Some firms opt for turbocharging their engines to boost power, others supercharge them and some go for larger capacity units – all of which are effective at reaching their goal of meeting drivers’ needs for higher performance, except that fuel economy and emissions levels tend to suffer.
It’s a double-edged sword, but Volkswagen is setting off on another path with its new range of engines, branded TSI. These petrol engines are similar to their FSI direct injection cousins with the exception of one thing – TSI models use both a supercharger and a turbocharger.
The TSI engine only has a capacity of 1.4 litres, but thanks to the turbo and supercharger it can offer up to 168bhp – a very high output for such a small unit.
It does this by using a supercharger at low revs to provide extra power which is instantaneous as the supercharger is driven by the engine and has no lag, unlike a turbo.
This means maximum torque is provided at just 1,750rpm – very low for a petrol engine. However, the supercharger’s work is done by 2,400rpm, which is when the turbo kicks in to provide continued boost.
Once up to the required speed, the turbo is rendered almost redundant, so if you’re cruising on a motorway at 70mph in top gear the TSI acts as a normal 1.4-litre engine.
The result of this clever technology is superior fuel economy and CO2 emissions over conventional petrol units.
The 1.4 TSI 170 in the Golf GT produces 168bhp, emits 178g/km of CO2 and returns a claimed average of 38.2mpg. Compare this to the existing 2.0-litre FSI 140 engine in the Golf which makes 138bhp, and has identical emissions but returns 36.2mpg.
The TSI engine will go on sale in the UK later this summer in the Golf, branded as the GT to reflect its status as a junior GTI. No mention will be made of its 1.4-litre capacity, perhaps because drivers may be put off by a lack of cubic inches under the bonnet. It will also find its way into the Touran mini-MPV in the spring of 2007.
However, before that a lower power version of the TSI will go into the Touran. On sale from June, the TSI 140 uses the same technology as in the Golf GT, only with less power to suit its more family-oriented role.
But it’s not just petrol technology where Volkswagen has been busy lately. It has also developed a high performance TDI 170 diesel, offering 168bhp and also set to find a home in a Golf GT this summer. The GT TDI 170 is the most powerful production Golf diesel ever built and builds on the strong performance offered by the existing TDI 140.
However, with an extra 30bhp and 22lb-ft of torque, the 170 unit is a flyer.
Yet it also retains the TDI virtues of strong fuel economy and low emissions. The 170 version emits 165g/km of CO2 and returns an average of 46.3mpg, compared with 154g/km and 49.6mpg for the TDI 140.
Behind the wheel
ASIDE from discreet GT badges on the rear hatchback and front grille, there’s little to distinguish the new TSI models from other Golfs.
It’s only when you sit behind the wheel and notice a turbo boost gauge in place of the engine temperature dial that you know this Golf is something different.
But once on the move it’s clear the TSI engine is far removed from its more humble stablemates. As soon as you press the accelerator there’s an instant response as the supercharger does its work and supplies extra boost.
For a 1.4 the TSI 170 accelerates really hard – in fact it feels more like a 2.0-litre-plus unit thanks to the amount of torque on offer. At higher revs the turbo chimes in and provides another level of boost – only this time much more urgent. And then, as you reach sixth gear, the engine settles into a relaxed gait at motorway speeds.
Even in TSI 140 spec, as found in the Touran, the unit continues to impress. While outright power is down on the 170, it makes the Touran feel as though it’s powered by an engine of at least 1.8 litres.
Finally, there’s the TDI 170 diesel. This unit, with 168bhp, is an absolute flyer and gives the Golf the kind of mid-range power usually only found in much more expensive sports cars.
THE TSI petrol units are deeply impressive, delivering strong performance without impacting on economy or emissions – for people who don’t like diesels, there’s now a real alternative. But for those who do, the TDI 170 is at the vanguard of diesel engine technology.
|Model:||TSI 140||TSI 170||TDI 170|
|Max power (bhp/rpm):||138/5,600||168/6,000||168/4,200|
|Max torque (lb-ft/rpm):||162/1,500||177/1,750||258/1,750|
|Max speed (mph):||124||136||137|
|Fuel consumption (mpg):||38.2||38.2||46.3|
|CO2 emissions (g/km):||N/A||178||165|
|On sale:||Late summer||Prices (est):||£18,000–£20,000|