Road test: BMW M3/Ford Cosworth RS500

Road-race rivals

Adopting Group A rules for rallying as well as racing was meant to close the gap between road and competition machines. That it has done, not by producing slow race and rally cars, but by bringing a new generation of affordable 150 mph road rockets. While last year's Group A hatchbacks were virtually as quick over rally stages as the previous Group B monsters, ordinary customers have been able to buy a car capable of more than doubling the speed limit which cost less on introduction than £17,000.

We have been used to the idea of homologation specials in runs of 200 or 400 from Lancia Stratos to Metro 6R4, but, the FIA reasoned, surely a minimum production of 5000 would preclude out-and-out hot-rods being built?

Five years ago, perhaps, no manufacturer would have dared to propose such a car for sale, but with the apparently insatiable demand of the enthusiast for more and more performance, we now have two near 150mph machines which fall easily within the executive car price bracket. And both are saloons with room for four or five people. Can a car such as this be a useable proposition?

Undoubtedly yes. Both the Ford Sierra Cosworth RS500 and BMW's M3 tested here offer blistering acceleration, outstanding grip, and razor-sharp responses in a packet which will stay cool and untroubled even in traffic queues. And at just under £20,000 for the Ford and £23,550 for the M3 they both offer performance value well above almost anything else.

To a lover of two-seater Italian exotics, it hardly seems right that these two should clothe the impulsion of a Ferrari in a family body, but it shows that the "sportscar" label gets more and more blurred year by year.

Ford's racer has become notorious for getting its owners into trouble, and has supplanted the Capri as the first choice for the light-fingered. Drivers have been caught out by the explosive performance, and more than one has caught fire, always a hazard with turbocharged cars. Yet this has only helped to give it rather a wicked image which does no harm at all to sales of such small-run devises. And having paved the way to the circuits with 5000 204-bhp cars, the next step was to take advantage of the FIA ruling which allows a further 10% of this number to be built with improvements -- the evolution process.

Even 5000 is a tiny number to an international giant like Ford, so the evolution cars, developed by Ford's Special Vehicle department at Dunton, were assembled instead by Coventry based Aston Martin Tickford.

Starting with fully-built Cosworths, Tickford's team removed the spoilers fore and aft, modifying the front air-dam to gulp more cool air where the spotlamps once sat, and then fitting a new boot-top spoiler to complement the extra lip on the tailplane.

The 204-bhp motors were removed and new 224 bhp units from Cosworth replaced them, boasting a larger turbo, revised inlet tracts and a new full-width intercooler which has to be mounted behind the radiator instead of above as before. Extra heat-shielding also appeared, and new location holes allowed for minor changes to the geometry of the rear trailing arms.

All 500 cars were ready for their homologation inspection by the end of July last year, and the Eggenberger team took the new car to a 1-2 victory immediately afterwards at Brno. There is, however, one substantial difference between road car and racer which helps to explain where more than 400 bhp of works horsepower comes from: a secondary injection system is built into the RS500 engine.

Inactive on road cars, the system is called into play in race-prepared cars through a different microchip, and allows the engine to swallow an even bigger fuel/air charge on each intake stroke.

With most of the private team cars converted up to RS500 spec, it has become difficult for anyone else to snatch overall victory from Ford, and indeed the world teams title eventually fell to the Sierras, after some wrangling over legality. But BMW's successes with the M3 have been if anything more consistent and wide-ranging: Roberto Ravaglia is WTCC champion driver, the less prestigious ETC crown fell to an M3, and the car has dominated various national Group A and Group N series.

For BMW, too, there was a sensational dispute over the legality of its cars: at the WTC opener in Monza, M3s finished 1-2-3-4-5-6-8, only to be disqualified when the scrutineers questioned the plastic boot and roof panels. Once that drama was settled, the Munich evolution car had arrived: enlarged from 2302cc to 2332cc, 12:1cr , improved breathing and an extra cooling slot in the front spoiler, pushing the total over 300 bhp.

While Ford was still undecided whether to back its Cosworth or XR4 x 4 Sierra for rallying, its German rival had been developed from the beginning to do both jobs, and proved this with the victory in Corsica of a car privately prepared in Britain by Dave Richards' Prodrive team.

If there is a benefit from the elimination of the specialist Group B rallycars, it must be that cars such as the Sierra Cosworth and the BMW M3 have a chance to shine both on tarmac and on dirt roads — broadening their useful return to the factory which has invested in their development, while still imparting an air of glamour to the more mundane cars in the High Street which they resemble.

