Some Notes on Carburation and other Fuel System Problems

Abstract

While both vertical down-draught and horizontal side-draught types of carburettor are produced in Great Britain, the majority of instruments manufactured are of the down-draught variety. There is a distinct trend in body style towards low bonnet-lines, and this has created a demand for shorter down-draught carburettors.

A considerable portion of the paper deals with carburettor icing. This has become a most troublesome factor in fuel system performance throughout recent years, during conditions of critical atmospheric temperature and humidity. Various palliatives are possible. At the other end of the temperature scale come vaporizing troubles, causing hot starting difficulties in summer; conditions which assist the one are usually detrimental to the other.

The need for every possible fuel economy has resulted in automatic economy systems being incorporated in most carburettors. By exploring the mixture range with loops the maximum economy of any particular engine can be determined. Too much attention is often given to some minor discrepancy in fuel flow between one carburettor and another, and not enough to the discrepancy between the fuel flow induced between one engine and another.

Automatic chokes provide a controversial subject for discussion and their advantages and disadvantages are evaluated. The author has had a very wide experience with this form of starting.

Petrol injection was once believed to be the panacea for all fuel system problems. Enough development has been carried out to indicate that while there are certain advantages to be obtained with some forms of petrol injection, it is likely to be too costly for employment on the medium and low priced mass production vehicle.