To­tal MX-5’ s UK road test

Total MX-5 - - CONTENTS - Words Steve Ben­nett Pho­to­graphs: Matt How­ell

The mk4 has al­ways felt like it could han­dle much more power – thanks to a turbo, BBR has now given it a stonk­ing 250bhp. It’s im­pres­sive

The nor­mally-as­pi­rated, high-revving ethos that comes stan­dard with ev­ery MX-5 since its in­cep­tion has al­ways been the road­ster’s dou­ble-edged sword. On the one hand a revvy, as­pi­rated en­gine that de­mands to be worked hard is a fun­da­men­tal part of the MX-5 ex­pe­ri­ence, one made sweeter by the sweet­est and snick­i­est of man­ual gear­boxes. On the other hand, though, it’s merely quick, rather than ac­tu­ally fast, ac­cen­tu­ated by the peaky na­ture of a 16-valver lack­ing in torque and de­liv­er­ing its peak well past 5000rpm.

Don’t get us wrong, Mazda was ab­so­lutely right to give the MX-5 a zingy NA en­gine, and for most folk it’s just fine and those oc­ca­sional jour­neys to the red­line are all part of the MX-5 vibe. But it is rather oned­i­men­sional and flat when you’re not on it, and some­times be­ing ‘on it’ is a bit too much like hard work. The road isn’t a race track, where you can con­sis­tently keep the en­gine buzzing at peak torque and power. In fact, for the road ‘torque’ is the op­er­a­tive word. It’s why our lit­tle MX-5S get seen off by all those mun­dane tur­bod­iesels. Ev­ery­one these days has a big wodge of turbo torque bang in the mid-range and un­less you’ve got your 16-valves danc­ing out of the bon­net, you’re left be­hind in a puff of soot.

Mazda knew that it wouldn’t take long for the mk1 MX-5 to be fit­ted with a turbo. In­deed they pos­i­tively en­cour­aged it, equip­ping it with an en­gine that was

The one we’ve been wait­ing for: BBR’S Stage 1 turbo con­ver­sion turns the mk4 MX-5 from a merely quick car into some­thing gen­uinely fast with Porsche-bust­ing pace

sur­pris­ingly low in com­pres­sion for a nor­mally as­pi­rated unit (so that it would run hap­pily on low oc­tane fuel). When BBR de­vel­oped a turbo kit for the mk1 in 1990, it did so with Mazda’s bless­ing, as­sis­tance and a war­ranty. The ad­di­tion of a turbo trans­formed the MX-5 from fun to fast. I’m old enough to have ex­pe­ri­enced that first press car in 1990 and was struck by how dra­mat­i­cally the char­ac­ter of the lit­tle Mazda had been changed. It of­fered choices as to how you wanted to pro­ceed. Fast and fran­tic or fast and re­laxed. The choice was yours. I loved it...

And of course BBR has been at the fore­front of MX-5 turbocharging pretty much ever since, which is why we’re back at Brack­ley to drive the hugely an­tic­i­pated turbo mk4. And here’s progress for you: back in 1990 the BBR mk1 Turbo MX-5 packed a 150bhp hit. For 2017, the turbo mk4 bangs out a ful­some 250bhp and weighs ap­prox­i­mately the same.

The orig­i­nal red mk1 press car stars on the wall in the re­cep­tion area at BBR’S work­shop, sit­u­ated bang next door to the Mercedes F1 team. I men­tion to chief en­gi­neer, Neil Mckay, that I drove the very same car 27 years ago, which im­me­di­ately makes me feel very old. Rack­ing my brain as to the last time I’d been at BBR, I re­alised it was prob­a­bly to drive one of its turbo Lotus Elises and be­fore that there were the mod­i­fied Sierra Cos­worths. Cue a trip down mem­ory lane and max­ing one of BBR’S fear­some ‘Mogul’ con­ver­sions on Brunt­ingth­orpe prov­ing ground’s twom­ile straight at 180mph...

