Honda HR-V: Catalytic Converter System Description - Overview (KA/KC)

Warm Up Three Way Catalytic Converter (WU-TWC), Under-Floor Three Way Catalytic Converter (Under-Floor TWC)

The warm up three way catalytic converter (WU-TWC) and the under-floor three way catalytic converter (Under-floor TWC) convert hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to carbon dioxide (CO2), nitrogen (N2), and water vapor. The WU-TWC is attached directly under the each cylinder head that is integrated into the exhaust manifold.

WU-TWC (Attached to the cylinder head)

Under-floor TWC

EGR SYSTEM DESCRIPTION - OVERVIEW (KA/KC)

The exhaust gas recirculation (EGR) system lowers combustion temperature and reduces oxides of nitrogen (NOx) emissions. The recirculating exhaust gas routes through the EGR pipe, the intake manifold, and into the combustion chambers. Routing the exhaust gas through the EGR pipe helps to prevent carbon deposits from forming in the intake manifold and the throttle body. The powertrain control module (PCM) memory includes the ideal EGR valve position for varying operating conditions. The EGR valve position sensor detects the amount of EGR valve lift and sends it to the PCM. The PCM then compares it with the ideal lift in its memory (based on signals sent from other sensors). If there is any difference between the two, the PCM cuts power to the EGR valve.

Exhaust Gas Recirculation Flow

The exhaust gas downstream of the warm up three way catalytic converter (WU-TWC) flows through the EGR pipe, the passage in the cylinder head, and the exhaust gas recirculation or EGR valve and position sensor.

EVAP SYSTEM DESCRIPTION (KA/KC)

The evaporative emission (EVAP) controls minimize the amount of fuel vapor escaping into the atmosphere.

Vapor from the fuel tank is temporarily stored in the EVAP canister until it can be purged from the canister into the engine and burned. The EVAP canister is purged by drawing fresh air through it and into a port on the intake manifold. The purging vacuum is controlled by the EVAP canister purge valve. Also attached to the EVAP canister are the EVAP canister vent shut valve and the fuel tank pressure (FTP) sensor.

Operation

When fuel tank pressure increases because of heat and fuel vapor generation, evaporated fuel vapors are sent to the EVAP canister where they are stored.When the engine coolant is hot enough, the PCM opens the EVAP canister purge valve to draw the stored fuel vapor in the EVAP canister into the intake manifold to be burned.

To regulate the amount of fuel vapor drawn into the engine, the PCM varies the EVAP canister purge valve opening using duty cycle control. When the outside air or other factor cools the fuel tank inside, the fuel tank pressure decreases. The EVAP canister vent shut valve is normally open and allows outside air to enter the fuel tank through the EVAP canister. If there is a system malfunction or blockage in the vent hose, a pressure valve in the fuel filler cap opens and allows outside air to enter preventing system damage. The PCM uses the FTP sensor and EVAP canister vent shut valve to check for leaks in the system. When the enabling conditions are met, the EVAP canister vent shut valve is closed, the PCM monitors for changes in the FTP sensor.

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