Although Austin Rover seem to be swimming against the tide by insisting on using a normally aspirated engine in its Metro 6R4 rally car, its Longbridge-based competitions department is convinced that the quick response and wide, flat torque curve of its new three-litre V6 engine makes up for any lack of horsepower. And the deficit is a large one. The current Audi Quattro Sport has at least 500 bhp from its turbocharged 2.1-litre engine, but as if to underline ARG’s point, the Peugeot 205 T16 has 360 bhp from its 1.7-litre turbo unit, and this is the car which has been the pacesetter in this year’s World Championship. By comparison, the new 24-valve fuelinjected Austin Rover V6 produces a maximum 410 bhp in its evolution form, whilst the clubman’s engine (that’s to say the one which will be installed in the 200 6R4s required for homologation into Group B) has 160 less horsepower due mainly to its use of a single butterfly injection system as opposed to the six venturi and separate butterflies of the “factory” engine.
The announcement of the new 2,991 cc oversquare (92 mm X 75 mm) aluminium four-camshaft V6 ARG engine marked the turning point in the Metro 6R4’s troubled development programme, its significance proved by Tony Pond scoring a debut victory on the Scottish National Championship Argyle Stages in May with a 6R4 which had been shipped to the event straight from its press announcement. Victory hadn’t been so easy with the first 6R4 which used an interim V6 of dubious parentage, the push-rod engine nothing more than a racing Rover V8 with two cylinders removed. It took a year, and seven rallies, none of them above national status, for the 6R4 to achieve its first win, a rather belated one which even ARG Motorsport’s Director John Davenport felt came “seven rallies too late”.
When the ambitious 6R4 project was’ announced in February, 1984, former codriver Davenport, the driving force behind Austin Rover’s comeback into World Championship rallying, was at pains to point out that the original V6 was simply a means of providing motivation for a new chassis with unique four-wheel-drive system, and gaining valuable development mileage whilst the pure engine was developed.
Development of the V64V engine has been the responsibility of former Ford Competitions Department employee David Wood, who was one of the most accomplished Escort Twin Cam/BDA engine builders in the early Seventies, and who has been with Austin Rover for the past nine years. He submitted the first drawings for the new engine 14 months ago, and the 90 degree V6 (the angle between the cylinder banks is the only detail in common with the interim unit, apart from the number of cylinders) first ran in February last year.
With its Lucas Micos engine management system, the torque curve of the 380/410 bhp evolution engine peaks at 6,500 rpm when it produces a healthy 270 lb/ft, but even more impressive is the fact that at 3,500 rpm and 9,000 rpm it gives 230 lb/ft. The less powerful club engine has 200 lb/ft at 2,000 rpm, and a MaXIMUM 230 lb/ft at 5,000, Wood adding that at a fraction over tick-over it delivers 170 lb/ft.
During its development period, the 6R4 sprouted aerodynamic aids to optimise its agility through corners, the original stubby shape having been modified quite considerably as a result of many hours in the MIRA wind-tunnel. The 6R4 is now a very ugly car, but the addition of an adjustable front aerofoil and roof-mounted rear wing has had a very noticeable effect on the Metro’s handling. Although the aerodynamics of the 6R4 were the responsibility of German engineer Bernie Marcus, the chassis / suspension and transmission of the car is the domain of Wynne Mitchell, a talented Welshman who joined the team in the middle of last year from Audi Sport UK. It was Mitchell oh was responsible for adding an additiona four inches to the car’s wheelbase in order tt overcome straight-line stability problems a well as a “nervousness” in corners. Boil front and rear tracks have also been widened and the 6R4 now runs on 16 inch wheel: instead of 13 inch, a decision which wasn’. of ARG Motorsport’s choosing, but out which tyre supplier Michelin fel appropriate if the team was to benefit Our its experiences gained from Audi anc Peugeot in rallying.
It is intended the production of the Mem 6R4 will begin at Cowley in July — th company first has to overcome the problen of getting the car type-approved — and to( cars will be entered on November’ Lombard RAC for Tony Pond and Belgiat Marc Doer. In 1986 it is planned that ARC Motorsport will enter all the Europeat rounds of the World Championship, agait with Pond and Duez. Sales of the costume cars should begin in August, and the price o a clubman’s specification Metro 604 i anticipated to be around 05,000 whirl makes it an excellent proposition tOr th, aspiring driver anxious to gain experience o a competitive, four-wheel-drive Group I rally car at a sensible price. — M.R.G.