Supercharger vs Turbocharger: What's the difference?

A couple of decades or so ago, any petrol-engined car with a supercharger or turbocharger was considered a performance car. Which it almost certainly was, because that was the way to squeeze more power out of a given engine.

These days, of course, it’s a bit different and you’ll actually struggle to find a brand-new petrol car without a turbocharger. And diesel-engined vehicles? Well, they’ve had turbochargers fitted to them for decades as a way of boosting performance while retaining the diesel engine’s other virtues.

So, given that turbocharging and supercharging technology is now the rule rather than the exception, it’s likely there’s one in your future.

But how does the technology work and what does it do in the first place? What does a supercharger do? And what’s the difference when it comes to turbocharger vs supercharger?

Let’s clear one thing up form the start: Whether it’s a supercharger or turbocharger we’re dealing with, the principles are the same. In fact, they’re both, technically, forms of supercharger. The word turbocharger (often shortened to turbo) is a mash up of the words 'turbine' and 'supercharger'. Hence 'turbocharger'.

Ever seen a set of bellows stoke up a furnace? Certainly you’ve blown on a small campfire to make it a bigger one. In both those cases, you’re adding air to the equation. And more air means you can burn more fuel (wood in the case of our campfire).

A petrol or diesel engine works exactly the same. You use a supercharger or turbocharger to blow more air into the engine, and it can suddenly burn more fuel and, therefore, make more power. Turbocharged vs supercharged doesn’t matter: The science is the same.

This process is also called forced induction (you’re forcing air into the engine) but supercharging and turbocharging  are the two main methods. And even though they acheive the same thing, a supercharger and turbocharger work in different ways. So what’s the difference between supercharger and turbocharger tech?

Supercharging arrived first, and is often credited to the aviation industry which needed to force air into engines at high altitude to make them run properly.

But what is a supercharger as we know it and how does a supercharger work? In essence, it’s an engine-driven pump that forces air into the engine under pressure.

The pump is driven either off the engine’s crankshaft (early Bentleys) or via a rubber belt (everything else). By cramming extra air in, more fuel can be added and you get a bigger bang inside the engine for more power and torque.

It sounds simple, and it is in a way, but making it work properly is the key. And that requires precise control over how much extra fuel is added and when.

So what is a turbocharger, then? And how do turbochargers work? And what does a turbo do that’s different to a supercharger?

Well, it’s exactly the same principle of being a pump to pressurise the air going in to the engine, but unlike a supercharger, turbo installations don’t require a belt to drive them.

Instead, the pump is driven by exhaust gas. The turbo’s fan blades are spun by the force of the exhaust leaving the engine. In effect, it’s free power because there’s no drag on the engine from a belt. In reality, the turbo is powered by a waste product (the exhaust gasses) so it’s guilt-free boost.

That’s what makes the turbo a potentially more efficient way to tackle the supercharged vs turbocharged debate and it’s why so many modern engines use it rather than supercharging.

Again, though, managing the amount of boost and extra fuel that gets added is the key to it all, and it’s why turbocharging only really took off in petrol cars after the mass adoption of electronic fuel injection which has the potential to micro-control those factors.

The advantage of supercharging over turbocharging is that there’s less heat produced in the engine bay. That keeps intake air temperatures lower and that’s good for power production and reliability.

There’s also a bit less hardware thanks to the turbo not needing a belt to run it, but the turbo does have a bit more plumbing involved as it needs to be tapped into the exhaust system, so the supercharger vs turbo thing is far from cut and dried.

Things get further complicated when you start to think about intercoolers (but that’s a whole other chapter).

The biggest gripe with turbos is that they contribute turbo lag. So what is turbo engine lag? It’s the delay between putting your foot down and the turbo building the boost.

Since it’s being driven by exhaust gasses, those gasses have to start flowing before anything happens. That’s unlike the belt-driven supercharger which starts to make boost the moment you start spinning it by revving up the engine.

To be fair, though, modern turbo tech has fixed a lot of this. So how does a turbo work around that lag problem?

With lightweight components, variable vane geometry and twin-scroll turbos, to make the turbo react faster to the throttle and making turbo lag almost a non-issue in modern cars.

Even though it’s difficult to buy a car without a turbo these days, many owners of older cars still make the decision to fit a turbo or supercharger to boost performance.

The big question remains, though, do you go for a supercharger or a turbocharger?

In many ways, the answer will be pretty, obvious purely on the basis of logistics and ergonomics.

A supercharger is a pretty natural fit with V8 engines as it requires no complex exhaust plumbing to drive the pump. And while a modern turbocharger needs a supply of oil from the engine (more plumbing) a supercharger is often a self-contained unit with its own lubrication system.

But a turbo installation on a V8 will still work, particularly if you want twin turbos, and the supercharge vs turbocharge argument will often come down to mundane things like the layout of the engine bay and how much physical space (and what shape it is) you have to work with.

Broadly speaking, supercharging is a better fit with carburetted engines and the old-school V8 market is where a lot of supercharger companies target their products.

Popular brands of supercharger include famous names such as Whipple, Procharger, B and M, Weiand, Holley and even the Australian-made Harrop supercharger which is exported all over the world.

And the most famous (to Australians) supercharged car of all time? It must be the black Ford Falcon Hardtop that starred alongside Mel Gibson in the original Mad Max movies.

Ironically, though, the Weiand supercharger was just a shell to give the appearance of a supercharged engine. It actually spun via an electric motor, but supercharge the Super Pursuit’s engine it did not.