Classic Racer In Detail I
t may have been nearly 200bhp and needed extra weight adding to get up to the 130kg minimum, but the Elf 500 was born of sidecar tech. Kind of. Words: Alan Cathcart Riding photographs: Chris de Beer.
The heart of any motorcycle is its engine, but all the more so in the case of the Elf 500, whose wide-angle Swissauto V4 motor gave rise to the whole bike’s creation. Yet, while the engine appeared at a cursory glance to follow the conventional Made in Japan route, it was far from effectively being a clone of a Yamaha (as the Cagiva certainly had been) and neither was it a Honda copy, as the Paton was unjustly tagged – when in fact it was Honda that had copied Paton!
The Elf V4 represented 500cc Grand Prix racing the European way, breaking new ground with technical innovation that worked – albeit by no means as radical as the series of hub-centre, Honda-powered Elf racers of the previous decade.
For a start, the Elf 500’s Swiss-made single-crankshaft crankcase reed-valve V4 engine was extremely light and compact. It scaled a whole 7kg lighter than a Yamaha YZR500 engine at 37kg (Max Biaggi’s World champion RSV250 Aprilia V-twin motor weighed 30kg!) and it was 130mm narrower than an NSR500 Honda and 100mm lower top to bottom than the Yamaha.
Unlike any other four-cylinder two-stroke 500 yet made, the Elf’s crankcases were split vertically rather than horizontally like all other 500GP motors of the day. Swissauto CTO Urs Wenger stated this was partly to improve crankcase stiffness, but mainly to enhance access to the engine – for example the crankshaft could be changed in just one hour. This was a key factor in determining the 108° included cylinder angle, which also allowed space for four large reed blocks and a row of powerjet-equipped Dell’Orto flatslide carbs that Swissauto cleverly combined into a single bank – the team fitted 39mm ones on faster tracks amd 36mm on slower ones, according to Wenger.
But while everyone else called the Elf/Swissauto engine a V4, Wenger insisted on labelling it a ‘deformed boxer’, because the two pairs of cylinders on each side of the motor fired together, opposed at 180° in terms of firing angle to their counterparts, just like the cylinders of a BMW flat twin. This resulted in the engine’s extremely distinctive gruff exhaust note from what was effectively a pair of V-twins mounted side by side on a common crankcase and firing 180° apart. However, Swissauto later introduced a Big Bang version of the engine, with the firing order closed right up with the intention of improving rideability. “We’ve already got more power from the Big Bang motor on the dyno, but we’re not really sure yet why!” admitted Wenger to me when I rode the bike in 1996. “We started out at with 90° firing angle, but if the riders say it makes a big difference, we’ll try a 60° format. But if not, we’ll leave it at 90°.”
Because of the extra vibration from the Big Bang version, Swissauto first needed to redesign the crankcases to incorporate a balance shaft in the 180° version of the engine, before messing about with the firing angle. This experimental motor was in the Elf 500 when I rode it, as raced by a solitary Chris Walker at Brno after team-mate Borja crashed there in qualifying, ruling himself out of the race with a hand injury. Fitting the balance shaft added 1.9kg in total to the weight of the engine – an acceptable penalty for reducing rider fatigue, as well as the risk of component breakage, said Wenger.
Unlike the JapaneseV4 500GP engines, the Elf/Swissauto motor used a single crankcase volume for each pair of opposed cylinders, resulting in a total of just six flywheels and four main bearings for the single crankshaft, whereas the V4 Honda NSR500’s single crank had five main bearings with four crankcase volumes and, of course, the Yamaha and Suzuki 500s had twin crankshafts, so a total of eight main bearings in all. On the Swiss motor, this feature not only helped reduce weight, bulk and friction, but was also a crucial factor in the engine’s impressive power output – over 190bhp at the clutch at 12,500rpm, according to Urs Wenger, compared to 185bhp from the Sidecar version in customer form. Speaking in 1997 Wenger said: “We have much higher pre-compression than any other engine with our crankcase design. But as well as good maximum power, this engine also has a lot of torque. We have over 200bhp at the clutch on the dyno, but the power characteristics aren’t satisfactory, so we must do more work on the electronics and cylinders before we run it in the bike. But the engine is still quite new, so we have lots of development still to come!”
