ONE OF THE FASTEST
Cecil [Clutton reports on the Road-performance of Robert Arbuthnot’s 2.9-litre Supercharged Alfa-Romeo
Is not often these days that one has the opportunity of testing anything
so exciting as a blown Alfa, so that when Robert Arbuthnot invited me to accompany him on a short business run in his ” 2.9 ” all other considerations and arrangements were hurriedly swept aside. High Speed Motors can always be relied upon to repay a visit by the sight of several interesting sports cars, but the Alfa has been Arbuthnot’s personal car for the past three years, and I had often inspected it with the greatest interest when calling on him to pass the time of day in the usual manner.
Particularly in the just pre-war period, Alfa’s had been turning Out some pretty shoddy work, but the ” 2.9 ” was evidently a model in which they had taken a genuine pride, worthy of their great tradition. The finish of the engine, in particular, is excellent, and it is only details such as instruments and filler caps that leave something to be desired.
This particular car is . a 1937 model, known as the “290013 Type 8c,” which was announced towards the end of 1936. The engine elosely resembles the ” monopost° ” roc ing type, being the well-known straight eight, with double o.it.e. driven from the centre of the engine—the only rational place, as reducing to a minimum the inevitable timing distortions which are brought about by torsional whip in the crankshaft and camshafts. On the offside of the engine lie the dynamo and waterpump, rather inaccessible behind the exhaust manifolds and steering equipment. The water drain tap, however, IS both accessible and readily manipulated—an important point. On the near side of the engine is the neat and imposing double Roots blower and double Weber carburetter, feeding to two separate four-cylinder manifolds. The plugs are, of course, between the camshafts, and the magneto is a Scintilla ” Vertex.”
, The cylinders measure 68 x 100 mm., giving a capacity a 2,905 c.c.., and one wonders why this engine was not brought nearer the 3-litre mark for purposes of class competition, by making the bore 69 mm. This would have prodaeed roughly a farther 6 b.h.p.
The engine is flexibly mounted, and one wonders, too, if this is wise, with so long an engine in a model intended almost exclusively for open coachwork. The chassis-stiffening effect of a rigidlymounted straight eight engine is a very Important factor in road -holding. The wheelbase is 9′ and the track 4′ 41.”. The forward suspension appears to be some form of Dubonnet and the rear independent, by transverse leaf spring. with the gearbox and differential housing bolted to the chassis. The brakes are hydraulic and the steering operation is of the usual Alfa worm and sector pattern. Shock absorbing is effected hydraulically, with assistance by friction.
The chassis price new in this country was £2,035.
Alfa-Romeo claims as to speeds and horse-power have always erred on the side of conservatism. In this case, the figures mentioned are a maximum speed of 115 m.p.h. and 180 b.h.p. at 5,000 r.p.m.
If ever there was need for justification for the supercharging of touring ears it is amply provided by the performance of this Alfa on ” Pool.” The argument put forward by the adherents of atmospheric induction through multi-carburetters is that, while a blower will admittedly give the highest output on doped fuels, it absorbs more power than it produces on normal pump fuels. Where it is possible to have one carburetter per cylinder and a really well-designed induction passage there is a good deal to be said for this, even for racing purposes, as has been shown by the phenomenal efficiency of single-cylinder racing motor-cycles and by Freddie Dixon’s Rileys, etc.
On a multi-cylinder car engine, however, the difficulty of keeping a number of carlturetters synchronised is considerable, while to obtain effective operation at high engine speed it is necessary to employ Such a high compression-ratio that running at low speeds is harsh, much subject to ” pinking ” and hard on the bearings. Most normally-aspirated sports cars now give off some 40 b.h.p. per litre on compression-ratios of about 7.0 to 1, and one or two exceptional machines, such as the Type 57S Bugatti, produce as much as 50 b.h.p. per litre without resorting to extravagant valve timing. ‘This is achieved at a piston speed of about 3,500 f.p.m. and some 5,000 r.p.m. To do this, however, a compression-ratio of between 9 and 10 to 1 is necessary, and even with the best of combustion chambers this means running on a 50 per cent. benzol mixture, with lavish use Of the
spark control. Difficult starting is another trouble which is also apt to be in evidence.
But this Alfa produces no less than 61 b.h.p. per litre on normal pump fuel, which represents an m.e.p. of 160 lb./ sq. in. at 5,000 r.p.m. It would certainly be forgivable if such an engine were to be quite inoperative on “Pool,” yet not only is it drivable, but it is quite impossible to make the engine “pink,” at any speed, on a full throttle opening.
Starting from cold is practically instantaneous with the assistance of Kigass, Champion R.16 plugs are suitable for all purposes, and the car will dawdle along smoothly in top gear at 1,000 r.p.m. and accelerate away hard on the same ratio with quite brutal use of the accelerator pedal.
