Let’s say you want to construct a more powerful engine. The most direct method is to increase the amount of air and fuel burned in each combustion cycle by adding more engine cylinders or increasing the size of the cylinders. But that makes the engine bigger and heavier, which means you need a bigger car to haul it around.
Assuming you don’t want a bigger, heavier car, what else can you do? You can pack more air and fuel into the existing cylinders. This, in a nutshell, is what a turbocharger does.
Some people think that turbos are only good for sports cars or racing. But there is more to a turbocharger than sheer horsepower and speed. In fact, the best reason for turbocharging the engine is to enhance your driving experience.
How Does a Turbocharger Work?
The turbocharger compresses the air entering the engine cylinders, which greatly increases the engine’s burning power. A turbocharger can typically pack 50% more air into the cylinders than normal. Due to inefficiencies in the process, not all of this air will translate into extra power. The actual improvement would be along the lines of 30-40% more power.
A turbocharger in a car is attached to the exhaust manifold and is powered by waste exhaust gases. The turbo has two main components, the turbine and the compressor. Exhaust coming from the engine cylinders passes through the turbine blades, causing the turbine wheel to spin.
The turbine connects to the compressor by a long shaft. As the turbine wheel rotates, it makes the compressor wheel spin, too. The compressor draws in air, pressurising it in the intake before pumping the air into the engine cylinders. The amount of pressure that the air is subjected to is called boost. The more the air is compressed, the higher the boost and the more extra power that is generated by the engine.
There are two other components that should be built into an efficient turbocharging system: the wastegate and the intercooler.
At high engine speeds, the turbine can spin too quickly and generate more boost than the system is designed to handle, especially if the turbocharger is small. The wastegate is a simple valve that senses the boost pressure. When the pressure reaches the desired level, the wastegate lets some of the exhaust gases bypass the turbine, limiting boost to safe amounts.
When air is compressed, it heats up, causing it to expand and become less dense. This partly defeats the purpose of turbocharging, which is to increase the density of the air going into the engine cylinders. To counteract the expansion effect, a cooling component such as an intercooler or charge air cooler is used. The intercooler lowers the temperature of the pressurised air before it enters the cylinders and mixes with the fuel.
One of the drawbacks of turbocharged engines is turbo lag. This is the delay between pushing down the accelerator and feeling the boost of power from the turbo. It occurs because the turbine takes a little time to get up to speed. Turbo lag can be decreased by reducing the size of the turbocharger and using lighter materials such as ceramic instead of steel in the turbine and compressor.
A small, light turbo can provide quicker boost and minimise lag, but it may not generate enough boost at high engine speeds. On the other hand, a large turbocharger will deliver massive boost at high speeds, but it will suffer from more lag because it has a heavier turbine wheel that takes longer to get moving.
Sometimes two turbos of different sizes are installed to overcome the drawbacks of both small and large turbochargers. In a twin turbo system, the smaller one gets up to speed quickly for less lag during driving, while the larger one provides the extra boost needed at higher engine speeds. This system is efficient in delivering power under all driving conditions, but it has the disadvantage of being much more complex than a single turbo, with two sets of everything that can potentially break down.
Benefits of a Turbocharger
The main benefits of a turbocharger are increased horsepower and torque, lower fuel costs, improved emissions, and better high altitude performance.
A turbocharged engine produces substantially more power than a non-turbo engine, with only a small weight increase. To look at it another way, you can put a smaller engine in the car and still obtain power equivalent to a larger, normally aspirated engine. The additional horsepower and torque enhance vehicle performance and drivability.
It’s worth pointing out that remapping a turbocharged engine is one of the best ways to fully optimise all that power and torque. A professional ECU remap gives you sharper throttle response and smoother power delivery through the entire rev range, making driving even more of a pleasure.
A turbocharger can also help you save money on fuel costs. Diesel fuel isn’t that much less expensive than petrol, but when you improve fuel economy with a turbocharger, you can obtain big fuel savings over a normally aspirated diesel or petrol engine.
A turbocharger offers environmental benefits, too. It delivers extra oxygen to the engine, which results in more complete fuel combustion and reduced NOx and CO2 emissions. Furthermore, a turbocharged engine can be built smaller and lighter than a non-turbo engine, which means that it consumes less fuel and puts out lower overall emissions while generating the same amount of power.
And finally, at high altitudes where the air is less dense, a turbocharged engine delivers more power and better performance than a normally aspirated engine can offer.
Precautions for Operating a Turbocharged Car
Oil system and air system problems are two major reasons for turbocharger failure. You should check the oil and air filters regularly and perform engine maintenance at the prescribed intervals. It’s also important to pay attention to engine start up and shut down procedures. This simply means allowing the turbocharger to warm up and cool down properly.
When you start the engine, let it idle for about one minute. Don’t rev the engine right away, as this forces the turbocharger to run at high speed with minimal lubrication. And before you turn off your engine, let it idle for one to five minutes to give the turbocharger time to cool down. A hot shut down the moment you arrive at your destination is hard on the turbo. Neglecting either of these steps can result in a shortened service life or big repair bills for your turbocharger.