Motoring: Road Test / Just a little injection does a world of good: Volkswagen's Golf TDI is a diesel to please environmentalists, it ekes out the fuel, but is fast and fun to drive, thanks to a little squirt, says John Simister

I have driven the engine of the future, and it works. All right, that is over-hyping things very slightly: the engine rattles a bit and its sound will not bring tears of joy to a Ferrari fancier. But the car it powers will keep up with a GTi on all but the fastest roads, and use just two-thirds of the fuel in the process.

This car, which can do 112mph, can sprint from a standstill to 60mph in 11.2 seconds, bound up a steepish hill in fifth gear and still return at least 44mpg, is Volkswagen's latest Golf - the TDI. It is a 'green' diesel that will please environmentalists, yet is genuinely fun to drive.

TDI stands for Turbo Direct Injection. The turbo bit you probably know about; it is an exhaust- driven compressor which forces extra air into the engine, so it can mix with more fuel and deliver extra power. Lots of diesel engines are turbocharged. But not many have direct injection, in which the diesel fuel is squirted straight into the top of the cylinders instead of into a pre-chamber joined to the cylinder by a narrow channel.

To the non-expert, direct injection might sound a much more obvious way of getting fuel in than a complicated system of pre- chambers and channels. But no: all other things being equal, a direct-injection engine is noisier, rougher and smokier because the burning of the fuel is more difficult to control. Just look at (or listen to) a diesel Montego or Ford Transit for proof.

These snags mean that, despite a direct-injection motor's better fuel economy, indirectly injected units are much more popular. Introduce some electronics, though, and

the picture changes. Volkswagen's Golf TDI has a 'drive-by-wire' accelerator, whereby your right foot is connected to a computer which ensures that exactly the right amount of diesel oil is delivered to the engine to satisfy its needs. This stops most of the exhaust smoke that normally results from overfuelling under hard acceleration, and a catalyst cleans up the rest.

The Golf's other trick is two- stage fuel injectors, which let the fuel in gradually instead of all in one go. This means there is less of a bang when the fuel ignites, so the engine is smoother. The electronics and the gentle injectors have been found in expensive, upmarket diesel motors before, and indeed the Audi 80 TDI has used a less muscular version of this Golf's engine for the past couple of years. But it is the first time an engine such as this has appeared in a mainstream family hatchback.

You know there is something different as soon as you start the engine. It goes straight away, even from cold, without making you wait for the glow-plugs to warm up. Then, when you drive off, you will hear the turbocharger's siren- like whistling more loudly than in most turbodiesel engines, as the power floods in. The most remarkable part, though, is the crisp, near-instant way the engine responds to the accelerator. Rival diesels from Peugeot and Citroen, the best available until now, more-or-less match the Golf for outright pace. But they feel much softer underfoot, unable to compete with the Golf's solid thrust from low speeds.

Nor can they compete with the Volkswagen's economy. When I drove the Golf and its Peugeot 306 rival over the same roads, I squeezed 44 miles from a gallon of fuel in the new car, compared with just under 37 miles in the Peugeot. If you want a diesel for economy (the main reason for having one), the Golf does the job better than any other car of its size.

There are, however, three drawbacks. First, the engine is noisier than the Peugeot/Citroen unit, although not unpleasantly so. Second, the Golf TDI is expensive: whether in CL or plusher GL trim, it costs pounds 1,200 more than

the slower, thirstier 75bhp Golf turbodiesel (which continues in production) and a good deal more than rival models from other manufacturers. Third, while the Golf has all the usual Volkswagen virtues of quality, solidity and rational design, its steering is soggy and its suspension bouncy and squashy.

Peugeot's 306 and Citroen's ZX manage to smother bumps while responding crisply to the driver's commands, so the Golf's ineptitude here is puzzling. But if you can live with that, and you want to enjoy peppy performance with eco-friendliness, the Golf TDI is your car.

Alternatively, you can have this engine in the Golf estate, the Golf- based Vento saloon or, soon, in the larger Passat.

SPECIFICATIONS

Volkswagen Golf TDI GL, pounds 14,149

Engine: 1896cc, four cylinders, direct injection turbodiesel, 90bhp at 4,000rpm. Five-speed gearbox, front-wheel drive. Top speed 112mph, 0-60mph in 11.2 seconds. Fuel consumption: 44- 50mpg.

COMPARISONS

Citroen ZX Aura Turbo D, pounds 12,065

Virtually matches the Golf for outright pace, though less energetic at low speeds. Economy, however, is merely good. A smooth-riding and well-equipped car which is fun to drive and excellent value. Volcane version is that novel idea, a diesel hot hatchback.

Ford Escort 1.8TD Ghia, pounds 12,495

Again, cheaper than the Golf and as well-equipped, but the turbodiesel-powered Escort is a pointless car. It is noisy, not especially economical and the engine is feeble at low speeds. An old-school diesel.

Peugeot 306 XTDt, pounds 12,580

Same blend of virtues as the ZX, whose smooth, muscular engine it shares, but with better rear seat space, more interesting styling and even more fluid handling. Greater weight blunts performance slightly.

Vauxhall Astra 1.7TD CD, pounds 13,340

Closest rival to the Golf on price (there are cheaper versions), but includes anti-lock brakes and, as with Escort, an airbag. Japanese-built engine is reasonably smooth and willing, but cannot match Golf for energy and economy.

(Photograph omitted)