. This design provides the most accurateair/fuel atomization to yield maximum combustion efficiency andpower. An ultra-sophisticated electronic control unit provides twodigital 3-D fuel injection maps for each cylinder and one digital 3-Dignition map for pairs of cylinders to deliver the ideal fuel mixtureand precise spark advance settings.
Four waterproof transistorized direct-ignition coils areintegrated into the spark plug caps and high-tension leads to producea long-duration, high-voltage spark for sure ignition. Iridium-tipspark plugs placed under the direct-ignition coils produce maximumspark performance, maximum spark-plug life, and minimal carbonbuild-up.
One secret of Honda's competitive edge is the elimination ofhigh-tension spark-plug wires. High-tension wires tend to look forignition system low-resistance paths in wet environments, such as ina watercraft bilge area. The resultant ignition "leakage" occurs inother PWCs when the humidity of the bilge area increases, giving thehigh-tension leads an opportunity to short-circuit or create anignition misfire. This phenomenon is increased by 1000 percent in asalt water environment.
A Turbocharged Path to Extra Power
Honda graced the X series AquaTrax engines with a forced inductionsystem to boost power output--substantially--while keeping the enginepackage as light and compact as possible. Turbocharging was thenatural method of choice; a turbo makes use of power in the exhaustsystem that merely goes to waste in normally aspirated systems, andits power-boosting characteristics are well suited to waterjet pumps.In addition, turbochargers don't exact a parasitic power loss assuperchargers do, and there is no need to devise a complicated andfragile crankshaft-driven mechanical power take-off system from theengine, 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 maximumboost of 13 psi. This pressurization generates 32 percent more powerthan a normally aspirated design, for an incredible 165 bhp. Thanksto the intercooler, an ongoing supply of cool, dense air/fuel mixtureis fed to the engine for maximum power and combustion efficiency. Anelectronic control unit (ECU) monitors atmospheric pressure, boostpressure, engine speed, engine temperature and an engine knock sensorto manage an electronic waste gate valve that controls turbochargerboost, thereby protecting vital engine components and maintaininglong engine life.
The turbo's turbine bearing is an enclosed, ceramic-ball designthat withstands sustained high-rpm compressor operation whileproviding nearly vibration- and friction-free performance. Forgedpistons and connecting rods help the R-12X engine handle theadditional horsepower created by the turbocharger.
A specific impeller design matches the engine's powercharacteristics, and Honda's engineers selected pump designs thatoptimized acceleration and top speed. Pressurized water from the jetpump circulates through two separate circuits to cool the engine andexhaust manifold, ensuring consistent operating temperatures for bothsystems.
Environmental factors have become major considerations in the PWCworld, and Honda is leading the way in this area of the industry aswell. The four-stroke engine is already an inherently quietpowerplant, and Honda's engineers designed the AquaTrax pumpsspecifically to produce less cavitation noise than conventionaldesigns. Since the R-12X also has a waste gate in the exhaust loop,it is especially quiet, almost uncannily so for such an impressivelypotent machine. All of which make noise virtually a non-issue withthe R-12X.
Just imagine: an eco-friendly, ultra-high-performance two-seatwatercraft that's so easy to live with you'll want to stay in thesaddle all day long. But it's no dream. It's the Honda AquaTraxR-12X. And it's here now.
