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Exhaust Gas Recirculation - EGR - is a well-known technique to reduce NOx and it’s been applied on Diesel engines for a long time. Later studies and application found that other benefits can be achieved with PFI and GDI gasoline engines, such as pumping loss minimization and efficient knock control. Variable valve actuation valve-trains brought broader application possibilities as it enables full internal EGR control without external paths, high precision and response, as required on transient work modes. Comprehensive investigation on PFI and GDI Spark Ignition engines with external Hot EGR and Cooled EGR are widely available. However, variable valve actuation EGR control review on a flexfuel application is not well explored, and this paper is aimed at doing such.

Knocking is one of the major issues on modern high compression spark ignition engines, and the actual challenge is how to effectively control its occurrence protecting the engine, without performance impact. Modern cars incorporate knock-sensor systems for engines to minimize knocking, which can maximize engine lifetime, increase power, and improve fuel economy.The choice of the sensor type may depend of a wide number of factors and boundary conditions as the engine size, market segment or fuel. It's very common to use for mass production engines a knock sensor with a wide range bandwidth in detriment of the tuned one.Wide range bandwidth knock sensors are sensible to all engine vibration frequencies, therefore, this knock sensor configuration implies in a more complex signal processing than the necessary for a tuned sensor.