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How it works

Turbo – How it works

Brief History of the Turbocharger

Saab with their 99 Turbo and Porsche with their 911/930 were the first to the market here in the UK and EU causing an explosion (not literally) in all things Turbo.

With their success, turbo came to represent anything that was just ‘better’, turbo hair dryers, turbo washing machines and even turbo fridges, yes…turbo fridges.

For passenger cars, Chevrolet were the first to the market in the USA, followed by Porsche and Saab. These were petrol engines. Mercedes had begun with Turbo Diesel on the 300SD around the same time. 

Invented by Alfred B├╝chi a Swiss engineer and inventor, he was trying to work out a way to improve the efficiency of the engine by harnessing the heat loss from the exhaust system. If you don’t somehow use the by-product of combustion, it’s energy going to waste.

In 1905 the turbocharger was born, only in design however as the materials and engineering to make one, didn’t exist. 10 years later in 1915 the first prototype was made and then it wasn’t until the 1920s that the first turbocharged marine engines were built, it was also during the 1920s turbos started appearing in aeroplanes.

So, how does a turbo work?

It’s a very simple design but one that works well and turbos from the 1920s up to current day, use the same principle.

A turbo has 2 sides, an inlet side and exhaust side. The clean air and exhaust gases don’t mix and are separated and controlled by the ‘cartridge’ which is simply two fans (a turbine fan and a compressor fan) connected via a shaft with a plate in between that separates the 2 sides and sits in the turbo housing. The cartridge is specially balanced, as turbo fans spin at up to 250,000 rpm. Any unmatched weight on either side of the cartridge would be catastrophic.

When your engine is running, it produces heat and exhaust gases that would normally be expelled immediately via the exhaust into the atmosphere, on a turbo car, these gases are passed through the exhaust turbine side of the turbo causing the inlet compressor fan to spin.

Simply put, a turbo, is a compressor, an air pump, so as it is made to spin, it sucks in and compresses air then forces it into the engine, the more air, the bigger the bang, the more power you get. You may have heard the term ‘Forced Induction’ this is exactly what a turbo and supercharger do.

Colder air is more dense than hot air, as the fresh air is sucked into the turbo, because the turbo is one unit and the inlet and exhaust side operate right next to one another, the fresh air is heated to about 200 degrees inside the turbo, this needs to be cooled down before it enters the engine, so an intercooler is needed. This is simply an air radiator, usually situated in front of your water radiator at the front of the car, the heated inlet air passes through here, being cooled, then entering the inlet manifold and subsequently into the cylinder.

Once the air has been forced into the engine and the revs climb, the exhaust pressure builds up which makes the turbo spin faster forcing in even more air, when driving a turbo vehicle you can feel this surge in power, the space in the lower rev band where you don’t feel as much ‘shove’, is called turbo lag.

The final part to mention is the actuator attached to the turbo, which is either vacuum controlled (via air pressure) or electronically controlled (by a little electric servo)… this regulates the boost pressure so that the turbo doesn’t over boost causing itself or the engine problems.

Turbos rely on the exhaust gases, so if the rpm is low, on a standard single turbo engine, it won’t provide much forced induction, as the rpm climbs, the turbo can do more work. Car manufacturers have tried different ways to avoid turbo lag as best as possible, such as using twin turbos (two turbos) one that runs at a lower pressure until the main one kicks in, an electric turbo that can spool up when programmed to or on hybrid cars, using the electric motors to give that extra push until the turbo comes on boost.

There are different types of turbos, single turbo, twin scroll turbo, variable geometry turbo, twin scroll variable geometry turbo and most recently electric turbos (Not the ebay rubbish, but a proper 48v unit fitted to an Audi SQ7 for example). All using the same principle as Alfreds original concept.

We’ll cover the different types of turbo in another post.

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