What Is The Essence of FSI?

FSI (Fuel Stratified Injection) is a kind of technologies based on GDI (Direct Injection). What is different from airway jet injection engine, FSI injects fuel directly into combustor. Due to gasification and cooling of atomization, FSI optimizes volumetric efficiency, realizing constant flow control on engine without throttle valve and reducing inlet losses greatly. Stratified combustion reduces heat loss of engine, increasing output power of full load and reducing fuel consumption of partial load. 

 

FSI is short for Fuel Stratified Injection, representing a development direction of engine in the future. FSI is a type of lean burn technologies. What is lean burn? The gas mixture in engine has low content of gasoline. The proportion of gasoline and gas is more than 1:25.

 

FSI manufactured by Volkswagen utilizes a high pressure pump so that gasoline can reach to high pressure injection valve controlled by electromagnetism through common rail. The variable vortex has been caused in inlet, making vortex form the best vortex and enter into combustor. Pushed by layer filling, the mixture is concentrated around the sparking plug inside combustor. If the mixture ratio is higher than 25:1, the mixture cannot be ignited. For this, stratified combustion from dense to sparse must be adopted. Mixture ration is about 12:1. Outer sphere is gradually thin. After dense mixture being ignited, the burning spreads rapidly to outer sphere. 

 

The essence of FIS

A computer collects the position of cam and crankshaft and the different working conditions of engine to control fuel entering into inlet manifold. Gasoline begins to mix in manifold, then, enters into manifold for burning. The best mixture ration between gas and gas online is 14.7:1, also called as theoretical air-fuel ratio. In conventional engine, gasoline mixed with air inside inlet manifold. They can only be mixed evenly. So, theoretical air-fuel ratio must be realized, then, good power and economical efficiency can be acquired. However, injector has distance from combustor. The mixture between gasoline and air is impacted by air inflow and air valve. What's more, tiny oil particles absorbs on the wall of pipe. It is hard for realizing theoretical air-fuel ratio. The main disadvantage exists in conventional engine. 

 

To solve the problem, the fuel must be injected directly into cylinder. This can be realized on FSI provided by Audi. Direct injection uses the oil supply technology similar to that on diesel engine. Through the pressure more than 100bar provided by a piston pump, the fuel is supplied to electromagnetic injector inside cylinder. Then through the injector controlled by computer, the furl is injected directly into combustor at the most appropriate time. Due to the interior form of combustor, the mixture can cause vortex to mix air with gasoline fully. So, there is dense mixture around the sparking plug while spare mixture exits in other regions. It ensures that lean-burn can be realized as far as possible, when mixture is ignited smoothly.