Tuning: the new-school

Iain Litchfield has been extracting comedy amounts of horsepower from engines for 20 years – most famously those of Nissan GT-Rs.

‘It’s about airflow,’ he says. ‘With turbocharged cars, it’s quite simple in theory: you fit a bigger turbocharger that will flow more air. Unfortunately, it’s not quite as simple as that, particularly if you’re after big increases in horsepower. The bigger the turbo the more lag you’re going to get, not just because of the mass of the turbine and compressor but because of aerodynamic drag on the bigger blades. To help solve the problem you can go up in engine displacement, which is what we do on the really powerful GT-Rs. It’s why McLaren has made the 720S’s engine larger.

‘Eventually you need larger injectors that can flow more fuel, bigger fuel lines and highercapacity fuel pumps. Then there are intercoolers that have to be made larger to cool the extra air. Manufacturers are turning to charge-coolers because they remove heat so quickly. The snag is that that heat goes into the cooling system, which on a circuit with hard use is a problem.’

Tuning modern, naturally aspirated engines presents other problems. Mainly because they’re just so good out of the factory.

‘The power gains tend to be very small,’ says Litchfield. ‘We can fit a new exhaust system to a Nissan 370Z and remap the ignition, fuelling and even valve timing, but still only get a gain of 15bhp. The next step is to fit new intake systems and camshafts and up the compression, but even then the gains aren’t huge.’