Development of a Higher Boost Turbocharged Diesel Engine for Better Fuel Economy in Heavy Vehicles

This paper presents technical solutions and a development process to accomplish not only superior fuel economy but also excellent driveability with a turbocharged diesel engine for heavy duty trucks. For better fuel economy, one of the basic considerations is how to decrease the friction losses of the engine itself while keeping the required horsepower and torque characteristics. A high boost turbocharged small engine offers this possibility, but it has serious disadvantages such as inferior low speed torque, poorer accelerating response, insufficient engine braking performance, and finally not always so good fuel consumption in the engine operating range away from the matching point between engine and turbocharger. These are not acceptable in complicated traffic conditions like those in Japan - a mixture of mountainous and hilly roads, city road with numerous traffic signals, and freeways. In order to overcome these shortages and obtain a better fuel economy, novel technologies were investigated and adapted to the engine. As a result of this earnest work, a new type of higher boost turbocharged diesel engine with an intercooler was completed. Numerous new technologies such as optimization of engine swept volume for a certain class of vehicle, variable controlled inertia charging system, turbo-charger with ultra backward curved impeller, electronically controlled fuel injection timer (ET-Control) and guillotine type exhaust brake system, etc. were applied to this new engine. The newly developed truck with aerodynamic cabine in which this engine is installed shows 20-30 percent better fuel economy than its predecessors.