THE DIESEL car sector is one of the very few areas of the British car market showing sustained growth and, inevitably, this is resulting in considerably more interest from a whole range of manufacturers keen to cash in on the mini-boom.

Last year just four manufacturers accounted for over 77 per cent of the British diesel market, with Peugeot way out in front at 31.2 per cent, and then Ford with 14.3 per cent, Citroen with 14.2 per cent and Rover with 14.0 per cent. But these four are now coming under increasing pressure from a host of new competitors being launched in recent months.

At the lower end of the market the Seat Ibiza 1.7D lays claim to be the cheapest diesel available in the UK at pounds 6,778, but it is fairly crude by comparison with some other more modern small car designs which are also offered with diesel engines. In particular, the recently improved Citroen AX range, the impressive Renault Clio, the Peugeot 205 and the new Rover Metro diesel all offer considerably higher levels of refinement and performance levels that are by no means put to shame by their petrol-engined equivalents.

Newest of these small cars to the market is the Rover Metro which was launched in May this year. With 61.4mpg on the urban cycle, 73.9mpg at 56mph and 49.9mpg at 75mph, economy can be taken for granted, but the Metro also scores on refinement and comfort levels. It uses the PSA Group (Peugeot/Citroen) 1.4-litre engine, the same unit that is found in the Citroen AX and Peugeot 205, and round-town performance is acceptable with a 0-60mph acceleration time of 16.8 seconds and a top speed of 90mph.

Rover's choice of the PSA engine for the Metro was a good one. Quite simply, Peugeot and Citroen are way ahead of the game in terms of diesel engine design, and their dominance of the market in Europe provides them with then luxury of being able to maintain a policy of continual improvement. The very latest product - the Citroen ZX Turbo Diesel - is so quiet in operation that it could easily be mistaken for a petrol-engined car, yet its performance is actual better than many petrol-engined rivals. The normally aspirated ZX Diesel was only launched in November of last year and yet it managed a top three place in the diesel sales chart in only its sixth month on sale. But far from sitting on its laurels, Citroen then launched a turbocharged version in late June with unparalleled 115mph performance, outstanding mid-range flexibility due to its high torque, and fuel consumption figures that are actually better than those of the normally aspirated ZX Diesel.

No wonder then that Citroen's UK managing director Pierre Boisjoly can boast that 'with the ZX Turbo Diesel, the best diesel car on sale has got even better. Its combination of performance, quality engineering, specification and economy will win customers away from competitive models and attract buyers who are considering diesel for the first time.' Prices of the ZX Turbo Diesel range from pounds 11,370 to pounds 11,970.

The ZX faces plenty of competition in the medium diesel hatchback market, from the likes of the Ford Escort diesel, the Fiat Tipo 1.9TD SX which offers a top speed of 109mph together with 56mpg fuel economy at a constant 56mph, the Renault 19 diesel, and the Rover 218 SD. In the larger car sector, there is also the Ford Sierra diesel, the Rover Montego diesel, the Peugeot 405 D, the Renault 21 GTD and the best-selling Citroen BX diesels to consider.

Another new entrant to the market at around the same price level is the Seat Toledo 1.9-litre Turbo Diesel, which is claimed by its makers to be the cleanest diesel saloon on sale in the UK thanks to its standard catalytic converter. Although diesel engines naturally produce lower levels of noxious emissions than petrol engines, the catalytic converter further reduces carbon monoxide by 90 per cent, unburnt hydrocarbons by 65 per cent and soot particles by 50 per cent. And although diesel engines cannot be fitted with a three-way 'cat', nitrogen oxides are still minimised in the Toledo Diesel by maximising combustion efficiency through an exhaust gas recirculation system that at idle and low engine speeds returns a small proportion of the exhaust gases to the engine. This cools the combustion chamber by reducing oxygen levels, which in turn reduces NOx levels and also improves low speed fuel consumption.

