What Size Turbo For A Stock Hayabusa Motorcycle

It'south the well-nigh powerful petrol-powered wheel in the world and it'south a Suzuki. And it's been congenital in Britain. And so we checked out Big CC Racing's ultimate turbocharged Hayabusa.

If we asked you where you'd observe the most powerful motorbike in the earth, you'd probably be thinking overseas. The USA probably – they like things big over there. Or maybe in a loftier-tech tuning bunker in Japan. Perhaps the work of a Russian billionaire or a Saudi oil prince. And what bike would information technology be? A handmade, machined-from-barracks one-off V-eight? Something with an aeroplane engine?

But the truth is a bit more prosaic. Because the most powerful, petrol-fuelled, production-based bike in the world lives in a small industrial estate in Wokingham, not far off the M3. And backside the huge turbocharger, long swingarm and garish drag-race paint lies ane of the very first Suzuki GSX1300R Hayabusas, launched dorsum in 1999.

Rather than a Russian oligarch though, the owner is an ex-para from Scarborough. Sean Mills started up Large CC Racing when he left the British Regular army in the early 1990s, and he's been building elevate race bikes and high-bhp turbo engines for nearly three decades now. This Hayabusa was bought by Sean make new in 2000 from UK dealer Robinsons Foundry, and it'due south now both his rolling test-bed, and his life's work. A magnum opus, if you lot volition.

The spec is fantastic, and the performance even more so – this bike makes 936-odd bhp, at the tyre, on the dyno. In other words, it produces about 785bhp more than the stock bike. Upwardly from effectually 152bhp to 936 – more than six times the original ability. Even more astonishing, that effigy equals about 1,050bhp at the crankshaft, one time you lot account for the usual frictional losses in the transmission.

So how do you lot get so much power from a bicycle? Well, merely about every function has been changed, although Sean'south Hayabusa withal uses the standard crankcases, barrels, oil pump and cylinder head, besides as stock gearbox bearings, gear selector, valve buckets, and fifty-fifty the valve spring retainers. But there are, essentially, three main elements to an engine build like this. Kickoff of all, you need to brand the internals strong enough to handle the torque produced at such huge power outputs. Then, you need to be able to pump the required amounts of air through the engine. Finally, you demand to add together the tremendous slugs of petrol needed for each combustion, and light it upwardly properly.

In some ways, the first part – holding the engine together against the enormous combustion forces – is the well-nigh straightforward to empathise. Sean'due south fitted out the Busa with the very strongest components he could specify – starting with custom-made 'Carrillo for Wossner' con-rods rated at 1,000bhp, made by rod-maker Carrillo, to tuning firm Wossner'southward design, and a billet stroker crank, balanced and polished. Forged pistons by Wossner are stock, off-the-shelf low-compression turbo slugs. A super-strong MTC barracks clutch assembly, and a billet race wide-ratio four-speed gearbox by Nova Racing. Finally, the crankcases, block and head are all clamped together by massively-strong oversized 12mm head bolts, heavy-duty crankcase studs and nuts, high tensile lower instance bolts and machined billet pins instead of stock locating dowels between the cases.

To make that power means flowing a veritable tornado of air through the engine on each cycle. Sean's started off with a bigger than stock motor – the long-stroke crankshaft increases the stroke past viii.5mm, upwards from 63mm to 71.5mm, and the diameter is up 2mm to 83mm, giving a total capacity of one,547cc. Kent Cams supply a custom super-radical cam profile, to slam open up the big valves as far every bit possible, as apace as possible, for as long as possible, to give enough fourth dimension and valve area to get all the air and fuel in.

Simply Sean needed to make this engine comport as if it's far bigger even than 1,547cc, and does that by using a turbocharger. The turbo uses pulses in the exhaust to spin upwardly a compressor wheel, pumping air into the combustion chambers at high pressure. More air means you tin burn down more fuel, and that means, ultimately, more power. On the 935bhp run, the turbo was pushing air into the cylinders at 46psi. To keep that pressure up, while supplying the huge amounts of air the engine is sucking in, takes a huge turbo. The Big CC wheel uses a heavily-modified, ane-off Owen Developments Garrett GT turbo, rated for over 1200bhp in a car engine. With all its paraphernalia and the manifold pipe, it'due south every bit heavy equally lifting an eight-year-old child. Running a turbo at such high levels makes a lot of estrus – heat that has to be gotten rid of. So the pressurised air is fed from the turbo, into a water-cooled chargecooler. Connected to a common cold h2o supply, and filled with ice for a drag run, the chargecooler keeps the intake air as cold and dense every bit possible, for the best ability.

So that'southward the super-strong engine, and the ways to get the right corporeality of cool, dense, high-pressure air inside it. All Sean at present needs to do is get the fuel in in that location.

