[psy31]

Pour ce qui est de la ducati, voici un extrait d'une interview de filippo Preziosi, le papa de la GP7 (spetembre 2006):

Ducati has already built an incredible 20 engines in
preparation for next year's new 800cc formula in
MotoGP, racing chief Filippo Preziosi has revealed.
Twenty engineers are working on the project in five
teams, including the areas of engine design, electronics
and what he called "the vehicle. We started the
project 15 months ago," he said. "The engine was on the
dyno six months ago. We have built 20 engines, all to
different specifications." All share the V4 platform, and
Ducati's trademark desmodromic valve-gear - unique in
motorcycle racing - which is apparently providing great
benefits with the higher rpm of the smaller engine. "We
have a big knowledge of the desmodromic system, and it
really helps us," Preziosi said. "It gives us good
performance and consumption. When you are at low and
medium rpm the system absorbs a lot less power than a
valve spring, so the fuel consumption is low and you can
use the fuel better." In some conditions the desmodromic
system absorbs 30 to 40% less friction than a valvespring
engine. With a valve-spring engine if you want to
run at 18,000 rpm you need a very strong spring. But at
four to eight thousand rpm you still have the same
spring, even though you don't need it. With the desmo
system you have no spring so the rockers operate with
the right force at all revs, with never more than you
need.
Preziosi declined to forecast the 800's rev ceiling
compared to the 17,000 rpm limit of the 990. "We have
to increase this, but we don't know by how much, because it
will be a compromise between performance, power and
driveability," he said. He suggested the bike's top speed
would be only 10-12 kph less than the 990, which seems
surprisingly optimistic considering its 20% reduction in
capacity, but the 800 should benefit aerodynamically
from a smaller frontal area.


En clair, le projet GP7 a commencé dès l'été 2005 !!! Ce qui explique une partie de la maturité de la GP7. Preziosi annonçait 10-15 km/h de moins que sur la 990 et grosso modo, la distribution desmodromique a l'air d'être la clé de la performance de la GP7 par rapport à un système classique.