Why eight is great
V8 conversions for the mk1 MX-5 are nothing new, but this largely DIY project has a neat twist – it uses a 4.3-litre Lexus powerplant
Since early times people have stuck V8 motors in the MX-5. But this conversion features a Japanese engine rather than American…
At a standstill, you’d be forgiven for thinking Matt Boot’s beautifully presented Eunos S Limited was little more than a regular mk1 with a few tasteful mods. Sure, there’s a TR Lane cage, a pair of retrimmed Lotus Elise seats and some gorgeous bronze Traklite 15-inch wheels, but nothing suggesting more than the kind of light personalisation any enthusiast might lavish on their pride and joy.
Then he starts it up…
It might only have a single, 2.5-inch Longlife tailpipe and backbox, but the noise that comes out of it is just extraordinary, the more so given the sleeper looks.your eyes tell you you’re looking at a regular mk1 Eunos: your ears say TVR or Corvette. The mismatch between sound and vision messes with your head.
It gets more interesting when you learn the source of that fantastic sound is not some old-fashioned Rover V8 or lump of American iron, but a sophisticated and distinctively Japanese V8 that pretty much trebles the original power output while barely adding to the weight or upsetting the finely-tuned balance that makes the standard mk1 such a joy to drive.
Chatting with Matt, the motivation for choosing the 4.3-litre V8 from a grey Lexus becomes abundantly clear. It may not be a Mazda engine but you get the sense that, if there ever had been a factory V8, it would have been more like this than the American-inspired transplants carried out by respected and established outfits such as Flyin’ Miata in the States.
Matt would have been happy to have gone down the Chevrolet LS engine route and there’s a huge amount of experience in such conversions. But for less than the price of a ‘crate’ Chevy V8, Matt has built an entire car with a distinctive and uniquely Japanese character all its own. And though you might not think it, given the slick looks of this particular car, it’s a lesson in DIY improvisation, well-informed scrapyard scavenging and proof that knowledge and determination can see a modest modification budget go a long, long way.
The immediate temptation is to jump behind the wheel, burn some rubber and find out exactly how a V8-powered mk1 actually goes. But there’s a story to be told first that makes that experience all the more enjoyable.
With a mechanic and compulsive car modder as a father, there was little question Matt would inherit the taste – and skills – to pursue similar passions. And whilst surrounded by spanners and engines from an early age, his dad gave him one important piece of advice – if you want to enjoy working with cars, keep it as a hobby, not a profession. As a carpenter Matt has that separation but is happy working with his hands and comfortable visualising the kind of brackets, adaptors and other fabricated parts required to swap an engine from one car into another. Just in metal rather than wood.
The Rover Vvc-engined Mini and sleeper £150 Metro with a K20 Honda Civic Type R motor also in the garage, prove how capable he is when it comes to engine transplants. Similarly, how useful it is to have an instinct for mixing and matching various engine bits from different manufacturers to make them all work. Suffice to say, for someone like Matt, local breakers’ yards are a land of opportunity.
Clearly a restless type, he’d never considered MX-5S before this one came along, writing them off, like so many do, as underpowered hairdressers’ cars. But a segment on Top Gear inspired him to think again and investigate buying one for his next project.‘they were all rotten though, or at least the ones I was looking at were,’ he sighs. By chance he mentioned his intentions to his accountant, who said he had a Eunos in his garage and was looking to move it on. And by good fortune it turned out to be a rust-free S Limited. It stayed standard for all of two weeks before Matt had turbocharged it with a Garrett GT28 from a Nissan S15 and a Megasquirt
ECU. ‘I liked it,’ he says simply, ‘but I wanted to do more…’
While the turbo gave him the performance, he found the car something of a pain to drive, the paddle clutch and power delivery great for the track but, he reckons, horrid on the road. A bigger engine, he decided, would be the best of both worlds in terms of performance and driveability. The Toyota 2JZ straight-six from the Supra was an option and famously accommodating of big horsepower. But Matt didn’t like the idea of a long, iron-blocked engine and, after reading up about V8 conversions in the US, was attracted to the all-aluminium 1UZ 4.0-litre V8 used in early Lexus models.
In typical Japanese style these Toyota engines are massively over-engineered and considered very reliable, if a little lazy in stock tune. That does, however, mean they often out-live the cars they’re fitted in, making them easy to source and cheap to buy. Matt didn’t want an
A bigger engine, he decided, would be the best of both worlds in terms of performance and driveability
automatic though and turned to the drifting scene where engine swaps are commonplace and BMW manual transmissions are the default conversion for Lexus V8s. Driftmoto supplied an adaptor plate and flywheel and Matt paid £100 for a gearbox, linkages, propshaft and clutch pedal from a BMW 328i and set about putting the two together. While he was waiting, he cut away and then reinforced the front chassis legs for more space, reflecting with hindsight that the engine would have fit anyway. But seeing as he had a bit of spare time…
Keeping the standard Eunos diff meant finding someone able to fabricate a new propshaft that could connect BMW gearbox and Mazda rear axle, but Matt’s location and contacts around his Birmingham home meant that was easily achieved at one of the many small automotive engineering shops in the area. He quickly found the standard diff was way too short for the new engine and went to a 3.6, but even this wasn’t enough – the car now runs a 2.47 and hardly feels over-geared. Theoretically, it’ll also run out to over 180mph.
With a third-party ECU and around 280bhp Matt was very happy with the setup and ran it in this tune for about three years before the temptation for more power started to get the better of him. The easy option would have been some manner of forced induction. But as you’ll have realised by now, that’s not really in his nature.
His appreciation of the Lexus engine made his next step an obvious, if complicated, one. The bigger and more sophisticated 4.3-litre 3UZ Lexus V8 has headroom for a lot more power and revs thanks to electronically-controlled VVTI. Physically the transplant would be easy, the source coming from a battered but mechanically sound GS430 bought for just £650. But making it work properly required delving into its electronic brain, for which Matt sought help from Phoenix Engine Management. He acknowledges there are third-party ECUS that would have made the engine function, but wanted the full range of OE calibration Toyota engineered for the VVTI. And no aftermarket code-cracking would fully be able to realise the breadth and refinement of the original Lexus setup.
Now with at least 300bhp Matt realised he needed a more substantial differential and fitted a BMW 330d unit sourced for £30, with custom driveshafts so he could keep the standard Mazda hubs. But big power, a light car and an open diff meant he had a problem and, as he puts it, whatever the road conditions, gear or throttle application, he basically had a one-wheel-drive V8.
Ever-ambitious, he rang Quaife, who clearly liked the cut of his jib and supplied an ATB unit to fit the BMW casing and make sure his extra horsepower was going to both wheels. That this was by far the most expensive part of the whole project speaks volumes for Matt’s improvisational skill and abilities. With his new V8 installed, a beefed-up BMW E39 M5 clutch tying the whole powertrain together, and the electronic brain happy, he was good to get out on the road.
He admits the 3UZ installation doesn’t look as pretty as the previous motor, and a chat around the engine bay reveals his knowledge and ability to pick the right bits to mix and match the right parts from an eclectic range of cars – the expansion tank is from a Suzuki Swift, while the radiator is a Nissan S13 unit. The engine mounts are burly Range Rover items that cost just a few quid but