Radical SR8

To the casual observer, it has always seemed so obvious. Take the top halves from two modern multi-cylindered motorcycle engines, complete with all the trimmings necessary for stratospheric revs, bolt them to a common crankcase and there you have it. A V8 of two litres or more, revving to 10,000 plus and churning out about 300bhp – or double the amount one bike engine gave in the first place. You don’t have to make all the clever bits like the cylinder heads and valvegear and the result will be destined for a gap in the market which the likes of highly modified K-series are still struggling to fill. Easy isn’t it…

Well, yes, but… no. As anyone who has ever tried to adapt anything modern and mechanical will know, every last part will have been developed to suit a unique purpose at the least possible cost, so it is never quite that simple. The two concerns which are currently making bike-based V8s will know that only too well but meanwhile the prospect of eight cylinders and 10,000-plus revs remains as massively exciting as ever. Small lightweight V8s just don’t exist and yet I’ve never encountered anyone who didn’t come over all wistful at their experience of Cosworth DFV power. Sadly, it will remain a thrill available only to those with about £60,000 to spend but a modern bike-derived V8 might just be affordable, and that makes it more tantalising still.

The first of those on offer, the Yamaha-based RST 2 litre, has endured a very lengthy gestation – the prototype was first mooted about 10 years ago and since then, progress has depended on funding which has not always been swift in coming. We tried it in last year, mounted in a Caterham, and with some allowance for minor development glitches in details like mapping of the engine management, it was very promising, and very exciting. If it really does cost a similar amount, you would never swap the V8 for a K-series, no matter what its state of tune.

The second is a 2.6 litre by Radical Motorsport’s engine partner Powertec and is based on the 1,300cc Suzuki Hayabusa, which powers the company’s Prosports race car. Radical is a much bigger organisation and its V8 has been much swifter in reaching fruition; it was just two years ago that the plastic mock-up was displayed at the NEC show. In addition, Radical’s customary dedication to the cause had already ensured it had its own test bed in the shape of a modified SR3.

Radical will sell you an engine if that’s what you want, but it can also sell you a fully-developed SR8 sports racer to go with it, complete with bespoke six-speed sequential transmission, and its after sales service even includes opportunities to compete with your new acquisition. Radical has been smart enough to realise that a place to race was an essential ingredient in the sales message, and that the current club infrastructure was unlikely to provide anything which suited its purpose.

Radicals at Brunters

I caught up with the Radicals at a damp and windy Bruntingthorpe where company principals Phil Abbott and Mick Hyde explained the details.

The Powertec 72 degree V8 is mounted in-line rather than across the engine bay, a detail which Hyde will admit immediately changes the complexion of the car. Radical have spent a huge amount of money and effort developing the 1,300cc four cylinder Hayabusa engine and the transmission solutions which replace the bike’s chain final drive, but there were still those put off by its origins.

That said, Radical’s original intention had been to use the bike transmission for the V8 and the turbo version -- which now looks like something of a blind alley -- was intended to research the possibility. Hyde insists the Suzuki box was man enough and could have worked but the decision was, nevertheless, made to put the engine north-south and to work jointly with transmission specialist Quaife to make a six-speed in-line transmission featuring an extra pair of drop gears to reduce the engine’s 10,000 revs. A conventional AP twin-plate clutch transmits the drive.

A special bellhousing mates the ‘box to the engine, forming a brace to tie the cylinder heads together, as well as incorporating the swirl pot and dry sump oil tank fed directly from the crankcase. The brace damps out resonance, which is a potential source of stress and, like much of the oil scavenge system, is a detail inspired by the likes of Audi’s RS Le Mans engines; the rest was the work of former Lotus, TWR and Jaguar designer Steve Prentice, and Powertec’s David ‘Ted’ Hurrell.

Engine internals examined

The crankshaft is flat rather than offset, guaranteeing a DFV wail rather than a Chevrolet rattle. To the offside is a shaft driven by a gear on one end that spins a separate scavenge pump for each of the engine’s pair of cylinders; recovery of oil is a notorious problem in racing vee engines. The shaft also drives a pair of oil pressure pumps and, on the back end nearest the gearbox, a rotary vane-type water pump. In the opposite side of the crankcase, a gear on the flywheel end of the crank drives a pair of counter-rotating balance shafts turning at twice engine speed. This leaves only a substantial alternator to be driven by a belt which, like the starter motor, is car rather than bike-derived.

