During cold engine startup, a secondary air injection system operates to minimize tailpipe emissions before closed-loop feedback begins. In what sequential order does this system deliver fresh air and accelerate catalyst heating?
- 1The powertrain control module detects cold-start operating parameters and energizes the secondary air pump.
- 2Pressurized fresh air flows past an opened one-way check valve into the exhaust passages.
- 3Injected oxygen mixes with rich exhaust gases to promote oxidation of unburned hydrocarbons and carbon monoxide.
- 4Thermal energy from secondary oxidation rapidly warms the catalytic converter to its light-off temperature.
Cevap
The correct sequence begins with the control module commanding the secondary air pump to turn on, followed by pressurized air passing through the one-way check valve, then mixing with exhaust gases to oxidize residual hydrocarbons, and finally heating the catalytic converter to operating light-off temperature.
The secondary air injection cycle starts when the powertrain control module energizes the pump during cold start conditions. The pump forces air through a protective one-way check valve into the exhaust manifold. There, injected oxygen reacts with rich unburned hydrocarbons, generating exothermic energy that rapidly brings the downstream catalytic converter to its operating light-off temperature.
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Anahtar Kavram
Secondary Air Injection Operation and Catalyst Light-Off
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