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A fast response NO detector has been developed to study fast transient emissions from internal combustion engines. The device combines the standard ChemiLuminescence Detector (CLD) measurement technique used in conventional NO detectors with the rapid sampling system of an existing Fast Flame Ionisation Detector (FFID) hydrocarbon detector. The 10-90% response time of the fast NO detector is approximately 3 milliseconds and enables resolution of transient NO concentration within individual engine cycles. Both the fast NO and fast HC detectors were fitted in the exhaust port of a firing SI engine. With the probe tips at the same position, simultaneous fast transient NO and HC concentration data have been recorded during steady state and transient engine load conditions. Cycle-by-cycle NO concentration, HC concentration, and cylinder pressure are compared and features of the transient NO and HC concentration are discussed.

Increasing pressure on lowering vehicle exhaust emissions to meet stringent California and Federal 1993/1994 TLEV emission standards of 0.125 gpm NMOG, 3.4 gpm CO and 0.4 gpm NOx and future ULEV emission standards of 0.04 gpm NMOG, 1.7 gpm CO and 0.2 gpm NOx has focused specific attention on the cold start characteristics of the vehicle's emission system, especially the catalytic converter. From test data it is evident that the major portion of the total HC and CO emissions occur within the first two minutes of the driving cycle while the catalyst is heating up to operating temperature. The use of an electrically heated catalyst (EHC) has been proposed to alleviate this problem but the cost and weight penalties are high and the durability has yet to be fully demonstrated (1)*. This paper describes a method of reducing the light-off time of the catalytic converter to less than 20 seconds by means of an afterburner.