In this ‘basic’ 2.6 litre version, the cylinder blocks, heads, pistons, rods, valves and cams are all standard Suzuki. Hyde says it made sense to use as many original parts as possible; not only would it be cheaper than making them specially but it meant they weren’t ‘re-inventing the difficult parts’. By that he means the top end of the engine in which the Japanese engineers have so cleverly installed longevity at 10,000rpm. The desire to retain such qualities is why one block is turned 180 degrees from the other in order that each one’s original chain cam drive can be retained – plus of course, the exhausts then exit on the outside.

Weight and power

The engine is extremely neat although not perhaps as small as you might have expected. It is light, though. Abbott says it weighs around 92Kg, a staggering 50Kg less than a DFV (140Kg). When Powertec develops a 3-litre version based on the company’s 1,500cc Hayabusa conversion -- already a favourite with SR3 buyers -- it should give similar power. The claim for the 1,500 is 250bhp so, for a V8 version, Hyde reckons a conservative estimate is an ‘easy 450bhp’ – or about what the first DFVs gave in 1967.

The 2.6 is extremely conservative as you would expect for a first effort (compression ratio is just 11:1 rather than the 13:1 of the 1.5 litre) but despite that it still pushed out 383bhp at 10,000rpm. Odd how that sounds so impressive whereas 140bhp from the latest 1300 might sound merely ordinary. As I said, it’s a niche which is waiting to be filled.


Abbott and Hyde are able to predict the all-important purchase and running costs, based on their extensive experience with the fours. They estimate between 30 and 50 hours of running – depending on state of tune -- before an overhaul is necessary, something which they hope should cost no more than £3,000. As Hyde says, they can think of no reason why it should be more than double the four-cylinder's price.

A ‘dressed’ 2.6 (with pumps, generator and starter) Hyde says, will be about £17,000, with another £3,000 for the ignition and ancillaries while the transaxle complete with limited slip will be about £6,000, all figures plus VAT.

Comparisons with historic Grand Prix engines like the DFV are not strictly fair – to my mind they serve more to illustrate what an exceptional thing that 35 year old power unit was – nor is any contrast with the much more powerful 4-litre Judd V10. You nevertheless have to note that after 10 hours a DFV has to be overhauled at a cost of £12,000 and a Judd is nearly double that. In a market where there is almost no competition – where else can you buy 380bhp from 92Kg? – the Powertec V8 almost can’t help but look like a bargain.

The SR8

Then there’s the car – the SR8, which without an SR3 on hand looks almost identical to a relative Radical novice like me. Not so, says Hyde who then takes me on a tour to prove it. The front end is different, both to accommodate the front-mounted radiators which exhaust via venturis on the flanks and louvres on top of the wheel arches, and to mount the new undertray. This, together with dive planes on the corners of the front wings, new rear underbody venturis fed by turning vanes in the sidepods plus a new biplane rear wing all combine to develop a staggering 2.5 times more downforce than previously.

The cynic in me was prompted to ask whether preceding efforts had been lacking or whether there was now sufficient power to make any extra drag worthwhile, but my question was politely ignored. Phil Abbott later mentioned that the rear undertray had torn itself off its mountings during the previous test – and the front would follow suit when I tried to better 160mph for the umpteenth time – so we’ll give them the benefit of the doubt. Let’s just say it obviously works.

Rear bodywork is different too because the engine’s vee drops the plenum down lower and a smaller hump can cover it, and the tail end is different where the exhausts exit. Brakes now feature floating discs and the driveshafts are bigger and tougher. So, yes, almost everything is different and you can have a race model for £55,000 (plus VAT) or a track day version for £50,000. Radical says it has more forward orders for the SR8 than any car in the company’s history and that deliveries will begin in April.

Driving the beast

And so to the drive, which if I say was completely uneventful, should read as the best possible compliment. The test engine had already undergone some 100 hours of testing on both dynamometer and rolling road and has undergone one precautionary strip to check for potential problems but thus far there has been nothing serious whatsoever to report. Apart from the car sucking itself apart, there has been nothing nasty during the track work either.

Clambering into the SR8 reveals standard Radical – that’s to say comfortable with everything to hand and in its proper place and with a quick shuffle of a long lever to check for neutral, you leave the accelerator alone and churn the starter. A second or two later and with a guttural bark, the V8 fires up.

Phil Abbott had already said the clutch was monstrously heavy and that the gearshift had become rather snicky during the latter half of the test programme and that these were items on the to-do list but clearly he doesn’t drive historic cars very often. I’d have said either was perfectly acceptable when compared with the majority of Hewland FT or Mk 9.

