February 2004 911 & PORSCHE WORLD
We have brought you stories about modified Porsches before, but this one's just a little bit special. Over the past 18 months or so we've been following the construction of a unique rally car, almost from the first fabrication right through to its mud-spraying special-stage tests last November.
When in 2002 Ian Jemison told us he was building a Porsche for special-stage rallying, it was a project that immediately caught our attention. Because Jemison hadn't chosen to go with the flow by building a replica 1960s' 911. He had decided instead to build a rally Boxster. And after you've seen how he went about it you'll wonder why no-one else has done the same. Jemison is a typically down-to-earth Yorkshireman who calls a spade a spade. And you can't help being swept along by his infectious enthusiasm and his obvious expertise in his work. Describing his extensive engineering background and long experience of national rallying in Britain, he delivers the perfect endorsement for his new Boxster project. He is certainly no stranger to top-quality mechanical engineering and rallying at the highest level - especially, as it turns out, with rallying Porsches.
'Twenty-five years ago I was co-driving with "Piggy" Thompson [father of British Touring car driver James Thompson - PM]. Piggy was the first man to win a national rally in a Porsche. At that time, though, I was more involved with Vauxhalls. In fact, I built a Chevette that he drove while I navigated, and that's what got me into rallying.
'I had done an engineering apprenticeship before all that. While I was at college I had realised that welding with metals such as aluminium and magnesium was very much an unknown art, so I applied myself to learning all I could about it.'
But instead of taking the easy option and working for an established engineering company, Jemison decided to go it alone, repairing light-alloy wheels for fellow rally competitors and doing other general engineering work. Meanwhile he continued to build rally cars for himself.
'After that first Chevette I built a second car for myself. Later I built a mid-engined Nova with a mid-mounted, two-litre, 16-valve Astra engine. It was very competitive because it was light and had plenty of traction. After that I went back to a Chevette with a 260bhp Omega V6 engine which I rallied for another ten years.'
The Chevette underwent continuous development through the 1990s, and the numerous awards that festoon Ian's workshops are testimony to the car's competitiveness. But almost inevitably he wanted more. 'The problem was that there wasn't much potential left in it, so I started to look around for something new.
'The RAC has a class for non-homologated, series-production cars. You have to keep the engine in the original position, but everything else is free. I thought about a Lotus Elise, but it was too small. It was also built out of aluminium and glassfibre bonded together, which didn't give much scope for development - or my welding skills. I briefly considered a Toyota MR2 and even an MGF, too, but I have a Porsche 911 as a road car. That set me thinking about the Boxster, and wondering if, just maybe, one of those could be the right way to go.
'One of our service crew had a Boxster "S" that he lent me for a weekend, and I did some back-to-back testing with my 911 [Remind me never to lend Mr Jemison my car for a weekend - PM]. After that we decided that, yes, the Boxster would make a very good rally car.'
To this end Ian acquired an insurance write-off 2.5-litre model from Prestige Salvage in Leeds towards the end of 2001. 'I do a lot of business with them, and they're probably the biggest Porsche breakers in the country,' he says. 'They've broken up a lot of Boxsters - and 911s, too - but the insurance companies normally insist that the body shells are destroyed. So, while there are plenty of mechanical parts around, there aren't too many shells.
'I told Prestige that if they could come up with a shell I'd buy the rest of the parts from them, so they found one from a car that had been reshelled in Holland. It was ideal because it had very little damage. But since the car has been constructed from an unregistered body shell it has to gain Special Vehicle Approval from the DVLA [Driver and Vehicle Licensing Agency, the UK registration authority - PM] prior to being given a certificate of roadworthiness.
'Luckily, the only difference between the left- and right-hand-drive models is a panel bonded into the front bulkhead. Prestige supplied me with a right-hand-drive panel, fuel tank, steering rack and dashboard panel, which all made for a remarkably straightforward replacement.'
The standard body shell is already very stiff, but Jemison has strengthened it still further to cope with the special demands of off-road rallying. The first addition was a comprehensive roll-cage.
'I'm a motorsport-approved manufacturer of roll-cages,' he continues. 'We've built all sorts for people over the years, and specialise in one-offs and prototypes. We built this one for the Boxster using guidelines laid down in the MSA Blue Book [the rule book of the British motorsport governing body - PM], adding what we felt was needed in order to achieve the maximum torsional stiffness. 'We took advantage of the strong bulkhead ahead of the windscreen to tie into the front section of the roll-cage. Porsche has used metal of varying thickness there, adding strength where it's most needed.'
