Twin-Turbocharger Types

Staged turbocharging

Using the same concepts as sequential turbocharging, staged turbocharging employs a’stepped’ procedure to increase air compression to exceptionally high levels before reaching the engine’s cylinders. Starting with a modest turbocharger, the air is routed immediately to a somewhat larger turbocharger, which compresses the air even further. The final boost pressure in a staged system can be much higher than in a standard twin-turbo system, but it is fairly disastrous in terms of lag. As a result, it is commonly found in diesel engines with high compression ratios and small rev ranges.

Twin-scroll turbos

You might use a twin-scroll turbocharger instead of two turbochargers to avoid the inconvenience of employing two turbochargers. This is essentially two turbos jammed into a single casing, with the exhaust manifold strategically split across the engine’s cylinders. This is because the exhaust cycles converge before and within the turbocharger in a standard single-scroll turbocharger, resulting in unpredictable and turbulent airflow. The twin-scroll technology allows the exhaust pulses to be kept away and enter the turbocharger through their inlets, reducing pulse conflicts.

Twin-scrolling, which has been used prominently in recent BMWs, particularly the M2, has made the art of turbocharging much more economical in terms of both packaging and efficiency, giving four-cylinder engines the abilities of much bigger capacity 6-cylinder engines from a prior generation.

The future

Other methods of enhancing the capabilities of twin-turbocharger installations have lately been developed, with Audi’s SQ7 performance SUV being the most extreme. A typical twin-turbocharger system is augmented upstream by an electric compressor in the Range Rover Sport SVR-rivaling barge. The electric fan, designed to pre-compress air directly from the intercooler, runs at up to 70,000rpm to raise the pressure of the air that finally hits the cylinders.

Though Audi claims that this substantially eliminates latency, one should be wary about incorporating such a component into their turbocharged system because many aftermarket ‘electric turbochargers’ is merely electric fans that restrict the exhaust gas supply to the turbine vanes.

Whether twin-turbocharging is a pipe dream that will never come true in your stalled project vehicle or you’re the lucky owner of a car that comes standard with it.

Useful links

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