Much is being made at the moment of the five-cilinder engine which is to be offered in the new Audi 100. Just in case we all get depressed about German ingenuity and engineering, here's a pick -me -up. Five-cylinder engines were designed, built and succesfully tested in Britain some years ago- by Rover! And they have a published patent to prove it.

In the motor industry, the pundits are often quick to say that "therels nothing new under the sun". However in the case of "straight-fives" for private car use, there is little doubt that all the serious wordk has taken place in recent years.

Rover first sat down and thought seriously about their straight-five in 1964. It was not done for any way-out reasons , but merely to rationlize a need , Peter Wilks and Spen King wanted more power and a bigger engine for the newly-developed Rover 2000 - the P6 - and wanted to do it without altering the structural "base unit: or any of the expensive skin panels. They had already proposed a straight-six - virtually one-and -a-half Rover 2000 engines - but this had been long and heavy, needing a new vehicle nose, and much revised suspension. Fertile design brains, led by Gordon Bashford and Brian Silvester, then proposed a compromise. If a four was too small, and a six too large, why not try a five?

Spen King's advance design team already had a reputation for bright ideas that worked - the T3 turbine car and the Rover 2000 among them - so they were not howled down by management. Instead of saying "It won't work", Peter Wilks authorised prototypes, and sat back to await results.

There was every reason for using the new P6 as a base. For all the right reasons, this could mean common components and the ability to send major castings down transfer lines which were already churning out the P6 2000 engine in thousands.

The proposed five, quite simply, was an amalgram of bits, pieces and dimensions from that P6 engine. It had the same bore and stroke, the same cylinder spacings, and a swept volume of 2,472 c.c. Like the P7 six-cylinder engine that was also being developed, the prototypes were made up in the best blacksmith fashion by cutting off bits of production four cylinder castings, and welding the necessary pieces together again. Rover's Jack Swaine, who led the design team, told me: "We used the front two cylinders from one 2000TC engine and the back three cylinders from another! We did the cutting up - that was easy - but experts like Barimar had to do the re-welding!"

The original 2,472 cc. Rover Five cylinder engine with three SU's

The added legth, compared with a P6, was only four inches, and the extra weight about 100lb. The engine could just be squeezed into the 2000's structure without major changes, and there was no width problem.
All this was in 1964, probably before Mercedes had thought of their five-cylinder diesel unit, and well before Audi had begun work on their new engine. It was very promising, it was theoretically and actually feasible, it was a serious venture, and two engines were actually built. One example, incidentally, survives to this day.

Cancellation was not because the five didn't work, but because the newly-pruchased ex-Buick V8 was so sensationally good. There were well into the fight to smooth out development of their own engine.

Silvester and his assistans Mike Lewis and Eric Branson went so far as to analyse the dynamics of a five, suggest ways of ballancing - internally and externally - and took out a British patent, granted in October 1972, under no. 1 293 135. This ratioonalizes the rather difficult rotating balance situation in such a way that engine mounts positioned at the engine's centre of gravity could control the out-of-balance forces very neatlt. In Brians Silvester's succint phrase to me: "You can arrange for a straight five to be balanced either so that it tends to wobble about, or to nod! We thought it was easy to control the 'nod'- which is pitching of course - and arranged the crankshaft and balance weights accordingly".

It is worth nothing that on a five, only one heavy piston is halted, and its direction reversed, at any instant. With a six, this occurs to two pistons at once, and with a four, to all four pistons at the same time.
Jack Swaine's reminiwcences tell all about development problems: I had my reservations about the five from the start, not because of balancing difficulties, but because I knew it would be difficult to carburate. First of all we made a three carburattor version which looked a bit comical because one of the Su's had a cylinder to itself, while the other fed a pair each.

We didn's reckon on using single carburettor (you must remember that Rover were firmly wedded to constant -depression SUs by then), and I didn't want to have to go for petrol injection if that could be avoided.
"The induction system we then conceived had two SU carburettors, one at each end of a gallery, one pointing forwards and on pointing backwards! It was quite logical to do this, but a bit on the bulky side.
"Even so, because we were using constant-depression instruments, there was an operating problem- the carbs had what was in effect an infinitely long balance pipe. The engine never quite knew which carburettor piston to lift first! We eventually got round that one in two ways - either we vould mechanically link the SU pistons, or have a pneumatic link between them".

Rover engineers admit that in the time they had with these engines they never established an acceptable in-car balance, but they were confident that (like Audi in 1976) this could be done. The problem was mainly one of tuning the rotational and vertical stiffnesses of the engine mounts themselves.

There was no mechanical reason why a five-cylinder engined Rover should not succeed. It never reached production because it was decided that a Rover 2500 would not have been all that much quicker than a 2000 - and because of the new P6 3500 was so much more inviting.
But is you meet an Audi owner who insists that his car is unique, don't believe him. Apart from Mr Gardner's splendid large truck diesel engines, and the diesel five fitted to the £ 8.000,- Mercedes 240 D 3.0 there was Rover's project of the 1960s.
Further, there is no doubt that in this case the British were first.