Ian replaced the standard car's aluminium rear crossmember with a tubular-steel structure, which picks up on the standard engine mountings but is much stiffer and stronger. 'And although it's made out of steel tube,' he adds, 'it actually weighs the same as the aluminium crossmember.'
In the front compartment a specially constructed steel enclosure for the central water radiator adds to the front-end stiffness. The radiator is a one-off by Pace, one of many specialist motorsport suppliers which supplied parts for the car. It has 50 per cent more capacity than a pair of Boxster 'S' radiators and with twin fans is more than enough to keep the engine cool.
Perhaps surprisingly, Ian left all of the external body panels as they were, in their original steel. As he explains, there was little reason to change them. 'I don't think there's anything to be gained by swapping them for glassfibre panels. They've already been designed to be as light as possible. And when you consider what a rally car routinely has to cope with, glassfibre panels begin to seem a little fragile.'
The external appearance is completed with a fixed rear spoiler and a standard (removable) Boxster hard-top, which covers the roll-cage and gives the car at least an air of normality from the outside. The cockpit, on the other hand, looks quite unlike that of any other Boxster you've ever seen. It has been totally stripped of trim and is now dominated by two OMP racing seats and six-point harnesses with three inch-wide webbing.
The car is equipped with heating - an important asset if you wish to prevent the windscreen fogging up - or even icing up - at the wrong moment. Although the standard dashboard panel remains in place, complete with fresh-air outlets at the top of the centre console, a Stack digital display now allows Ian to monitor the engine.
What remains of the centre console also contains controls for the on-board fire-extinguisher system, a battery master switch and the fuse panel. A Coralba trip computer allows the navigator to keep track of the car's position on the road. The other non-standard item is the fly-off handbrake, a tall lever next to the driver's left hand that allows him to swing the tail around on loose surfaces. Without a doubt this is as purposeful a cockpit as you will find in any well-prepared rally machine.
Having completed the initial fabrication work needed to stiffen the body shell, Ian turned his attentions to the suspension and engine. The results are nothing short of works of art.
'For a road car the original suspension was perfectly adequate, but the aluminium parts – the links and the bearing carriers, for instance – were likely to break under rally conditions. They would be particularly vulnerable on forest stages, where it's very easy to clip a rock or tree root.
'A broken suspension arm means you're out of the event, but a bent one might let you drive slowly back to the service area. So we decided to replace the cast-aluminium suspension links with fabricated steel tubes, which are more likely to simply bend than to fracture. A thin-walled steel tube also tends to be lighter than a thick aluminium casting.
'Because after-market parts for Porsches are generally aimed at racing rather than rallying, the only after-market suspension kit available from Bilstein would have resulted in reduced suspension travel. But that was completely the wrong way to go for us. Even on Tarmac stages you need a lot of suspension travel.
We approached Pro-Flex, which supplies struts to several of the World Rally teams. The company made us a one-off set-up for this car that has 40mm more travel than standard, with adjustable spring platforms to alter the ride height. They also have a nitrogen cylinder feeding them that increases the capacity of the strut itself.
'The Pro-Flex units offer the facility to adjust the bump, rebound and the response speed of the strut. That's useful for a rally car that drives on many different types of road surface. Rally suspension is always a compromise, but you need to be able to keep the wheels on the road. We can turn an adjuster and tune the handling to the road surface, whether it's hard for smooth Tarmac, or soft for a rough, forest track.
'The struts have spherical top bearings with roller bearings in the body to prevent the struts sticking under load. And while the suspension geometry is exactly the same as standard at the front, we've gone for two parallel lower links at the rear – they give it more strength. All these links are located with spherical bearings.
'Having decided to go for the Pro-Flex struts we then had to fabricate new wheel-bearing carriers in steel all round. As a result we can adjust the camber at the front from negative to positive, which you can't do with the standard set-up because the strut and carrier are built as one.' A close look at these black powder-coated fabrications reveals the exquisite build-quality that's the hallmark of every aspect of this car. In fact, the entire front strut, brake and hub assembly weighs a mere 21 kg per side, which compares very favourably to the 31 kg of the standard components.
The brakes are by AP Racing, with four-piston calipers working on ventilated discs. The brakes had to be changed because the necessarily smaller 15-inch OZ forged-magnesium rally wheels wouldn't fit over the standard calipers.
