Motor Sport Review: The 4 1/2-litre supercharged 'Blower' Bentley

The 4 1/2-litre supercharged Bentley: A race-bred car of outstanding performance

WHEN Bentley first introduced the supercharged edition of its famous 4 1/2 litre model, a number of prospective owners of this type of car held back from purchase until they had seen how the car performed in the chief racing events of the season. In view of the reputation of the firm, and the way it has been gained, it would hardly seem likely that a model would become available to the public which would not give complete satisfaction, and now that the racing season is over, the most cautious buyer must have complete confidence in this model. The few minor troubles encountered early in the year, due to the amazing speed of which Birkin’s Bentley team were capable, were soon overcome by a firm quick to apply the lessons of racing to their production cars.

The ‘4 1/2’s’ had a season which grew progressively more successful, until it culminated in the remarkable performance of Messrs Hall and Benjafield in the 500 Miles Race, in which they averaged over 112mph for the full distance, a higher speed than has ever been achieved in a long-distance race on any track in the world. From a car bred in such an atmosphere of speed one expects an abnormal performance, and one is not disappointed. The production model is a genuine hundred-mile-an-hour car, and as such it takes its place without question among the elite of the world’s sporting cars. It is, however, more in the manner in which it accomplishes things, rather than in the bald figures themselves, that the true character of the car becomes apparent. It is possible to get excellent performance figures with quite a small engine, but it needs a power unit of more generous dimensions to give the refined and effortless performance which is the great characteristic of this Bentley. It is now well known that supercharging confers many benefits apart from the actual increase in speed and power. The greatly improved distribution gives qualities of smoothness not hitherto associated with a fast car, and it is a fact that the supercharged edition is more docile at really low engine speeds than the standard 4 1/2litre model. On top gear the car can be driven perfectly smoothly at less than 10mph, which is truly remarkable when it is remembered that this ratio is 3.5 to I. The supercharging has also made possible remarkable acceleration, and when a stretch of open road appears, and the gears are used as they should be, the car momentarily doffs its sheep’s clothing and reveals its ancestry of well-tried racers.

The delights of a close ratio gearbox can only be enjoyed to the full when the change is naturally easy, and in this respect it leaves nothing to be desired, and is a marked improvement over the older 41/2 litres. Using the gears, 90mph can be reached from a crawl in just over half a minute, while 60 and 75 m.p.h. can be comfortably attained on second and third respectively. The actual car we tested was nearly new and somewhat stiff, so it was not advisable to force the revs too high.

The maximum speed on the level was 95mph, while over 100mph was attained under slightly more favourable conditions. When fully run in there is no doubt that 100mph would be well within its range without any assistance from the force of gravity.

The steadiness at all speeds is what one would expect from a car from this factory, while modifications to the front springs have increased the comfort at low speeds over indifferent surfaces. The steering is, for a car weighing approximately 2 tons, very light, and it is the sensitive lightness of the thoroughbred and not the lifeless lightness of the stodgy town carriage. It has just the right amount of self-centering, and makes driving very pleasant under all conditions. The brakes, which include semi-servo shoes in the front wheels, are smooth, light to operate, and extremely powerful. They will bring the car to rest in just over 50 feet from 40 mph, and their great power inspires confidence and makes high average speeds safe and comfortable.

In common with all the most successful engineering productions, the chassis is simple and free from any freakish innovations, the engine being a straightforward four-cylinder of very robust design and construction, having overhead valves operated by an overhead camshaft.

The Villiers supercharger is bolted to the front of the crankcase and is driven from the crankshaft. Oil is supplied by a separate pump to the gears of the blower, while a scavenging pump collects any surplus and returns it to the crankcase. Two Autopulse pumps supply fuel to the two S.U. carburettors from which the blower draws its mixture.

The four-seater body by Van den Plas is in keeping with the rest of the car, while detail improvements include slightly greater breadth, and improved comfort in the rear seats. Pneumatic upholstery ensures the luxury one expects in a car of this class, where every detail receives a consideration which is impossible in a low-priced vehicle, however excellent the value for money offered. In spite of the very critical attitude in which one examines the qualities of a vehicle in the £1,000 category, about the most serious fault we could find was the rather small clearance between the outside brake lever and the body, a matter easily remedied at a word to the makers.

In short, the 4 1/2-litre supercharged Bentley is a car for the connoisseur of sporting cars, and moreover, proof that this country can still make a car which can compete withm confidence and success with the best the world produces.