UK-based SB Developments used modern technologies to improve three
tried and tested motorsport powerplants.
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.
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 variant],
again with very smooth performance. We figured then that torque
delivery was the key...'
British Aerospace engineer Steve Broughton established SBD
Motorsport in 1992. A club rally driver himself, he initially
supplied parts but then moved into engine building and, after
a fraught first six months, hasn't looked back. His early
engines proved durable and strong, attracting attention outside
rallying and, when a rally engine he built beat the works'
Vauxhall Astras, business took off. Work for various UK teams
was followed by a contract with Opel in Turkey involving rally
and Touring Car engines, as well as developing the FIA-homologated
'Kit Car' kit for the Astra Mk3. However , the time spent
arranging these works deals convinced him his heart lay with
club motorsport, and the business now focuses on developing
engine parts rather than engine building. A key aspect of
this is proving products in its own competition cars, so Broughton's
hillclimbing OMS is being used for Hayabusa development, while
long time friend Dick Hulbert's SBD Westfield runs the development
2.0-litre Duratec. SBD also develops software for MBE engine
management systems, for whom it is the main UK agent and engine
mapping services occupy much of Broughton's time.
what to do with the old GM XE then? 'The engine was getting
on a bit, so people were going to more extreme measures on
parts. But with demand for more performance we had to see
what was possible. The first thing was a two-ring slipper
piston, which Omega helped us with. This had a raised crown
enabling a higher compression ratio, although up to 1mm could
be machined off if required. And the pin was higher up in
the piston, too. The pistons alone released an extra 10bhp,
partly due to reduced friction but also through reduced side
thrust loads [which also gives very good wear characteristics].'
this time an ex-Formula 1 cylinder head design engineer approached
SBD with some work he had done on an XE head. This had yielded
an extra 25cfm of airflow across the valve lift range. Using
old SBD 'hydraulic' camshaft profiles and standard valves
this head developed 268bhp on an engine configuration whose
previous best was 252bhp. Steve Broughton: 'So we started
more work with this chap. Going up 2mm on valve size but using
a stock valve with a standard diameter stem [so that other
stock valvetrain parts could be used] he was achieving 155-156cfm
at 12mm valve lift, where the standard XE head gave 120cfm.
I'd never really gone much on flow bench work, and even now
it doesn't seem to necessarily correlate with more power.
But it this case certain areas such as the valve seats were
being carefully relieved. and with the cams as they were we
were getting more flow at high lift.
we decided to develop new cams with 10 degrees shorter duration
to flow better at lower rpm. To keep things affordable we
decided to limit lift so exotic valve springs weren't needed.
We then went to long time supplier and partner Kent Cams (see
sidebar). In the past we have tried high lift, long duration
cams but that's no good. And in this case we decided that
mid-range was key so we came up with new profiles combining
shorter duration with reasonable lift. As it happens we did
have to obtain new, improved springs but they're not too costly.
then went to Track N Road's rolling road in Essex, where a
number of well know engine developers do their testing because
it's an amazing, highly repeatable facility. We had also fitted
some new fuel injectors, 'disc valve' - types from Siemans,
which produce a very good fan pattern from two to 7bar. We'd
have been happy with anything over 270bhp. As it turned out
we got very impressive torque. I'd never seen anything like
the torque plot before (see figure 1, Vauxhall
TP290+bhp kit ). The engine pulled on full
throttle from idle and we saw peak power at 292bhp.
was understandably very pleased with this result, which almost certainly
surpassed what had been achieved in earlier years by the works GM Touring
and rally cars. But as well as the new cams profiles and CNC head and
inlet manifold work, the engine also utilised 35mm inlet and 31mm exhaust
valves, with slim 7mm valve stems, steel conrods, slipper pistons, a lightweight
steel crankshaft, dry sump lubrication and all the requisite high quality
studs, bolts and bearings to keep it all safe.
subsequently supplied a number of these kits to rallying customers in
Northern Ireland. 'But we then started getting calls from Duratec owners
who had spotted these fast XE-powered cars!'
chosen camshaft manufacturer is Kent Cams (www.kentcams.com). Steve
Broughton, company principal at SBD, explained why: 'In the past
there were limitations on how a profile could be shaped. Kent uses
a Lotus Engineering licensed software package called Lotus Concept
Valve Train (www.lesoft.co.uk) to assist with cam profile design.
This tells you about velocity peaks and so on, and allows you to
keep clear of high stress areas to avoid valve bounce, running off
the buckets, stress that causes wear and so on. 'Coupled to that,
Kent has invested heavily in the latest CNC equipment, much improved
grindstones and so on. This offers fantastic repeatability (plus
or minus two or three microns), and this really helps, especially
where there is little adjustment available. And it saves cost.'
in it al reservations about the Duratec engine centred on the lubrication
system and the hydraulic cam chain tensioner: 'The oil return has been
a bit of a problem, so we did some modifications to overcome that. And
we also developed a new cam tensioner, too. Subsequently, we have seen
no oil pressure fluctuations and minimal wear.'
Duratec's well-known strengths include significantly lower weight than
the XE (95kg compared to over 110kg), a fundamentally good head design
and a larger bore size (87.5mm compared to 86mm). This, together with
its pent roof combustion chamber design, allows decent size valves,
the standard sizes being 35.5mm inlet and 29.9mm exhaust. So for 2007
SBD started out developing a strong, reliable Duratec, initially using
the standard crankshaft but with steel conrods, 'pot type' pistons and
bigger throttle bodies fitted with eight injectors, four upper and four
lower for improved fuel dispersion. With what Steve Broughton called
'a sensible camshaft and just a little CNC head and port work' this
produced 283bhp and 192lb.ft.
continued Broughton, 'Ford produced a new head in the USA that allowed
10 per cent greater flow. We put in 1mm bigger valves and fitted this.
And with no other changes at all, the engine produced 304bhp and 195lb.ft
(see figure 2,Duratec
TP300+bhp kit ). It pulled from 1000rpm on full throttle,
it was smooth and there were no bottom end losses.' and this was still
mild cams. Running with just four lower injectors only dropped the power
by 10bhp, which was still impressive and ahead of the XE.
efficacy of SBD's cam profiles on the GM unit, the logical next step
was to apply this principle to the Duratec. So new cams were designed
based on the shorter duration, high-lift ones that worked so well in
the XE. To considerable consternation through, the result was 4bhp less
and 10lb.ft less torque. Broughton: 'The engine peaked 300rpm later,
made less torque from 4000rpm, and only made the power it did because
it revved more. It shouldn't have suffered a loss with the increased
lift though, suggesting the duration is just too short for this engine.
The fact that it peaked later is odd too. And that's where we are now
[in April 2008]. The next step is some slipper pistons with smaller
valve pockets and cam profiles that will combine the original duration
with the lift of the cam that didn't quite work.'
already produced a 2.0-litre engine generating over 300bhp is no mean
achievement, and to publicly admit a backward step in development emphasizes
Broughton's determination (and confidence) that yet more performance
is still to be obtained from the Duratec.
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.'
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.
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.'
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 trade, especially when it involves product that others can't
obtain reasonably quickly.
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.
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.
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
Taper Throttle Kits | Duratec
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