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Four samples of three different types of gasoline found in Brazil were tested to verify their aging effects on engine performance and exhaust emissions: two samples of regular gasoline, one sample of regular gasoline plus additives, and one sample of premium gasoline. The regular gasoline is the most commonly used automotive fuel in Brazil; regular plus additives contains an improved detergent capacity; and premium is a gasoline of higher octane number. All these types of gasoline are, in fact, a blend of approximately 75% gasoline and 25% ethanol, with the ethanol having an anti-knocking function. The gasoline samples were tested in a total period of six months, using a production 1.3-liter, four-cylinder, sixteen-valve engine mounted on a bench test dynamometer. Performance parameters and exhaust emissions levels were obtained for engine speeds of 1000 to 6000 rev/min. The general test results point to an increase in HC and CO emissions and in fuel consumption with fuel aging.

The intake valves of a 1.0 liter, 16-valve production engine has been phase shifted to increase the intake air charge, aiming at improved performance. The engine has been tested in a dynamometer bench to verify the performance attained with the modification and its influence on raw exhaust emissions. Total hydrocarbons, carbon monoxide, nitric oxide and oxides of nitrogen emissions were analyzed for varying load and engine speed. The results have shown that shifting the valves of a dual intake valves engine can provide increased performance, while keeping emissions at acceptable levels.