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An inhibitor package which is silicate-, nitrate-, borate- and phosphate-free has been developed as the basis for a world-wide automotive coolant formulation. The formulation contains aliphatic mono- and dicarboxylic acids and tolyltriazole as the sole inhibitors. Formulations containing carboxylic acid inhibitors have been studied in ASTM bench tests and found to sufficiently protect all prevalent cooling system metals. In addition, fleet tests have shown that carboxylic acid inhibitors deplete much more slowly than conventional inhibitors, making possible a much longer life coolant. Results from laboratory tests which simulate extended usage indicated that carboxylic acid-containing coolants have a significantly longer life span for the protection of all cooling system metals. Finally, the carboxylic acid/tolyltriazole inhibitor package is completely adaptable to a propylene glycol base.

This paper presents results of studies investigating the effect of octane enhancing ethers on the reactivity of an 87 octane mixture of primary reference fuels, 87 PRF, in a motored engine. 87 PRF was blended with small percentages of MTBE, ETBE, TAME and DIPE based on a constant gravimetric oxygen percentage in the fuel. The experiments were conducted in a modified single-cylinder Wisconsin AENL engine at compression ratios of 5.2 and 8.2. Supercharging and heating of the intake charge were used to control reactivity. The inlet gas temperature was increased from 320 K, where no reactivity occurred, until either autoignition occurred or the maximum temperature of the facility was reached. Exhaust carbon monoxide levels and in-cylinder pressure histories were monitored in order to determine and quantify reactivity.

Automobile coolant pump failure rates have been observed to be influenced by the coolant inhibitor package. A fleet test consisting of 196 1991 Ford Crown Victoria taxi cabs was utilized to test six coolant formulations. Four of the test formulations were monobasic/dibasic organic acid technology coolants and two were traditional technology coolants containing nitrate, phosphate, and silicate. Coolant pump failure rates were monitored as a function of mileage. Results indicate that the service life of coolant pumps for those systems employing organic acid technology coolants was significantly greater than those systems utilizing traditional inhibitor technology coolants.

Autoignition chemistry of n-heptane, iso-octane and an 87 octane blend, 87 PRF, was studied in a single-cylinder modified Wisconsin model AENL engine under motored conditions. Use of a fast-acting sampling valve and gas chromatographic analysis allowed measurement of in-cylinder gas composition during the ignition process. Crank angle resolved species evolution profiles were generated for all three fuels at a fixed inlet temperature of 376 K. For n-heptane, the measurements were made during a cyclically repeatable two stage ignition process up to the point of hot ignition (the second stage ignition). These n-heptane experiments were run at ø = 0.3 to avoid excessive pressure rise at hot ignition which might damage our engine. iso-Octane and 87 PRF were run at stoichiometric equivalence ratio which did not have a second stage ignition, and species were measured only during the first stage of ignition.