The turbo, that windy power source of the 1970s and '80s, is back. Paddy Comyn looks at its renaissance
There was a time in the late 1970s and early 1980s when the word turbo would cause a tingle down the spine of any motoring fan. It stood for performance and power.
But not everyone was convinced. BMW was one such company. Now, with the arrival of the new 335i, we see even these Bavarian turbo naysayers returning to the windy ways as a means of improving performance. They are not the only ones. So what has brought about the turbo revival?
BMW was among the first of the European manufacturers to employ turbos with the 1973 2002 Turbo, with Porsche following with their 911 Turbo, introduced at the 1974 Paris Motor Show. The first production turbo diesel car was in 1978, and that was the 115bhp 3.0-litre 5-cylinder 300SD, available only in the US. In Europe, the Peugeot 604 with a 2.3-litre turbo diesel was introduced in 1979, followed by the 300 TD turbo.
But adding turbos to small-engined cars made things really exciting. The 1979 Renault 5 Turbo was one. It managed 160bhp, thanks to a 1.4-litre engine with a turbo attached, the first time a turbocharger had been fitted to a four-cylinder engine.
The difficulty with many of these early turbos was that in many cases you would put the foot down and wait. And wait. And then you would get a kick up the pants and end up upside down in a hedge.
Any BMW 2002 Turbos, Renault 5 Turbos and early 911 Turbos were nothing short of scary. This was because of a problem that blighted this early technology - turbo lag. This is caused by the time taken for the exhaust system driving the turbine to come to high pressure and for the turbine motor to overcome its rotational inertia and reach the speed necessary to supply boost pressure.
The same was true of the small Japanese cars of the era. Many an owner of a Datsun Cherry Turbo will tell you of scary overtaking moments, where nothing at all happens, before all of a sudden you have eaten your front tyres and you are facing the wrong way.
Thus turbos were banished for a time by many manufacturers - BMW included, as it claimed that the high-revving engine made a much better choice for a performance car. But then things began to change, as carmakers figured out that they could combat lag by using more than one turbo.
By using two turbos you can have one turbo active across the entire rev range, and another coming on stream at a higher rpm. Some work parallel to each other but others work sequentially, almost eliminating lag and reducing fuel consumption. BMW employ a Twin Turbo with their new 335i.
Each one supplies compressed air to three cylinders and this makes the response from the pedal rapid. By using a smaller turbocharger on 3-cylinders, rather than one larger one on six cylinders, there is a low level of inertia - thus preventing the lag.
A prize winner at the 2006 International Engine of the Year Awards, Volkswagen's new 1.4-litre TSI (or Torque Strong Twincharger) is coming to us soon and will return 170bhp in the Golf GT. VW engineers have combined a turbocharger and a supercharger (see panel) that allows a high compression ratio of 10:1 to be used. The rapid response of the exhaust turbo means that the supercharger, which supplied the low-end boost, can be disengaged by an electromagnetic clutch, thus saving fuel.
This in theory could be the perfect engine for Ireland. Prices start €25,100 for the 140bhp version, and €30,275 for the 170bhp GT version.
After 100 years, the turbo is still a dominant force and for now, thanks to improvements in technology, it looks set to remain. Whether it is a pocket rocket or a luxury cruiser, the turbo has proven its worth time and time again.*The key difference between a turbocharger and a supercharger is its power supply.
A turbocharger gets the power to run the air compressor from the exhaust stream, while in a supercharger there is a belt that is connected directly to the engine