|
By Daniel Coe Images By Tom Riles Layout by Mark Lesselyoung
Imagine the confidence - or daring - of Ducati North America.
The importer decided to introduce the new 998 Ducati flagship at Buttonwillow,
California, a track with the shimmering ambience of a desert parking lot.
The 998 would have to dazzle the U.S. and Canadian press without the help
from glamorous surroundings. Buttonwilllow, better suited to launch something
powered by solid-fuel, has nothing in common with the rich atmospheres
of the great racetracks like Monza and Misano. So Circuit Primitivo Buttonwillow
may have shocked and somewhat embarrassed the official entourage from
Ducati Motor SPA, a group that included factory engineers, technicians,
and Ducati's new Public Relations Manager, Ms. Myrianne Gaeta. Not to
worry, the 998 overcame all.
At first glance, with its bodywork in place, the 998 appears
to be a 996 with a one-digit difference. Just standing there looking at
the 998, a satisfied 996 owner might well be unmoved and register no changes
in his vital signs... until his first ride. Then the 998 will electrify
him, his vital signs will soar, and later his 996 will feel a little empty,
as if something were missing.
The 998 is evolutionary, but it developed from a clean
ream of drafting paper. There are a few carryovers, but not much: connecting
rods, dry clutch, and a few transmission gears. Otherwise the whole engine
has been totally redesigned. Ducati engineers call the 998 V-twin the
"Testa Stretta" which means, "compact head." With such changes in a model
year one might expect equally significant changes with the chassis of
the 998. However given Ducati's recent successes in the world championship,
the current design was more than capable to handle the increase in 998/999
horsepower.
The heads are quite different from the 996's. Both intake
and exhaust tracks have been reconfigured using much steeper, more vertical
angles into the combustion chamber. The included valve angle between intake
and exhaust valves has been dramatically reduced, thus making way for
larger valves. But the narrower valve angle reduces the room for the desmo
system, so the closing rocker mechanisms were relocated outside the cavity
between the camshafts. The journals that locate the closing rocker pivot
pins now reside outboard of the camshafts. Meanwhile, the intake rocker
system has been moved closer to the centerline of the cylinder head. To
further reduce reciprocating weight and increase longevity, newly designed
rocker arms are lighter and have received thicker, more improved chrome
surfaces. The tub or channel housing each spark plug have been replaced
with steel, while the spark plug diameter has been reduced from twelve
to ten millimeters. These modifications allow for the additional space
needed in accommodation of the larger valves. The addition of steel in
the center section of the head also serves to strengthen the area immediately
surrounding the pin journals of the rocker arms. Gone are the roller bearings
supporting the camshafts, which have been replaced with a simple retainer
and plain bearing design. Ducati engineer Gennaro Cugnetto notes that
you would not find roller bearings supporting F1 camshafts, adding, "This
is only another part to fail." Both the intake and exhaust valves have
grown considerably. Intake valve diameter has increased from 36 to 40
millimeters. Exhaust valves grew three millimeters, from 30 to 33. These
are not small increases and these changes would have been impossible within
the confines of the previous 40-degree (20/20 included angle) 996 cylinder
head design. The narrower included valve angle in the 998 of 25 degrees
(intake valve 12 degrees/exhaust 13 degrees) combined with the fitment
of the smaller diameter spark plug made everything more compact and therefore
possible. Can we say breathe?
|