Celtic Tuning Alfa Romeo Giulia Quadrifoglio review – Alfa’s supersaloon gets 585bhp

At face value, you could be forgiven for thinking that Celtic Tuning’s Alfa Romeo Giulia Quadrifoglio is just another one-dimensional, big-power machine. The sort of car where a headline grabbing power figure – this time of 585bhp – is more important than drivability or how much of that extra performance you can actually use. But Celtic Tuning’s modifications to the twin-turbo V6-powered Giulia mostly only add to the car’s on-road pace and wild character.

> Read our review of the standard Alfa Romeo Giulia Quadrifoglio

Engine, transmission and 0-60 time

The Newquay tuner has developed a software package to take the saloon’s twin-turbo V6 from 503bhp and 442lb ft of torque to an even more generous 585bhp and 489lb ft. With no mechanical changes involved, the necessary modifications to the ECU can be carried out by Celtic’s network of dealer and mobile tuners. Very useful if you don’t happen to live in Cornwall.

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What’s it like to drive?

During normal driving, you can feel the extra performance right from the bottom of the rev range. Small throttle movements have the car surging forward no matter what the revs or which gear you’re in, and you soon recalibrate your own ECU and use one gear higher than you would in the standard car. There’s a perverse pleasure to be had from deploying as little of the huge reserves of power as possible, using the tiniest amounts of throttle to pull away from others or overtake, safe in the knowledge that very few cars could keep up if you dropped a few gears and used more than a quarter of the accelerator’s travel.

Celtic Tuning’s modifications also allow the exhaust flaps to open when the car is in Dynamic mode, so you can savour the Giulia’s louder, Race-mode exhaust noise but keep the traction and stability controls on. If you want just the exhaust modification it will cost you £400, rather than the £600 for the full package.

> Find out what the Alfa Romeo Stelvio Quadrifoglio, an SUV with the same engine is like

To really appreciate the extra noise you need to work the V6, and as you explore the upper half of the rev range the Giulia’s new-found performance is just as startling. The engine is incredibly responsive, much like in the standard car but even punchier. This extra force can cause traction issues out of slower corners, and with the added low-down grunt you can’t compensate with higher gears as it’ll still spin its wheels easily in third or fourth, especially in the wet. It gives the Giulia a genuine edge that’s usually the preserve of its rival, BMW’s M3. However, as the ultra-fast steering and supple yet predictable chassis haven’t been changed, it remains delightfully controllable and exploitable.

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Although the chassis isn’t overwhelmed by the extra power, the electronically controlled limited-slip differential doesn’t cope quite so well. Even with the Giulia’s regular power the diff doesn’t lock up every time you think it should, then at other times it works tirelessly to keep the car straight rather than letting it react naturally to your inputs. Sadly, the extra performance magnifies the diff’s quirks. However, it’s only slightly more frustrating and certainly doesn’t ruin the experience.

There’s something very grown-up about the way Celtic Tuning has approached fettling the Quadrifoglio. A 660bhp version, with bigger turbos and a raised rev limiter, is on its way, too. If this 585bhp car is anything to go by, it’ll be far more sane than the numbers suggest. Let’s hope the diff also gets an upgrade.

Price and rivals

Considering the car’s ultimate power, a £600 addition to the Giulia’s £61,625 basic price makes it quite the bargain. With that much performance on offer the Celtic Tuning Giulia is closer to special limited-run coupes and saloons like the 493bhp BMW M4 GTS and the new 592bhp Jaguar Project 8 than its regular rivals. The Giulia might not have the same track-focussed chassis as either of those two, but even with the cost of Celtic Tuning’s software and exhaust changes, this car is less than half the price of both.