CARBON DEPOSITS

Rotorua Morning Post, Volume 3, Issue 700, 28 November 1933, Page 2

CARBON DEPOSITS

CARBURETTER ADJUSTING AND YOLATILE FUEL A REMEDY. TENDENOY OF E'NGINES. •All oil ia,nd fuels wh'en burned in •the Comibustion chamber of the engine are likely to leave a residue whieh may not be entirely expelled through the exhaust and beCome carb'on. Carbon deposit in automotive engines is largely due to imperfect •combustion. Correct carburetter adjustment and the .constant use of the •most volatile fuel obtainable are of mia.jor imrportance. The carbon deposit from lubricat•ing oil in th'e comibustion chamber will depend largely upon four things: 1. The charao'ter of the oil.— Some (oils are clean-burning; others burn to gurnrny sticky . m'asses, and still others "coke" to^ hard and dry but abundant carbon formation. 2. Th'e body .of the oil. — Usually, oils of heavy body tend to leave more carbon than the lighter-bodied lubricants under the same operating conditions. 3. En'gine operation temperatures. — fWith' any oil, there is a certain cri•tioal temperatufre above which the carbon formed is consumed and below which the carbon formation will vary in quantity and chanaeter, depending upon the aotual temperature.

|4. Oil reaching the combustion chamiber. — IThe more oil th'at reaches th'e combustion cbambers th'e m'ore possibilities for carbon. The am'ount of this oil depends largely upon engine design, construction and use. Before an oil of correct body and •character can be selected, every feiature of engine design affecting carbon formation must be carefully considered. The tendency toward carbon formation in any engine is analys'ed from three distdnot standpoints: — 1. Do operating conditions promote carbon accumulation ? — ilf so, as in average car service in contrast to tractor or aircraft service, such carbonising tendencies must be carefully studied. 2. Is the engine construction such that an excessive amount of oil will work past the piston rings dnto the combustion chamber ? — fWhere too much oil reaches the combustion chamber, due to features of design which control the oil supply, it is •essential that the oil used be of cleanburning charia.cter and preferably of light or medium body. 3. Is tbe engine of a type in wbich a sligh't amount of carbon interferes seriously with its perf ormance ? — Engines developing bigh compr'ession tend to "knock" when carbon is present to a greater extent than in moderate and low compression types. Engines with small compression cbambers aot in a similar manner. For these types, therefore, the greatest care must be exercised in the selection of th'e lubricating oil.