Turbocharging boosts engine torque by increasing pressure in the cylinders through allowing stronger combustion, giving that characteristic surge in acceleration. A turbo engine's total power output - its peak horsepower - will also increase, but it is the enhancement of torque that is most noticeable. Higher torque is also spread across a wider engine speed range than is possible with a naturally-aspirated engine.



Behind the wheel

The driver feels the benefit of turbocharging every time acceleration is required: taking off from rest, overtaking in traffic or when encountering an incline. The full effect is felt at those engine speeds, roughly 2 - 4,000 rpm, which we use in everyday driving.


For strong acceleration, there is no need to keep a turbo engine 'on the boil' by maintaining high engine revs through constant gear changing. Without the assistance of such high torque, the driver of a car with a naturally-aspirated engine must keep up the pursuit of maximum brake horsepower*, while the turbo driver can ride the crest of a wave of torque.


Although turocharging can be successfully applied to an engine of any displacement size, Saab originally introduced the technology to give its two-liter engines the performance characteristics of a far bigger powerplant. In effect, it gives the driver the use of 'two' engines instead of one. At medium to high throttle openings, a turbocharged unit provides the power of a much bigger engine, while under a light throttle, it will behave much like a smaller, naturally-aspirated engine because the turbo is not, or only partially, engaged. 'Big' engine power is available as and when required, without the downside of continuously high fuel consumption.


Turbocharging is part of Saab's DNA. In taming the technology for road cars, Saab engineers demonstrated a capacity for innovative thinking that continues to drive the brand forward. And in leveraging the power of torque, Saab injects its products with an exhilarating dose of acceleration that is a hallmark of their sporty appeal.


* The expression 'brake horsepower' (bhp) refers to horsepower measured at the engine's crankshaft when it is running on a dynomometer, often called a 'brake' as it controls the crankshaft's speed of rotation.


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