There's no such thing as a bad MX-5 – so how much improvement does a supercharger really deliver?
By Matt Bird / Saturday, January 8, 2022 / Loading comments
It’s not often a supercharged car makes it to the news. In fact, once the JLR 5.0-litre V8 has breathed its last, it’s hard to think of any other new cars with superchargers out there – besides the Lotus Emira, of course, but it too is using an old engine. As both turbos and electrified powertrains have improved, so the requirement for a belt-driven ‘charger has waned. Which is a bit of a shame, given they offer a different powertrain experience. But such is the way of the world.
Thank goodness, then, for BBR, and its work with Corten Miller and its Rotrex conversions for the Mazda MX-5. Offered as another option alongside its turbocharger conversions and naturally-aspirated upgrades, the supercharged kit is pitched to those MX-5 customers keen to use their car more on track, given it needs revs for its best (peak power is at 7,000rpm) and is easier to keep cool in continuous hard use than the turbo. Specifically, exhaust gas and inlet air temps are kept lower with a supercharger rather than a turbo – and not hot is good as far as regular track driving goes. Buyers with existing N/A kits like the Super 200 will be pleased to know the ‘charger works just fine with those upgrades, so it ought to be ideal if you need the extra muscle to deal with Fiesta STs on track days – keep the character, but with a dollop more performance.
Even in the cheaper, less powerful Stage 1 tune, this is still a 250hp NC MX-5 – 90hp more than the most potent standard car. Torque is up substantially, too, with 213lb ft at 5,350rpm, compared to 147lb ft for the regular 2.0-litre unit. With the temperature hovering around freezing, there’s not much desire to try Stage 2 with more than 300hp and a smidge (227lb ft) extra torque. Let’s save that for a hot summer’s evening on track.
Nevertheless, this remains a very rapid little Mazda, even when dawdling about waiting for everything (the seat heaters, mainly) to get up to temperature. Though less about torque than the turbo conversions, this BBR MX-5 immediately feels more muscular; limiting the car to 3,500rpm while it warms through doesn’t feel a hardship, because there’s so much more performance everywhere.
Really, though, the supercharged cars want revs. By way of comparison, the turbo 1.5 version of the current MX-5 by BBR offers 197lb ft; even with the extra 500cc of capacity for this 2.0-litre, the older car musters just another 16lb ft, and needs more revs to do it. The turbochargers have always done a good job of mimicking the naturally-aspirated feel, but utilising a supercharger improves the situation even further. Any MX-5 thrives on engine speed, and never more so than here – but now there’s some proper performance to support your commitment.
It’s a right hoot, frankly. The final couple of thousand revs or so from peak torque to peak power really thrill as the MX-5 fizzes to its limiter. There’s no hint of delay or reluctance, just power and noise building with revs like all the best sports cars, all the way to 7,500rpm; the supercharger simply lends the MX-5 the characteristics of a larger, gruntier, atmospheric engine. And the experience is just as good, if not better, than that summary suggests.
Handily, like so many tuned MX-5s, BBR’s efforts broaden the inherent appeal of the car without fundamentally altering its character. It still responds dutifully to wringing out every gear, but also satisfies pulling fourth out of a village or overtaking confidently on an A-road. The feel of an MX-5 powertrain is undoubtedly retained, just with more oomph alongside a fine four-cylinder medley of a soundtrack. There really a bit of everything: it gurgles, rasps, screams, pops, and zings. There isn’t any supercharger whine, but that has always felt an acquired taste anyway – it’s not missed.
Now, clearly, such increases would be too much for a standard chassis to handle, so it’s worth pointing out the other modifications belonging to BBR’s demonstrator that will add some more heft to your final bill. As a more focused build designed for track, this one has coilover suspension to go with the uprated brakes, OZ wheels and Michelin PS4 tyres. While the new dampers are probably a bit much for a car not regularly tracked (they’re too stiff for the body’s rigidity on the road, making it a bit brittle), in the right situation they make the MX-5 feel pointy, alert, and alive like no other. In combination with the rev-happy engine overhaul, it’s a really exhilarating, old-school roadster driving experience.
Consequently, the overall impression (if you’ll excuse a well-worn cliche) is of a chunky and better trimmed Caterham. The supercharger gives the same effervescent nature to the power delivery that the senior Sevens offer, and suspension work confers incredible agility. Of course, the overall experience from the heavier, less powerful sports car isn’t quite so intense, yet there are parallels to be drawn, most certainly.
Interestingly, BBR’s main man says he prefers the turbo conversion, based on that slug of mid-range torque, although, subjectively speaking, the supercharger feels even more in keeping with the MX-5 ethos. Of course, that’s the joy of the aftermarket scene – there’s something to suit every preference. That said, a familiar level of fun also means the same observations apply to this conversion as to turbos and individual throttle bodies and V6 swaps: making an MX-5 noticeably faster is a lot of money to spend on what’s typically an old, fairly cheap car. With a less than impressive interior. ‘Twas ever thus, unfortunately.
To some, that’ll remain a stumbling block, especially when someone points out the Porsche you could have had instead. But, honestly, as a driver’s car, as something to get you up on a Sunday morning but also take to the shops when needed, a supercharged NC MX-5 must be one of the best ways to spend £20k. None of the standard charm has been sacrificed in the pursuit of improved performance (optional coilovers notwithstanding) – this is just a likeable and familiar sports car package made tangibly faster – and a whole lot better. Simple as that.
SPECIFICATION | BBR MAZDA MX-5 RC SUPERCHARGED
Engine: 1,999cc 4-cyl, supercharged
Transmission: 6-speed manual, rear-wheel drive
Power (hp): 250@7,000rpm (160@7,000rpm)
Torque (lb ft): 213@5,350rpm (147@5,050rpm)
0-60mph: 5.3sec (7.9sec)
Top speed: 145mph (est.) (136mph)
Weight: 1,248kg (standard car)
MPG: 36.2mpg (standard, NEDC combined)
CO2: 181g/km (standard)
Price: c. £20k, assuming £10k purchase price for standard car. This one equipped with BBR Stage 1 Supercharger kit (£5,994), BBR 4-1 manifold (£534), BBR GT Silencer (£594), Tein Flex Z Damper Kit (including 4-wheel alignment), OZ Formula HLT wheels (£1,235), including VAT and fitting, for a total spend of £9,551.
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