IT WON’T be too long before you can’t buy more than a handful of normally-aspirated cars beneath the £75,000 mark, which is both a good and a bad thing.
Whether it’s done for power or for economy – or both – turbocharging is here to stay and most keen drivers’ favourites from yesteryear have already gone over to forced induction.
The BMW M3, most of the Mercedes AMG range and even the 2013 Renaultsport Clio have all sprouted turbos, which re-circulate air from the exhaust system back into the cylinders under high pressure and achieve a number of things. First; the good. Compared to normally-aspirated engines they can increase power massively, they can provide the same acceleration for less fuel and everybody loves to be able to say they have a turbo. Or is that just me…?
But here’s the not-so-good. They have lag, they’re temperamental as far as fuel economy goes and if they’re not spinning you can find yourself caught out with little or no power. If we’re talking about performance cars turbos also dampen exhaust noise and soften power delivery, taking the edge off the experience.
On the one hand they seem like the perfect solution; lowering CO2 and therefore road tax bills, increasing fuel efficiency and yet giving us more speed than we ever had before when we get busy with the accelerator. But on the other hand there are a few cases in point to make you think twice.
The Ford Focus 1.0 EcoBoost petrol has done well for itself, recording 56.5mpg in the EU’s standard tests at the same time as offering zesty performance and a properly fun drive. But in reality the engine struggles to get above 40mpg according to long-term real-world tests, which is frankly rubbish by comparison. I managed to get 56mpg out of a normally-aspirated 1.6-litre petrol Toyota Auris with a stint through hilly suburbs outside Lisbon recently, so either I’m an eco-driving demon or turbocharging has some questions to answer.
There’s also a practical issue with turbo lag. Turbochargers spin at incredibly high speeds; tens or even hundreds of thousands of revolutions per minute in some cases. But when they’re not spinning they’re not providing the extra boost the engine is designed to need, so there’s no performance. This lag can be a big problem: just try rolling up to a roundabout and dashing out into a gap when you’re ‘off boost’. For a terrifying moment you’re nothing but a rolling crash barrier.
The problem is compounded by downsizing, where turbo technology allows manufacturers to make smaller engines and still reach the same or better power figures. Instead of a 1.6-litre engine’s increased natural low-down grunt you now have a briefly but thoroughly feeble 1.0-litre or 1.2, which in a car the weight of modern family hatchbacks is woefully inadequate. You end up having to drive around town one or even two gears lower than you could, or else you just put up with it and have patience.
And for performance cars the thrill is definitely lower in a turbo’d engine. You can get huge, punching acceleration that turns your internal organs to soup, but they can’t rev as highly as normally-aspirated engines without major engineering taking place, and they’re undeniably quieter. Even the mighty 5.5-litre twin-turbo AMG engine, and boy is it good, can’t match the 6.2-litre non-turbo unit it replaced in most AMG models. It doesn’t sound quite as good and it doesn’t drive quite as well. The thing is, even Mercedes knows it. That’s why they’ve hung onto the 6.2 in the C63 AMG and SLS; the two most symbolic cars the AMG division makes. They’ll only lose that engine when European legislation forces them to.
So where does that leave turbocharging? Well, as you might expect, emissions are driving everything in the car industry. Every last potential avenue has to be explored in order to get CO2 as low as currently possible, because if EU targets are missed it’s going to mean big, big fines for manufacturers that haven’t made the cut. Some of them literally can’t afford to fail right now, so companies have frantically yanked out all the stops to cut CO2. Turbocharging is essential to that, so for better or worse its gradual takeover will continue.