Ricci's Garage: single or twin turbochargers for the modified R34 GT-R project?

Internationally renowned photographer Mark has been working with TG for many, many years. When not taking photos he’s buying inappropriate cars. Here he shares his addiction with the world

Whoever said there's no replacement for displacement is likely having quite a tough time these days. Because there’s no escaping the efficiency of turbochargers in 2024. These miracle snails allow smaller, downsized engines to deliver a punch equal to (or greater) than their larger predecessors. And, when utilised cleverly with PHEV powertrains like Ferrari’s 296 GTB, the results are pretty mind blowing.

But turbocharging smaller engines for more power is far from a new phase. Just about every performance Japanese car from the Eighties and Nineties went down this route and, in the case of the Nissan Skyline, its RB26 engine utilised two smaller turbos for better response and less lag. Some cars – like Mazda’s FD3S RX-7 – even used sequential turbos (one small, one big) to quite literally give the best of both worlds.

Within the older Skyline tuning circles, the debate for going down a twin-turbo route or big single turbo has divided many for years. Twin turbos are often looked upon as the go-to choice for builds that favour throttle response and (less) lag over outright power. But turbocharger tech is so much more advanced now; getting a larger, single turbo to be just as responsive – and make even more power – seems the preferred choice.

When my R34 GT-R first arrived from Japan it’d been converted to a single turbo setup producing 650bhp. After a few years, I then upgraded this turbo to a more modern Xona Rotor unit which bumped the power all the way up to 830bhp, which even made more power earlier in the rev range despite being a larger unit. So clearly, for the final engine I’ll ever fit in this cursed car, the obvious choice would be the big single.

That would make the most sense. But sense is not something that often accompanies GT-R ownership. And, having grown up in the Nineties watching old Japanese tuning videos, the urge to fit two giant turbos together is strong. Back in the day, this method seemed best for chasing 1,000+ horsepower builds because few single turbos could offer that kind of flow without using engine-bending levels of boost. But in 2024? Two big turbos give all the drawbacks with none of the positives.

They’re beyond laggy – even with different pistons, crank or an RB30 block, you’re unlikely to get a Skyline engine beyond around 3.0 litres. So don’t expect any ‘proper’ boost until at least 5,500rpm. Two turbos require twice the pipework, twice the space and twice as many parts to go wrong. They even sound noticeably different; a six into one big single turbo screams with all the rpm. But two turbos splitting the manifold sound more like a traditional straight six.

And yet, despite all of this, I’ve gone and bought a set of top-mount turbos for my GT-R. Not just any kind either, but a broken set which will need overhauling at great expense before they can go anywhere near an engine. Each of the KKK turbos (no, not that kind) should be good for around 450–500bhp apiece when actually working. Not that I even have an engine to turbocharge currently, that’s still in Australia being finished.

And, if I’m being completely honest with you, reader, I didn’t even buy these to fit to my R34 GT-R. I really bought ’em to use in an R32 GT-R project instead. Something I haven’t actually started – or even bought – yet. Because everyone knows the best way to finish one long term project car is by starting yet another.