Monday 11 February 2013

Ducati 916 SP/SPS - Ultimate Desmoquattro Superbikes, Part I

Seems that lately I’ve been on a Ducati kick. So far we’ve covered bevel heads and belt heads, so lets continue with the next generation of Ducati performance – the Desmoquattro. In this two part article I will cover the development and execution of the 916 Sport Production models, the ultimate Desmoquattro Superbikes. 
Seems I cover the 916 a lot on this site. Funny that.  

It’s 1985 and Ducati, with fresh capital and encouragement from new parent company Cagiva, is making a major gamble on the engine design of a talented young Italian engineer by the name of Massimo Bordi. Bordi’s engineering thesis was for a four-valve per cylinder desmodromic cylinder head, based on the principles of desmo valvetrains that had become a signature of the Ducati brand. Famed engineer Fabio Taglioni had developed the original Ducati desmo system, and then refined it with his belt-driven overhead cam Pantah design, but it was clear by the mid 80s that further development would be needed to keep Ducati twins on the podium.

In the mid 80s Ducati was doing well in TT1 and TT2 categories with their Pantah-based racers, and in the bigger categories the top-dog 750F1 was doing reasonably well in endurance racing and Battle of the Twins. The writing was on the wall for the air-cooled L-twins, however, and it was clear that more power was needed to keep pace. And if Ducati wanted to compete head to head against the Japanese superbikes, they needed something hotter than the little F1. 

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Massimo Bordi and Fabio Taglioni, with a Pantah twin on the test bench.

Taglioni, at this point in semi-retirement but still a driving force in the engineering department, was a staunch traditionalist when it came to engine design. He had experimented with belt driven, double cam, four valve heads on an air cooled 500cc Grand Prix prototype racer. He found that he was unable to produce power gains to justify the extra complexity of the design, and abandoned the idea to further refine the Pantah single-cam design. For Taglioni, the best way to improve the breed for racing was to develop an air-cooled Pantah V-4 by mating two L-twins together. He pursued this angle while Bordi worked in semi-secrecy on his liquid cooled design - legend has it Taglioni, famous for his stubborn temper, was so opposed to a four valve design that Bordi worked on the project at home to keep it secret.
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Bordi’s job was to further develop the Pantah design to include liquid cooling and a four-valve cylinder head with a narrow included valve angle for better combustion efficiency - and more power. He had to succeed where Taglioni, Ducati's most revered engineer, had failed. It was thus up to Bordi to prove his mettle and make the forthcoming Desmoquattro motor work.
The liquid-cooled, double overhead cam 748cc Otto Valvole Desmo prototype debuted at the 1986 Bol d’Or endurance race. Based on Pantah architecture with a combustion chamber design developed by Cosworth and state of the art fuel injection by Weber-Marelli the 748 i.e. OVD was a remarkable leap forward for Ducati. After some promising results and an healthy power boost over the air cooled 750F1 racers, Bordi developed the platform into an 851cc superbike that would achieve stunning success on the track and catapult Ducati into the winner’s circle against tough competition from overseas. Taglioni's objections were silenced when the new 851cc prototype cleared the 100hp mark on the Ducati test bed - the first time one of their twins had broken the triple-digit horsepower barrier. 
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Despite steadfastly sticking to their signature L-twin layout, and working with the associated power deficit compared to the Japanese fours, Ducati’s 851 and 888 racers achieved remarkable successes that lead to Superbike racing being facetiously labelled “the Ducati Cup” during the early 1990s.

The best, however, was yet to come in the form of the jaw-dropping Ducati 916, which slotted the (by now) well-developed Desmoquattro mill into a new chassis that allowed Ducati to remain competitive in a field of increasingly tough opposition. And if you wanted the ultimate 916 for the street, and one of the hottest and sport twins of the 1990s, you would order the magnificent 916SP/SPS.

Let’s step back a bit. While the 916 was unveiled to much fanfare in 1994, development had begun years before to address the limitations of the 851 in racing. The 916 took the existing motor and put it into a state-of-the-art frame and running gear that was developed as a unified whole by Massimo Tamburini and a team of engineers working over a period of six years. That fact that it was one of the most beautiful bikes of the 20th century was a happy coincidence and a product of Tamburini’s clever vision of a bike that was purposeful as it was pretty – the 916 was built to win races, not beauty pageants. The fact it did both is a testament to Tamburini’s genius.
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One of the final evolutions of the Desmoquattro before it was phased out in the mid 2000s in favour of the newer Testastretta motor design.
While the 851 had been developed in-house at the Ducati factory, the 916 project was contracted to a team in Rimini in led by Massimo Tamburini. A team of engineers and designers had to develop a platform for the Desmoquattro that would address a few of the deficiencies of the 851 and make the forthcoming, as yet unnamed, bike a better racer. The basic problem with the 851 is that the swingarm pivots through bearings in the engine cases while the frame bolts to the top half of the engine. The crankcases thus serve as the stressed member between the frame and the swingarm, which combined with the prodigious output of the factory racers was testing the limits of the Pantah crankcases. You see, the Desmoquattro shares its bottom end with the Desmodue, aka the Pantah. The original OVD prototype used the 750F1 crankcase with some slight modifications. Keep in mind that the Pantah mill started life as a 499cc, 50 hp air-cooled twin, and now the same basic crankcases and crankshaft were expected to deal with more than double that horsepower. Cracking cases were common and chassis stiffness was limited by the nature of the design, which owed a lot to the earlier 750 TT1 – an air cooled bike that wasn’t expected to handle triple-digit horsepower. 
Massimo Tamburini had been with Cagiva and Ducati since 1984, and had already designed the heavily streamlined but unpopular Paso sport-tourer. He had come to the company after leaving Bimota where he had cut his teeth in high-performance motorcycle design (Tamburini was a founder of the company, and is actually the “ta” in Bimota, along with Valerio Bianchi and Giuseppe Morri). He was assigned to project “2887” in 1988. Development took six years, but by 1991 the basic elements and styling had been finalized. Key areas of improvement over the 851/888 were specified – shorter wheelbase, better weight distribution, stiffer frame, better mass centralization, less weight, and a more aerodynamic design. Engine development was limited to a slight evolution of the 888 – based on experience on the track the 888cc motor was given a 2mm increase in stroke (now 94mm bore with 66mm stroke) and reinforced main bearings, resulting in a 916cc capacity with the same bore, pistons, barrels, cams, rods, crankcases, and cylinder head as the outgoing 888 Strada.