But enough of the rem­i­nisc­ing. Back in the real world there’s work to be done. The Turbo MX-5 mk4 has been a long time com­ing. In­deed, we were an­tic­i­pat­ing a first drive way back in Sept 2016, when we were putting to­gether the first is­sue of To­tal MX-5. Why the de­lay? Well, while the hard­ware side of things has been pretty straight­for­ward, the is­sues have all sur­rounded in­fil­trat­ing and ma­nip­u­lat­ing the mk4’s com­plex en­gine man­age­ment and con­nected soft­ware. Throw­ing the stan­dard ECU away and start­ing again would be throw­ing the baby out with the bath­wa­ter. Much bet­ter to try work­ing with the stan­dard sys­tem and take ad­van­tage of Mazda’s ex­per­tise and 1000s of hours of devel­op­ment. To that end BBR worked with ecutek to cre­ate a turbo map within the stan­dard ECU, sup­ply­ing the ECU guru with a kit to work on for its own mk4 MX-5. It may have taken a while to mas­ter the stan­dard sys­tem, but it has been worth it.

Elec­tron­ics aside, the rest of the kit is about hard­ware. The 2.0-litre SKYACTIVG en­gine is left alone in­ter­nally. It will hap­pily han­dle the ex­tra power and torque. The heart of the con­ver­sion is a sur­pris­ingly large twin-scroll turbo mated to BBR’S own in­let man­i­fold. A twin-scroll turbo is rather like a two-in­one turbo with two ex­haust gas in­lets and two noz­zles – one for low-rev, quick re­sponse and the other one for peak per­for­mance. With­out wish­ing to get too techy, the twin-scroll turbo works in tan­dem with a split-ex­haust man­i­fold, which chan­nels the turbo pulses be­tween the cylin­ders in a rather more ef­fi­cient and pre­cise man­ner. Most mod­ern en­gines use the twin-scroll sys­tem now and it’s largely re­spon­si­ble for the near elim­i­na­tion of turbo lag and turbo en­gines be­ing able to run a higher com­pres­sion ra­tio. Or in the case of the BBR con­ver­sion, the mk4’s stan­dard com­pres­sion ra­tio of 13:1. The twin-scroll turbo also works well with Mazda’s 4-2-1 ex­haust man­i­fold de­vel­oped specif­i­cally for the SKYACTIV-G en­gine to over­come the mar­ginal ex­haust re­stric­tion of a cat­a­lyst close to the cylin­der head.

Cool­ing the charge air go­ing into the

en­gine is an air-to-air in­ter­cooler and as­so­ci­ated pipework. Peer­ing un­der the bon­net, the ef­fect is of a fac­tory fit. The turbo sits neatly on the left-hand side of the en­gine, un­der a car­bon­fi­bre shield. The in­ter­cooler is po­si­tioned in front of the ra­di­a­tor.

Power – as we’ve in­ti­mated – is 250bhp, which equates to 234bhp per tonne. To put that into per­spec­tive, a Porsche Boxster with 300bhp has 213bhp per tonne. More tellingly, though, is the torque fig­ure – 236lb ft at 3800rpm, com­pared with the stan­dard car’s 152lb ft at 4950rpm. And a whole­some 200lb ft is avail­able be­tween 2750rpm and 6500rpm, against the stan­dard 148lb ft. You don’t even need to get be­hind the wheel to know that sort of torque curve is go­ing to make it­self felt and in­deed trans­form the char­ac­ter of the car. But get be­hind the wheel we must, so let’s get go­ing.

BBR has used a Re­caro Sport Edi­tion as its demo car. A good choice be­cause it comes with Bil­stein dampers and the Re­caro seats are a real cut above the stan­dard perches. BBR has added its own pro­gres­sive springs to the sus­pen­sion mix and slightly wider OZ Ul­tra Leg­gera wheels booted up with 215/45 x 17in Yoko­hama tyres for a bit of ex­tra grip. Not a bad idea with the ex­tra oomph on of­fer. This car is now also be­ing used to de­velop the Stage 2 300bhp kit and so has a slightly stronger, grab­bier clutch: the stan­dard clutch hap­pily han­dles the 250bhp and ex­tra torque of this Stage 1 setup.

An MX-5 with 250bhp and a mass of mid-range is in­deed a very dif­fer­ent an­i­mal but it doesn’t ac­tu­ally feel typ­i­cally tur­bocharged. The twin-scroll turbo, com­bined with the stan­dard high com­pres­sion ra­tio, means there’s next to no lag at low revs. It just feels like the stan­dard en­gine. Con­versely that means that it will also hap­pily rev round to 7000rpm. It’s what oc­curs in be­tween that’s sig­nif­i­cant, as the above fig­ures tes­tify. On the road that means a sub­tle rush from the turbo and a not so sub­tle rush of power.

