Lexus understands that in order for an internal combustion engine to work efficiently at all times and in all weathers it is necessary to carefully manage its operating temperatures.
In the case of the highly advanced Lexus CT 200h, this management begins with the introduction of an exhaust gas recirculation system to cool intake temperatures, which reduces the need to enrich the air/fuel ratio, thereby improving fuel economy and emissions. At the opposite end is a third-generation exhaust heat recovery (EHR) system that accelerates the time it takes for the engine to warm up; a process which generates similar efficiencies.
Both methods were crucial in securing the Lexus CT 200h its position as the environmental leader within its class, but the EHR system is particularly useful in cold weather and has an additional benefit for those inside the car.
The EHR system is located within the exhaust between the engine and catalytic converter (see image above – EHR unit in silver), and it uses a valve to redirect exhaust gases to begin heating engine coolant immediately after ignition. As well as helping the cabin warm up more quickly, this process improves the hybrid system’s efficiency and fuel economy by significantly reducing the time it takes for the engine to reach normal operating temperature. Because only when the engine is warm can it be shut down for longer electric motor-only running.
In traditionally powered vehicles, stopping the engine halts coolant flow and the normal functioning of the air-conditioning system. But once again, the thorough engineering of the Lexus CT 200h shines through because it employs an electric water pump to maintain coolant flow without the need for the engine to be running. Not only does this delete the mechanical losses associated with belt-driven water pumps but it means an uninterrupted supply of warm air on cold days.
Working in harmony with the EHR system is an adjustable air inlet control that uses a windscreen-mounted sensor pack (see image above) to measure interior humidity as well as cabin and glass temperatures. This information is decoded by the air conditioning system to calculate the optimum ratio of recirculated and fresh air within the cabin to prevent the windscreen fogging up and warm air escaping – all without damaging the fuel economy.
The final way the Lexus CT 200h defends its occupants against the cold is through seat heaters that work pro-actively with the air conditioning system to cut the heater’s workload and improve fuel efficiency.
When the driver switches on the air conditioning to heat the cabin, the seat heaters are also automatically activated to warm the occupants’ bodies directly. This shared heating method allows the air conditioning heater to work at a lower, more efficient temperature, which in turn retains essential heat in the engine’s core and reduces the amount of time it needs to run in order to warm the cabin. However, when passengers are detected in the rear seats, this automatic seat heater control is overridden to protect the comfort of all passengers.
For further information on the most affordable Lexus, read our CT 200h review here. Alternatively, why not experience the cosy ambience of the CT 200h for yourself by visiting your local Lexus Centre.