BBR MX-5 Supercharged

BBR’S supercharger kit for the Mk3 (NC) MX-5 releases an extra 90bhp and a whole new level of excitement

IT’S A FAIR BET THAT BBR DOESN’T NEED any introduction, particularly in relation to tuning Mazda’s perennial roadster. We’ve driven a number of its conversions in recent years – some tuned but still naturally aspirated, others turbocharged – and generally enjoyed them enormously.

More recently, BBR had been working on conversions for the different MX-5 generations using a Rotrex supercharger, when part-way through its development cycle it was approached by another tuning firm, Corten Miller, who had already designed, developed and extensively tested a supercharger installation for the Mk3 (NC) model. As BBR’S own research had already suggested there was no real alternative in terms of how the Rotrex should be installed, and since Corten Miller was moving on to other things, a deal was struck where BBR took over all the rights, made a few further tweaks, and added it to its tuning range. The conversion is based on a C30-94 Rotrex unit and features its own oil cooler, cold-air intake system, upgraded fuel injectors and front-mounted air-to-air intercooler amongst what, when laid out, is a considerable kit of parts. We’re driving a Stage 1 kit on a 2-litre NC – peak figures 248bhp and 213lb ft, compared with 158bhp and 139lb ft for the standard car – but there’s also a Stage 2 conversion with 304bhp and 227lb ft. The latter uses a new fuel module and NGK iridium spark plugs and requires an upgraded clutch and full 2.25-inch exhaust system, too, but in the process it drops the 0-60mph time to 4.8sec (5.3sec for the Stage 1, 7.6sec for a standard 2.0). Conversions can be applied to 1.8-litre cars, too. Theoretically, the supercharger could offer over 400bhp, but you’d need forged engine internals for that.

This demo car also features BBR’S four-into-one exhaust manifold and ‘GT Silencer’ back box, plus further modifications in the form of Tein ‘Flex D’ coilovers and 17-inch OZ rims with Michelin Pilot Sport 4 S tyres. BBR’S Neil Mckay describes this suspension set-up as being aimed primarily at trackdays, so I’m expecting it to be on the firm side. What strikes me first is just how purposeful this Mk3 looks at its newfound ride height, each OZ rim filling the arch perfectly.

The second impression is the rort from the twin rear pipes on start-up, and the zap of revs when you brush the throttle pedal. Actually, while the exhaust is stridently noisy under full load, it hushes down dramatically once you’re just cruising or ambling around on urban roads and I soon decide it is something I could live with. The next revelation is that while the ride on the Teins is indeed firm, it couldn’t be labelled harsh; it deals with bumps and intrusions in an authoritative manner and smooths out as speeds rise. As with the exhaust, you’ll have to be a genuine enthusiast if it’s your everyday car, but it’s far from annoying.

The star attraction, though, is the engine, and here it’s all about the delivery. The Rotrex doesn’t alter the characteristics of the standard engine at all, it merely amplifies what the engine already has, to the tune of some 90bhp. That means there’s no spike of torque in the engine’s delivery as you’d get with one of BBR’S turbo conversions, but rather a linear rush of power.

There are, of course, two ways of looking at this: if you want to feel that madcap burst of excitement, an almost overwhelming hit of power in a small car, then you might be mildly disappointed. But what it does mean is that you can really concentrate on the driving, on getting your cornering line just so (the steering feedback and response with this geo set-up and suspension mods are leagues better than the original’s), on using every last rev and on generally driving the car as best you can. The engine seems to make power all the way to the red line, so you’ll often find yourself up at 7500rpm, aided by that lovely gearchange, and while the Stage 1 is appreciably faster than the standard car, it’s not so fast that on the public road you can’t thrash it really hard without straying into licence-troubling and/or socially questionable speeds.

Neil says the supercharged conversion is the pick of the bunch for trackday work, as the underbonnet temperatures are much lower compared with BBR’S turbo cars. He also tells me he can get brand new 2.5-litre Duratec engines ‘at a price you wouldn’t believe’ and is working on a supercharged transplant with one of those that should net upwards of 400bhp without the need for any internal engine surgery. Sounds hilarious.

In the meantime, £5994 (including VAT) for the Stage 1 conversion, fitted, plus a further £534 for the exhaust manifold, £594 for the exhaust, £1194 for the suspension and geo, plus £1235 for the wheels and tyres, means the full conversion cost

Above: Stage 1 kit includes Rotrex supercharger with its own oil-cooler, upgraded fuel injectors and intercooler; bespoke exhaust and chassis upgrades also available on this car comes in at under ten grand. In other words, for under 20 grand overall you’ve a sports car that’s great fun to drive, hopefully very reliable, and simple enough that even the DIY mechanic can service it. As it turned out, I drove the BBR just days after melting rear tyres in the 296 GTB (see p54), yet the little Mazda had me grinning all day long. Sounds like a great deal to me. ☒

Engine In-line 4-cyl, 1999cc, supercharged Power 248bhp @ 7000rpm Torque 213lb ft @ 5350rpm Weight c1100kg (230bhp/ton) 0-60mph 5.3sec Top speed 140mph+ Price See text

+ Seamless conversion amplifies best of MX-5

- Some might miss the thump of a turbo evo rating