Forced induction has one main principle, more air equals more power – by compressing intake air before feeding it into the engine’s combustion chamber. Forced induction simply means squeezing more air in, along with a corresponding amount of fuel which results in faster, and more powerful rotations at the crankshaft. Speaking of horsepower and torque, forced induction is good in increasing them and will always have an advantage over naturally aspirated engines.
In forced induction, two systems primarily make this possible: turbochargers and superchargers. Both differ greatly in how they generate the extra boost, which we’ll see in a bit. Let us first take a gander at some boosting basics applicable in both systems.
In essence, both turbochargers and superchargers work by introducing compressed air to the engine. Oxygen, to be precise, is one component of the combustion pyramid, together with fuel and a source of ignition, i.e., the “spark.” There’s need for a careful balance of these three for combustion to happen more efficiently.
Finding this intricate balance has been a problem for engine designers for quite a while, with the better part of internal combustion history being delivering enough fuel. However, courtesy of the recent development of high-pressure direct fuel injection, this conundrum seems to have been solved. Now another limitation has arisen, providing enough air into the engine.
Both turbochargers and superchargers attempt to address this deficiency through the process called forced induction, a fancy term to denote’ forcing more air into the engine’ as mentioned above.
Turbocharges are everywhere, they are the most common form of forced induction and automakers love them, simply because they can be used to improve both power and fuel economy, well, at least in theory. However, why are these turbochargers popular and how do they work?
Well, it would appear that anything capable of ‘turbocharging’ must be immensely complex, however, they are deceptively simple. Turbochargers are basically a pair of fans linked by an axle.
Hot engine exhaust spins the first fan which then drives the second one, which compresses the air flowing in. The compressed air is then forced back into the engine and this allows for more fuel to be injected to allow for total combustion.
When it comes to performance, these benefits clearly stand out, turbochargers increase the air volume allowing for more fuel to be pumped into each combustion cycle for total combustion and subsequently more performance power. Even a small engine fitted with a turbocharger can appear to be a large one.
However, the benefits of turbocharging relative to engine efficiency are quite hard to place. First off, turbochargers improve efficiency by ensuring adequate air is present to support combustion and moreover, optimizes the engine temperature thereby making it thermodynamically efficiency. Plainly speaking, turbochargers run by using “free” energy (i.e., engine exhaust), therefore they have little effect on engine efficiency.
Since turbochargers are driven by engine exhaust, produced sufficiently when an engine is working hard, but when the driver isn’t too hard on the throttle, the turbocharger effect isn’t activated. This is good news, since the car, in theory, has the potential to be efficient and powerful at the same time.
However, the reality is not always so, turbocharged engines will either deliver power or economize the fuel, but not provide both. Driving full throttle simply means you’ll guzzle more fuel, and driving slowly will not activate the turbo.
The beauty of turbochargers is that it provides drivers with driving flexibility and perhaps this is why automobile makers are popularizing turbocharged engines.
Next up is superchargers, which may seem to work with the same principal as turbochargers, but are more complicated. Rather than being driven by “free energy” (i.e., exhaust gases), superchargers are mechanically driven. Superchargers are connected to the engine’s crankshaft through a belt or chain and the engine’s power is used to drive one of the compressors. Superchargers apply a variation of “Roots” type blower, twin, and overlapping rotors to compress air. Compared to turbochargers, superchargers are an excellent compromise.
Superchargers don’t experience lag, since they are directly driven by the drive shaft, i.e., mechanically. This feature is highly crucial on large displacement-low revving engines, which is why most high-performance vehicles are often supercharged rather than turbocharged. Additionally, superchargers deliver torque over a wider range of engine rpm, a plus for high-performance vehicles.
In essence, superchargers use the engine’s power to create more power, and thus brings about certain disadvantages, among them, being their complexity over turbochargers and they are heavy and large and can only be mounted over the engine. This poses a serious challenge to automakers who are going towards space conservation and limiting the overall weight of modern cars.
Furthermore, in terms of engine efficiency, superchargers reduce engine efficiency compared to turbochargers, this is due to the fact that superchargers are constantly using a portion of the engine’s power to turn. When little power is needed, the energy is basically wasted, this is the reason why the supercharged engine is a rarity outside high-performance applications.
For those looking to buy a car in the coming years, will undoubtedly face a dilemma over a getting a turbocharged or a supercharged model. There is no clear-cut winner among the two, and moreover, it’s no easy task deciding which is best over the other. For instance, turbochargers may offer advantages in performance, they won’t live up to the promise of unparalleled engine efficiency. Turbochargers merely provide extra power whenever it’s needed and on the opposite end provide quality engine efficiency but superchargers and purely built for 24/7 performance.
For enthusiasts and buyers alike with the knack for big displacement engine power, a supercharger is an excellent option.
All in all, the decision to get a turbocharged or a supercharged vehicle is neither going to depend upon the car model nor the driving style of the buyer but with another myriad of factors. Regardless, forced induction has more to offer for any type of driver.