Motoring: Wow, it didn't do that in the showroom]: Success at Silverstone in the touring car races, which open tomorrow, has a subtle effect on sales, says Roger Bell

SILVERSTONE will be no place for the faint-hearted tomorrow. If the kids insist, half a diazepam might settle the butterflies before the scream of 8,000 horsepower signals the start of not just another motor race, but Car Wars: the Sequel, round one of this year's British Touring Car Championship.

Thrills are guaranteed in BTCC racing, incidents frequent. Britain's foremost championship, contested by garishly coloured bill-board cars, draws crowds that only Formula One can better. Given good weather, 25,000 spectators are expected. Three million viewers will tune into the BBC's highlights.

Touring (or saloon) car racing has two vital ingredients that Formula One lacks: close-quarter combat and spectator empathy. Emotions run high - much is at stake besides pride. It may seem childish for grown men to hurl abuse, sometimes punches, at each other over custody of the same bit of track, but it makes riveting television.

BMW, Ford, Mazda, Nissan, Peugeot, Renault, Toyota, Vauxhall and (by mid-season) Mercedes-Benz will vie for race-track supremacy in the belief that competition success and prime-time exposure convert into sales. The most notable absentee is Rover.

'We can't afford not to be there,' says Mark Carbery of Toyota, whose Carinas were title contenders (and race winners) last year. Tim Jackson of Renault - new to the series - agrees. 'We've decided it's a form of motor racing we cannot ignore any more.'

'Winning is not everything, provided you are competitive,' says Mike Nicholson of Vauxhall, which won the manufacturer's (but not the driver's) title last year with its Cavaliers. 'We cannot quantify the sales benefit. All we know is it stimulates great interest.'

Renault has poured millions into Formula One (a Renault engine powered Nigel Mansell's Williams to the world championship last year) in a bid to raise its profile. Showroom customers find it more difficult to relate to the world of F1 racing, however, as Ford's Nick Palmer concedes: 'It is hard for the man in the street to make a rational connection between F1 and his own car.' Renault's director of communications, Phil Horton, says: 'If a Renault 19 is seen to do well in competition, it raises expectations in showrooms. It's a more direct link than F1.'

Most teams are coy about their budgets, but Mr Llewellyn dropped a hint: 'You wouldn't see much change from pounds 1m.'

One big spender is Ford, whose two Mondeos have been prepared by Andy Rouse, winner of 60 touring car races. Like their rivals, his Mondeos will not be quite what they seem. They may look like their showroom siblings, but beneath the steel skin, which cannot be altered, there is little the owner of an ordinary Mondeo would recognise.

BTCC cars are purpose-built, highly tuned racers conforming to a one-class 2.0-litre formula. The rules allow Mr Rouse to use any Ford engine (an American V6 from the Probe coupe will power his BTCC racer) and rear-wheel drive (even though the Mondeo normally has front-wheel drive).

Engines are limited to 8,500rpm and develop up to 300bhp - more than twice as much as a normal 2.0-litre engine. Six-speed racing gearboxes, mighty brakes and treadless 'slick' tyres are de rigueur. Bodyshells, bereft of trim, are tube-cage-braced to protect the driver. Although safety is paramount, BTCC cars are denied anti-skid brakes - used to good advantage by BMW last year but now banned: skidding adds excitement.

Pre-season favourites are a crack team of German BMWs, masquerading as 318s. In Steve Soper, BMW has a thrusting driver. The promotion of BTCC racing through television advertising could turn Mr Soper and his rivals into household names. 'It is in our interests to spread the word. We want to attract families,' says Mike Nicholson of Vauxhall, which is sharing the cost of the pre-race advertisements on ITV with Ford and Renault.

According to the BBC's Grandstand editor, Dave Gordon, the biggest ad for this year's championship was last year's championship. 'The racing was brilliant.'

(Photograph omitted)