Engine‑X comparison
Turbocharger vs supercharger: what's the difference?
By Parth Parmar, mechanical design engineer · Updated
Both force extra air into an engine so it can burn more fuel and make more power. A turbocharger is spun by the engine's exhaust gas, so it reuses energy that would otherwise be wasted and is more fuel-efficient, but boost can arrive with a short lag. A supercharger is driven by a belt or gears from the crankshaft, so it gives instant boost but uses some of the engine's own power to run.
Side-by-side comparison
| Turbocharger | Supercharger | |
|---|---|---|
| Driven by | Exhaust gas spinning a turbine | Belt or gears from the crankshaft |
| Throttle response | Short lag at low engine speed | Instant, from idle |
| Efficiency | Higher: recovers waste exhaust energy | Lower: takes power from the crankshaft |
| Heat | Very hot; needs oil (often coolant) cooling | Runs cooler |
| Installation | More plumbing: exhaust, oil lines, wastegate, intercooler | Simpler to package and fit |
| Sound | Whoosh and spool | Distinct whine |
| Typical use | Most modern petrol and nearly all diesel engines, trucks, ships | Performance and muscle cars, drag racing |
Which one should you choose?
- Choose a turbocharger for fuel economy, smaller engines with big-engine power, diesels and high boost.
- Choose a supercharger for instant, linear throttle response and simpler installation on a performance engine.
How a turbocharger makes boost
Exhaust gas leaving the cylinders flows through the turbine housing and spins the turbine wheel, on small car turbos often at more than 100,000 rpm. A shaft joins the turbine to the compressor wheel on the intake side, which sucks in fresh air and pushes it into the engine under pressure. Two parts keep it under control: a wastegate lets some exhaust bypass the turbine so boost does not climb too high, and an intercooler cools the compressed air so more of it fits in each cylinder.
Because the turbine needs exhaust flow before it can spin up, a turbocharger gives little boost at idle and full boost higher in the rev range. Smaller turbines, twin-scroll housings and variable-geometry turbines are all ways of making the turbo respond sooner.
How a supercharger makes boost
A supercharger is driven by a belt or gears from the crankshaft, so it turns whenever the engine turns and boost rises with engine speed from the moment the throttle opens. There are three common types:
- Roots — two lobed rotors carry air around the outside of the casing and push it into the intake manifold. Simple and strong at low speed, but it heats the air more than the other types.
- Twin-screw — two meshing screw rotors squeeze the air inside the casing before it leaves, which is more efficient than a Roots blower.
- Centrifugal — a belt-driven impeller, much like the compressor side of a turbo. Boost builds strongly with engine speed, so it feels similar to a turbo without the exhaust plumbing.
The price of instant boost is the drive power: the engine has to spend part of its own output turning the supercharger, which is why a supercharged engine usually uses more fuel than a turbocharged one making the same power.
Turbochargers on ship engines
Almost every large marine diesel is turbocharged, because a slow-running ship engine produces a huge, steady flow of exhaust that a turbocharger can turn into charge air for free. On big two-stroke engines the turbocharger supplies the scavenge air that clears the cylinders. At low load there is not enough exhaust energy for that, so electric auxiliary blowers start automatically and help until the turbocharger takes over. Read more in how a ship turbocharger works on a two-stroke engine, or explore the marine diesel engine in 3D.
Maintenance: what each one needs
| Turbocharger | Supercharger | |
|---|---|---|
| Lubrication | Engine oil feeds the bearings; clean oil and on-time oil changes matter most | Often its own sealed oil, changed at long intervals; some share engine oil |
| Heat care | Let the engine idle briefly after hard running so oil does not burn on the hot bearing housing | No special cool-down needed |
| Checks | Oil leaks, shaft play, cracked turbine housing, boost leaks in hoses | Drive belt wear and tension, rotor or bearing noise |
| Common failure cause | Oil starvation or dirty oil | Worn belt or bearings |
See how it works inside, part by part, in 3D.
Explore the 3D turbocharger →Common questions
Is a turbocharger better than a supercharger?
Neither is better for every job. A turbocharger is more efficient and is why most modern engines use one, while a supercharger responds instantly and is simpler to fit. The right choice depends on whether economy or instant response matters more.
Can an engine have both a turbo and a supercharger?
Yes. This is called twincharging: the supercharger gives boost at low engine speed and the turbocharger takes over higher up. Some production engines have used it, such as Volkswagen's 1.4 TSI Twincharger.
Why do diesel engines use turbochargers?
Diesels need a lot of air and run at low engine speeds where exhaust energy is plentiful. A turbocharger uses that exhaust energy for free, which raises power and efficiency without taking power from the crankshaft.
What causes turbo lag?
The turbine needs enough exhaust flow to spin the rotating group up to speed. At low engine speed there is less exhaust, so boost builds a moment after the throttle opens. A supercharger has no lag because it is geared directly to the engine.
Does a supercharger use more fuel than a turbocharger?
Usually yes, for the same power. A supercharger takes its drive power from the crankshaft, while a turbocharger is driven by exhaust energy that would otherwise be wasted, so the turbocharged engine is normally more economical.
Is a turbocharger a type of supercharger?
In a broad sense, yes. Both are forced induction: they push more air into the engine than it could draw in by itself. Early turbochargers were even called turbo-superchargers. Today the word supercharger normally means one driven mechanically by the engine.
Sources
References for the facts on this page, and further reading:
- Mobil — How turbochargers and superchargers differ
- Garrett Motion — How a turbocharger works: types of turbos
- Garrett Motion — Turbo Tech 101: Understanding the parts of the turbocharger
Related guides
How does a turbocharger work? · How does a centrifugal pump work? · How does a V-belt pulley drive work? · How does a gear reducer work? · How does a planetary gearbox work? · How does a reciprocating air compressor work? · How does a plate heat exchanger work? · Centrifugal vs positive displacement pump: what's the difference? · Belt vs chain vs gear drive: which is better? · How does a marine diesel engine work?
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