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KTM RC8 1190 LAUNCH TEST TECHNICAL: Chasing Kilos
An MSL online special feature
If ever one man can be considered the father of the RC8 Superbike project, surely it’s KTM’s 45-year old project leader Wolfgang Felber, who’s been working for the Mattighofen company ever since he left technical college 26 years ago, at the age of 20. Starting work there as a draughtsman responsible for drawing up the company’s 125cc and 250cc two-stroke engines, he combined this with racing a very different kind of ring-dinger from KTM’s offroad bikes at weekends - a Rotax tandem-twin 250GP racer with which Felber competed at the highest level as a privateer back in those days when GP racers had to fund their passion with a ‘real’ job. In 1990, increased work commitments dictated a step back from the Grand Prix scene, in favour of building his own KTM Single Racer for the flourishing Supermono class, powered by the firm’s LC4 motor, with which Felber won the hard-fought German SoS/Sound of Singles road race series that year. As a spinoff from that, he was the project leader for the creation of KTM’s first streetbike, the Duke, selecting a styling format tendered in open competition by a promising young bike-mad designer based in nearby Salzburg, Gerald Kiska, who’s designed every single KTM motorcycle ever since, including of course the RC8.
In the wake of KTM’s bailout from bankruptcy in 1993 by a group headed by today’s company owners Stefan Pierer and Rudi Knünz, Felber has been the driving force behind the Austrian company’s product development that’s fuelled its resurgence, en route to becoming Europe’s second largest manufacturer, scheduled to break the 100,000-unit barrier in 2008. He first became chief engineer for all two-stroke engines in 1993, rising to Head of R&D for the whole company in 1997, initially with 39 engineers working under him, rising to more than 100 after KTM’s new Technical Centre was opened across the road from the main Mattighofen factory. In this role, Felber had overall responsibility for the creation of KTM’s LC8 75-degree V-twin dry-sump engine, as well as for initiating the series of customer models equipped with it - the Adventure, Superduke, Supermoto and now RC8. But after four busy years, during which KTM achieved total dominance of the Rally scene, as well as maintaining its role as a multiple World title winner in MX and Enduro, Wolfgang retrenched to being a project engineer once again. “I decided to step back because I wanted to be more myself again, not a manager type person, but a guy who just wants to work on motorcycles,” he explains. “I was involved with the V4 MotoGP project, but it was a parallel job to the R&D side of things, which was a bit of a problem - though it was nice to build the first pneumatic-valve V4 which all the Japanese are now copying! But it was a very exciting time for us, even with the problems that we had with some projects like the V4. We've trained people in R&D who have now turned out to be first class engineers, and a few of them have been integrated into the RC8 project. It cost a lot of money, took a lot of time, but the benefits of this investment in people and training are now paying off, as the company moves up to a higher level, with a continually expanding range of products that are individual and performing.”
Still, it was quite a shock when KTM President Stefan Pierer announced in 2003 that he and his partners had taken the tough decision to call a halt to the V4 MotoGP project, in favour of developing a Superbike based on their dominant V-twin LC8 dirtbike engine. “We now realise that this high-tech form of two-wheeled Formula 1 does not conform with KTM’s policy of selling to the customer the bikes we go racing with as a factory,” said Pierer of MotoGP. “And racing is the main issue for KTM - it’s the fundamental basis of the company, the roots of our existence. We could never do this with our MotoGP bike - but we can make the link between going racing and our production street models, and that’s with Superbike. This is our future.”
Hence the debut of the RC8, which had already been under development since 2002, having begun as a what-if project instigated by tarmac tyro Felber, run as a semi-detached operation from the main KTM factory after he’d asked Pierer for a small budget to build the first bike. “Our main target from the beginning was to create the most lightweight twin-cylinder Supersports bike yet made, with an extremely compact design which would let us take maximum benefit from the small size of the LC8 motor,” he recalls. “To construct the prototype I called on my former rivals from my Supermono racing days, the Uno specialist chassis concern in Germany. Normally with something like this you have a lot of meetings with marketing men and design consultants - but this was so uncomplicated. We just sat around a table with a blank sheet of paper and a glass of beer, out in the garden outside their small workshop near Munich, and started drawing up frame concepts and bike layouts - and this was the right atmosphere to create something very special, which I believe we have done with this bike.”
