Electric turbochargers and superchargers explained

The majority of new cars on sale today use turbochargers to offer increased fuel efficiency and better performance. This technology has been around for many years, but a small number of manufacturers are now fitting electric turbochargers to their cars. What exactly are these systems and how do they work? Read on to find out…

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Remind me, what are turbos and superchargers?

Engines produce power by burning a mixture of air and fuel. The faster an engine burns this mixture, the more power it produces. Superchargers and turbos force more air into the engine than it would consume on its own, allowing it to burn more fuel and produce more power. Superchargers are driven by a pulley from the engine, while turbos use high pressure exhaust gases to spin a turbine.

Superchargers are driven directly by the engine itself and, as a result, help produce extra power immediately – at the expense of fuel efficiency. Turbos tend to be more efficient because they convert the wasted energy from hot exhaust into useful power. They can, however, take a little time to spin up to speed after the driver hits the throttle, meaning they can’t deliver power as smoothly as supercharged engines. This delay is known as turbo lag.

So why do we need electric turbos?

Electric turbos are designed to blend the efficiency of a turbocharged system with the responsiveness of a supercharger by eliminating turbo lag. They combine a traditional turbo with a small electric air compressor driven by a powerful motor. When the accelerator is pressed, the motor drives the air compressor to instantly force cold air into the engine. This ensures power delivery is smooth, even before the exhaust-driven turbo gets up to speed. Once the conventional turbocharger is spinning fast enough, the electric system shuts off to save energy.

The first production car to be fitted with this technology was the Audi SQ7. Its 4.0-litre twin-turbo V8 diesel engine is assisted by an electric turbo system to help it produce 435hp – enough to launch it to 62mph from rest in a sports car worrying 4.8 seconds.

Volvo has developed an alternative system that stores compressed air in a tank in the engine bay. When a instant burst of acceleration is required, a valve is opened and this high pressure air is allowed to escape through the turbo itself, rapidly spinning it up to speed in the process. This system has been fitted to S90V90 and XC90 D5 Powerpulse diesel models and has helped to reduce their respective 0-62mph sprint times by more than 0.5 seconds.

Are there any downsides to electric turbos?

Electric turbo systems aim to increase a car’s performance rather than reduce fuel consumption or CO2 emissions. They can, however, be switched off when not in use, allowing the engine to run at its maximum efficiency – ideal for long motorway cruises.

As with any new technology, electric turbochargers are likely to prove quite expensive until their adoption is more widespread. The reliability of these systems is somewhat of an unknown, too. It could also be argued that they are a way of extending the lifespan of combustion engines when the industry arguably needs to move towards fully electric cars.

Haven’t I seen electric turbos for sale on eBay?

You may have seen products advertised online as electric turbos that claim to be capable of increasing your car’s performance or fuel economy. Unfortunately, the overwhelming majority of these aftermarket parts are simply not capable of delivering on either of these promises.

For the most part, these systems consist of a small fan, not unlike a desktop PC cooling fan, that blows air into the engine through its intake. For an engine to produce any more power, however, the air must be forced into its cylinders under high pressure – the higher the pressure, the greater the power output. These fans aren’t able to pressurise air anywhere near the levels an engine needs and will probably be detrimental to power output and fuel efficiency.

What models come fitted with electric turbochargers?

Currently this technology is still relatively new and only a couple of manufacturers have experimented with fitted these systems to their cars. The Audi SQ7 comes as standard with electric turbo technology and Volvo’s S90, V90 estate and XC90 SUV are available with a broadly similar system if you choose D5 Powerpulse models.

We expect electric turbos to become more and more common as numerous car makers compete to offer faster vehicles. It’s likely that high performance vehicles and expensive executive cars will be among the first to reap the benefits of this fledgling technology, however.

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Audi SQ7

Super fast SUV with space for seven
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