Fuel Effects on Emissions from Two Electrically Heated Catalyst Equipped Vehicles

The effect of gasoline composition on the exhaust emissions from two vehicles equipped with electrically heated catalysts (EHC) and secondary air injection was studied. The two vehicles used were a 1991 Ford Tempo and a 1992 Chevrolet Lumina. One novel feature of the EHC system was automatic feedback control of secondary air injection using a heated oxygen sensor. This control scheme provided sufficient air for significant decreases in hydrocarbons (HC) and CO without an increase in NO_x. Exhaust emissions were measured for each vehicle, both with and without an EHC for three fuels: Indolene certification fuel, a high emissions fuel (high aromatics/T₉₀), and a low emissions fuel (low aromatics/T₉₀).

The average total hydrocarbon (THC) reduction in both EHC equipped vehicles tested on three different fuels was 52%, with a high of 62% and a low of 36%. NO_x was not adversely affected by secondary air injection for all fuels tested because of the feedback control scheme used. Fuel composition effects on hydrocarbon emissions during the cold start portion of the FTP were substantially reduced in the EHC equipped vehicles compared to the base vehicles.