Motoring: Don't let buying power go to your head: A turbocharged bargain might give you a kick, says James Ruppert, but it could also hit you where it hurts, in the wallet

If 'GTi' was the most fashionable bootlid badge of the Eighties, 'turbo' was the most macho. 'Turbo' meant muscle- power, with speed-record performance. On the used market, a turbocharged car promised more fun than any other car. More mechanical upsets, too.

Longevity and reliability were not a turbo's strong points. It was - and still is - possible to make a big, turbo-powered mistake. Turbochargers have, however, been improved in recent years, so provided you shop carefully, a turbo can be a sensible as well as a macho motoring option.

The trouble with turbochargers is that they are at once a beautifully simple and a remarkably crude solution to extracting the maximum power from an engine. Basically, the turbocharger consists of two turbines, one on either end of a shaft. Exhaust gases coming out of the engine sets one turbine spinning; the shaft turns, and the other turbine forces more fuel and air into the engine, boosting its power.

The Achilles' heel is the 'wastegate' control system, which regulates the boost pressure to prevent the engine from destroying itself. A mucky wastegate or dodgy electrics could make it lose control. Then there is the engine itself, which operates at much higher temperatures than normal. Such stresses can lead to premature failure.

But the real trouble with turbos is the drivers who fail to look after them, who skip the shorter service intervals (turbos usually need an oil change every 5,000 miles), who fail to let the turbo cool down after a run, and generally hammer the car at every opportunity. As a result, costly turbocharger failure becomes a certainty.

To avoid being landed with the bill, make sure there is a full, main-agent service history, and contact the garage concerned to verify it. Before looking at the turbo, check the ancillary parts that have to take the strain. Wheels, tyres and brakes are vital to the performance characteristics and will cost a fortune to replace. Also, an eager turbo-user may have skidded into the scenery, so check the bodywork for poor-quality repairs.

You'll find out about the turbocharger on the test drive, especially when it kicks in: a dashboard warning light comes on and you feel a nudge in the back. More important, though, after a 10-mile run, leave the engine running and accelerate hard: black smoke from the exhaust means serious turbocharger trouble.

When it comes to choosing a used turbo, you soon realise that not every manufacturer understood the concept, or could cope with the technology, and many unsuitable bangers have been 'blown' to no useful effect. When properly installed, however, they make great sense.

Diesels are a case in point. Turbocharging, a technology borrowed from diesel truck engines, makes overtaking in diesel cars less of a risk, and makes them as civilised as petrol-engined versions. Citroen, for example, applied turbocharging with great effect to the BX17.

The turbocharger is also largely responsible for the 'pocket rocket' category, by turning little cars with little engines into mini-supercars. Renault has always had faith in turbochargers, and its 5GT Turbo is electrifying.

Turbocharged sports saloons are numerous, but few are as well balanced as those of the pioneers, Saab, the company which proved that turbo need not equal trauma. A 900 promises, and delivers, reliability and performance. And in the super-league, Porsche has blazed the trail with its classic 911 Turbo since the mid- Seventies, while Lotus joined the club with the Esprit Turbo, which despite its humble four-cylinder engine challenges Ferrari's finest V12s for sheer brute performance.

To track down a turbo was hardly difficult, but I kept to the specialists and main agents to reduce my chance of buying a blown one. It seemed only right to look at Saabs first. At the Swedish Car Centre, I warmed to the practicality offered by a 900S five-door, which, with the later 16- valve engine, promised plenty of performance. Mileage was 49,000, there had been one owner, and the nicest surprise of all was that the advertised price had dropped by pounds 1,000 to pounds 7,995.

Saab saloons used to dominate the rally scene, but now you can pretend to be a participant behind the wheel of the all- conquering Subaru Legacy. I found one of these outwardly ordinary but dynamically impressive cars at Phoenix Garage, in Surrey. It boasted not only turbo power, but also four-wheel drive. This 1992 car had covered 49,000 miles with one owner, and at no small expense Phoenix had invested in a new cam belt and clutch. It came with a full AA condition report, warranty, history and every available extra, including air-conditioning. All for pounds 11,995.

For final proof of how far turbos have come from their truck origins, I popped into Weybridge Automobiles to look at some Bentleys. There were two '87 model Turbo Rs in preparation for the showroom: you could choose between a 38,000-miler at pounds 36,950 and a 60,000-miler at pounds 34,950.

From the ridiculously large to the sublimely small . . . it was time to find a Renault 5. Autotek, near Guildford, had two new arrivals. Both showed why these otherwise flimsy cars should be bought only if they have been fastidiously looked after by a careful owner who can produce a full service history. So the choice was between a 1986 example with 38,000 miles at pounds 2,995 in stiletto white, or a 1990 35,000-miler at pounds 4,895 in metallic grey.

The antithesis of such hot roller-skates is, of course, the supercars. Porsche 911 Turbos, after becoming blue-chip investments, then crashing, are on the up again, and increasingly rare. If I fancied a trip to Scotland, Glenvarigill had a 1985 example for pounds 22,950. Otherwise, at AFN in Reading, a 1991 model cost pounds 49,950.

Closer to home is a marque that offers similar excitement at a fraction of the cost. The London Lotus Centre had a brace of Esprit SEs for between pounds 20,000 and pounds 30,000, as well as the smaller open- topped Elan, prices starting at pounds 16,950.

At Kent Sports Cars, a Lotus specialist, I could choose from an early 1982 example at pounds 9,950 right up to the restyled 1990 SE at pounds 19,950. That turbo had done 34,000 miles, and had red paintwork, sand-coloured leather, air-conditioning and a sunroof. I had to hunt around for the less- than-obvious turbo badge; but a car with as much machismo as this doesn't need a badge to prove it.

(Photograph omitted)