Intro To Turbo Control

Turbochargers work by compressing the air that is directed into the engine. When the air is compressed more fuel is able to be added resulting in more power.

The concept is best illustrated by the following example. If you have a 2.0L engine and want it to make the same power of a 4.0L engine just double the intake volume of the 2.0L engine. By doubling the intake volume you must compress the air that is taken in by the engine.

The compressor of the turbocharger is driven by exhaust gasses that are directed through a turbine. To slow the compressor speed the exhaust gasses are redirected from the turbine through a port in the exhaust known as a wastegate.

The wastegate is controlled by a pressure activated piston. When the intake reaches the desired pressure the piston opens the wastegate and slows the compressor. This in turn lowers the intake pressure.

To raise turbo boost levels beyond the wastegates preset level we need a way to not let the wastegate actuator see the actual boost pressure.

In the air supply line from the intake manifold to the wastegate actuator a bleed valve is installed.

A PWM signal controls the bleed valve. Length of duty cycle varies the amount of air bled from the wastegate actuator. This in turn determines the pressure equilibrium, the pressure at which the leak is overcome and the wastegate is actuated.

We are then able to use a microprocessor to control the maximum pressure reached.