Is a Turbo Upgrade Legal in the US?

Conditional

A turbo upgrade or turbo kit is legal in the US if the car still meets emissions and keeps its emissions equipment. In California and CARB states, a forced-induction kit generally needs a CARB Executive Order to be street-legal.

Why?

Forced induction itself is not banned, but it changes how the engine breathes and burns, which is emissions-relevant. Federally, the car must keep its catalytic converter and other controls and remain compliant; a turbo paired with a defeat tune is illegal tampering.

In California and the states that follow CARB, an add-on turbo or supercharger kit needs a CARB Executive Order (EO) to be legal on the street, and a smog check will reject a non-EO forced-induction setup. Kits designed for those markets carry an EO.

So a compliant turbo upgrade that keeps the emissions system intact can be road-legal, especially outside CARB states; without the required EO in a CARB state, or with an emissions-defeating tune anywhere, it is not.

What decides if it's legal

The vehicle must keep all its emissions equipment and stay compliant.
In California/CARB states a forced-induction kit needs a CARB EO.
It must not be paired with a tune that defeats emissions controls.
Adding boost to a naturally-aspirated car is a major, declarable change.

Does it depend on your state?

Yes. In CARB states a turbo kit needs an Executive Order to be street-legal; in non-CARB states an emissions-compliant kit is generally allowed. The tune it runs must never defeat emissions controls anywhere.

Related guides

Supercharger or Turbo: Which Adds Power Better?

Related legality guides

Find your car in the garage

Sources

This page is general guidance, not legal advice, on the rules in the US for turbo upgrade. The detail varies by exact vehicle and changes over time - confirm with your insurer and the EPA, NHTSA and your state DMV before modifying.