Programmed Fuel Injection-- A Primer
Honda Programmed Fuel Injection was originally developed on road racing machines. Later it was applied to street bikes, including the exotic oval-piston NR750 sportbike. This system now appears on many Honda production street bikes, and this year makes its first appearance on a Honda ATV.
The essence of this system is the continuous use of several variables to control the injected-fuel quantity. Technically, the PGM-FI is an n-alpha mapped injection system, meaning that the basic variables are the engine speed (n) and the throttle angle (alpha). Based mainly on those measurements, the system looks upon its fuel map for the fuel delivery corresponding to the n and alpha of the moment. The computer then adjusts this fuel delivery according to four additional variables; airbox pressure, engine coolant temperature, intake air temperature and atmospheric pressure.
This process of recalculation of fuel delivery is repeated many times per second to ensure continuously correct mixture for conditions, and to provide optimal performance and remarkably crisp throttle response over a wide operating range.
History of Honda's PGM-FI development for motorcycles
More than 20 years ago, Honda began development of a fuel-injection system to constantly provide the optimum air/fuel ratio required by the engine using electronic control techniques. Since then, Honda has actively applied fuel injection to motorcycles as a technique to meet environmental, performance and high-level drivability targets.
In 1982, Honda marketed the first-in-the-world, fuel-injected motorcycle--the CX500TURBO--which attained both better acceleration performance than the CB900F and better fuel economy than the base-model CX500. In 1998, the environmentally friendly VFR800FI made its mark using Honda's PGM-FI and a newly developed three-way catalyst to meet stringent European exhaust emissions regulations. Today, PGM-FI development continues at the highest levels of competition on Honda's RC211V® MotoGP machine, allowing the immense power output of the RC211V to be better controlled by the rider.
In the late 1970s, Honda R&D was filled with enthusiasm toward attaining "core technologies that would lead to the development of new technologies in the 1980s." Through discussions on what should be the core technologies, turbocharging was chosen, and the CX500 was selected as the base model.
Honda defined the purpose of turbocharging not merely as a boost of extra power output from a large-displacement engine, but an increase of specific power from a small-displacement engine and an increase in thermal efficiency by reducing the frictional losses per output. Simply stated, it was to attain both an increase in power output and a reduction in energy loss. Most critical in the development were the turbocharger and the fuel-injection control systems.
One of the features of the CX500TURBO was the use of a computer-controlled fuel-injection system. Instead of using the then-conventional airflow meter, the computer-controlled fuel-injection system calculated the injection volume using the two control maps, i.e., one for the boost zone where the basic injection volume was determined by the engine revolutions and the boost pressure, and the other for the throttle zone where the basic injection volume was determined by the engine revolutions and the throttle opening. The actual injection volume was adjusted by the intake density compensation, the intake air pressure and/or intake air temperatures, the supplement for acceleration, warming up, starting, the compensation for battery voltage, and so on. Also incorporated in the computer-controlled fuel-injection system was a self-diagnosis function that activated the warning lamp and the backup system to keep the engine running when a failure occurred in the system.
RC211V-- fuel injection for superb drivability
Honda's RC211V MotoGP machine uses fully closed or partially opened throttle conditions way more frequently than the Formula One race cars, for example. Compared to the Formula One cars, which use fully opened throttle frequently, the controllability of the power output on the RC211V is more critical than the maximum power output.
Honda developed and applied new technologies to provide superb drivability for the PGM-FI used in the RC211V, including a twin-injector system, variable fuel pressure control and technology Honda calls "predictive control of residual injected fuel." When the RC211V throttle is fully opened or fully closed, the amount of fuel adhering to the inlet port walls and flowing into the combustion chamber during the following combustion cycle is predicted by the RC211V's electronic control unit (ECU), and calculated into the equation to ensure the most suitable air/fuel ratio for maximum drivability and fuel economy.
Honda's PGM-FI is one of the core technologies used to attain the goals of clean exhaust emissions, high fuel economy and performance. With the advent of fuel injection on the new Rincon, Honda has extended the application of PGM-FI from racing to street bikes, and into the ATV field where its benefits will be exposed to and enjoyed by a whole new segment of customers.