DF350A
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PROLOGUE | A REVOLUTION IN INNOVATION Over the course of our history in the marine industry, Suzuki has been recognized for our 4-stroke seven times by the National Marine Manufacturers Association for having the most innovative new outboards. This recognition for innovation has also been coupled with many firsts, including the first fuel injected 4-stroke outboards in 1997, the first 250 horsepower 4-stroke outboard in 2003 and the world’s first 300 horsepower 4-stroke outboard in 2006. Join us as we introduce the next milestone in our storied history, the 350 horsepower DF350A, Suzuki’s...

A FORCE TO MATCH THE POWER OF NATURE AND THE SEA

HOW THE DF350A CAME TO BE It’s no secret that there is a growing demand for more powerful outboard motors. These new outboards have, in turn, fueled a move to newer, larger boat designs that previously may have been powered by stern drive or inboard power. So, as more powerful outboards are introduced, the boats get bigger and as the boats get bigger, outboards are getting more muscular. Suzuki embarked on a major engineering expedition to build the Ultimate 4-Stroke outboard. Is The Sky The Limit? Making more horsepower is no mystery. Increasing displacement, or the use of a turbocharger...

GEKI: PARTING SEAS A Force to Match the Power of Nature and the Sea Representing Suzuki’s Identity and Heritage A Symbol of Our Passion and Commitment to the Ultimate in Marine Innovation

THE COMPRESSION RATIO SOLUTION As we mentioned earlier, designing an outboard with more power and torque is complicated by the need for lighter weight, better fuel economy and improved reliability. The new V6 DF350A features 4.4 liter displacement, making it the largest displacement V6 on the market today. That being said, how do we develop 80 horsepower per liter and still achieve our design goals? Our solution was to increase the compression ratio to 12.0:1, the highest compression ratio ever for a production outboard engine. In order to make this work without knocking (a typical problem...

DUAL INJECTORS FOR BOTH COOLING AND POWER As we mentioned earlier, our decision to use a 12.0:1 compression ratio provided us with the power we wanted, but also introduced several design challenges. With the Dual Louver System and the Direct Intake System, we got the dryer and cooler intake air that we needed. Next was fuel delivery. Injecting fuel does two things, it atomizes the fuel and, incidentally, it cools the cylinder. Cooling the cylinder was an important factor in minimizing knock. To achieve the power we wanted, we needed to inject 100% of the fuel into the cylinder at once, at a...

DEVELOPMENT OF SUZUKI’S FIRST CONTRA-ROTATING PROPELLER With the engine challenges met, Suzuki engineers moved to the lower unit. Again, the real world imposed itself on the theoretical thinking of the engineers. After years of outboard design, Suzuki engineers knew that the shape of the lower unit and the design of the propeller would have a critical impact on performance. The increased power of the new engine required more powerful gears, and more powerful gears were typically larger. Larger gears would require a larger gear case to spin a larger propeller. A larger gear case created more...

GEAR CASE DESIGN Designing the actual shape of the gear case was another significant challenge. Top speeds, even with the new contra-rotating propeller, were not up to expectations. Analysis revealed that cavitation voids around the gear case were still causing excessive resistance. While Suzuki engineers had extensive experience in designing gear case profiles, these new, faster speeds presented new challenges. After many late nights, repeated simulations using computational fluid dynamics (CFD) and countless test drives, a breakthrough design was developed that both minimized resistance...

Katsuhiro FUKUDA Chief Engineer

Atsushi OHTANI, Product Designer Innovative, aggressive, and sporty design. Dynamic design that you can recognize as a Suzuki outboard at a glance. Quality design that is suitable for the flagship model and gives you the joy of possession. These were the most important factors in developing DF350A. As for the details of its design, we expressed the characteristics of Suzuki outboards with the dynamic silhouette of a slant shape with an obliquely scraped forehead and raised rear end. And as a characteristic feature, we designed the side openings to show the vertical fins of Suzuki Dual...

Tetsushi Achiwa Design Group, in charge of Engine "Form follows function." This is one of my favorite words. The lower unit of the DF350A is a realization of these words. A gentle, elegant periphery of the shell, an outstandingly tough and strong material surface, and a contra-rotating propeller that helps them harmonize with each other. Each of them has its own function and gives it shape. The DF350A is our next step for specification without counter-rotation after the Suzuki Selective Rotation, which was developed in 2011. It was a very valuable experience for lower unit designers to be...

At the first trial production of DF350A after obtaining some prospects through repeated preliminary tests using DF300AP as the base, the output performance was far from that we had expected. As a result of aiming at the high compression ratio of 12.0, knocking inevitably occurred, and therefore we could not achieve the ideal high output. To achieve 350 horsepower with a small displacement, the compression ratio of 12.0 is indispensable, and also there was a concept of a compact engine. So, we could not change the layout largely. Then, we returned to the starting point and thought of...

O U R PROVEN TECH N OLO GI ES ARE BACK I N THE DF3 5 0A SUZUKI’S LEAN BURN CONTROL SYSTEM Suzuki’s innovative Lean Burn Control System was first introduced on the DF90A/80A/70A to great acclaim. The system predicts fuel needs according to operating conditions, allowing the engine to run on a leaner, more efficient airfuel ratio. It delivers its benefits over a wide operating range, providing significant improvements in fuel economy from low-speed operation into the cruising range. In combination with Suzuki Precision Control electronic throttle and shift system, the operator can precisely,...