Wasserjet: A Clean Lightweight Engine

The 2-stroke engine, to date, is the most common engine used in the stand up PWC. California, New York, and several US National Parks have already banned them and it is only a matter of time until they will be banned from all waterways.

The most common alternative to a 2-stroke is a 4-stroke reciprocating piston engine. These engines are not adequate for the stand-up PWC because of their weight and over-all dimensions (power-to-weight ratio). The need for a better solution, in the wake of recent EPA regulations, is crucial to sustaining the standup PWC market.

Reflecting on the current issues with the standard 4-stroke engine for the stand-up PWC, Wasserjet took a hard look at the Wankel rotary engine. One big advantage, of the Wankel engine, is the power-to-weight ratio. It exceeds that of the 2-stroke engine. In addition, take note to the processes within the engine. Due to the long timings and high exhaust temperature, any oil entering the combustion chamber burns almost without residue. Emissions of a Wankel can be as low as 1% of comparable 2-stroke engines and levels equal to a 4-stroke.

Wasserjet engines are charge cooled. They use the intake air for cooling and lubrication of its main components. There is no crankcase oil, making the engine extremely light. Our engines use a quad fuel injected intake system: Fresh gases flowing through the first port, enter the engine from one side plate. Then they flow through the rotor and the eccentric shaft in axial direction to cool and lubricate the rotor, eccentric shaft and main bearing, and from there they enter the combustion chamber through a transfer port in the opposite side plate. The second inlet is used for direct airflow to “Boost” the power. With 4-stroke combustion and fuel injection the efficiency is 20-30% better than comparable 2-stroke engines. Plus, not bulky

For development of this engine, we have teamed Woelfle Engineering GmbH. Woelfle has been building proven rotary engines for both racing and aerospace applications. Using a rotary engine is simple. Making it, though, requires the highest precision, state of the art technology and technical expertise. In addition every engine is tested on a dynamometer before shipment.

Along with Woelfle, Rick and Rick Roy Products have been an important part for the implementation of our engine into the PWC hull. Rick Roy Products builds stand-up and sit down hulls along with a large array of aftermarket components. Rick’s commitment to the stand-up PWC market is apparent and we thank him for his involvement in this project.

The engine will include Carbs/throttle body, ECU, Ignition and charging system, starter, and mounting plates. The first release will be a direct fit for a Yamaha Superjet type hull.

The Wankel Rotary Engine

The Wankel engine is a 4-stroke engine, because the combustion processes in four independent strokes. Its main components are:

• Rotor with seals (equivalent to the piston and rings of a piston engine)
• Eccentric shaft (equivalent to the crankshaft)
• Housing, also called trochoid due to its oval-like epitrochiod shape
• Side plates, closing the sides of the housing

The rotor has a triangular shape, and the edges of the rotor are in permanent contact with the trochoid through the apex seals. This creates three separate combustion chambers along the flanges of the rotor and allows three 4-stroke processes to run simultaneously. The rotor only rotates at 1/3 of the speed of the eccentric shaft, so with every rotation of the shaft a different combustion chamber passes the spark plug.

Since the rotor only rotates at 1/3 of the eccentric shaft’s speed, the working stroke is distributed over 270° rotation of the eccentric shaft. A 2-stroke reciprocating piston engine only has approx. 100° available for the same stroke. Therefore the load on the power transmission, as well as the vehicle the engine is used in, is lower despite higher nominal power.

The particular advantages of Wankel engines are the lack of vibration due to fully dynamically balanced rotating masses, the very compact design, the extreme performance with a very flat torque curve, as well as very low emissions.