“SUN” SERVICE STATION

Sun (Auckland), Volume III, Issue 776, 24 September 1929, Page 6

“SUN” SERVICE STATION

fTIHE "Motordom” section of The Sun includes in its service to readers a J- Queries and Answers Department, the object of which is to give accurate information regarding mechanical and touring subjects. What- " ever the particular puzzle may be in either diagnosing irritating troubles or motoring information of any kind. “Headlight' will endeavour to help, or refer the point to men who are recognised automobile experts In their respective lines. All communications must be accompanied by the inquirer s name and address (not for publication), and sent to TILE SUN “Service Station, Motordom,” THE SUN, Auckland. Answers will appear weekly in this column.

Could you please tell me the agents for the following cars: Renault, Fiat and Bean? I intend to buy a light English or Continental job. but do not know the agents’ names. * * * Renault, Wright, Stephenson and Co., Ltd., Eden Terrace; Fiat and Bean, Dominion Motors, Ltd., Albert Street. “D.” —I have an extra air attachment on my Austin 6/16, and would like to know through the columns of your valuable paper the best method of using this. Some tell me that after you become proficient in the use of it you can travel for miles with the extra air switched on a few points, and so save a lot of petrol and obtain an increased mileage a gallon. Is this so? (2) I shall be glad if you will also t.ell me whether or not it is advisable to fit to my car a Nujay lubricator. Some tell me that it. is all right for a new car until it is run in, but after that it is useless. Others tell me that the same result can be obtained by adding a pint of ordinary lubricating oil to the petrol. So you see I am in a fix as to the best thing to do, and would value your advice in the matter, also any information re’garding 'same as to the advantages of such a fitting. Does it increase the mileage a gallon of petrol, and does it save having the engine decarbonised for a longer period? * * 5? (1) Extra air is used as a brake or for cooling the motor when descending hills. It prevents oil being sucked from the crankcase into the combustion chamber by filling the partial vacuum that exists there when the throttle is closed. At the same time *it saves fouled plugs. Frequently it can be opened a little when the engine is warmed, and so save petrol, but too great use defeats this purpose by overweakening the mixture. It is the best indicator of the condition of the mixture. If the motor speeds up when the air is opened, the mixture is too rich, and should be cut down. I have found in altitudes that the extra air can be opened fully with benefit to the motor's performance. Probably this is due to the thinner air on mountains. (2) I have had a Xujay on my car for 3,000 miles, and find that it tremendously improves the performance. After a 6.000-mile period I had the head removed for curiosity, and found only a little soft carbon on the piston heads and around the valves. There was not enough carbon to cause pre-ignition

nor to pit Hie valve seats. It improves the petrol consumption by do- ' creasing power losses through friction, lubricates the valves and guides, and minimises carbon formation. I believe it to be useful for any car at any stage of its life. Adding thir. oil to the petrol is better than nothing, but causes a constant variation in the mixture, and an uncertain supply of lubricant. An automatic lubricator. working at a pre-determined volume, and entering the induction manifold without affecting the carburettor, obviously is better. “Mac.”—As a reader of your valuable paper, I will be pleased if you can advise me gf the method of removing duco. Have tried paint removers of several kinds, also caustic, without result. These will not touch it, and it will not scrape off. Our object is to get it perfectly clean, so as to repaint it with Ripolin. Use either Amyl Acetate or Duco thinner or a mixture of both. These will remove Duco, but it is a long, tedious job. Get the car into the open air when working on it, as there will be lots of odours, and the Duco solvents are highly inflammable, and should be handled with care. . PISTON WEAR At the present moment a good deal of thought is being expended on the subject of the design of the aluminium piston, which is now almost universal, but which has not proved to be ideal. These alloy pistons are excellent as regards their light weight and good heat conductivity, but they wear rather rapidly, and they also have a tendency to wear the cylinder bores. There is a further disadvantage in the high co-efficiency of expansion possessed by most aluminium alloys which necessitates large clearances with a consequent tendency to piston slap until the engine has warmed up. j Designers are tackling the problems j by making bi-metal pistons—one metal jan aluminium alloy and another a better-wearing material. Thus a com ! promise is made between the light | fast-wearing aluminium and the hear;, long-lived cast iron.