Hi!: the SAE paper 930680, 'Catalytic Glow plugs in the JDTI SCRE', describes mainly their results with modified NGK CY01 silicon nitride tip plugs custom made for their RCE research, to which a catalyst coat was added; because of failures, they overcoated the silicon nitride with a non-permeable alumina coating, the catalyst formulation containing platinum only, applied by chloroplatinic acid solution, and applied by calcination, a second plug was given an additional platinum coat by sputtering additional platinum onto the surface.

The aim in the modified plugs being that, working at lower temperature, its life span will be lengthened. Background of this program was in the patents by Pfefferle W,  US3,923,011 and US4,646,707; Haslett R, US 4,092,967; also in several publications: Schefer R.W. et al: 'Catalyzed combustion of lean fuel/air mixtures', proc of 4th Workshop on Catalytic Combustion, 1980; Coward HF et al: 'Ignition of Natural gas-Air Mixtures by heated metal bars', J Am Chem Soc, 49, 2479, 1927.

Results were that the modified catalytic plug was able to operate with Diesel fuel at low load with a temperature more than 260� C lower than that required for an standard non-catalytic glow-plug of same design, however, no differences were seen in exhaust gas temperatures and chamber pressures between that with the experimental plug and the chamber with standard plug.

Regards, + Salut

Jose Gros-Aymerich
 Madrid, Spain