After debuting the bike in 1995 with peaky HH cylinders from their Sidecar motor, complete with light-switch power delivery and no powervalve - that must have made life exciting for Swiss test rider Adrian Bosshard - Swissauto had been working on developing their own cylinders to be made in-house like all the rest of the engine, which did indeed arrive for the 1997 season. Before that, for 1996 the Elf 500 motor featured five transfer/ two exhaust port Bartol cylinders, which the Austrian rider/engineer who later built the KTM 125/250 two-stroke GP contenders had previously developed for use on Yamahas.
"Our Swissauto cylinders give more power and incorporate an absolutely original flap- type powervalve system, as different from the others as our crankcase design is." said Wenger at Brno in 1996. "But reliability is a problem at the moment, so we won't race with them until next season."
The Bartol cylinders employed a conventional powervalve, controlled by the usual electric motor via sensors monitoring throttle position and rpm. These were linked to a programmable Swissauto digital ignition, which was powered by a totaNoss solid-state battery running without a generator, but boosted by four magnetic triggers inserted into one of the crankshaft flywheels, and a crankcase pick-up.
Wenger revealed that for each gear ratio there was a different ignition curve, a different powervalve curve and a different powerjet curve, resulting in more than 1000 separate items of data the team had to programme at each different circuit to optimise performance. “Track time – that’s the biggest problem we have at the moment,” he said at Brno. “Each track we come to, we have no data, because it’s our first time there with a new bike, and we must start from scratch programming the different electronic systems, quite apart from the usual stuff like chassis set-up and jetting. Each race, usually only in the pre-race warm-up the bike begins to work well for the first time, and sometimes not even then. The only exception was Paul Ricard, where we did some testing over the winter. There, the fact that Borja was up to fifth place before he crashed shows how crucial this set-up time is. So, 1996 has been a learning year for us in making an investment I’m certain will pay off next season, ”Wenger said. Any modern Moto GP team would sympathise with this problem!
The Swissauto had a dual radiator cooling system with an external waterpump driven by a toothed belt directly off the right end of the crank, unlike its rival two-stroke Japanese race engines, while the clutch sat outside the crankcase on the other side of the motor and could be detached from its driveshaft via a cleverly-designed circlip system, thus allowing the team to change the entire clutch in just 30sec if it showed signs of slipping!
Clutch removal allowed access to the extractable six-speed cassette gearbox, for which there was a choice of 36 different ratios in total, all of which Swissauto also manufactured themselves. Really, apart from the pistons from Japan, the Austrian cylinders used at the time of my test and the Dell’Orto carbs, the entire Elf 500 engine was made on a mountain somewhere in Switzerland by some very clever people working with a superbly equipped machine shop housing state-of-the-art equipment.
Swissauto was indeed a class act, and the only surprise is that they ended up being acquired by a company 6000 miles/10,000km away on the other side of the Atlantic, rather than one much closer at hand in Europe.
ELF 500 – SPECIFICATION
Engine: Watercooled 108º V4 single-crankshaft crankcase reed-valve two-stroke with contra-rotating balance shaft and each pair of cylinders firing together at 180º intervals
Dimensions: 54 x 54.5mm
Output: 192bhp @ 12,500rpm (at clutch)
Carburation: 4 x 39mm Dell’Orto flatslide with electronic powerjet
Ignition: Swissauto CDI
Gearbox: Six-speed cassette-type
Clutch: Multiplate dry
Chassis: ROC aluminium twin-spar
Suspension: Front: 46mmÖhlins inverted telescopic forks. Rear: Fabricated aluminium swingarm with Öhlins monoshock and rising rate link
Head angle: 23°
Weight: 129kg with oil/water and telemetry, without 35l fuel tank
Brakes: Front: 2 x 320mmMitsubishi carbon composite discs with four-piston Nissin calipers.