It’s not like an old school turbo – all and then noth­ing – it’s smooth, lin­ear and large. And while it will rev to the red, there’s very lit­tle need to go there, as the torque curve sug­gests. And strangely, per­haps, it suits the chas­sis well. It’s still not a car that likes to be hus­tled, and if you re­ally start to stamp on things it will (just like the stan­dard car) get ragged and lose its shape. Sure it will show­boat, but it re­wards smooth in­puts, only now there’s more to play with and dif­fer­ent an­gles of at­tack to ex­plore and more to ex­ploit. The ex­tra rub­ber means you can get the power down and the lim­ited-slip diff has more work to do, but it can be re­lied on to ef­fi­ciently shuf­fle the power be­tween the driven wheels for some eas­ily pro­voked slides. The sim­ple ad­di­tion of BBR’S own springs has wiped out the mk4’s in­her­ent wob­bli­ness and roll, with added con­trol and no loss of ride com­fort. A rare trick when it comes to mod­ded sus­pen­sion and, at £495 fit­ted with a ge­om­e­try set-up, worth­while for any mk4 MX-5.

Any down­sides? Not re­ally. It de­pends, re­ally, how vi­tal you feel a high-revving, nat­u­rally as­pi­rated en­gine is to the MX-5’S ap­peal and how you feel about mod­i­fied cars in gen­eral. Cer­tainly there is very lit­tle ‘tuner’ about this con­ver­sion. It’s as much ‘fac­tory’ as you could pos­si­bly ex­pect and in­cor­po­rates all the stan­dard car’s safety func­tions and dayto-day map­ping and func­tion­al­ity.

Speed costs, of course, and here’s where you start pay­ing. If you want to go big, then you can buy a BBR turbo mod­ded MX-5 brand new for £29,995, with a three-year war­ranty. Is that ex­pen­sive? Not when you con­sider that a Fiat 124 Abarth Spy­der costs the same, but with a mere 170bhp from its 1.4-litre tur­bocharged en­gine.

At the other end of the spec­trum you can get a DIY fit­ment kit for £4395. BBR as­sures us that it’s an OK job if you’re rea­son­ably adept with the span­ners: it would be fun to find out. Al­ter­na­tively you can take your car to BBR, or one of its ap­proved fit­ting part­ners, and get the job for £4995. There are other costs, such as the springs, which we would cer­tainly go for, and the op­tion of four-pot or six­pot Wil­wood brake calipers at £595/£895 re­spec­tively. In the great scheme of things, and for the power in­crease, we don’t think the pric­ing is out­ra­geous. In­deed it’s still very much in keep­ing with the MX-5’S af­ford­able sports car mantra. Oh, and there’s a kit on the way for the 1.5-litre mk4, which prom­ises 210bhp–220bhp, and BBR is de­vel­op­ing Her­itage Turbo kits for the mk1 and mk2, which we’ll be test­ing in the next is­sue.

So would we buy one? Should you buy one? For us, if the stars aligned and we found our­selves with a mk4 MX-5, per­haps se­cond­hand, at a rea­son­able price, with some man maths, then yes. Mk4 2.0-litre cars can be found at around £17,500. Go on, do the sums... Tempt­ing, isn’t it? And if you’ve al­ready got a mk4? Oh, you’re al­ready on BBR’S web­site and you now ap­pear to be pick­ing up the phone. Our work here is done.

Quite aside from pack­ing a 250bhp punch, BBR’S demo car looks just right on its slightly low­ered sus­pen­sion and wider rub­ber Be­low: Wil­wood four-pot calipers hide be­hind OZ wheels Be­low right: Re­caro op­tion seats worth ev­ery penny

Right: in­stal­la­tion could pass as fac­tory fit­ted. Dual-scroll turbo sits un­der car­bon­fi­bre heat shield Left: test car is fit­ted with slightly wider Yoko­hama rub­ber and OZ wheels, plus BBR’S own spec springs, which work a treat with Mazda’s op­tional...

This is what you get for your £4395

The graphs tell the story – 248bhp and 236lb ft of torque, and a com­mend­able 234bhp per tonne

CON­TACT: BBR, Unit 1, Ox­ford Rd, Brack­ley, Northants NN13 7DY 01280 700700

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