The frame was all new and much improved over the outgoing Superbikes. It had larger tubing and a much more compact design that was both stiffer and more centralized. An ALS 450 steel trellis frame was chosen over an aluminium beam design, and thus continued what would become a long standing Ducati tradition. The swingarm pivot, still in the same place, was now supported by the lower part of the frame and bearings were now in the swingarm rather than the crankcase. A trick single-sided-swingarm was used, based on the concept developed by Honda and ELF for quick tire changes in endurance racing (but sufficiently different so as not to infringe on the ELF patent…). Suspension front and rear was developed for the 916 and the 916 alone – Tamburini’s vision was to build a fully integrated motorcycle that shared as little as possible with existing models.

Almost every component outside of the motor and fuel injection system was developed exclusively for the 916, and designed as a unified whole. Thus each component was optimized and purposeful. Aerodynamics were improved by a slippery new shape with organic curves (based on the silhouette of a beautiful woman, as Tamburini continues to claim – presumably in a low voice between drags on his ever-present cigarette). A narrow frontal section contributed to a much-improved top speed despite a very modest power increase. Underseat exhausts streamlined the rear. Intake was improved by a larger airbox and a pressurized ram-air system with intakes fed from the front of the motorcycle.

Handling and performance were much improved. Chassis stiffness was way up, and the geometry was much better overall, with further capacity for adjustment via an eccentric headstock that allowed rapid rake and trail changes. Weight distribution was almost perfect, nearly 50/50. The whole package was much more compact, weighed less than the 888 (about 435lbs dry for solo seat versions), and the massaged motor with improved intake and exhaust provided much more midrange punch. The 916 was set to be a race winner.
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Racing team manager Virginio Ferrari, Cagiva boss Claudio Castiglioni, and engineer Massimo Bordi 
But it was the public response that truly created a legend when the 916 prototype was officially unveiled in 1993 with production scheduled for 1994. Dubbed the "Hypersport" series to distinguish it from the previous 851/888 "Superbike" (it would be renamed Superbike in the late 90s), the design and aesthetics were so advanced, so well integrated, and so beautiful that buyers immediately lined up with deposits. It was unlike anything seen before. Once reviewers got their hands on test models and discovered it went as well as it looked, the 916 became a mythical machine – one of the best bikes of the 20th century, and the object of lust and desire the world over. The late Kevin Ash was one of the first to review the 916 in 1994 and immediately recognized that the goal post had been moved forward by a fair margin.

Today we have become jaded and have forgotten just how much of a leap forward the 916 was in terms of design and performance. The design has been copied and bastardized ad-naseum to the point where a 916 looks good, but not unique. We mustn’t forget that in 1994 that people could scarcely believe how amazing and advanced it looked. The mechanical bits may have been evolutionary but the looks were revolutionary. It would become poster fodder for an entire generation of riders.

While the standard 916 “Strada” was hard enough to get, and provided scintillating performance, there was a need for something a bit hotter and more exclusive. Not for the sake of better performance so much as to homologate a tricked-out version of the 916 for racing. While the bread-and-butter models will keep the profits rolling, homologation specials are needed to ensure that the best possible components are available for the racing versions. Certain cheaty bits can be incorporated as well, if you aren’t planning on making it emissions or noise regulation compliant worldwide. As per Superbike rules, a minimum number of “street legal” models must be produced that feature the basic elements present in the fully prepped racer. Back in the 1990s it was common for manufacturers to build thousands of standard bikes, then a few hundred tricked out homologation specials, that shared little with the bog standard bike, at exorbitant prices to legalize special components for racing.

Before 2008 the rules for World Superbike were such that as little as 150 bikes could be produced to meet the requirements, while AMA Superbike in the USA only required 50. The legendary Yamaha OW01 and OW02 (aka the R7), as well as the Honda RC30 and RC45 - all were limited production specials to legalize race versions. You can’t take a standard version and then modify beyond recognition – a middle-ground compromise is needed to meet the rules (barely) and allow you to build a better race bike. The SP (for Sport Production) was that compromise.
Tune in next week for Part II of the 916 story. Same OddBike time, same OddBike place.

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