That resemblance can be stretched, of course, and while Ford has retained the two-door Sierra shell essentially unaltered under a layer of air-smoothing dressings, BMW has made some radical changes to the 3-series shape.

All-new wing panels incorporate smoothly flared arches which will swallow tyres of up to 10in width (the maximum allowed in this 2500cc class), but even more striking are the changes to the rear window area. To help fill in the low-pressure patch behind the relatively steep window of the standard saloon, the whole glass is lifted from the bottom edge, giving it a flatter rake. A new 11/2in higher plastic bootlid carrying a tall spoiler fairs the new panels into the rest of the tail, and the result is less lift and better stability. Careful use of GRP and impact-absorbing foam means that the bumper/airdam at each end fulfils all the various impact regulations, even those in the USA, and simple flared sills below the doors tidy up the airflow between the wheels, giving the M3 a drag-coefficient of 0.33 despite its extra width.

Powering this taut little saloon is not the six-cylinder one might expect but a slanted 2.3-litre four related to the Formula Two and Formula One engines. This choice was based on the greater strength of a shorter crankshaft, allowing higher sustained engine revs with all the advantages that implies for racing. Valvegear closely follows the pattern of the six-cylinder M1 engine which continues in the other two M-cars, the M635 and M5, the twin cams being driven by a duplex chain, and the spark plug sitting centrally between the four valves.

Although this four-cylinder block has been in production for many years, the M3's 2.3-litres capacity means that it now has the biggest bore possible. As a result the two centre cylinder-liners have to be cast as a pair like those on BMW's big six-cylinder engines, a principle which helps stiffen the whole unit in preparation for racing revs of 4000 and more. A complex sump and an oil cooler ensure that the oil can do its job under racetrack extremes.

BMW's Motronic injection system fuels the engine and is linked on the home market to the compulsory catalytic converter, which knocks 5 bhp off the unrestricted output: down to 195 bhp. Torque shows the sarne small drop, from 177 lb ft in British specification to 170 at home. Yet the clean-breathing version still breaks the 7-second barrier for the 0-60 mph dash, and any loss in top speed is marginal — 143 as opposed to 146 mph. Should an environmentally-concerned UK buyer want to convert his car, the catalyst may be added later with a simple adjustment of the electronics.

A close-ratio five-speed Getrag gearbox with first down to the left leaves the top four gears in a simple H, while the clutch has its lining bonded as well as riveted in place. For maximum grip a 25% limited-slip differential is standard equipment.

To give the M3 its arrow-like stability and instant response the chassis alterations have been extensive. Castor is three times the standard amount, while new stub axles allow larger 5-series bearings to be fitted. The power-assisted steering has a very quick ratio, and not only is the anti-roll bar substantially stiffer, but it now pivots on the outside of the spring strut, giving extra leverage. Wheel movement is controlled by new twin-tube gas-pressurised dampers, tuned to different response curves front and rear. Revised damping plus harder springing are the modifications on the rear axle, which retains the geometry of the semi-trailing arm swept back at 15°. Both the front and rear brake discs are larger and thicker, the fronts being vented, and ABS is a standard fitment. There is plenty of rubber in touch with the road, as the I5in alloy wheels carry 205/55 VR 15 Michelin MXX tyres.

But climb inside the M3 and nearly all these changes are invisible; true, the speedometer now reads to 160 mph, and the top edge of the free standing rear spoiler intrudes slightly into the rear view, but the fascia looks perfectly standard 3-series, and the square-cut sports seats could be those fitted to many other fancy German cars. A steering wheel on the left looks out of place in a car with British plates, but as long as the car stands still it appears to be an ordinary small Munich saloon.

That feeling disappears within a few yards when the M3 sets off. There is a bark as the engine starts, and with the lever slotted down to the left for first, the quick positive clutch and hard responsive feel through the leather rimmed wheel indicate the character of the car even before the lever slips into fifth gear.

Everything feels tight and sharp: the gear ratios are close together, the steering is rapid, and there is an immediate answering surge when you depress the throttle. It does not seem to matter that the revs have nearly reached 5000 before the torque levels off; the engine pulls firmly even from a rather rumbly 2000 rpm, getting stronger and stronger as the 4000 mark is passed on the way to its 6750 power peak, accompanied all the while by an almost Italian raspberry from the exhaust.

