Turbocharger vs supercharger, there are two major kinds of forced induction in the automotive world – but determining which is superior is a little more tricky than you would think.
Of all the developments that the internal combustion engine has gone through over the decades, it is arguably forced induction that is one of the most important. Originally developed as a way for aircraft engines to continue producing power at higher altitudes where the air is thinner, closer to earth it has applications both in efficiency and high performance.
But not all forced induction is the same. There are two main methods: supercharging, and turbocharging. Both have the same goal of cramming more air into the engine than it would normally be able to take in, in order to burn more fuel and make more power. That being said, they go about doing this in two very different ways.
You see, cramming extra air into the engine takes energy, and that energy has to be taken from some other part of the engine. There are modern forms of forced induction that use high voltage battery power, a-la-Formula 1, but these are meant more to supplement larger forms of forced inductions attached to the engine.
In the case of supercharging, that extra energy is taken directly from the crankshaft of the engine. That spinning of the crankshaft – which is also what generates the power that is sent to the wheels – is used to spin something else that pumps extra air into the engine. There are a couple of different designs, from twin screw to roots, to even centrifugal designs that look a lot like turbochargers, but they all take their energy from the crankshaft.
As for turbochargers, they get their energy from the exhaust gas of the engine. It’s similar to how a hydroelectric dam or windmill works – the gas in the exhaust passes through the hot side of a turbocharger and spins a small turbine which is connected to the cold side of the turbocharger. Another turbine there then sucks air in and crams it into the engine in the form of boost.
Each form of forced induction has its benefits and drawbacks, and for that reason you see it in different applications. There are also different ways in which they deliver that extra air and power, which can be extremely polarizing among car enthusiasts.
The main benefit of supercharging is the fact that it delivers its extra air instantaneously – in fact, as long as the supercharger is spinning at any point, it is providing additional air. This means that for a driver, the engine feels extremely responsive and torquey, reacting almost instantly whenever you press the gas pedal. In that regard it works better for cars where you need that razor sharp response, like with mid-engine cars where you can drastically change the attitude of a car mid-corner using the throttle pedal alone.
However, there are obviously some drawbacks. Even with more innovative designs that allow for aggressive ramp rates in terms of supercharger speed compared to engine speed, the end result is that a supercharger still has a pretty low ceiling for how much additional air it can provide. Two other massive drawbacks are the fact that by attaching it to the crankshaft you create a parasitic loss, and that superchargers generate immense amounts of heat which leads to all kinds of other issues like excessive crankshaft bearing wear and heatsoak.
On the other hand, turbochargers can provide extremely large amounts of additional air – as long as you have the exhaust gas flow to get them spinning. That’s part of the reason you could see four digit horsepower figures from the turbocharged 1.5-litre Formula 1 engines in the 1980s, and how they can create some truly impressive power figures when sized and tuned properly.
What turbochargers can’t get around is the delay between resting and generating boost, the proverbial term for cramming more air into an engine. Since a turbocharger relies on exhaust gas flow to spin, if you lift off the throttle at any point you immediately decrease the amount of exhaust gas flow supplied to the turbocharger, and it slows down drastically. Getting it back up to speed takes time, and this delay can make a car feel more difficult to drive and imprecise if a driver can’t anticipate the delay.
So far things have been kept fairly simple, but the reality is that turbocharger technology has come a long way – not so much the case for superchargers. Turbocharging sees so much use in OEM factory cars as well as the aftermarket that there is a much bigger push to improve them in terms of response and efficiency, which is why the traditional drawbacks of a turbocharger aren’t really as prominent.
There is also a change in mindset with how turbochargers are applied and implemented, in conjunction with improvements in engine exhaust gas flow and efficiency. In the old days, turbochargers were relatively large compared to the engine size, which meant they needed more engine speed and exhaust gas flow to start working, with significantly more lag.
Nowadays the turbochargers you find on cars like the Volkswagen Golf GTI are sized just right for the displacement – while they don’t produce massive amounts of power for the engine size, they do respond extremely quickly to driver inputs and there is a significant decrease in perceived turbo lag, as well as massive amounts of torque from low to mid-range engine speeds.
It’s because of this that turbocharging is simply the superior form of forced induction, especially as manufacturers and tuners alike have come up with innovative ways to reduce turbo lag and make turbocharged engines more responsive and drivable. With the right sized turbocharger for the application, you can have an incredibly potent powertrain that responds quickly to your inputs when you are in whatever target rpm range you have chosen.
If we ever get to the point where electrically assisted turbochargers of sufficient sizes are made available to the aftermarket, you are going to see some immensely powerful, incredibly responsive tuned cars that could easily get to supercar levels of speed. All of the power with none of the lag. That being said, a supercharged performance car in this day and age is a rarity - which makes them perhaps a little more special.