Dual Injection System on D-4ST of Toyota Crown

The D-4ST on Crown manufactured by FAW-Toyota attracts tremendous attention for the new technologies leading other competitors. However, dual injection system causes disputes. Direct injection system is welcomed nowadays. Engine equipped with direct injection system is sufficient. However, D-4ST on new Crown is not only equipped with direct injection system, but also has manifold injection system which is considered as fall behind direct injection system. 

 

For higher requirement for energy and environmental protection, traditional manifold injection system cannot afford it. The engineers develop direct injection whose injector is internally installed inside cylinder. Meanwhile, improve injection pressure further, making atomization better, mixing gasoline and air completely and realizing combustion efficiency which cannot be realized by manifold injection system. When the engine is equipped with direct injection system, power is also improved definitely besides fuel consumption reducing obviously. 

 

But direct injection system still has disadvantages. On the one hand, direct injection system can cause carbon deposition more easily. So the engine should be maintained specially. On the other hand, under low load, refrigerating or idling, direct injection has poor mixed effect of fuel and air. Heat engine is slow which produces large amounts of oxynitride, having higher requirements for three-way catalysts. 

 

Dual injection system can adjust injection ways under different operating conditions, making power, efficiency and fuel consumption always in the best situations. Dual injection system can prevent carbon deposition from being formed further. Main reason for direct injection system causing carbon deposition is that poor efficiency under low load. Under low load, manifold injection having higher efficiency is adapted. Reduce carbon deposition inside cylinder. Moreover, inlet is cleaned through manifold injection, avoiding carbon deposition multi-directionally. The maintenance is more convenient, compared with other engines which are only equipped with direct injection system. 

 

What’s more, dual injection system also realizes stratified combustion having low fuel consumption. In other countries, direct injection system is always accompanying stratified combustion. However, in China, when using direct injection system, stratified combustion is canceled because of fuel quality. D-4ST can mix up with direct injection system and manifold injection system under different working conditions, deploying fuels which have different concentrations and realizing stratified combustion of fuel-air mixture. It can be seen that stratified combustion can still be realized for poor fuel quality.