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Downpipe

Car culture term

What is Downpipe?

The exhaust pipe immediately after the turbocharger. Aftermarket downpipes reduce restriction and boost lag, often used with tunes.

Downpipe is the exhaust pipe immediately after the turbocharger. Stock downpipes typically include a small catalytic converter (especially on European market cars) and have flow restrictions designed to meet emissions and noise requirements. Aftermarket downpipes replace the stock unit with a larger-diameter, less-restrictive design that improves exhaust flow from the turbo, reducing turbo lag and increasing power potential.

Downpipes are an essential modification for serious tuning of turbocharged cars. The stock downpipe restriction is one of the major bottlenecks limiting the engine power potential at higher boost levels. Replacing the downpipe with an aftermarket unit (typically 3 to 4 inches in diameter versus 2 to 2.5 inches for stock) allows the turbo to spool faster and the engine to flow more exhaust gas at high load.

Downpipe modifications often raise emissions concerns. Catless downpipes (with no catalytic converter) maximize flow but are illegal for street use in most jurisdictions due to emissions regulations. Catted downpipes (with high-flow catalytic converters) maintain emissions compliance but cost more. Some markets (particularly the European Union and California) have specific requirements for downpipe certification. Tunes specifically designed for downpipe modifications are typically required to extract the full power benefit.

Related terms

Cat-back exhaustTurboECU tune

Frequently asked questions

How much power does a downpipe add?
On a turbocharged car: 30-60 horsepower with a quality downpipe and matching tune. The gain is largest on cars where the stock downpipe is heavily restrictive. Without a tune, the downpipe alone may only add 5-15 horsepower because the ECU does not adjust to take advantage of the increased flow.
Are catless downpipes legal?
Generally illegal for street use in the United States and most other markets due to emissions regulations. Cars with catless downpipes will fail emissions inspections. Some jurisdictions (typically rural or non-emissions-inspecting states) tolerate catless modifications. For racing applications (off-road only), catless downpipes are legal. For street use, catted downpipes are the legal alternative.
Do I need a tune for a downpipe?
Yes, for full benefit. Without a tune, the ECU does not take advantage of the increased exhaust flow. The car may run at the same boost levels as stock, with only modest power gains. With a tune designed for downpipe modifications, the ECU increases boost and adjusts ignition timing for the new flow capability.
How much do downpipes cost?
Catted (legal) downpipes: $800-$2,500. Catless (race-only) downpipes: $400-$1,500. Premium downpipes (Akrapovic, Capristo): $2,000-$5,000+. Installation typically adds $300-$800. The total investment for a downpipe + tune package is typically $2,000-$5,000 depending on the platform and quality choices.
Will a downpipe make my car louder?
Yes, typically. The increased flow and reduced muffling produce louder and more aggressive exhaust notes. The change is most apparent at high RPM and under boost. Combined with a cat-back exhaust, the sound character changes significantly. Some downpipes include resonators to manage the sound; cheap downpipes often produce significant drone and amplified noise.
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