The technology of the Seat's engine comes from the parent company Volkswagen, which pioneered work on cleaning up the diesel. In January 1990 VW launched in Britain its Umwelt Diesel engine in the Golf and the Jetta which was then claimed to be the cleanest engine available in any diesel or petrol-engined car. Set against the tough American US 1983 emission standards the VW Umwelt Golf produces 0.11 gramme of particulates per mile, undercutting the legal limit of 0.20 by a factor of almost two. Carbon monoxide, barely measurable at 0.08 gramme per mile, undercuts the limit of 3.40 by a factor of more than 40, and hydrocarbons, at 0.06, are one seventh the limit of 0.41. NOx emissions are 0.8 against the limit of 1.00 gramme per mile.

VW's commitment to the diesel engine is further demonstrated by the recent May launch of the new Passat L Turbo Diesel which is offered at the same price as the 90bhp petrol-engined equivalents. Powered by the 1.6-litre 80bhp turbo diesel engine fitted to the current Passat CL and GL Turbo Diesels, the Passat L Turbo Diesel has the same specification as well as the same price ( pounds 11,744 for the saloon and pounds 12,388 for the estate) as the Passat L petrol-engined versions.

'This highly competitive pricing means that the Volkswagen Passat comes within reach of many diesel buyers for the first time,' said VW's product marketing manager, Nigel Brotherton.

Another company reaching out to new diesel buyers is Vauxhall, whose UK diesel sales are 124 per cent up on the first six months of last year. Indeed, the company sold more diesels in the first six months of 1992 than it did in the whole of 1991. The growth comes from a dramatically expanded model range which includes new turbo-diesel versions of the Astra and Cavalier plus additional Nova and Carlton variants. Vauxhall now offers diesel buyers no fewer than 36 versions, including 10 body styles, 11 trim levels and six engines ranging from the 1.5D in the Nova to the new 2.3TD fitted to the Carlton and Frontera.

Much of Vauxhall's diesel success comes from the fleet market which it dominates along with Ford and Rover. Ford also offers diesel-engined derivatives of all its models except the Granada, but it seems to be losing ground in this sector as its nnarket share has dropped from 27.5 per cent in 1988 to just 14.3 per cent in the first six months of 1992.

Britain's two newest motor manufacturers - Nissan and Toyota - have also introduced diesel variants at an early stage. Nissan offers both Sunny and Primera diesels, with the Primeras built at its Sunderland factory, while Toyota has just launched an imported diesel version of the latest Carina E - the model that is due to go into production at Toyota's Derby factory later this year.

Despite limited sales volume due to Britain's ludicrous company car benefit-in-kind taxation scales, which discriminate against diesel cars simply because of their larger engine capacity, there is still plenty of competition in the executive car sector of the market.

Peugeot's 605 diesels slug it out with Rover's 825 D models, the Vauxhall Carlton 2.3 CD and the Citroen XM Diesel and Turbo Diesel models. In terms of sheer refinement and performance, once again it is the PSA models which have the edge, with both the 605 SR td at pounds 19,472 and the Citroen XM Turbo SD at pounds 19,423 offering a rare combination of pace, space and quiet refinement. Citroen in addition can offer enormous practicality in the XM Turbo SD Estate, one of the largest estate cars on the market, for not much more - pounds 20,240.

Competing with that model are the Volvo 940 TD Estate at pounds 21,495, the Mercedes-Benz 200 TE Estate at pounds 22,375 and the Audi 100 TDI Estate at pounds 22,623. For those with yet more money to spend, the Mercedes-Benz 300 TD Estate is the costliest diesel on the UK market at pounds 27,865.

----------------------------------------------------------------- UK DIESEL CAR SALES ----------------------------------------------------------------- Year Cars sold % market 1980 5828 0.39 1981 9712 0.65 1982 14530 0.93 1983 24602 1.37 1984 45382 2.54 1985 66181 3.61 1986 77549 4.12 1987 93233 4.56 1988 101138 4.56 1989 123345 5.36 1990 128167 6.38 1991 139810 8.78 ----------------------------------------------------------------- Source: SMMT -----------------------------------------------------------------

(Photographs omitted)

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