CYLINDER WEAR

Evening Post, Volume CXVIII, Issue 54, 1 September 1934, Page 26

CYLINDER WEAR

INFLUENCE OF ACIDS

SECOND RESEARCH REPORT

A second report on cylinder-wear experiments has been, issued by the Research and Standardisation Committee of the Institution of Automobile Engineers. The first report, issued in March, 1933, showed that excessive bore wear occurs at low engine temperatures, this being attributed to the corrosion caused by deposits of acid-bearing moisture on the walls under such conditions.

The second report explains the ingenious experiments since carried out by Mr. C. G. Williams and his staff in an endeavour to ascertain the influence of the various acids likely to cause.corrosion: nitric, formic, sulphuric, and carbonic. .The effect of upper cylinder lubricants was also studied.

To ascertain whether the absence of nitric acid would reduce the rate of wear an engine was fed with an artificial atmosphere containing 33 per cent, oxygen ,and-.G7 per cent, carbon dioxide, the latter replacing the nitrogen pre-

sent; in ordinary air. A very big increase in wear was unexpectedly obtaincdj showing that the absence of nitric acid was much more than counterbalanced by the presence of carbon dioxide.

Further experiments showed that carbouie acid must bo responsible for an important proportion of' the corrosion, which occurs in petrol engines at low temperatures. Although the solubility of carbon dioxide in water is low, it increases' almost in proportion to the pressure, which explains the formation of carbonic acid in an engine.

Tests were made to investigate the influence of sulphuric.''.acid' by using a series of fuels,. containing yarious percentages 6f sulphur., Broadly speaking,' the sulplnir' content^ did- not.' affect.' the. rate of ,wea,r .'appreciably' up to ,a pro-; portion qf '.0.08 ( pei.. eenl;.,."but.from' this point onwards 'aiiy. increase of sulphur produced accelerated wear. - As the oxidation .of'alcohols produces formic, acetic, and other, organic acids, wear tests were made on a fuel.containing 17 per cent, of ethyl alcohol to ascertain the effects of these acids. At low 'temperatures the presence of the alcohol was found -to . increase the rate of wear, but at nprmal operating temperatures .the wear was tho same, whether running on petrol/or on the alcohol blend. . In further,tests a iow-pricod -unbranded petrol compared with a good? No. I:spirit, ; the.formcr showing to a disadvantage at; low temperatures, but givrng/an- equal rate of wear at high^te'mpdratures.- ,-;•.: ; -.-., '■ |•. The'report as ■concluded by an account of oxperinients.mado with uppct cylinder lubridation. These: tests, are being- coritrnuedy but ■■■ the ~main - conclusions -which- Mr,' WiUiams has;reached, so farj'arc:-- (1)-That -the introduction of a small proportion of oil with the petrol leaves bore and ring wear unaffected at normal working temperatures; (2) that improved bore lubrication'at low temperatures- reduces the rate of wear materially. _ The tests were made with engine oil and spindle' oil; further trials are in progress with proprietary cylinder lubricants. ' ; '; ■ '