Turbocharging, Supercharging To Help With Engine Downsizing, Emissions Compliance

Due to increasingly stringent emissions norms and the need for improved fuel efficiency, one option that auto motive OEMs are increasingly going in for is engine downsizing. Fewer cylinders and smaller engine capacities help OEMs reduce emissions and achieve better fuel economy. However, to ensure that smaller engines are still able to deliver the kind of power and performance that customers expect, manufacturers often use forced induction – turbocharging, supercharging or even both. Here, we take a look at some of the latest advancements in forced induction and their implications for manufacturers, suppliers and customers.

- Sameer Kumar

PERFORMANCE AND EFFICIENCY

Once the exclusive preserve of high-performance sports cars, forced induction engines are now commonly used across many vehicle segments, including smaller sedans and hatchbacks. In India, while turbocharged diesel engines have already seen widespread use over the last 10-15 years, a few turbocharged petrol engines have also been introduced in recent years, by OEMs like Maruti, Volkswagen and Skoda. With the upcoming BS VI norms, this trend is likely to continue and grow, with more OEMs following suit.

Between 2015 and 2020, due to upcoming regulations, car manufacturers will be required to reduce the average CO2 figure for their entire range of cars from 130 g/km to 95 g/km or less. This will necessitate the replacement of bigger, naturally aspirated engines with smaller, turbocharged or supercharged units that not only deliver the required horsepower, but are also more fuel efficient. The advantages are manifold – fewer, smaller cylinders in a forced induction engine means reduced internal friction levels, and better torque output even at lower engine rpm. And yes, it’s important for new engines to strong torque delivery at relatively lower rpms, since high engine revs often means bigger valve overlap (between intake and exhaust valve operation), which often means increased emissions.

Naturally aspirated engines can have a brake mean effective pressure (BMEP) of anywhere between 80 to 200 psi, while turbocharged engines start at around 220 psi, going up all the way to 320 psi, with the potential being there for even higher pressure. Hence, with better volumetric efficiency and higher specific output (the ratio between an engine’s size vis-à-vis its power and torque output), smaller forced induction engines will inevitably continue to replace bigger naturally aspirated engines.

TURBOCHARGING vs SUPERCHARGING