The first RC8 prototype was completed exactly one year before the project’s Tokyo Show launch in October 2003, by which time it had covered thousands of kilometres on the street completely unnoticed by paparazzi cameras thanks to its extremely slender build, which allowed it to masquerade as a home-built special clad in a replica Honda NSR500V V-twin race fairing, with a hole cut in the nose to make room for a headlamp! Responsible for clocking up his fair share of that mileage was chief engineer-turned test rider Wolfgang Felber. “The first time I rode the RC8 was in very bad weather in the middle of winter, on wet roads in quite dangerous conditions,” he says. “To be honest, I wasn’t looking forward to it at all - but then when I got on the bike I was so surprised that I nevertheless started enjoying myself so much, because it was so small and light and easy-handling, you got lots of confidence from it. That was when I realised we had a fantastic bike.”
One which however almost stalled on takeoff en route to dealer showrooms, in spite of the rapturous reception accorded to the RC8’s Tokyo Show debut clad in Gerald Kiska’s striking styling. “We built a dynamic test bike based on the showbike in the spring of 2004 - but then the project was stopped for more than one year,” says Wolfgang with a wry smile. “This was while we discussed the possibility of using a V4 or even a V6 engine instead, and investigated various other concepts. But finally we came back to the original idea, and in July 2005 the project really started again. We took the prototype and completely revised it, because it turned out we needed to make a bigger engine anyway. Although the Superbike rules hadn’t been altered yet, if you put two and two together you could see the changes were coming - Ducati were already pushing for them. So that’s why we decided to make a new 1200 engine - but then that also required a new chassis! With every KTM we try to make the bike very compact, so if you change one thing, like having a 10mm taller cylinder head, you have to make everything new. For example, when we put the new 1190 engine in the old chassis, there was no room left to remove the rear cylinder head rocker cover to inspect the valves. This is why we had to redesign everything. It's like a game of dominos, and finally you end up with a completely new bike. We completed building the first RC8 1190 prototype in March 2006 - and literally an hour after we finished the bike, we started testing it! From then until now has been just two years - we had much to do in a short time, but we’ve done a lot of testing. We must have blown up more than 50 engines, and covered hundreds of thousands of kilometres, but now the engine is very strong, and is not very stressed delivering 155 bhp in this debut model.”
OK - so now let’s look at the concept. What were KTM's goals in developing the RC8? “First of all we wanted to have a simple bike which is simple to work on and maintain,” declares Wolfgang Felber. “This is something that is often forgotten. Racing is part of our DNA, so the RC8 was designed with this in mind, and while you can win some races with a fast bike, to have a consistently winning motorcycle it must be easy to work on between sessions. We also wanted to have a good handling bike as well as a fast one, so one of the things we have used to achieve a good compromise between ease of turn-in and stability is the unique design of the silencer system, mounted very low down between the wheels, beneath the engine. This was a key issue for the RC8, but it was very difficult to do - we needed six or seven versions get it to work. That’s why the 1190 engine still has a dry sump like the 990, to give space for the underslung exhaust system, but with an integrated oil tank cast as one piece with the crankcase, in comparison with the 990 engine’s separate tank. It‘s a very clean design, and the dry sump format has certain advantages over a wet sump in terms of reduced pumping losses. This is one of the main areas that we were able to take from our MotoGP experience and put directly into the design for the RC8 engine - especially the oil pump setup, where two separate pumps work negative pressure inside the crankcase to draw out the oil from the cases and reduce inner friction, with a third feed pump.”
The RC8’s 1148cc engine measures 103 x 69 mm, and is vertically-split, not only to save weight (no need for long engine bolts to hold everything together), but also as the easiest way of arranging the crankshaft and twin gearbox shafts on different planes to reduce the overall length of the engine, R1-style. The four-litre oil tank is integrated into the front of the crankcases, counterbalancing the six-speed transmission (the only holdover parts from the 990 Superduke motor) weight-wise down the centre line of the engine, thus making it stronger. The engine weighs 62 kg. complete with the oil tank, so is actually slightly lighter than the combined weight of the smaller 990 motor and its separate oil tank. There’s a strong but light forged one-piece plain-bearing crankshaft with small, semi-circular flywheels, and short H-section forged steel conrods mounted on a common crankpin. These carry very light three-ring Mahle forged pistons which deliver a quite high 12.5:1 compression that’s a spinoff from a short-stroke engine like this. The twin counterbalancers needed to eliminate the 75-degree V-twin’s primary vibration, are driven off the crank and are now diagonally opposed, to resolve the problem of a rocking couple.
