Now, turbocharging is pretty much a norm in the car industry. Even before cars came with a turbo as stock, people have fitted turbochargers to their engines in an effort to increase their car’s power output.
(Related Story: Forced Induction – Superchargers)
As explained in my previous article on superchargers, forced induction simply means adding more air into the combustion chambers. More air equals more oxygen. More oxygen in the suck/squeeze/bang/blow cycle equals more combustion. And more bang, equals more power. Still with me?
Now, just like a supercharger, a turbocharger’s job is to increase the density of the air so more oxygen enters the cylinder, improving the air-fuel mixture. But a turbo differs from a supercharger by the way it compresses air.
Unlike a supercharger that relies on the engine crank to improve airflow and increase power, a turbo uses the engine’s exhaust gases to spin an impeller to force air into the engine.
Another difference between a supercharger and a turbocharger is the response time. Because a supercharger is tied directly to the engine crank, there is no delay in response from the second you put your foot down. But because a turbo uses the exiting exhaust gases, it takes longer for that influx of air to enter the cylinders.
That delay in response is commonly called ‘turbo lag’. Or ‘boost lag’. And that is the biggest drawback of a turbo. You see, in order for a turbo to effectively generate more boost, the engine’s revs per minute (RPMs) have to be higher. More RPMs, more boost. And the only way to do that is to have enough exhaust air exiting the engine for the turbos to spool up.
However, there are a number of ways to mitigate the lag. In old WRC (World Rally Championship) and Formula 1 cars, the engines are fitted with Anti-Lag Systems (ALS for short) to keep the boost levels high. Even when the engine is not under load. But anti-lag systems cause stock engine parts to wear out due to the immense pressure and heat. And it’ll kill any catalytic converter, which makes ALS illegal on a road car.
But there are more common (and street legal) methods to improve turbo efficiency. Changing the aspect ratio of the turbos, using lightweight components for the impeller, or by adding an electric motor to the turbocharger.
Some manufacturers also employ a Hot-V turbo setup. Manufacturers do this by placing the turbochargers within the cylinder banks of the engine, within the “V” of the engine. As a result, the distance between the exhaust manifold to the turbo is shorter. This enables the turbos to spool up sooner, reducing the lag. And it also makes for a neater package under the hood, aiding weight distribution.
So, like superchargers, turbochargers have their own pros and cons as well. It’s all a matter of preference. Or manufacturer specifications.