A screamer pipe is a type of exhaust configuration fitted to some automotive turbocharged petrol engines with an external wastegate set-up, known for its loud noise.
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Principle of Operation
To regulate the boost pressure on turbocharged engines a wastegate is fitted to allow exhaust gases to bypass the turbine and flow straight down the exhaust down pipe. This can cause turbulent airflow around the turbine and high exhaust back pressure. To overcome this problem, gases can be re-routed down a separate pipe and vented straight to atmosphere resulting in improved performance.
Limitations
By definition, this configuration allows exhaust gases to flow straight to atmosphere. Consequently the gases do not pass through the catalytic converter or exhaust silencer which renders it illegal for street use due to noise and exhaust emission regulations in many countries. Whilst exhaust emission laws do not apply away from the public highways in most countries, many race tracks have strict noise rules in place once again outlawing screamer pipe use.