Electronic fuel injection, which started in the automotive industry, gained acceptance, then moved to the industrial engine markets, has now officially reached small engines. The technology has established a solid foothold in the small gasoline engine marketplace through Kohler Co., which now offers a factory-installed EFI system on its Command Pro 26 hp engine. According to the Kohler, Wis., engine manufacturer, it is the only air-cooled, V-twin, port fuel-injected model in the utility engine market.
Full-scale production of the Command Pro 26 is underway and initial customer deliveries commenced in June. Initially, the engines are being sold directly to equipment manufacturers, with service available through Kohler's Expert Dealer network.
"Our main markets for this utility engine are the commercial turf industry, as well as industrial equipment builders and high-end consumer lawn and garden applications," said Cam Litt, product manager for twin cylinder engines. "It's designed for anyone who wants the extra horsepower, fuel savings, improved startability, quicker throttle response and computer capabilities that are available through electronic fuel injection.The horizontal shaft Command Pro 26 has a bore x stroke of 3.27 x 2.64 in., peak torque of 41.6 ft.lb. at 2200 rpm, compression ratio of 9:1 and weighs 94 lb. The engine features a full-pressure lubrication system with an automotive-style oil filter and Kohler's nickel-silicon plated Power-Bore cylinder design for improved cylinder life.
Based on the company's successful Command 25 engine, which was unveiled in mid-1993, the Command Pro 26 brings Kohler to the power limit for that engine chassis, according to Mike Campbell, director of engineering for Kohler Engines. "We could have gotten more power as a result of the EFI, but because we adapted the system to an existing crankcase, we were concerned about putting too much power into it. The role of thumb is a 10 to 15 percent increase going from a carburetor to fuel injection."
The EFI fuel system, manufactured by Robert Bosch Corp. and originally designated Alpha N (see Nov. 1996, Diesel Progress), is reportedly the first production port fuel injection system manufactured for the small gasoline engine market. With port fuel injection, fuel is injected into the intake manifold ahead of the intake valve. This allows more precise control of the fuel/air mixture, which optimizes horsepower, torque and fuel economy, Bosch said.
According to Campbell, exhaust emissions benefits from electronically controlled fuel injection are readily apparent, as the Command Pro 26 is certified in both California and with the EPA for Tier 1/Phase One emissions standards and will meet proposed Tier 2/Phase Two regulations. Certified at 4.2 HC+NOx g/hp-hr, the Command Pro 26 offers a significant improvement in exhaust emissions, Campbell said.
EFI system components include an electric fuel pump; fuel injectors and a pressure regulator; temperature, oxygen, speed and throttle position sensors; and an electronic control unit (ECU). In addition to the fuel system components, new components on the Command Pro 26 include a reconfigured intake manifold, ignition coils, wiring harness, flywheel, as well as the army of new sensors.
The key component of the EFI system is the ECU, which integrates fuel maps and ignition control calculations based on the throttle angle and engine speed. The system has simultaneous fuel injection in the intake port, as well as mapped injection and it uses high-volume production parts that are common in the automotive industry. The system has also been simplified to eliminate components such as intake manifold pressure and temperature sensors. The closed-loop system uses an oxygen sensor to provide the feedback loop, which enables the engine to compensate for changes, such as wear, as well as environmental changes such as altitude.
As an extension of the EFI option, Kohler also offers customers a user-friendly system that can provide complete vehicle management. By utilizing the microprocessor, the system's abilities expand functions such as electronic governor/throttle control; serial communications/diagnostics; display of engine speed, hours and load indication; safety interlocks/warnings; service intervals; and high temperature shutdown.
"For many of our customers, it's the first time that they are getting a microprocessor on their application." said Campbell, "so it really just opens up a world of possibilities for them."
Aside from enhanced engine and vehicle diagnostic capabilities, the fuel system's ECU has plenty of capacity to perform other electronically controlled functions for typical commercial turf equipment, according to Kohler.
"Your imagination is the limit," said Hal Johnson, Kohler's chief engineer for current product engineering. "The capability is there and we have drivers yet available in the ECU for different high-powered functions, such as adjusting cutter speed according to ground speed or controlling wheel slip in applying pesticides and fertilizers
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