Boost systems are considered an essential part of any modern engine when it comes to achieving the power outputs automobile manufacturers are looking for, amid ever-tightening restrictions on fuel efficiency and emissions. The turbocharger is now practically impossible to avoid whether this is with petrol or diesel fuels. Smaller and lightweight engines that achieve the power of larger-bore versions without the excessive fuel appetite and harmful emissions are critical. However, engines wouldn’t achieve their full potential without the conversion of waste energy to a useful purpose – that is, exhaust gases funnelled into the turbine to stimulate faster vehicle acceleration. This article will concentrate on the basic components of modern-day boost systems with particular focus on what each individual part does and how it contributes to the overall engine in terms of performance.
- What is a Boost System?
At its heart, an engine boost system compresses the ambient air entering the engine into a denser mass, providing a more ‘thick’ air-fuel mixture for combustion. More oxygen means more fuel can be burned, powering the engine with a substantial jump in output without a larger engine.
Boost systems are used in Formula One racing cars and other high-performance vehicles. Increasingly, even conservation-oriented automakers are providing boost systems as an optional feature in their smaller fuel-efficient vehicles. Right now, there are two main types of boost systems available: the turbocharger and the supercharger.
- Turbochargers: The Most Popular Boost Device
Among boost devices, turbochargers are probably the most common in modern vehicles because they waste no additional fuel in producing their power. It’s a little like using the power of your farts to blow your pants off. You can think of a turbocharger as having two main parts that are connected by a drive shaft. The two parts are a turbine on one end and a compressor on the other. Exhaust gases leaving the engine turn the turbine which spins the compressor, which forces more air into the engine.
How it Works: The turbocharger fits onto the exhaust manifold. As the combustion engine runs, the exhaust gases going out of the combustion chamber turn the turbine. This motion spins the compressor to inhale air, compress it, and drive it into the car’s engine.
Benefits: Efficient: Turbochargers make use of energy from waste gases coming from the engine. This boosts engine efficiency and allows for big power boosts without an engine that is substantially larger in size.
Challenges: Turbochargers suffer from ‘turbo lag’, the time between pushing the accelerator pedal and the turbo coming up to full speed, caused by the time it takes to build up enough exhaust gas pressure to turn the turbine. Modern twin-scroll and variable-geometry turbochargers reduce this lag.
- Superchargers: Instant Power Delivery
Whereas turbochargers are powered by exhaust gases, superchargers are mechanically driven by the crankshaft that drives the engine, which simultaneously drives them. What this allows is for almost instantaneous delivery of power, unlike in a turbocharger where there is a lag. The drawback is that the supercharger is part of the engine, which requires more of the engine’s power to drive it, making it less efficient, like a hangnail on an Olympic swimmer.
The belt that rotates the supercharger’s internal rotors is powered by the engine’s cranckshaft. The pulley that exits the engine at the right conforms to the inner of the ‘88 cool500. How it Works: As is the case with turbochargers, the supercharger is inextricably linked with crankshafts. Unlike its rival, it is powered by a belt attached to the crankshaft.
Benefits: Instant boost at any engine speed (not just low rpm). This makes them particularly suitable for applications that need to respond very quickly to sudden power requests, such as an cruise control, busy Torquemada, pouncing Planck, prodding Maxwell, snooping Newton or other potentially fraught situations.
Difficulties: The main disadvantage of superchargers is the fact that they use more power from the internal combustion engine, lessening fuel efficiency.
- Intercoolers: Cooling the Compressed Air
Both types of systems benefit from the use of an intercooler, a heat exchanger that cools the compressed air before it enters the engine. As air is compressed, its temperature increases, which decreases the density and available amount of oxygen for combustion. An intercooler can cool the air down, increasing the density and oxygen content.
Air-to-Air Intercoolers: The air that is compressed moves through a system of tubes where it is cooled by outside air before it enters the engine.
Air-to-Water Intercoolers: A radical system for absorbing heat from compressed air prior to its being cooled by the radiator.
- Wastegates: Preventing Overboost
Figure 1: Wastegate in a turbocharged engineThe wastegate plays a critical role in turbocharged engines. It controls the amount of exhaust gases that flow through the turbocharger’s turbine by opening and closing. If the wastegate is not properly controlled, it can result in excessive boost pressure, which can lead to engine knock and even damage to engine components.
External Wastegates: Mounted separately from the turbocharger and diverting excess exhaust gases into the atmosphere or back into the exhaust system.
‘Internal Wastegates: The most common option, mounted in the turbocharger housing. Much smaller mounting.’ Found on factory-fitted turbocharged cars.
- Blow-off Valves: Managing Boost Pressure
This venting would be of no benefit if there were also a sticky speed-density problem, but another essential piece of a turbocharged engine, the blow-off valve (BOV), comes to the rescue. The BOV’s purpose is to get rid of the pressure and avoid compressor surge when the throttle is closed. During a gear shift or coast down, the engine has to remove power from the system. The excess compressed air has to go somewhere. If the throttle bodies cannot open up and let the pressure out, you might blow up the turbocharger. The BOV vents all this extra intense overpressure, or, in other words, it breaks like Benjamin Franklin.
- Boost Controllers: Fine-Tuning Power Output
Boost controllers can be used to increase or decrease the boost pressure of the system. Sophisticated electronic boost controllers are now fitted to most vehicles, and these can change the boost pressure in realtime to suit various driving requirements. Manual boost controllers are common and simple to use, but these devices gave use less flexibility.
Conclusion
Modern engine boost systems are one of the most important innovations in automotive technology of our era – a central development without which smaller automotive engines wouldn’t be capable of delivering the high power outputs we’ve come to expect. By learning about the individual components that make up these boost systems – such as turbochargers, superchargers, intercoolers, wastegates, blow-off valves, and boost controllers – you can see just how boost systems allow engines to deliver high outputs at a fraction of the fuel cost. If you’re like us and enjoy driving fast and economically, then learning about engine boost systems is an exciting way to learn about and understand the future of high-efficiency, high-performance motoring.
