In order to reduce the content of harmful substances in the exhaust gases during a cold start of the engine, atmospheric ("secondary") air is supplied to the exhaust manifold in the immediate vicinity of the exhaust valves using a secondary air supply system

The operation of the secondary air filter

A HENGST FILTER brand Secondary Air Filter keeps dirt particles out of the engine to improve combustion. Improve your vehicle's fuel efficiency, engine performance and life with a secondary air filter that improves air-fuel balance and reduces engine emissions.

1. 3 - series
2. 3 - series bus
3. K - series
4. 4 - series bus
5. F - series bus
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Secondary air filter options such as protective foam, paper and cleanable calibration paper are designed especially for different car models and brands. Made from quality and durable materials, secondary air filters are economical, efficient, and easy to install, and provide excellent performance to keep your engine in optimum working condition. Naturally, secondary air filters have their own consumable resource. They are able to clean all dirt particles from your engine for several months before they need to be replaced.