Rear: 1 x 220mm Nissin steel disc with two-piston Nissin caliper
Wheels/tyres: Front: 12/60-17 Michelin radial on 3.50in. PVM cast aluminium wheel. Rear: 18/67-17 Michelin radial on 6.00 in. PVM cast aluminium wheel
Top speed: Over 192mph
Year of construction: 1996
Owner: Elf Huiles Minerales SA, Etagnières, Switzerland
THE FAMILY LINE
The 1996 Elf 500 marked the return to the GP arena of the French petroleum giant with a bike bearing its own name for the first time since 1988. However, whereas Elf’s previous involvement in GP racing was concerned with pushing back the frontiers of two-wheeled chassis design, this time around the emphasis was on the avantgarde design features of the Swissauto engine, housed in a relatively conventional ROC chassis. The originality of many of these features was thoroughly in keeping with Elf’s emphasis on breaking new ground technically, which has been displayed down the years by the bikes bearing its own name. Here’s a walk down Elf’s memory lane:
1978: French car designer André de Cortanze, an enthusiastic biker, builds a radical hub-centre racer for the French oil company with a TZ750 Yamaha engine, known as the Elf X. It’s never raced, but the enthusiastic public response dictates a follow-up. 1981-83: Elf links with Honda to produce the Elfe endurance racer, designed by de Cortanze and powered by a Honda RSC 1000 four-stroke engine, and raced by top riders like Dave Aldana, Didier de Radiguès, Walter Villa and Christian Leliard to a series of impressive results. Among the ground-breaking features of this hub-centre design were the first use of carbon brakes in motorcycle racing and the single-sided rear swingarm design later christened the Pro-Arm, and used by Honda on the RC30 and its many successors under licence.
1984: ELF switches to 500cc GP racing with another hub-centre de Cortanze design, the Elf2, powered by Honda’s NS500 two-stroke triple and equipped with a unique push-pull steering design. But this is hard to become accustomed to, and the bike does not prove to be a success.
1985: De Cortanze produces the Elf2A, with which Leliard makes Elf’s 500cc GP debut, using an ever greater number of car-derived design features. It isn’t a success either – André returns to the car world, later to become the chief engineer of the Ligier Formula 1 team.
1986: Elf gets pragmatic, without sacrificing original thought, and hires Serge Rosset to run their GP team, with de Cortanze’s former right-hand man Dan Trema designing the Elf3, equipped with a special front end design called the VGC system. Ron Haslam takes it to ninth place in the 500cc World Championship, still powered by Honda’s now outdated three-cylinder engine. Trema later becomes ‘le grand fromage’ of Elf sponsorship, in charge of the company’s entire motorsports activity.
1987: Honda agrees to supply Elf with its NSR500 four-cylinder engine, but this doesn’t turn up until after the start of the season, so the Trema-designed Elf4, broadly based on the Elf3, arrives late and is never properly developed.
1988: The NSR500-engined Elf5 takes Haslam to 11th place in the World Championship and proves the fundamental worth of the Trema/Rosset design module. Elf retires from direct involvement in racing at the end of the season...
1989-1995: ...but still stays involved in GP racing as a trade sponsor, winning the 125cc world title with Loris Capirossi and the 500cc world crown with Mick Doohan, etc.
1996-1997: ELF is back in business in 500GP racing – but shouldn’t they have called the Swissauto-engined, ROC-framed Elf 500 the Elf6?
RIDING THE THING
All of Swissauto’s hard work in smoothing out the power delivery of its V4 engine for solo use was paying off when I got out on the bike in Brno in 1996. It wasn’t exactly a pussycat – no bike that powerful that carried full-time telemetry just to beat the 130kg class weight limit could possibly be – but it certainly wasn’t the vicious accident-waiting-to-happen I’d been led to expect. In terms of transition into the strong powerband, the Elf was a lot more progressive than the last 500 four I rode whose engine was derived from a Sidecar application, the Fior 500 back in 1988. Funny – that was French, as well.
