Filippo Preziosi
Ducati Desmosedici Gp7-How And Why
The man primarily responsible for creating the MotoGP title-winning Ducati GP7 is 39-year-old Filippo Preziosi, the direttore generale of Ducati Corse since 2005. Preziosi was the racing subsidiary's technical director starting in 2000, heading up engine and electronics R&D for both Superbike and MotoGP race projects. When Ducati announced it was entering MotoGP with a V-four-powered prototype, the big engineering decisions regarding the Desmosedici's layout and detail during development fell upon his shoulders.
"We at Ducati were very opposed to the change of rules from 990cc to 800cc for MotoGP, because that means you have to throw away your old engine and build a completely new bike, which costs a lot of money," Preziosi recalls. "Our company is a small one, our resources are limited, so for us it would have been much better to keep what was already working well. We needed to understand what in the GP6 was working correctly and try not to change any of that. So we concentrated only on what was absolutely necessary to change in going to 800cc.
Big 320mm carbon discs help slow the Ducati's impressive speed. Note the heat-sensitive paint on the disc edge, as well as the quick-release disconnect on the brake line just behind the data line; the disconnect allows replacement of the caliper without having to bleed the brake hydraulics.
"We decided to keep several parts. For example, we kept the front end of the bike: the front fork, the rims, brake calipers and so on. And we did the same thing with the rear; we kept the swingarm, the link, the shock absorber, the brakes, wheels, we kept everything more or less exactly the same. We also kept the same clutch from 2006; it was working properly, so we didn't find any reason to change it, and the same was true for the gearbox. The torque of the engine is greater on the 990 than the 800, but there are some differences in the firing order, so that made us think we should keep the same transmission. Just because you have a smaller-capacity 800cc engine, you might think that because the power and torque will therefore be less, you can make a smaller, lighter gearbox. But in reality, the power you are using is limited by the vehicle dynamics, not by the engine. So even if you have a 990 with more power and more torque, at the end of the day the power you are using when you are exiting the corner in third gear is the power allowed by the dynamics: wheelies, tire grip and so on.
"The marketing people at Ducati were not at all happy with the way we designed the GP7," Preziosi reveals, "because we kept more or less the same bodywork as the GP6, and that means it's more or less the same fairing as the GP3! Because people were expecting a big difference from 990 to 800, a lot of journalists were upset that we designed the GP7 bodywork to be so similar to the GP6. But the main point for a racing bike is to be fast, not to be different, so we tried to concentrate our efforts to have a faster bike, not a different bike."
Obviously the engine is where the majority of development was concentrated. "So we started to think what was the best configuration, with how many cylinders and how they should be arranged," says Preziosi. "We absolutely did not commit to simply downsizing the existing Desmosedici motor-all options were open. We did many simulations, but at the end of the day the answer was the same. We think that the 90-degree V-four is the best configuration, not only for engine performance, but also the entire layout of the bike. The mass is very concentrated, the internal balance of the engine is very good, the weight distribution of the motorcycle is what we are searching for, and the fuel consumption is under control, and the engine is very efficient."
Petroleum giant Shell also played a significant role in the Desmosedici's design. "In creating the new engine, we worked very closely with our partners at Shell. We relied on them to help deliver the efficiency that was so important for the kind of bike that we were planning to build, and that meant working on the fuel and oil side as well as the mechanical design. The first key ingredient of this was to reach high revs in order to achieve high power figures. With the 990 the power was not so important, because the performance was more defined by the vehicle dynamics; if the front wheel isn't touching the ground, there's no reason to have more power. But moving from 990 to 800, it seemed that output would be less, so the amount of power compared to our rivals would be more important, in which case the easiest way to reach more power is to increase revs. But unfortunately there are a lot of problems in doing that, and the first one is that fuel efficiency becomes an issue, so you have to make some decisions to avoid fuel consumption getting too high, especially with the smaller 21-liter fuel tank introduced for this season. We worked a lot on engine fluid dynamics to resolve this problem.
This is the view that the competition had of Casey Stoner all year. Two single exhaust collectors are possible with the 800cc GP7 due to the 180-degree screamer firing order. Note the bracing on the engine cases where the frame mount is located just behind the main fairing.
"The second key decision was to keep the screamer firing order," Preziosi continues. "This was completely the opposite compared to the rest of the MotoGP paddock, where technicians, riders, mechanics, journalists, everyone all insisted the screamer engine was too aggressive, that rideability was the most important thing in the world. We're fighting with Valentino Rossi, who is seven times world champion, we're fighting against Honda, who are 14 times world champion, we're fighting against Michelin, who are 26 times world champion. So if we choose to follow the same way as them, there is no chance to win. Ducati has to change something; we have to do things differently. So we felt this was the right choice. We thought that with the high revs and the screamer firing order, we could get more power, and that fuel consumption wasn't going to be an issue because the engine was more efficient. Of course, if Casey was not the Casey we know and admire so much, maybe we would have had a very bad season, and now I would have had to apologize for making the wrong choice! But thanks to Casey we're laughing and I can tell you how intelligent we were!"
During chassis development with the GP7, Ducati engineers made a surprising discovery. "On the chassis side, we believed our 990 GP6 had some problems, and we worked a lot on the frame to try to understand where these came from," Preziosi explains. "Loris [Capirossi, Stoner's teammate] complained the bike was not so stiff; he said there was some delay in its response. So we studied this a lot and eventually realized the problem was not on the chassis itself but on the stiffness of the footrest hangers! As you know, when you ride a bike you steer it not only with the handlebars, but also by shifting your body weight on the footrests. So in creating the GP7 we extended the concept we introduced in 2003, making the engine the central part of the motorcycle. Usually in every MotoGP bike the engine is a stressed component of the rolling chassis, so without the engine the wheel-to-wheel stiffness is less. But on the GP7 the engine is a part of the frame, so it's not possible to place the two wheels on the ground without it. This allows us to have a different structure with less weight, and the rear section of the frame is now a lot different to the GP3-GP6, with a carbon-fiber subframe that makes a really stiff structure, and the footrest hangers are now well supported."
The Desmosedici GP7's cockpit bristles with numerous switches that control a wide array of rider aids.
Preziosi then reveals how much a role electronic rider aids now play in MotoGP. "We did a lot of work during the 2007 season on the electronics management and continued improving the electronics race by race, just as we did in 2006. The hardware is basically the same; we just changed the software strategy we wanted to apply for the 800 against the 990. The main point of the electronics was to improve rideability, because the specification we decided on for the engine was very good in delivering power, very good in fuel efficiency, but maybe not so good in rideability. This meant we just did different things with the same hardware for the GP7, because this is something very easy and cheap to do. If you have a good idea lying in bed at night, and you put the idea on the software in the morning, look at it in the system and you find that it's working well, you just have to use the ADSL connection to send it to Sepang or Le Mans or wherever the team is, and they can test it and find they have a different bike. With this kind of electronic management we can practically make a different bike with the same hardware for every track, for every rider, for every corner, in every weather condition. We can have a lot of different bikes in the same bike!"