He uses enormous high-flow race injectors, running off a high-pressure race fuel pump, and controlled past a Motec ECU engine management system. The fuel itself is interesting – non for what it is, merely what information technology isn't. Most superlative-ability engine builders, especially in the The states become for booze (methanol) every bit the fuel instead of petrol. Alcohol is easier to become big power from, since it resists knock much meliorate than petrol, plus information technology has a very strong cooling event inside the cylinder, and most people reckon there's a fifteen per cent power gain from using alcohol. Sean stuck with petrol though (albeit high-octane MaxNOS 118 race gas), partly considering he started tuning this bike on petrol back in 2000, and partly because alcohol is much more maintenance-intensive on the fuel system. Perhaps surprisingly, the cycle uses stock non-resistor spark plugs, merely with a smaller gap and fired by a very-loftier-free energy Motec CDI ignition system.

Finally though, all that power needs putting down. The MTC clutch uses a special lock-upwards machinery, using centrifugal weights that clamp the plates harder together the faster information technology spins, and Sean swears by standard Suzuki clutch plates.

The output shaft is a special long design, which uses a Psycle Workz external outrigger bearing plate, so the gearbox sprocket is supported on both sides. An EK DRZ2 racing non-'O'-ring chain drives the rear Mickey Thompson drag tyre, and Sean'south so confident in the EK quality that he sticks to a 530 concatenation, rather than a larger 630.

We watched Sean every bit he went for the ultimate power runs on the bike. He'd been building the bike all terminal yr, fine-tuning the turbo and engine management setup, computing the heave required for his 1000bhp+ target. Unproblematic maths told him he needed to striking 46psi from the turbo, and he gradually worked upward to that betoken over a serial of runs. There were hiccups: dyno straps broke, the dyno itself doesn't similar its drum going over 200mph, and the loftier-power ignition organization was confusing the dyno's rpm sensors.

And information technology'due south not a simple task running a bike on the dyno at this level either. You can't just open up the throttle, and wait for the rev limiter, because with this much ability, hitting the rev limiter can snap the crankshaft, or blow the engine completely. Cut the spark to i cylinder suddenly, and the unbalanced torque going through the creepo can break it. And if you take the massive quantities of high-octane MaxNOS 118 race petrol swilling nearly unburnt in the cylinders, it tin explode when the sparks come back, or even hydraulically lock the engine. None of this is skilful news, and Sean has to exist incredibly careful – especially since the motor spins up so chop-chop at peak ability. Indeed, plotted over fourth dimension, the Hayabusa gains 630bhp in 0.ix seconds on the dyno – explosive power indeed.

Sean's fix to get for broke though. He's planning to tear the engine down subsequently these runs, and he's spent the last week troubleshooting the dyno with a series of 800bhp+ runs. At these levels, the slightest problem can cease everything. He had to stop measuring the tacho RPM signal because the high-energy ignition system was crashing the dyno's sensors. Then, the bike started to hit 200mph, over again, exceeding the dyno'southward parameters, and giving an error message. The dyno ratchet straps started to give, and at that place was a constant battle against clutch and tyre slip.

But the solar day we're there, the final 24-hour interval, all is set. Sean had hit nearly 900bhp the previous day, at a lower level of turbo heave, but he'd cranked it all up for one concluding go. With 46psi dialled into the turbo controller, he set off for the terminal big run. Standing in the dyno prison cell is a mixture of apprehension and excitement. The bike starts easily enough, and then Sean clicks up in to first, second, tertiary gear. A pause while he hits various buttons on the dyno, and boom – full throttle. The bike lurches frontwards, even though the straps are bowstring-tight, and the dissonance rises, slowly at start, and then in an inexorable torrent of sound and fury. The heave judge hanging off the side of the bike whips circular in an instant, and Sean whips the throttle closed, trying to catch the motor merely equally it hits meridian revs and power. Phew. No boom, no con-rods out the front end of the engine, no flames or explosion…

A wait at the screen shows an incredible 936bhp! Sean looks kinda satisfied, but reckons in that location's something amiss. Information technology's the most power he's had, and he'll settle for that for now. Merely comparing today'southward run with the best from yesterday, information technology's clear that this run, while better at the height, is running less well than yesterday. Sean later on discovers that at 1 point, the stainless steel strap bolting the plenum bedroom onto the intake stubs had really fractured from the stress. And then the boost was leaking all the mode upward to 936bhp on the terminal run. If this £15 part had held together? Sean reckons he'd easily have had 1000bhp at the tyre…

Just plenty'southward enough. Mayhap next time. Information technology's notwithstanding a ferociously fast, enormously powerful Hayabusa.