Roots and twin-screw superchargers are both positive displacement blowers that sit on top of the engine and make strong boost from low engine speed. The difference is where the air gets compressed. A Roots blower moves air into the intake manifold without compressing it inside the case, so compression happens in the manifold. A twin-screw compresses the air between its meshing screws before it leaves the case, which makes it more efficient at higher boost and keeps the air cooler.
Twin-screw vs Roots at a glance
| Roots | Twin-screw | |
|---|---|---|
| Compression | External, in the manifold | Internal, between the screws |
| Efficiency at high boost | Lower; more heat | Higher; cooler air |
| Low-speed response | Immediate | Immediate |
| Sound | Classic blower whine | Sharper, higher-pitched whine |
| Complexity | Simpler rotors | Precision-machined screws |
How a Roots blower works
Two lobed rotors spin in opposite directions and carry pockets of air around the outside of the case to the outlet. Because there is no compression inside the case, the blower pushes more air than the engine can swallow, and pressure builds in the manifold. Modern Roots designs with twisted multi-lobe rotors are far more efficient than older straight-lobe blowers.
How a twin-screw works
A male and a female screw mesh together. As they turn, the space between them shrinks along their length, compressing the air before it is delivered. Less heat is added for a given boost level, which helps at higher boost.
And centrifugal superchargers?
A centrifugal supercharger is a different design: a belt-driven impeller like the compressor side of a turbo, mounted at the front of the engine. Boost rises with engine speed instead of arriving at low speed, which suits engines that make their power high in the rev range. See centrifugal supercharger for the full comparison. Our Corvette kits are listed on C6 Corvette supercharger kits and C7 Corvette supercharger kits.
Which is right for you?
- Street driving and towing: both positive displacement types give instant low-speed torque.
- Higher boost: the twin-screw’s internal compression keeps intake temperatures lower.
- Top-end power and easy intercooling: consider a centrifugal unit.
- Hood clearance: top-mounted blowers may need a different hood; centrifugal units sit low.
Intercooling and heat
Compressing air heats it, and hot air is less dense and raises the risk of detonation. Top-mounted Roots and twin-screw kits usually use an air-to-water intercooler built into the manifold under the blower, with its own pump and front heat exchanger. Because a Roots blower adds more heat at high boost, the intercooler matters even more on Roots setups pushed hard. See what does an intercooler do?
Sound
Both whine; the twin-screw’s is usually sharper. See supercharger whine.
Learn more
See what does a supercharger do?, supercharger vs turbo, how much horsepower a supercharger adds and what does an intercooler do?
More guides: how long a supercharger lasts.
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