The RC8’s separate cylinders and dohc four-valve cylinder heads are evenly located on the crankcase, for optimum weight balance and to help reduce the wheelbase. But unlike the 990 motor fitted with bucket tappets, the 1190 engine’s 43.5mm inlet valves and 38mm exhausts (up from 38/33mm on the 990), each with a single valve spring (the 990 has two), are operated via finger followers as a spinoff from the V4 MotoGP engine aimed at delivering increased revs, at the expense of increased weight and a bulkier cylinder head casting. Each cylinder’s pair of twin overhead camshafts is driven by a separate chain with hydraulic tensioner, rather than the 990’s composite chain and gear drive, after Felber admits that KTM considered gear camshaft drive for greater timing accuracy. ”But it’s too loud and not really reliable enough,” he says. “In my opinion that you should only use gear drive when you have a very even firing motor like a four-cylinder. In this application on a V-twin engine there is too much gear shock, so we didn't use it.”
The engine management is controlled by a Keihin ECU, with a single side mounted injector per cylinder located under the butterfly, and circular (not elliptic) choke 52mm throttle bodies, which are very small for such a big engine. “We recognise this, but it’s chosen so that we can have a very smooth, homogeneous torque and power curve,” says Felber. “This loses us some top end power, but we have a much better torque curve and better rideability - we can always fit bigger ones in future when we need more power! Our calculations are that we can have around 195hp very reliably from this engine in Superbike form, while the Superstock bike we’re racing this year will have about 168hp at the crank at 10,000rpm. Currently the hard revlimiter is set at 11,000 rpm, but in Superstock we already rev to 11,300 at the moment, and the valvetrain is designed for 12,300 revs. It’s early days!”
KTM’s established Keihin partners - “We've had a great relationship with them - they only sponsor Honda besides us,” declares Wolfgang proudly - have also delivered a further asset in the form of a throttle kicker system to counter the effects of engine braking, without fitting the slipper clutch which KTM’s R&D team has tried in prototype form, and is still working on. “Basically, the ECU decides to open the rear throttle butterfly a bit on the overrun,” says Felber. “We use that to balance the braking of the engine by reducing the power output of the rear cylinder. It works well, I think.”
It was decided from the very first that the RC8 should employ a chrome-moly steel tubular spaceframe, with the engine used as a fully-stressed member unlike on KTM’s other V-twin designs like the Adventure and Superduke. This means the LC8 motor is mounted at four separate points within the chassis, including both cylinder heads, with the swingarm pivoting in both the engine crankcases and the rear mounting point. “This creates a stiff structure which still allows the bike to ‘talk’ to the rider,” says Felber. “We believe it’s the best solution.”
When it came to installing the engine in the chassis, obtaining the RC8’s exceptional 54/46% forward weight bias for a V-twin was one consideration, but not the only one. “The main priority was ground clearance, that the position of the engine should be optimised to allow the bike to be leaned over as far as possible,” confirms Wolfgang. “Plus the cylinders are actually not mounted evenly on the crankcase, but rotated four degrees backwards to provide more space for the front wheel, especially with fork deflection under braking.” But that’s not the only reason, for it’s confirmed in talking with KTM engineers that the 1190 motor is headed for a future offroad application, most likely in an über-Adventure model which would certainly require the space for a 20-inch front wheel that the rotated cylinders apparently provide - one reason that KTM opted not to produce a 90-degree V-twin 1190 motor for the RC8 at design stage in 2005, once it was decide to develop an all-new engine for the Superbike family. That, and the degree of individuality their established 75-degree layout confers.....
Weight was a key issue in creating the RC8, especially with the bigger 1190 engine that weighs the same as the smaller motor. “We wanted to make the bike as light as possible, but I’m extremely disappointed that I've failed by six or eight kilos,” says Wolfgang Felber with a frown. “My aim was to get it below 190 kg. with 16 litres of fuel, but 198 kg. is as light as we could make it. I’m pretty unhappy about that! That’s why we worked with smaller 320mm discs than Ducati - this saves weight, reduces the inertia of the front wheel to improve turn-in, and also helps with access to the front wheel. And our special Marchesini wheels are very light, plus we use Pirelli tyres not only because they have good grip, and are the World Superstock tyre, but also because they are so light, about 1.2 kilos less than the competition. After a year of extensive testing, we found that they are also the best for durability and grip, which made it an easy choice. And at the start of the RC8 project we were working with 48mm WP forks, but now we went back to the 43mm design because it saved us 1.5kg of weight. Every little bit is important - but if we were to strip the bike right down to full race condition without regard for Superstock minimum weight rules, I estimate it could weigh between 18 and 21 kg. less than standard, so around 168 kg. dry. I want to get below that 190 kg. wet barrier with a future version!”
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