Although the smoothness of the six is missing, the harsh edge obvious at low revs quickly fades out; and no matter what the revs a stab of the throttle flicks the sack needle round smartly for very rapid gearchanges.

Only the pronounced angling of the steering wheel spoils the otherwise excellent driving position; the driver sits rather upright in the black leather Recaro seats with all instruments visible and all controls comfortably placed, but the axis of the wheel points strongly towards the centre of the car, stretching the left arm more than the right. Yes, one gets used to it, but it never feels quite right.

Amongst the instrumentation (lit at night by a pink glow) there is an oil-temperature gauge set into the tach but no pressure reading, surprisingly. BMW's neat computer is installed in the centre console, but without the handy column stalk button of the 7-series, and incorporates an ice-warning which saw a lot of action on a trip north. A chime sounds and the readout flashes if the temperature drops to 38°F, and again when it drops to 34; if you get into the car in freezing conditions the alarm sounds when the ignition switch is turned.

Good heat and ventilation control is provided by rotary knobs, the horn buttons are set in the wheel spokes, and the door mirrors are electrically operated, although the windows are not, to save weight on the track. In all other respects, though, the M3 is equipped as a luxury saloon despite its uncompromising competition breeding; not surprising when you remember that, like Ford Cosworth, even if 300 of these cars are sold to private race or rally teams, that leaves 4700 to be sold to the general public.

For the driver the biggest contrast between Cosworth 500 and M3 is in power delivery. A racing car in road trim sounds a doubtful proposition to make available to the man in the showroom, even though the horsepower he gets is considerably less than what the big teams are playing with: 120 bhp down on a top M3, and at least 200 bhp less for the Ford than the Eggenberger Texaco Sierras which took the WTC teams title in 1987.

While turbocharging allows extra horsepower to be added relatively easily, by enlarging the blower and revising the settings in the engine control system, the result in the RS500 shows up all the disadvantages of turbos for road use. Low compression means slow reactions while the little boost needle wavers below atmospheric pressure, but as it flicks to positive boost the urge redoubles and the car bolts forward like a cycle racer breaking away from the pack. It is a Jekyll-into-Hyde switch; sudden but predictable if you keep an ear open to the engine and an eye on boost gauge and such. Where the plain Cosworth had something to offer from 3000 but lost interest before 6000, the RS500 spins to seven thousand but waits until four to set off.

In a straight line it is exhilarating to keep the pedal hard down, listening to the squeal and puff of the blower in each gear while the arm-stretching thrust of second steps down to the calmer but no less exciting fifth-gears-rush into the realm of three-figure speeds — for this is where a turbo extols. At 95 mph the boom needle is quivering with anticipation: a twitch of the right foot and the speed whistles without effort to 120 or more.

But while the upward transition is controllable, the reverse is more likely to catch you out, when the snarling Mr Hyde reverts to mild-mannered Dr Jekyll. Settled in a corner with all four tyres sharing the work and a steady throttle, the Sierra feels completely flat and stable, little clonks coming through the small wheel to make you imagine that this is Donington's Redgate corner; but when the real world intrudes with some mud on the road or a tighter kink than you allowed for, the risks of lifting off are magnified. If that boost gauge drops, a large chunk of horsepower will evaporate in an instant, and when pressing on hard that could spell disaster, promoting a spin so fast that even the Sierra's quick steering might not save you.

With normal aspiration, the penalty for such a mistake is less severe, and the BMW's 2in-shorter wheelbase means it is easy to catch should the rear wheels get out of line. Its top-gear performance, of course, cannot match the Cosworth, but both cars are exceptional anyway; from 70 mph the M3 will hit 90 in just over seven seconds using third and fourth gears, which is impressive enough.

The unit revs willingly past maximum power (6750 rpm) and on beyond the 7000 mark to a maximum of 8000. In fact it is so keen to rev even in top that I repeatedly wanted a sixth gear, although the car is by no means under-geared — at 70 mph the engine is turning at a comfortable 3000 rpm, and the ratios are nicely spaced.

Driving the Ford quickly around country roads demands much more concentration. It is certainly the more extreme, the more racer-like of the two Group A cars: spherical joints instead of rubber in the suspension means the occupants know all about potholes, which reverberate through the interior. Spring rates are very stiff, too, and the trade-off for the ultra-flat cornering and tremendous roadholding is the rattle and shudder over broken surfaces and bumps. This is where the difference between the base cars begins to show; BMW's fine standards of assembly carry through to its race-special, with solidly fitted panels and trim. Basic Sierras are aimed at a lesser market, and even the addition of all the luxuries such as velour Recaro seats and high-quality radio/cassette cannot disguise the tinnier sound of the doors shutting and the odd creaks from the fascia panels.

