Common Heritage

The Esso British Car Championship is like all other forms of motor sport, continually changing. This year will almost certainly be the last in which the enormously powerful and spectactular, turbocharged Group A cars such as the Ford Sierra Cosworth will be allowed to race in unrestricted form.

Cars such as my Labbatt's Sierra RS500 now develop around 560 bhp, giving a top speed of over 170 mph, while running costs for a team can be as high as over a quarter of a million pounds per year. In an attempt to reduce the spiralling increase in both speeds and costs, the RAC introduced the current Class B category for cars with engines of up to 2-litres at the start of the 1990 season. Next year it looks likely that this will become the mainstay of the Touring Car Championship, with the remaining turbocharged Sierra Cosworths being subject to some form of power restriction.

In view of this — and the fact that the British Grand Prix meeting at Silverstone is the most important race on the BTCC calendar — I jumped at the chance to compare one of the new 2-litre challengers with my regular turbo-car in a recent test session at the Northamptonshire track.

The Rouse Sport Sierra Sapphire 2-litre and my own Labbatt's Sierra Cosworth both share a common heritage. They are both based on Ford Sierra bodyshells and both prepared at the Coventry workshops of Andy Rouse, one of the world's leading touring car engineers and no mean driver too, as our battles on the race track continually prove!

In terms of the bodywork, suspension and brakes, both cars comply fairly closely to the International Group A regulations, to which the turbocharged Sierra Cosworth is built. Basically this ensures that you utilise an unmodified bodyshell from a homologated model (in our case the Ford Sierra Cosworth RS500), which is stripped of all wax and sound proofing before the installation of a built-in, computer designed, roll cage. In addition to offering enhanced driver safety, this also makes the bodyshell more rigid under the stresses fed back during cornering by the ultra-stiff competition suspension. Spring rates of over 1000 lbs per inch are not uncommon on Sierra Cosworth racers.

The unmodified wheel arches impose a physical restriction on the size of wheels and tyres which we can utilise. As you can imagine therefore, feeding over 500 bhp through 10-inch wide rear tyres is an acquired art! The turbocharged cars are dramatically overpowered and even in the dry will spin their rear wheels in top gear. This year we are helping to develop radial-ply racing tyres for Dunlop, in preference to the more generally used crossplies and as the season progresses we're reaping more and more benefit from the development programme.

Both cars take advantage of relaxed rules covering brakes, utilising 13" diameter ventilated discs, which have awesome stopping power, but there the similarity between the two cars ends.

Opening the bonnet on the Sierra Cosworth reveals an evolution of the 2-litre, 16 valve, turbocharged Ford Cosworth engine, which with the benefit of a Zytec computer-mapped engine management and fuel injection system, more than doubles its normal power output from around 225 to 560 horsepower at 7500 rpm and feeds it to the track through a Getrag 5-speed box and a viscous coupling, limited slip differential.

The Rouse Sport Sierra 2-litre though, is a very different animal. Opening the bonnet here reveals the familiar cam covers of the Ford Escort engine, but in place of the turbocharger and all its attendant pipework, there are four fuel injection trumpets to feed the normally aspirated engine, developing around 280 bhp at a compulsory 8500 rpm limit. Class B of the Touring Championship basically specifies that any homologated car of over 4.2 metres in length can carry a race-tuned 2-litre engine from another model in the manufacturer's range. In this case, the engine is a normally aspirated conversion of the Sierra Cosworth, but other cars in the class include 2.3-litre BMW M3s, 'sleeved down' to the capacity limit and even a Mitsubishi Starion fitted with a non-turbocharged unit from the Galant VR-4 rally car.

The two cars demand a very different driving style, as I discovered when I climbed out of the Labatt's car into the Sapphire, after a briefing from the car's regular driver Ray Bellm. Formerly a mainstay of the Spice Group C team, Ray has been developing this car in the opening rounds of the BTCC and although the team are the first to admit that there have been some early race teething troubles, the potential for the future looks good.

It really is quite a culture shock to climb from the Cosworth into the 2-litre car. The first surprise is the totally different nature of the power delivery. The huge power output of the turbo car is spread over quite a wide rev range, with the power coming in smoothly from as low as 4500 rpm and then building rapidly as the boost rises. In comparison, no matter what the throttle position, below 7500 rpm it has no effect on the normally aspirated Sapphire's performance! The entire powerband is concentrated in the final 1000 rpm below the 8500 limit, you need to be busy, busy, busy on the closely stacked six-speed gearbox all the time, simply to keep the engine 'on the boil'. At least the gearchange is good, with that distinctive clunk as you go from gear to gear, that is the hallmark of a X-Trac box.

The other thing which is immediately noticeable about the 2-litre car is that it handles much better than the Cosworth. This is partly because it is 10% lighter, but principally because the turbo-car is set up much more stiffly to handle the awesome power output and the braking and acceleration loads are greater.

Although the two-litre car is less powerful, it feels as if it has a more sensitive chassis and this along with sharper throttle response, lends itself to a different cornering technique to the Sierra RS500.

In the Labatt's car for example, the first corner on a flying lap, Copse Corner is reached at around 150mph in top gear and after braking to enter the corner in third, accurate timing is absolutely vital to exit the corner quickly and tidily. You get on the throttle very early in the turbo car, much sooner than in the 2-litre, because there is a noticeable delay as the boost builds up. However, you don't want to be on the power too soon; the consequences of getting your timing wrong with 560 bhp doesn't bear thinking about!

A different technique is necessary too, after taking the flat out, 150mph kink at Maggots and then breaking hard for the second gear right hander at Becketts. You normally aim to hold the turbocharged Sierra Cosworth in the middle of the track so that you can immediately take the right line for the entrance to Chapel Curve. In the two-litre Sapphire, you let the car run out across the full width of the track — allowing the less powerful car to carry as much speed onto the straight as possible. Through Chapel and onto Hangar Straight, where you hit 170mph in the Cosworth on the way into the fourth gear Stowe Corner. The 2-litre Sapphire with its better balanced chassis, is actually quicker through the curve than the Cosworth, but its very exciting indeed in the turbo-car as you attempt to control the wheelspin at over 120mph!

From Club, you take the long, left hand, Abbey Curve up to the Bridge Corner complex. It is just possible to take this flat out in the Labatt's car, but if the chassis is understeering at all, you will simply run out of road, I normally prefer to lift off at the entrance to the corner, in contrast the Sapphire goes through flat-out with ease, but of course it is travelling around 30mph slower.

The final corners, Bridge and Woodcote are the slowest part of the Silverstone circuit — taken at 50-60mph. The biggest problem with both cars is preventing huge power oversteer at the exit and again, the lighter 2-litre car is much later onto the brakes and with its more forgiving chassis, a lot quicker through it.

While I personally enjoy the challenge and spectacle of racing the Sierra Cosworth, I am sure that despite the lower power output the 2-litre car will continue to offer both the sight and sound of exciting Touring Car Racing. Although you are not conscious of it as a driver, the muted tones of the turbo cars are replaced by the more aggressive howl of a normally aspirated four running hard on the rev limiter which also adds to the atmosphere for a spectator.

My only concern about the 2-litre class is that it is a lot more difficult to overtake. The shorter braking areas will lead to drivers attempting higher risk overtaking manoeuvres and I suspect, but hope not, more 'panel bashing' and contact. Certainly this has been seen similar championships in Germany and in one-make saloon car racing. It certainly makes it more exciting for the fans I just hope it doesn't begin to cause headaches for the race organisers and drivers.

Tim Harvey

(With thanks to Team Labatt's, Bristow Motorsport, Andy Rouse Engineering and Ray Bellm).