Nurse Your Diesel

Lake County Mail, Issue 17, 17 September 1947, Page 2

Nurse Your Diesel

If you have any problems, forward them to “Aerial,” P.O. Box 928 Dunedin. (Please note change of Box No.).

Q. What is the usual maximum of a high-speed diesel commercial engine? A . Up to, say, 2000 r.p.m. as against 3200 r.p.m. for a lorry engine. Q. How much fuel does the injection pump deliver to each cylinder at 2000 r.p.m., and at say, idling speed of 300 r.p.m.? A. A spot of fuel oil half the size of u grain of wheat and idling smaller than the head of a small pin; and the pump must deliver precisely the same amount to each cylinder, hence the need for extreme accuracy of manufacture and extreme care in keeping filters clean to protect this delicate mechanism. Q. Why does the diesel use less fuel than the petrol engine for a given quantity of work. A. The petrol engine delivers only 23 or 24 per cent, of the theoretical heat value of the fuel wasting in internal work (driving valves, generator, distributor, camshaft,- oil pump, etc.) 77 or 76 per cent., whereas the diesel delivers 33 per cent., wasting 67 per cent, only, in internal work, friction cooling water, radiation and exhaust heat. Q. .Why does the diesel pull better at low speeds, particularly, or when nearly stalled? A.. When slowed, the governor on the diesel immediately and positively causes the injection pump to deliver more fuel over a longer period —lienee the punch; whereas the petrol engine, although the governor opens the throttle; can only deliver more power as the speed increases and the petrol in the jet and passages is accelerated, which takes an appreciable time. Q. It has been said that diesels will run on any kind of oil, even waste oil from other machinery. Is this advisable, if true? A. It is a fact, but it is definitely not advisable, as the small high speed diesel of your tfaetor .or stationary engine is extremely critical as to the quality of its fuel and waste oil may contain acid or sludge which will ruin your injection pump and injectors if nothing else. As has been repeatedly stressed, extreme cleanliness of fuel is necessary to safeguard the fuel pump, etc., which arc made to limits as fine as .1-10,000 of an inch clearances.