MOTORING / A diesel with Gallic charisma: John Fordham reports on Citroen's ZX Turbo, as good as they come in its class

LAST year, Citroen put aside traditional idiosyncrasies - such as gas suspension that surged like a departing hovercraft and concept-car cockpit exotica - to get down and mix it in the Ford Escort market. Without losing its individuality or regular fans, the company pulled off a spectacular coup with the glamorous, four-model ZX range, and increased its market share in the UK by over 20 per cent.

The car's virtues were outstanding refinement and driver-friendliness. The excellent free-revving engines were hushed by voluminous sound-deadening, the gear-change was slick, seating good and the ride and handling startling for the class, niftily assisted by sophisticated rear suspension that allowed a discreet form of rear-wheel steering. Boot space was good, instruments well laid out, and the sound system was Citroen's own shape, so it wouldn't fit anything else.

Then came the ZX diesel at the turn of the year. This deft, quiet, oil-burning machine immediately began snapping up the prizes as the most classy diesel in the small-car range, with that fine chassis able to get the most out of a lively engine, and remarkably low noise levels. After six months in the market, it was third in the UK diesel sales charts, behind the Peugeot 405 and 205, and comfortably ahead of Vauxhall, Ford and Rover competition. This came against a background of burgeoning diesel sales, up to 11 per cent of the overall market by April 1992 against barely 1 per cent 10 years ago.

Its charismatic successor is the ZX Turbo Diesel, an even more remarkable example of the genre that not only improves performance so sharply that its 0-60mph sprint potential is possible in little under 11 seconds, but achieves really impressive mid-range hauling power. All this for fuel consumption figures that manage to be better at steady cruising speeds than the regular ZX diesel. Along with the Fiat Tipo, it is now the most powerful and tractable small diesel in the business.

The heart of the Turbo D is a 1.9 litre version of Citroen's successful XUD engine, of which four million have now been built, way ahead of any comparable engine. Citroen engineers built their prototype cylinder blocks for the Turbo Diesel with see-through sections, so that they could observe the behaviour of the combustion process and the cooling system, and modifications to the latter have resulted in further refinements in the engine's efficiency. Bolted to the top of this engine is a big intercooler, which looks like a central-heating radiator nicked from someone's loo and gulps in cold air in such quantities as to keep this engine unflustered in the most extreme conditions and improve on the longevity already legendary with diesels.

The car comes in Avantage and Aura trim, which means the furnishings and general specification are slightly more modest than petrol ZX buyers can have with the Vulcane. But it's still the same bright, roomy interior, boldly curvy fascia and door-trim designs, good ergonomics and relaxed driving position, helped by excellent visibility. In Aura form there are four electric windows, electric sunroof and mirrors, power steering, central locking, and Citroen's sensible, odd-sized radio cassette. Boot space is good for the hatchback class, and there's a split, fold-down rear seat.

A big plus for the regular ZX diesel was its relative silence, and the sound-deadening is just as effective in this car, particularly when it's warmed up. More and more customers are becoming convinced that modern oil-burners are infinitely cleaner than their predecessors (in all but the emission of soot, which the manufacturers will certainly have to contend with, probably via a form of catalytic converter, as the market develops). But that taxi-like rattle remains an objection for many potential buyers. At cold start-up the characteristic diesel sound isn't inaudible even on such a well-built version as this, but it's unobtrusive - and after a few minutes for the engine to warm (glo- plugs that stay alight for longer assist this process and reduce muck) you stop noticing it.

What you notice instead is the Turbo D's remarkably smooth surge. On paper, this is because the power output over the earlier car has risen from 71 brake horsepower to 92. But equally important is the fact that the torque (the energy the machinery can put into just twisting the wheels against loads) is significantly up. What does this feel like? It takes a lot of the arm-waving out of in-town gearchanging for a start, because walking-pace traffic can easily be coped with in second, and the average roundabout you can filter straight into will rarely involve dropping below third. A glance at the figures shows that a very big slice of the available torque is on hand at around 2,000 revs (the only stage at which the car feels slow in its throttle responses is below this rev range), which explains the flexibility. But a by- product of it is to reduce the intrusiveness of diesel-motor noise still further, because you rarely need to rev the engine to anything like its outer limits. The only significant sound you do hear from the engine is the one that's a distinct pleasure to most car fans, and indistinguishable from the general hum to everybody else - the whistling of the turbocharger, or 'blower', which becomes distinctly animated as the car gets its act together.

Although this is fundamentally the same car as the accomplished petrol ZX, the superb ride of that car has had to be slightly compromised on this one, since the diesel is a couple of hundred pounds heavier, thanks to its iron crankcase and all the paraphernalia of the turbocharger and its intercooling system. It does make the ride a little less cushioned than the Vulcane tested on this page last year, and steering responses feel fractionally more dull and remote. But the set-up still makes the car feel delightfully taut and predictable, particularly since the performance in this version encourages the kind of purposeful driving on weaving country roads that demands stability, balance and minimal roll. Its most impressive and safety-enhancing accelerating performance is also in the 50-70mph overtaking range, in which it outstrips all the competition.

The Aura has some additional refinements, including lumbar seat adjustment, head-rests adjustable for height and angle, rear passenger door bins and alloy wheels. It sells at pounds 12,138; its top speed is 110mph, its urban fuel mileage is 39mpg with over 65mpg at a constant 56mph, 0-60mph comes up in a little under 11 seconds, with 50-70mph achievable in 10.5. Anti-lock braking is available as an option.-

(Photograph omitted)