Abstract: An exhaust reaction chamber for an internal combustion engine has an outer downstream chamber section surrounding and enclosing an inner upstream chamber section which receives exhaust gases from the engine. Intake mixture for the engine is heated by exhaust gases in the outer chamber section. A leak hole is provided in the inner chamber section for accelerating heat transfer to the intake mixture during warmup operation of the engine.

Abstract: A spark-advance mechanism for an internal combustion engine is operated by vacuum pressure in the engine intake manifold. A conduit connecting the spark-advance mechanism to the intake manifold includes a solenoid operated valve which is normally open, and which is closed by either of two switches connected in parallel. One of the switches is closed when the engine temperature is low, and the other is closed when the engine RPM is high. When the solenoid valve is energized by either or both switches to close the conduit, atmospheric air is bled through an orifice to cause slow advance of the spark timing.