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

Total MX-5 - - CONTENTS - Words: Dan Trent Pho­tos: Sim Mainey

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

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