Turbocharger kit basics

The five main components which all safely increase the power your automobile is making. A brief look at this technology.

The turbocharger is easily one of the most powerful and efficient performance parts that can be added to a car as it can raise the power output of an engine by over 40%! While some cars come with a turbo straight from the factory (e.g. Dodge Neon SRT-4, Mitsubishi Lancer Evolution, Audi A4 1.8T and the Subaru WRX STI), most cars are lacking one, which creates a big demand for turbocharger kits in the automotive aftermarket industry. So what’s included in the basic turbocharger conversion kit available on the market?

There are five main components that are included in most aftermarket turbocharger kits:

1) Turbocharger

2) Exhaust manifold

3) Wastegate & Blow-off valve

4) Oil supply

5) Intercooler

Turbocharger: The turbocharger or turbo is the heart of any aftermarket turbocharger kit. In basic terms, a turbo works by compressing the air contained in the exhaust gases, that’s expelled from an engine after combustion. The compressed air is then directed back into the intake pipes to the engine. This compressed, dense air allows more power to be created during the combustion process (when a spark ignites a mixture of air and fuel) which results in the engine producing more power. Turbos come in varying sizes, and generally speaking, the larger the size of the turbo, the greater its flow potential or ability to make power. One downside of large turbochargers is that the spooling time of its turbine/compressor wheels will take longer to reach peak speed, which causes a noticeable lag during acceleration before full power is generated!

Exhaust Manifold: The exhaust manifold is used to direct exhaust gases away from an engine after combustion. In a turbocharged engine, these gases can’t be expelled directly into the exhaust pipes as this exhaust flow is used to power the turbocharger. As a result, a modified exhaust manifold is needed to direct these gases towards the turbocharger. Most aftermarket kits will include one as this is an essential component in the turbocharger kit.

Wastegate & Blow-off Valve: The wastegate and blow-off valve are used to regulate the pressure in a turbocharged system. In simple terms the wastegate regulates the pressure in the exhaust manifold leading up to the turbo, while the blow-off valve regulates the pressure of the compressed air that leaves the turbo directed back to the intake of the engine.

Most wastegates on aftermarket turbocharger kits are built into the turbo specific exhaust manifold and directs exhaust gases away from the turbocharger housing if too much pressure is built up in the manifold. The wastegate is controlled by a vacuum actuator that constantly monitors the pressure in the exhaust manifold and opens the wastegate if pressure surpasses a pre-set value.

A blow-off valve is used to control the pressure or ‘boost levels’ that are being directed into the engine as well as to ensure that the airflow doesn’t reverse direction. As the revolutions per minute or ‘rpms’ rise in an engine, the exhaust flow directed towards the turbocharger housing will increase causing the turbine wheels to spin faster and faster (some turbos spin up to 150,000 rpms). The faster the turbine wheels spin, the more the gases are compressed, resulting in more boost or pressurized air being directed back into the engine. While higher boost generates more power, most engines have a maximum boost level that they can utilize safely. In situations where boost levels exceed a pre-set value, a valve in the blow-off valve opens releasing the excess pressure out of the system. The second purpose of the blow-off valve is to ensure that the airflow in the system moves in one direction. In situations where throttle input is quickly reduced – such as during transmission shifts – it is possible for the airflow to become reversed towards a region of lower pressure (e.g. the turbocharger housing). Due to this risk, the blow-off valve is programmed to open during these situations.

Oil Supply: This is a crucial but simple part of the turbocharger kit as all turbos will need an oil supply to lubricate moving parts and take heat away from the turbine housing. Most aftermarket turbo kits will include both an oil supply and return line that are plumbed into the engine’s oil system, at specific points.

Intercooler – Some inexpensive turbocharger kits will not include an intercooler but this is a vital component needed in order to extract as much power as possible from turbocharging. The one downside of compressing any gas very quickly is heat. The hotter a gas the more it expands decreasing the density of its molecules. Cooler, denser air is therefore needed to enable an engine to produce as much power as possible. Without an intercooler, turbocharged systems can produce compressed air that’s over 200 degrees Fahrenheit in temperature. This is where the intercooler comes in, and it is used to cool the compressed gases before directing them into the engine. Intercoolers are generally located in regions that receive an unobstructed airflow such as the front of a car. The most efficient intercoolers can reduce the temperature of the compressed air to within a few degrees of the outside ambient air temperature.