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An engine dynamometer test facility-capable of controlling temperatures from 0°F to 150°F was used to investigate A/F control characteristics of a 1.6 liter engine with single point fuel injection. Two types of tests were run. In the first, the effect of induction system temperature on manifold wall wetting and transient A/F control was determined. In the second, a cold start procedure was developed to determine the effect of engine temperature on the percent of fuel which burns by observing exhaust A/F during steady state operation while the engine warms up. It was found that transient A/F control problems due to manifold wall wetting are much greater than steady state problems associated with incomplete fuel burning.

An investigation of transient A/F characteristics was conducted using a 1.6 liter engine equipped with a Sequential Electronic Fuel Injection (SEFI) system. The engine was tested on a dynamometer facility capable of providing environmental temperatures as low as 10°F. A test procedure was developed to determine the effects of steady state A/F, engine speed, size of throttle ramp, injection timing, and hardware changes, on the transient A/F characteristics while the engine warmed up. It was found that, under cold operating conditions, the A/F excursions for the SEFI system were similar to those previously measured for a Central Fuel Injection (CFI) system on the same engine. It was also found that the sensitivity of the A/F excursions to variations in the test parameters, while quite dramatic at reduced temperatures, decreased as the engine warmed up.