de Blueboy » Mer 21 Déc 2005 04:25
tres tres interressant article dans ESPN aujoudhui, sur les V8 et leurs developement!
Ross Brawn, norbert haug etc...
en anglais, pour traduire allez sur babelfish
"Bits falling off that never fell off before and were never a problem before are just some of the challenges Formula One engineers and designers have to overcome as they develop the new V-8 engines that will replace the V-10s in 2006.
The V-10s have been around since 1989, although some teams continued to use V-8s and V-12s until it became mandatory to run V-10s in 1998.
One of the biggest challenges the engineers have faced is the increased and different vibration the V-8 creates compared to the V-10. The more cylinders an engine has, the smoother it runs. For example, the Harley-Davidson V-Twin two-cylinder motorcycle engine really "thumps, thumps" compared to other bikes with more cylinders.
"Having probably raced one of the last V-8 cars in F1, I have fond memories of the vibration issues that you get with the configuration of a V-8," said Ferrari technical director Ross Brawn, who won the 1994 World Championship with Michael Schumacher driving a Ford V-8 powered Benetton.
"My colleagues and staff at Ferrari haven't had that experience," Brawn said, "and it's still been a new experience for them to have bits falling off that never fell off before and were never a problem before. The biggest single change is just the vibration of a V-8 -- certainly, in certain planes and certain modes, it is very high. You have to rubber-mount everything; you have to give it plenty of clearance. We are having components fail which have done high mileage on a V-10."
The V-8 might have more vibrations than a V-10, but that has not stopped the never-ending quest to get engines to rev higher. The best V-10s in 2005 managed to top the 19,000-rpm mark, but Cosworth claims its V-8 has already exceeded 20,000 rpm.
The FIA, F1's sanctioning body, changed the engine rules for two main reasons.
First, a power cut to slow the cars down was needed for safety reasons. A 2.4-liter V-8 will generate about 750 horsepower compared to the 3-liter V-10s that were producing more than 900 horsepower and heading for the 1,000 mark.
Second, theoretically, the V-8 should cut costs, as it requires less mechanical parts than a V-10.
Not everybody agreed with the way the FIA went about accomplishing its goals. Mercedes-Benz racing chief Norbert Haug said all that has happened is that F1 has gone from the most expensive way to produce 900 horsepower to the most expensive way to produce 750 horsepower.
Still, a majority of the F1 engine manufacturers voted for the change. And engineers being engineers, they are relishing the new task.
"It's an interesting engineering challenge for everyone," Brawn said. "The engine has less torque and less power, but that actually has some benefits in the way that the tires work and the handling of the car."
Virtually all the teams have their V-8s out on the track testing this month, and this marks the first time that their engines have gone head-to-head.
"The exciting bit and the difficult bit about a big change in the rules is you don't really know where the benchmark is," Honda technical director Geoff Willis said. "It will be quite interesting for the early testing of the V-8s when all the teams are trying to work out whether they have got it right and whether they are strong in the right areas."
Brawn agrees that there are few reference points with the V-8s yet.
"We don't really know where we should be," he said. "What level of power, what rpm, what fuel consumption, what is the reference? Over a period in F1 you acquire that information. You can observe what other teams are doing; you can see what's achievable, and therefore you know what you have to try to achieve yourself. Nobody really knows with a V-8 whether 700 horsepower is enough, 750 or 800, who knows?"
Besides the switch to V-8s, there have been other changes to the engine rules.
Some exotic materials have been banned, as have the moveable, variable-length, air-inlet trumpets.
"That will have an effect on the torque characteristics of the engine," Willis said, "particularly during the start, which is another new challenge and something we won't have a good measure on until we get track testing"
Toyota test driver Ricardo Zonta said that "a little girl" could drive the 2.4-liter V-8s that feel underpowered compared to the 3-liter V-10s they replace. That's understandable. Have you ever heard a racing driver complain about too much horsepower!?
But former world Champion Jacques Villeneuve said he was pleasantly surprised by his first taste of the BMW V-8.
"It's hard to compare the V-8 with the V-10," he said, "but I was expecting a bigger loss of power and more vibrations. It was not too bad and actually quite nice to drive. In fact, you do feel a little loss of power, but it doesn't make driving less fun. The speed in the corners seems to be the same while you are going slower on the straights. Nevertheless, the driving will still be exciting and physical. Hopefully, since we are all going less fast on the straights, this will give us a bigger tow and this could mean more overtaking in the future."
The V-10s have not disappeared completely, as the rules will allow the smaller teams that do not have access to V-8s to run a power-restricted V-10. At the moment, only Scuderia Toro Rosso -- the former Minardi team now owned by Red Bull and featuring Californian Scott Speed as one of its drivers -- will use a Cosworth V-10. Some teams are already grumbling that the restricted V-10 will still be more powerful than the V-8s.
World champion Renault is the only team that will not test its V-8s in an interim chassis, as it deemed it too expensive and time-consuming. Instead, the Renault V-8 continues to test on the dyno until the new car is ready in January.
"We began our initial studies [with the V8] in September 2004," Renault F1 project manager Leon Taillieu said. "We have not taken any major risks with this engine. That means we are building on what we already know. The [2006 engine] will benefit from everything we learned on our championship-winning engine. The targets we set were the same as for every engine: to make it powerful and reliable, to optimize injection and combustion."
Bits may have been falling of the new V-8s on the dyno, and more than one V-8 has blown up during on-track testing, but Brawn predicts that the engines will be reliable once everything is sorted out.
"If you can start with a completely new engine design, then you can incorporate the features you want to achieve: reliability with best performance," he said. "