it works on the principle of direct injection system of petrol engine

FSI stands for Fuel Stratified Injection, which describes the stratified petrol direct injection attained by this engine designed by Volkswagen.

Hung Lee Nguyen has written:

'Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-II' -- subject(s): Fluid mechanics

'Performance and combustion characteristics of direct-injection stratified-charge rotary engines' -- subject(s): Stratified charge engines, Internal combustion engines, Wankel engine

A FSI or Fuel Stratified Injection engine functions by having the gasoline injected directly into the combustion chamber of each cylinder in the engine.

Stratified refers to layers. The epithelial cells are arranged as such.