Whereas persuading the Fior’s back wheel to hook up out of a turn when I rode it at Nogaro was a two-wheeled formof Russian roulette, the Elf was much more rideable thanks to its electronically-aided refinement. You just had to be sure you were ready for the strong rush of horsepower that was unleashed when you twisted your wrist hard with the tacho needle reading anywhere over 10 grand. It was the sheer fact of having that much power available that made the bike a little daunting to ride – okay, a lot! – not the way it was delivered.
The similar single-crank NSR500 Honda was just as hard to ride, and while by then I hadn’t ridden the RGV500 Suzuki for a couple of years, judging by the last time I’d done so that may have been harder still. In fact, the Elf reminded me more of a worksYZR500Yamaha. It didn’t rev as high as the Suzuki, but it had really massive torque and a surprisingly powerful midrange, with a relatively progressive transition into the strong power band from low down, reflecting all the hard development Urs Wenger and his team had wrought on taming the engine that year. Moreover, on-track race comparisons with Borja aboard had shown the Elf to be actually faster at top speed than the factory Yamahas, and it was on terms with the best Hondas. Some going for a new bike.
The Elf began to make good power from just over 8000rpm, but it wasn’t until the exhaust valve was fully open at just under 10,000 revs that it came on really strong, so in terms of selecting ratios for the cassette-type gearbox it was pretty peaky, with just under 3000 revs of strong power. Okay, very Sidecar-style – but it was the way Swissauto’s electronics had rationalised the actual delivery of all that horsepower that made it pretty rideable.
Jetted slightly rich for a journalist to ride, the delivery flattened out around the 12,500rpm power peak, but while there was normally some over-rev available, apparently it wasn’t advisable to use too much of this – especially on the overrun – because the crankshaft didn’t like it, and this point was still work in progress on the engine when I rode it. While the innovative engine design’s vertical crankcase split meant the crank could be changed in only an hour, the fact it had fewer main bearings than anything else on the GP grid meant crank life was only 1000km and sometimes not even that. It was common practice for the Elf team to change cranks after each day of qualifying, and the one on the test bike went soon after my final session on it. This was the Achilles heel of the bike at that stage, not the way the power was delivered.
The bike I was riding was the same one Chris Walker had ridden to 20th place in the Czech GP the day before, after scoring his first World Championship point for the team the previous weekend in the Austrian GP at the Salzburgring. Its engine was carrying a balance shaft for the first time as a preliminary step towards the Big Bangmotor Swissauto then had under development. There was still a little vibration through the footrests, though Chris said it was much smoother than before.
The engine was mounted in Silentbloc rubber bushes, which ROC had made to contain the vibration, although the rear pair out of the six mounting points could apparently also be rigid to give a ‘semi-floating’ engine position, which ROC boss Serge Rosset claimed worked better at reducing vibes. The new version of the motor I was sampling had different crankcases, so ROC had had to modify the chassis to install the smoother engine. Worth doing. I didn’t really care for the gearbox’s shift action – it had a heavy, mechanical-feel to it and lacked the precision I expected. The 500 Cagiva’s gearshift felt similarly harsh each time I rode it, but at least it had a speed-shifter that helped counter this. The Elf 500 didn’t have one yet – I told Rosset this should be a priority and would surely drop lap times when it arrived. Guess what – it did!
The bottom line after riding the Elf 500 towards the end of its first season of competition was that it was a project with a genuine potential future that was already repaying the hard work put into it. Thanks to the support of the French oil company, the valuable Euro-dimension had been restored to 500GP grids, bringing a technical breath of fresh air with it. This wasn’t an exercise in alternative technology for the sake of being different, but a genuine contender for GP racing’s top honours that was in the process of growing up so it could go play with the older kids. To have achieved so much already in the bike’s development season must have been very rewarding for the Elf team. My Brno ride on their new 500 four showed they had a genuine contender on the grid.