SB Developments built its reputation producing potent, reliable GM (Vauxhall/Opel) XE engines upgrades, especially in 2.0-litre guise. But latterly, demand and market shifts have seen the company take on the new clubmans' favourites, the Ford duratec and the Suzuki Hayabusa. And SBD has been adding the benefits of some new technologies to its existing tuning expertise to tackle the task. THe results are a new lease of life for the venerable GM units, and tractability and power from the Duratec and Hayabusa.Those latest engine developments began when some of SBD's GM XE rally customers in Northern Ireland wanted to know why the Duratec appeared to be so strong.

So company principal Steve Broughton decided to start two parallel development programmes, one to see what more could be done with the XE, the other essentially to square up to the inevitable shift to the Duratec in club rallying, sprinting, hillclimbing and short oval racing. 'I wasn't to keen on the Duratec initially,' remarked Broughton, 'although in the mild state of tune we first tested it I couldn't believe how smooth and strong it was throughout the rev range. It was very tractable. We then did another upgrade, but this time with a little bit of cylinder head work and we easily produced 250bhp [all this work was one on the 2.0-litre varient], again with very smooth performance. We figured then that torque delivery was the key...'

CAMSHAFT DEVELOPMENT

The Hayabusa

'The thing with bike engines,' muses Broughton, 'is that they're highly tuned already. The standard 1300cc Suzuki Hayabusa produces 155-175bhp, depending on the year of manufacture. So it has taken a while to make good improvements, but a lot of what we have done carried over the work we did on the GM XE. The standard head is a better design than the XE - it has 33mm inlet valves and flows about 136cfm. However, we're now up to 155cfm at 1mm less valve lift than the XE uses. But it took us (ourselves initially, then our ex-F1 chap) two years to achieve all the improvements. We're using rather high valve lift, about 2mm more than most tuners.'

So, as well as applying the new-found techniques on headwork and cam profile design, what other modifications have these engines received? Broughton replies: 'I realised most bike engine tuners were doing similar things to each other, perhaps being somewhat conservative in areas such as cam lift, so I decided to develop it in my own way. With these engines it's about low weight, responsiveness and the way the power is delivered. And making power here means high rpm. So we've developed new, lighter con rods and again moved the gudgeon pin higher up to reduce side thrust, friction and wear. We've also had some special 'bridge' pistons made. Many tuners here buy pistons in from the USA, which are very cheap at £250 per set because of the current exchange rate, but they are actually heavier than the standard pistons. Ours are £850 a set, partly because the relatively low number we currently make means they are CNC machined from billet. However, they are made on the same machine as Moto GP race pistons, and they are lighter than the production pistons!' he exclaims.

This programme perhaps exemplifies SBD's attention to detail, and the effort has produced a remarkable 251bhp from the 1396cc version (see figure 3, Hayabusa 1396cc kit), representing 180bhp per litre. 'But,' say Broughton with his usual honesty, 'we haven't yet proved this for longer than hillclimbs so far.'

SBD carries a broad range of products for the GM XE, Ford Duratec and Suzuki Hayabusa engines, but company principal Steve Broughton reckons its best seller is ready-to-run fuel injection systems that come with pre-mapped MBE ECUs. Individuals, trade customers and racing schools have all bought such systems and, if required, Broughton will visit to carry out mapping refinements. Con rod and pistons kits are the number two best seller, and many go direct to the rade, especially when it involves product that others can't obtain reasonably quickly.

Engine kits are available from throttle body upgrades to full race specification. Prices start at under £2000 ($4000) for a taper throttle body kit and pre-mapped MBE ECU for the 2.0-litre GM XE (208bhp and 172lb.ft) to around £12000 ($24000) for the company's top end XE or Duratec kits.

An impressive 292bhp and 197lb.ft of torque have now been coaxed out of the 2.0-litre GM XE...leading to its continued use in a wide variety of clubman disciplines, from sprinting to hillclimbing.

As well as the works' Westfield, SBD Duratecs are also proving popular in singer-seater applications...as are the company's Hayabusa engines. Here a 1.6-litre version installed in an OMS hillclimb single seater.