These wheels are extremely light, have the right offset for the Boxster, and accommodate the special 15-inch-diameter rally tyres. Ian Jemison has also designed an ingenious brake-balance mechanism that allows the driver or navigator to change the balance front to rear from the cockpit – a particularly useful feature on loose-surface rallies. But why the use of smaller wheels, which, incidentally, have only four-stud fixings?
'For forest rallying we have to run a 15-inch wheel because all the WRC tyre development is on these smaller rims,' Ian explains. In the forests he's going to try Spanish-made Matador tyres. Their high 180/65 profile gives a little compliance if the tyre hits a rock or a deep rut. For asphalt driving, though, 18-inch wheels are used with mainstream Pirelli or Michelin tyres. And this isn't a pursuit where you worry too much about tyre wear. In fact, Ian would expect to get through about four rear tyres in a single event, each lasting only 20 to 30 miles. Fortunately there's a good supply of partly used ex-WRC tyres.
Ian is modest about the modifications he has made to the 996-model, 3.4-litre flat-six.
'Nothing much has been done to the engine yet,' he says somewhat dismissively. `And the fact that nobody has really raced or rallied one of these means that we're a bit in the dark as well.'
The motor was built up by David Sunderland, the engine expert at independent Porsche specialist Strasse in Leeds, which also supplied invaluable technical support and new parts for the car.
'From the beginning it was quite obvious that we needed to make a completely new exhaust,' says Jemison.
'Wun-Off Exhausts of Shipley fabricated the beautifully made stainless-steel exhaust, which includes the standard catalytic converters and repackable silencers. We also had to alter the fuel-injection system to fit the Boxster. To that end, we made new throttle bodies and added a new ECU.'
The fuel-injection system is a masterpiece of fabrication. Ian had previously developed a system for the Omega V6 engine in his rally Chevette. 'We changed the injection on that and gained another 60bhp,' he recalls with a smile. For the Boxster he has had six gorgeous-looking injection trumpets fabricated in place of the standard induction system.
'It gives a much better airflow into the engine, while putting the injectors high up behind the butterfly gives better fuel mixing. The only reason for putting the injectors close to the ports in the road cars is to achieve lower exhaust emissions. For power, which is obviously what we're after, it makes much more sense to mix the fuel and air early in the induction system.
'We've also optimised the injector trumpets for the capacity of the engine. That work was done by Jenvey Dynamics, who make throttle bodies and manifolds for most of the major tuning firms in the UK. We used their computer programme which optimises the length of the exhaust for maximum torque,' Jemison explains.
The other feature that promises much is the programmable electronic control unit (ECU) supplied by DTA in Bradford, with the installation optimised by Wayne Schofield of Chip Wizards. The ECU even gives Ian the facility to include traction control and a launch control for starting — definitely exotic features for a national rally machine!
Bolting the 996 engine into the Boxster was straightforward once the tall inlet ducting had been removed, although Ian has fabricated a stronger front mounting. 'You make some hard landings in rallying,' he explains, 'and I was concerned about the strength of the standard pick-up points, which only bolt on to the water manifold. Just to be on the safe side I made up some new steel supports.'
The other aspect that demanded attention was the tendency of the standard water-cooled flat-six to suffer from oil surge during fast cornering. Ian discussed this at length with others who've coped with the standard 996 engine in competition. Porsche itself couldn't help — the 911 GT3 and the engines Porsche uses in motorsport are based on the block developed for the prototype GT1 race cars, rather than that of the production 996 Carrera. After considering an ingenious American oil accumulator system Ian eventually installed another oil pump in the left-hand cylinder head, known to be the worst-affected area. He has yet to test this solution in the heat of competition, but everything looks promising so far.
After seeing Ian's car take shape over almost two years we were excited to be invited back to York to see the car last November. Now painted, signwritten and fully equipped ready for competition, it looks — and sounds — absolutely amazing.
The finished Boxster rally car now weighs just 986kg without fuel, oil or crew — that's a whopping 334kg lighter than a standard Boxster 'S'. And there's a good 350bhp at the flywheel, reckons Ian, so it's not hard to understand why he has such high hopes for this extraordinary car.
We watched in awe as Jemison confidently flung the Boxster around the disused airfield at Acaster, just south of York, marvelling at the car's obvious power and superb balance. After he had demonstrated what it could do his grin stretched from ear to ear. This is clearly a machine to watch in the future.
'We'll do what we want to do,' he says, answering our question about where and when he'll compete. 'It'll be a mixture of Tarmac, forest and national events.' But he does enjoy competing in Ireland and on the Isle of Man.