I find this performance a convincing justification for touring car supercharging, and it would be interesting to read in equal detail the arguments of some prominent adherent of multi-carburetter atmospheric induction. The day appointed for the run, and the only one possible, turned out foggy, so that great was my disappointment when it seemed that anything beyond 50 m.p.h. would be out of the question. However, once out on the Barnet By pass, Arbuthnot handed over to me to make what I could of it. A short run round country lanes revealed that the suspension is by no means sloppy, although, curiously enough, the front of the car seems to be subject to a surprising amount of up-anddown movement. The extent of the test did not enable me to form any proper judgment of the suspension, though Arbuthnot assures me that it is very effective. Soon we were back on the By-pass and the fog showed signs of lifting, but, even so, a little over 100 m.p.h. was the highest speed of which visibility
permitted. At this speed, however, the acceleration available is still vivid, more reminiscent of the sort that most sports cars can only produce at about half the speed, and it is evident that the maker’s claim of 115 m.p.h. is conservative. Probably it represents the advertised maximum of 5,000 r.p.m., which would thus be equivAent to 23 m.p.h. per 1,000 r.p.m. ; but, in point of fact, Arbuthnot has attained 5,700 r.p.m. in top, which would thus equal 180 m.p.h. Unfortunately, the speedometer, which is calibrated in kilometres, is completely lunatic and palpably bears no relationship to the truth.
The acceleration through the gears is electrifying and suggested that, on reasonable petrol, it would be somewhere in the class of Forrest Lycett’s Bentley. Indeed, it is on a similar model that Hunter bases his claim to ownership of “the fastest sports car.” No acceleration times taken on ” Pool ” could, of course, give a genuine indication of maximum performance, but in any case the fog made tests of this kind out of the question.
The maximum on third gear must be around 100 m.p.h., and all the ratios are reasonably, though not unusually, close. With such superb flexibility there is no need for ultra close ratios. The all-day cruising speed of the car would appear to be in the neighbourhood of 90 m.p.h. The engine is remarkably smooth and silent, but during acceleration there is a pronounced vibration period at 3,500
r.p.m., and it is above this speed that the performance really becomes so astonishing. At 100 m.p.h. there is little to be heard except the whine of the various gear drives and conversation can be conducted in quite a normal voice. At the same time, the noise from the supercharger and camshaft drives would have to be considerably reduced before they would be acceptable in a closed car.
The gearbox, which is of the plain crash variety, is not unduly silent, and the change needs considerable judgment to effect in complete silence, owing to the remarkable suddenness with which engine speed rises and falls in neutral. The multiplate clutch is of the all-metal variety, with alternate plates of aluminium. It is light in operation and delightfully positive, but for getting away from rest it would be hard to find anything more difficult. The only means of moving off is to set the engine at a 1,000-r.p.m. tickover, drop in the clutch, and then accelerate. At the same time, owing to the fairly high bottom gear, one cannot absolutely rely on the continued operation of the engine under this use, and I do not think it would be practicable to get away on any sort of gradient. Any attempt to let the clutch in at higher engine speed merely gives rise to fierce chattering and kicking, without perceptible forward movement. This is a Bad Thing, and reminds one that it is in the transmission department that Alfas have been somewhat noted for trouble in recent years ; their engines have always been reliable.
It is a pity that they should have sacrificed so much in the direction of lightness to gain so little.
If my spell of driving did not enable me to test the suspension system effectively, it at least displayed the remarkable efficacy of rear independent suspension in a car of this kind as an antidote to wheel spin. The roads were distinctly greasy, yet one could accelerate hard out of a roundabout with barely a trace of spin. Yet, if one did, by sheer violence, succeed in setting up a power spin, the car showed no tendency to get out of control and was instantaneously returnable to the correct line of travel.
The same result Ls, of course, achieved with a de Dion type axle, and most recent experience indicates that it is probably the most generally satisfactory solution to the problem of rear drive and suspension.
The steering is light and high geared and gives every confidence at high speed. The wheel must, however, be held lightly and the car must be left to do most of its steering for itself, so to speak. Attempts to bully the steering wheel would not be crowned with much success. The brakes, too, are light in operation and powerfully reassuring in action. The driving position is of the pronouncedly upright type favoured by Bugatti and Alfa, and there is no doubt that it is at once restful and facilitates the highest possible measure of control on the part of the driver. Continued on opposite page As we once more approached London, the fog thickened again and soon we were threading our way back to Lancaster Mews at an unprotesting 1,000 r.p.m. in top. Opinion is always sharply divided about any motor-car of high performance and pronounced character, but whatever one’s views about Alfas in general, here was a car which could not fail to increase one’s respect for this famous marque, and
which can certainly lay a strong claim to being the world’s fastest production sports car. [The illustrations do not profess to show the actual car tested.—Ed.j