by David Finlay (20 Jul 02)

This business of driving performance road vehicles on a race circuit can work both ways. On the one hand it can fail hopelessly, as cars which deal well with road conditions suddenly turn into bars of soap when you're trying to go for a good lap time. At the same time, though, it can be a good way of releasing a car's potential in conditions which are far more favourable than you would ever find on the public highway.

Vauxhall clearly took the latter view when it invited the motoring press to Croft race circuit to try out its most powerful Corsa and Astra variants, as well as the VX220 sports car.

A word about Croft: marvellous. More words about Croft: it's an airfield circuit just outside Darlington which was re-established, after a long gap, in the mid 1990s. Since then it has hosted races for Formula 3 and GT cars, and is regularly visited by the British Touring Car Championship. In fact, the BTCC was there a couple of days before I was, an event at which Vauxhall Motorsport works drivers James Thompson and Yvan Muller were dominant in their Astra Coupés.

Croft used to be a very fast, flowing circuit until an infield section was added to create extra length. This new part begins with two fast right-handers, Sunny In and Sunny Out (which are preceded by an even faster right-hander, Barcroft, after which there isn't quite enough time to brake for Sunny In, making this one of the trickiest parts of the course). From then on the infield becomes progressively tighter, ending with a slow hairpin leading on to the pit straight.

The older parts of the circuit include the first corner, Clervaux, which is much faster than you think it's going to be as you approach it, a never-ending right-hander called Hawthorn which leads into a flat-out chicane and then a long straight down to Tower. Unlike Clervaux, Tower is slower than you expect, but you build up enough speed on the next straight to make the Jim Clark Esses a pretty hairy prospect. Then it's back to Barcroft and the alarming prospect of slowing down for Sunny In.

Mixed Conditions

Although we didn't think so at the time, the weather gods did us a favour at Croft. Early rain had made the track very slippery for the morning session, but the surface was bone dry by the afternoon, so it was possible to find out how all the cars behaved in quite different conditions.

I reckon it's always a good idea to start with the slowest car, especially on a wet surface, so I picked the Corsa SRi first, assuming it would feel pretty sluggish. That theory went out of the window as soon as I left the pits - flooring the throttle produced a pleasantly rorty note from the 1.8-litre engine and better acceleration than I was expecting.

The limiting factor became apparent very quickly - huge amounts of front-end body roll causing wheelspin and understeer at the sort of entry speeds that you can get away with on a track day. On the other hand, the effect was at its worst on corners like the long, relatively slow Hawthorn, or that damned hairpin. The Esses were a different matter. You could go through here pretty much flat out, countering the understeer with tiny lifts of the right foot to nudge the back end round and keep the car on the intended line (best to apply this sort of technique sparingly, since you wouldn't want to start spinning at 90mph).

The Corsa's relative lack of power, compared with the other cars present, also meant that it wasn't affected so much by the traction control - in fact, during the wet periods I reckoned the Corsa was able to accelerate harder through Hawthorn than any of the turbocharged cars, simply because in those the electronics kept calling a halt to my attempts to get the power down.

The car most seriously affected by traction control was the Astra SRi, the most softly suspended of the Astras available for test. This was a problem even in the dry, since the amount of body roll (less than on the Corsa but still considerable) kept picking up the inside front wheel. The system would sense impending wheelspin and shut off the engine, leaving the driver feeling helpless.

No Easy Way Out

So the answer is to switch off the traction control, then? Well, on the SRi you can't do that. For road use I never would anyway, since I think traction control is excellent on the road and should be left on at all times. But at Croft it definitely masked the SRi's potential and left it several seconds a lap slower than the car is really capable of.

The Astra Coupé Turbo is a good deal stiffer, so although the traction control came into play quite a lot with this car too, it didn't spoil the fun to anything like the same extent. In the dry the Coupé was quite impressive, though again its ultimate performance was limited by a road-inspired safety feature, in this case the Cornering Brake Control system.

It was most obvious at Clervaux. As mentioned before, Clervaux is very fast, but it's also quite tight, and if you're really going for a good lap time in a race car you tend to slide across the apex. Well, CBC won't have any of that. At the first sign of a slide, it applies the brakes in such a way that the car loses a lot of speed while also regaining full traction at all four corners. Again, it's a very good system on the road, but it doesn't help you get round a track as quickly as possible, since you have to sacrifice a lot of entry speed simply so that you can keep the power on through the corner.

The most impressive Astra on the day was the Triple Eight, an example of the limited edition 100-off run of cars named after, and developed by, the team which runs the BTCC cars for Vauxhall Motorsport and Egg Sport. Compared with most other road cars, it looks like a racer, with its deep bumpers and sills, rear spoiler and huge wheels. Actually it isn't a racer at all, but of all the saloons Vauxhall brought along it was definitely the one you might imagine using for some sort of competition. It's the stiffest of the lot, body movement is very well controlled, the turn-in understeer which all the cars suffered to some extent was least obvious, and the traction control came into play less often. Altogether a splendid experience.

Our driving guide for the day was Mark Ticehurst, a very under-rated competitor himself who drove the LPG-fuelled Vectra Challenge car for Triple Eight a few seasons ago, and who by rights should be running in the BTCC himself. Mark was involved in the development of the Triple Eight road car, and he reported that during testing at the MIRA test track it was two seconds faster than the standard Coupé round a lap which takes just under a minute to complete. That's a very impressive margin.

Maybe Not At Croft

Oddly enough, though, I don't think the Triple Eight is two seconds faster than the Coupé round Croft. It certainly makes up time through the tighter part of the infield section, where the inside front wheel has less of a tendency to leave the track surface, but elsewhere the two cars were much more equal. My best exit speed from Tower was just over 60mph in each case, and both cars came through the Jim Clark Esses at around 100mph. Given a more open circuit like Donington, or Castle Combe before the chicanes were added, or Croft itself without the infield section, I reckon they would be a lot more evenly matched than the looks suggest.

I just about managed to fit inside the VX220 while wearing a crash helmet, so I had the opportunity to try something quite different from the various saloons. The VX220 engine isn't turbocharged, so it's way down on power compared with the SRi, Coupé and Triple Eight, but it's also much lighter and carries its weight much lower down. Nobody was taking lap times on the day (or at least if they were they didn't tell me about it), but I'd guess that it was possible to get the VX220 round Croft at roughly the same rate as the Triple Eight Astra with about half the effort.

The lack of weight is the key. The chassis - basically that of the Lotus Elise - carries the engine at the rear, so there is very little pressing down on the front tyres to cause turn-in understeer. The VX220 therefore enters corners very sharply, and since you can also brake far later than in the saloons the general effect is that you make up a huge amount of time in the first part of each corner. With less power than the turbo cars, exit speeds are about the same, but by then the advantage has already been gained.

I was tempted to cut short my run in the VX220 when it decided not to slow down for one of the infield corners. A trouser-browning moment, as you can imagine, but all became clear when I shifted my right foot slightly and normal braking service was resumed. The problem was that I wasn't wearing racing boots, and my size 11 hoof had caught the throttle pedal. When the same thing happened again two laps later it was definitely time to call it a day. By then, though, I'd become a real fan of the VX220 and vowed that I'd take one out on track again at the next opportunity, as long as I brought the right footwear with me.

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