Yet it is a comfortable place to be, at the wheel of the Ford, cradled by the prominent bolsters of the firm seats. A smaller leather-covered wheel means less of a stretch, for like all the lesser Fords the wheel is not adjustable. Instead there is a crank to alter the height of the seat, though I should have been happier if the tilt angle were controllable separately. A leather gear-knob tops the lever with its notchy action, less crisp than the M3 but fast enough when trying to shift from second to third without losing boost; the boost gauge itself is hidden by the wheelrim.

Other than this the dials are all in plain view, and the 90° quadrant tachometer, for many years standard pattern for racing bikes, is particularly easy to take it in out of the corner of the eye as the next double-bend unravels ahead of the Sierra's blunt nose.

With its outrageous tail spoiler, strongly sculpted side-sills and bulky airdam, there is no fear of overlooking the Cosworth, and of course the choice of the three-door shell which the UK does not otherwise see distinguishes it from all other Sierras. Undoubtedly the spoiler's effect is significant, amplified on the RS500 by the rubber lip and additional XR4 x 4 spoiler below which is the quick way to tell a "normal" Cosworth from the evolution car. Where the unadorned Sierra sways about in side-winds (improved in the latest cars but still unacceptable in the estates), the RS500 runs like a torpedo for the horizon, and the faster it goes the more dogged its aim.

Many a joke has been cracked about Cosworth drivers blissfully unaware of a police car in the shadow of this tailplane, but the serious fact is that nothing at all is visible in the RS500's interior mirror. It may be the best anti-dazzle device ever, but it is frankly unsafe on the packed roads of southern England, and the tiny number of these cars which will be sold is not an excuse.

Away from the worst of the traffic, the RS500 simply leaves behind just about anything else available in power-per-pound terms. It is not surprising that, at less than £17,000, dealers and public alike were quick to absorb the original batch of 5000 cars, though not all of these left the dealers' forecourts in a hurry, and advertisements still appear from time to time offering delivery mileage cars.

Theoretically, all 500 evolution cars, converted from plain Cosworths, have been sold too, though no doubt some will surface again having been stored by optimistic investors. Though it is eclipsed by the Ford in sheer brute performance, it has to be said that BMW has produced the more useable car. On a dry, open piece of road, the Cosworth offers the closest feeling to a rose-jointed racer, tiny movements of the wheel translating into a precise dart left or right while its adhesion squeezes the driver against the seat bolsters. Gently straightening the car and feeding in more boost makes the stomach tense with excitement and concentration — a wonderful sensation.

But venture out on a soggy day, and a different tension grips you. The front wheels skitter from puddle to puddle, and finding it will spin its wheels in third keeps you well away from the outside of the performance envelope. Only the relentless action of the brakes with their four-pot front calipers and ABS seems well suited to these conditions.

Try the same weather in the M3, and confidence returns. You can tell exactly how close to the edge those fat Michelins are treading, the balance is unaffected, and that sparkling engine continues to churn out instantly-controllable torque. With adequate forethought on road-positioning, LHD is not a problem; it demonstrates that the view past a slow lorry is from hanging back rather than being near the centre-line and this is a car which will whistle past in the smallest gaps. Undoubtedly the more rounded of the two in its blend of abilities, the little M3 is a gem.

BMW has been proved right in its belief that it would continue to sell to performance-hungry enthusiasts; an extra 1500 have been built over and above the FIA' s arbitrary figure of 5000 units, justifying its choice of a full-scale assembly line.

Ford, on the other hand, never intended to extend production of the homologated car beyond the minimum, being content that its relative cheapness and scarcity would ensure sufficient buyers, but instead planned a "new" model, a saloon version with more emphasis on comfort. That car, the Sapphire RS Cosworth, will be announced at the beginning of this month and we will report our impressions in the next issue. Its arrival will close the price gap between these two racetrack rivals, and make choosing between them a harder task.

As things are, there is a £4000 difference, so the man who can afford the BMW is possibly not going to see the RS500 as being in the same part of the market. But the Sierra Sapphire is an altogether more refined machine than the previous hatches, and with the right suspension compromise, ever better build quality, and the more responsive 204 bhp engine, a Sapphire Cosworth might tread on BMW's toes. GC