'They tend to be Tarmac events and they have better roads,' he says, smiling at the prospect. Whatever adventures await Ian Jemison's Boxster, you can be sure that we shall bring you the news here. Like Ian himself, we can't wait to see if the huge potential this stunning-looking machine promises will be realised. And one thing is absolutely certain — the Jemison Boxster is going to make headlines wherever it appears.
Earning a living
The process of building his Porsche Boxster rally car has inevitably had to fit in around Ian Jemison's mainstream business which, after 25 years of growth, today goes from strength to strength.
We do all kinds of one-off and prototype work,' he says, 'but these days the bulk of the business is repairing aluminium and magnesium castings. People come to me with an idea on a piece of paper and I turn it into reality. We do a lot of car and motorcycle components, but we're not geared up for mass-production.'
Ian's wife, Alison, runs the alloy-wheel refurbishment and powder-coating business from a dedicated unit within the Jemison workshops. Alison has developed such a breadth of experience on the finishes, surface preparation and processes involved that their customers include several top WRC (World Rally Championship) teams.
'We have literally thousands of wheels in for repair,' says Ian. 'And you'd be amazed at the condition of some of them after a rally. The cars are frequently driven at racing speeds with whole lumps missing from one or more wheels — and then we have to repair them!'
Indeed, so busy has Ian been with his main business that the Boxster's progress, of necessity, hasn't been as fast as he would have liked. But he puts build-quality ahead of any desire to finish the car quickly.
'This isn't a project that can be rushed. Everything needs to be thought through,' says Jemison, 'and that's why it has taken two years before we were able to test the car. I could have bought a Mitsubishi Evo or something like that, but I pride myself in doing things in a completely different way.'
Porsche 914Turning back the clock
Ian Jemison's Boxster isn't quite the first mid-engined Porsche to see rally action, writes Keith Seume. Back in 1970 Porsche's competition department looked towards the 914-6 as a possible alternative to the 911 as a rally weapon. It made sense, too, because the car had won much praise for its exemplary handling.
The first public outing for the works cars was in the 1970 RAC Rally for a lone 914-6 GT, crewed by Claude Haldi and John Gretener. And even though the event was seen more as an evaluation exercise, the 914-6 GT finished a creditable 12th overall.
All eyes were then set on the Monte Carlo Rally, an event in which the 914-6 was expected to excel. Three works-prepared cars were entered, driven by Bjorn Waldegard, Ake Andersson and Gerard Larrousse – all highly skilled drivers who knew the Monte like the backs of their hands. But the weather was to deal the Porsche team a cruel blow.
The 1971 Monte Carlo Rally was the snowiest on record, and the drivers were quoted as preferring the more tail-happy handling of the 911 under such conditions. Had the event been dry their views might have been quite different, because the neutral handling of the mid-engined 914-6 GT would have been a positive advantage on dry Tarmac stages.
Unfortunately two cars – those of Andersson and Larrousse – were forced to retire with gearbox problems, but Waldegard (shown above) soldiered on to finish a worthy third overall. Sadly, though, this marked the end of Porsche's support for the 914-6 in competition – despite the fact that a 914-6 GT had won its class at Le Mans in 1970.
It was a shortsighted decision, because the 914 in all its forms went on to become a formidable competitor in many areas of motorsport, especially in the USA. Let's hope that Ian Jemison can once again realise the potential that lies within every mid-engined Porsche.
DTA Competition Engine Management Systems
Florence Street, Bradford BD3 8EX;
tel: 01274 667960;
Redline Performance Exhausts Unit 6B, Oaklands Road Trading Estate, Oaklands Road, Rodley,
Leeds LS13 1 LQ;
tel: 0113 204 0404;
Jenvey Dynamics Ltd
Building 2, Stanmore Industrial Estate, Bridgnorth, Shropshire WV15 5HP;
tel: 01746 768363;
Bridge Road, Holbeck,
Leeds LS11 9UG;
tel: 0113 234 0911 / 07977 004476;
GDB Motorsport Services,
Thorn Street Garage, Thorn Street, Clitheroe, Lancashire BB72LJ;
tel: 01200 442345;
Water Lane, Holbeck,
Leeds LS11 5PP;
tel: 0113 243 1392;
lan Jemison Engineering Home Farm Buildings,
Main Street, Bishopthorpe,
York Y023 2RA;
tel: 01904 703863