Global automotive supplier DENSO Corporation has developed a new electronic fuel injection system for small motorcycles called DIET-FI (DENSO Intelligent Economical Technology-Fuel Injection).

DIET-FI is the first fuel injection system that doesn’t use a throttle position sensor or engine temperature sensor. Rather, it uses newly developed control technologies that ensure the same fuel economy and environmental performance as conventional fuel injection systems, thus cutting costs.

In the two-wheeler segment, fuel injection systems are usually only used in motorcycles; however, in recent years there has been a growing need to apply these systems to smaller motorized bikes up to the size of 150cc that are used in emerging markets, such as China.

DENSO researched this trend and identified a low-cost fuel injection system that delivers similar fuel economy and environmental performance as conventional systems but with fewer components.

Conventional FI systems for motorcycles comprise sensors, actuators, and ECUs to ensure high-precision control of the air-fuel ratio. The optimal fuel injection volume is calculated based on the air volume, engine condition, etc., which are detected by sensors. The fuel from the fuel pump is fed into the engine by injectors with high precision.

However, applying FI systems to small motorcycles will require smaller components, simpler systems, fewer components, and lower cost compared with four-wheelers and large motorcycles, DENSO said.

DENSO’s DIET-FI has fewer components than conventional systems. DENSO developed control technologies that were able to eliminate the throttle position sensor; intake air temperature sensor; engine temperature sensor; and ISC idle speed control step motor.

Specific compensation technologies include a temperature estimation control that integrates a thermistor into an electronic control unit and a fuel metering control to determine acceleration/deceleration using an intake air pipe pressure sensor.

DIET-FI is currently manufactured by Gongcheng DENSO (Chongqing) Co., Ltd., a group company that manufactures motorcycle components and supplied to Wuyang-Honda Motors (Guangzhou) Co., Ltd.