Bosch has introduced an innovative technology designed to significantly reduce harmful emissions from gasoline engines, particularly during the critical cold-start phase. This new system, called the Bosch Rapid Catalyst Heater (RCH), directly addresses the challenge of criteria emissions—such as ozone, particulate matter, carbon monoxide, lead, sulfur dioxide, and nitrogen dioxide—which are recognized as hazardous and remain fully regulated despite recent rollbacks in CO2 emission rules. The RCH promises to make all gas-powered cars operate cleaner and has the potential to dramatically improve the emissions performance of plug-in hybrid electric vehicles (PHEVs).

The fundamental issue lies with conventional three-way catalytic converters. While these devices are remarkably effective, removing up to 98 percent of a gas engine’s criteria emissions, their efficiency is only achieved once they reach their optimal operating temperature, typically between 750–1,100 degrees Fahrenheit. Consequently, the initial 20 to 60 seconds after a cold engine start are the 'dirtiest' period for emissions, making this brief interval a primary focus for engineers aiming to pass stringent EPA emissions tests.

Historically, engineers have employed various strategies to accelerate catalyst warm-up. These methods include physically locating the catalyst closer to the engine cylinders, utilizing a rich fuel mixture during startup, retarding ignition timing, adjusting exhaust-cam timing, adding secondary air injection, and even using electricity for direct catalyst heating. However, each method comes with its own trade-offs, often involving increased cost or complexity. Direct electric catalyst heaters, for instance, typically supply 1–10 kW of power to the catalyst brick. Supplying 5 kW, which is comparable to the draw of a large high-compression engine's starter, is particularly challenging for a standard 12-volt electrical system without the aid of a dedicated hybrid battery.

Bosch's RCH technology offers a novel and powerful solution. Instead of relying on electricity, it employs a gas burner capable of almost instantly delivering a substantial 25 kW of heating energy directly into the exhaust stream, precisely ahead of the catalytic converter. This significantly higher energy output compared to typical electric heaters allows for a much faster warm-up of the catalyst.

The operation of the Bosch RCH is carefully orchestrated. When the engine-start button is pressed, a dedicated burner-control unit activates a secondary air-injection type pump. This pump draws filtered air, precisely measured by a Bosch mass airflow sensor, at approximately 15 cubic feet per minute. This air then enters a combustion module where low-pressure fuel is introduced via a standard Bosch port injector, featuring a unique nozzle hole pattern. The air-fuel mixture is ignited by a Bosch diesel glow plug, and the resulting hot gas mixture flows past a Bosch oxygen sensor, which ensures a precise stoichiometric 14.7:1 air-fuel ratio. This precisely controlled, hot mixture is then directed into the exhaust system right at the entrance to the catalyst, ensuring its rapid and efficient heating.