Turbochargers

What is Forced Induction?

Forced indcution is the process of delivering compressed air to the intake of an internal combustion engine. It increases total compression and maximizes the amount of useful engergy from the fuel.

What is a Turbocharger?

A turbocharger is a form of forced induction that uses the exhaust stream for energy by allowing exiting exhaust to spin a turbine that then spins a compressor.

How does a Turbocharger Work?

As exhaust exits the cylinders, it is directed into the turbo's turbine inlet, allowing this movement

of exhuast to spin the turbine. The spinning of this turbine causes the spinning of the compressor. As the compressor spins, it pulls in air either from the engine bay or from outside the vehicle. This new, compressed air flows through an air cooler and is then directed into the engine cylinders through the intake valve to be mixed with fuel and combusted. The exhaust from the explosion then flows out through the exhaust valve and is directed to flow through the turbine to continue the process before exiting the vehicle.

Lag Time

Lag time is the time between which the engine is engaged and the turbo begins supplying boost. The turbo does not immediately produce boost because it must wait until the engine is engaged and can produce the exhaust that spins the turbine. This can cause the car to lunge forward once the turbo kicks in.

Turbo Sizes

There are many different turbo sizes. Smaller turbos create less boost but they have less lag time and vice versa for large turbos. Turbo sizes are measured in A/R values, or the internal area of the turbine divided by the radius of the turbine housing. These values are given in the form of .35, .84, 1.15, etc. The larger the A/R, the larger the turbo.

Benefits of Turbos

At high altitudes, turbochargers are more effective due to the thinner air.

Twin Turbos

What is a Twin Turbo?

Twin Turbos work the same way as a regular turbos, but there are two present. There are also two types of twin turbos: parallel and sequential.

Parallel

2 separate turbos for 2 separate cylinder banks.
Both turbos are the same size.
Both turbos are always active.
The image to the left is one parallel twin turbo layout.

Sequential

Bypass valve present to control amount of exhaust entering turbos.
Both turbos are the same size.
At Low RPM, one turbo is active and the bypass valve is closed, limiting the exhaust entering the system.
At High RPM, both turbos are active and the bypass valve is open, allowing more exhaust to enter, creating more boost.
The image to the left is a sequential twin turbo layout in an MK4 Supra.