Clonk it gently into first, ride the clutch against a stack of revs and away you go. Seems perfectly natural as well but Phil says this is another thing that will be fixed. Mapping at the bottom end is still not finite. They had recently taken some fuel out to reduce the two foot long gobs of flame exiting the exhausts on each downshift, introducing some kangaroo factor at pit exit speed. Radicals are perfectionists, no doubt about that: had this been a BD, FVC or almost any car engine with the potential for 380bhp, you’d have said it was fine. Then comes the exciting bit.

Track attack

The SR8 attacks the track in a style that only a light car with a powerful engine can affect. The flat out twitch and slither in fourth which tugs your head in all directions as you sear onto the puddle-strewn main straight is the stuff of a proper prototype, and yet once above tickover the engine is as refined as any in the best road cars. Unlike the DFV which tickles every part of your anatomy, the SR8 feels utterly, completely smooth at all times.

In addition to the balancer shafts inside, the engine is rubber rather than solid mounted like its four cylinder brethren, and it’s quiet too; the silencer had by then blown out most of its stuffing but the V8 howl was still sufficiently muted that the Bruntingnoise police felt no need to intervene.

Not that you need to wind it past 10 in every gear unless you want to, because the spread of power is wide. The engine pulls smoothly from as little as 2,000rpm, then grows ever stronger all the way through the range towards 10. Which, without wanting to damn with faint praise, is exactly what the standard Hayabusa does and exactly what Radical is trying to harness in double measures.


Which it has and, more to the point, made it usable and reliable. Make no mistake, 380bhp in a 550Kg sports racer is mighty quick in anybody’s terms. The track was damp, the tyres were worn out, the SR8’s ride height had been raised by a large chunk to cope with passengers and the track’s surface (Bumpingthorpe…) and the rear undertray was missing. Despite that I managed a lap time less than a second shy of the best Radical test driver and all round superfast Dutch chap Michael Vergers ever did in the turbo version on a dry road.

And no, that ain’t because I am a hero. It was cold and the road was wet and with its hobbled setup, the SR8 was understeering far too much through the slow and medium speed corners, and was picking up an inside rear and snapping into oversteer on the exits.

The time came simply from the acceleration of the new engine which produced a genuine 160mph before the right turn off the straight on Gruntingthorpe’s short circuit. It was a terminal velocity that finally brought a rattle and shake from the front that sounded and felt for all the world like two shredded tyres. The front undertray – which Abbott says had previously proved capable of supporting his entire body weight – had torn through its mountings and was flapping in the breeze.

By that time, I had already done a fair few laps and so had Phil, yet the engine displayed no serious temperament of any kind. Radical will now do what it is good at and refine the last few details to make sure the track day market faces as few challenges as possible. There's no doubt in my mind though that the engine will have a similar effect on the amateur race world – not to mention the low-volume car market - as did the K-series, or Ford Kent, or perhaps more relevant, the overrated bulky old donkey that was the Rover V8.

Future plans

Radical has ambitious plans for the future that include the international sports car categories and even Le Mans, a race which he reckons you might soon be able to tackle with an LMP ‘costing less than £100,000’.

Can’t wait to try the 3-litre version, not least because I know Mick Hyde or Phil Abbott will say what they always say, which is to go out and do as many laps as I like. At £10 per mile, DFV owners just never say that.

Comments (11) Join the discussion on the forum

  • MEMSDesign 17 Feb 2005

    Top article. Any chance of some more pictures of the engine, since that's the star of the piece?

  • z_chromozone 17 Feb 2005

    "the overrated bulky old donkey that was the Rover V8."

    Will it still be powering cars in 50 years time, nah.

    The car and engine do sound fantastic though


  • jamieheasman 17 Feb 2005

    Fantastic, it's about time this sort of engine became available.

    My only surprise is that it requires a 'refresh' after 30-50hrs. I wonder how long the engine would be able to soldier-on as a road-going track-day car. Say 80% road use. I'd have thought the engine would have a similar life-span as the standard 'busa engine, after all most of the parts are standard.

    I wonder if it's possible to purchase conversion parts to allow two 'busa engine to be bolted together?

  • chunder 18 Feb 2005

    With overhaul at 50 hrs I'll stick with the overrated bulky old donkey that is the Rover V8 thank you.

    Mark Hales has a race team and sponsors to do that stuff - most don't.

  • Mark Benson 18 Feb 2005

    Should I cancel my subscription to Circuit Driver? Seems I can read the articles on PH for free these days (Boxster one a few eeeks ago was from CD too).

    You scanning them in on the sly Ted

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