Have a look at this engine cross-section line drawing. It purports to
be a patent drawing of a “super streetbike” that Honda will build as a
homologation special for the FIM Superbike World Championship. And it
is said to be closely related to the production racer Honda plans to
offer for sale to race teams for the 2014 MotoGP season.
As you can see, this is a 90-degree V-Four. The front cylinders’ axis
is 35 degrees above horizontal. Remind you of a Ducati? Why, yes! For
two years, some have been saying that Ducati’s problems in MotoGP come
from the excessive bulk of its 90-degree V-Four, pushing the engine’s
cg so far back from the front wheel that there’s not enough load on
the front to keep the tire hot. But wait! Recently, Honda arranged an
impromptu “photo op” in which its highly successful and series-leading
RC213V engine was seen to also have a 90-degree Vee angle. Revelation!
Honda has a historic commitment to V-Fours, having pioneered the
super-radical but never successful oval-piston NR500 in the late 1970s
then spun off a long series of V-Four street- and racebikes, including
the VFRs, RC30 and RC45. Why? Because its engineers did not like the
inherent vibration and crankcase flexure of inline-Fours. They should
know: Honda won many GP championships in the 1960s with air-cooled
inline-Fours, despite their problems.
What are the V-Four’s advantages? First, a 90-degree Vee engine can
easily be given perfect primary balance without resorting to balance
shafts. Second, a compact V-Four centralizes mass very well, as it is
the engine closest to being a cannonball. In your mind, compare the
ease of turning corners carrying a) a 12-foot ladder weighing 24
pounds or b) a 24-pound cannonball.
Ducati also has long experience with 90-degree Vee engines, both in
SBK, where they are Twins, and in MotoGP, where they are V-Fours. The
front cylinder of Ducati’s original, early 1970s’ V-Twin was only 15
degrees above the horizontal, so that long cylinder pushed the heavy
crank and crankcase rearward, giving that bike its long 60-inch
wheelbase and very low front tire loading. To get stability with so
little weight on the front, Ducati resorted to a 31-degree steering
rake angle and 4 1/2 inches of trail. Result? Very slow and rather
heavy steering.
Since then, Ducati has progressively raised the angle of the front
cylinder to allow the engine’s cg to move forward, allowing shorter
wheelbases and somewhat less-conservative steering geometry, but the
problem is not solved, only reduced. Every manufacturer picks a set of
compromises and works with it.
Now, comes the shock news that Honda is winning races with the very
same 90-degree Vee angle. How can this be? The drawing shows at least
three methods Honda has used to make its engine more compact, so it
can be moved forward enough to produce good performance, even on the
spec Bridgestone tires that have been such a problem for Ducati:
1) This engine has short connecting rods. Whereas Formula 1 racing
engines have a 2.5 rod ratio (center-to-center length divided by
stroke) and conventional race engines lie between 2.0 and 2.2, this
engine has a 1.8 ratio. One year at Daytona, John Britten reached into
his pocket and pulled out a titanium rod. “Cosworth is using a 1.8 rod
ratio, so that was good enough for me,” he said.
2) The wristpins in this engine’s extremely short pistons are as high
in the piston as they can possibly be. The outside diameter of the
con-rod’s small end barely clears the underside of the piston crown.
3) By making the exhaust valves shorter than the intakes, the cam
cover can be angled to give more cylinder-head-to-front-tire clearance
on the exhaust side (Ducati has also used this technique). Why not
shorten both? Long intake-valve stems allow the use of high-flowing,
nearly straight ports. These are not as essential on the exhaust side.
Yes, but maybe Ducati has already done all these things, right? Maybe
not. Think of how factory rider Andrea Dovizioso has recently
qualified a lot higher than he has finished. When I asked Ducati
MotoGP Project Manager Paolo Ciabatti about this, he said it is
because “our bike is quite physical to ride.” That is, it takes a lot
of muscle to heave it around. One or two fast laps in qualifying are
no problem, but 24 to 30 laps of racing are exhausting. This suggests
the Ducati still has the slower steering geometry required to
compensate for less-than-optimal weight on the front tire.
Another point is that we know Ducati’s general philosophy is to make
all the power that engineering can stuff into the engine, then use
electronics to make it rideable. Short rods are not preferred for the
highest power (greater rod angularity pushes the pistons harder
against the cylinder walls, generating extra friction), and Ducati
already has experience with the heat problem of high wristpin
location, causing lube breakdown and metal pickup on the pin.
Okay, maybe I’m building castles in the air, but the drawing is
suggestive. And the Ducatis are a second a lap slow. If Honda can do
it, Ducati, whose engineers are just as intelligent and well-educated,
should be able to do it, too. To add an element of crudity to the
discussion, an extra 30 million R&D dollars wouldn’t hurt, either.
MotoGP is not a contest of equals.
be a patent drawing of a “super streetbike” that Honda will build as a
homologation special for the FIM Superbike World Championship. And it
is said to be closely related to the production racer Honda plans to
offer for sale to race teams for the 2014 MotoGP season.
As you can see, this is a 90-degree V-Four. The front cylinders’ axis
is 35 degrees above horizontal. Remind you of a Ducati? Why, yes! For
two years, some have been saying that Ducati’s problems in MotoGP come
from the excessive bulk of its 90-degree V-Four, pushing the engine’s
cg so far back from the front wheel that there’s not enough load on
the front to keep the tire hot. But wait! Recently, Honda arranged an
impromptu “photo op” in which its highly successful and series-leading
RC213V engine was seen to also have a 90-degree Vee angle. Revelation!
Honda has a historic commitment to V-Fours, having pioneered the
super-radical but never successful oval-piston NR500 in the late 1970s
then spun off a long series of V-Four street- and racebikes, including
the VFRs, RC30 and RC45. Why? Because its engineers did not like the
inherent vibration and crankcase flexure of inline-Fours. They should
know: Honda won many GP championships in the 1960s with air-cooled
inline-Fours, despite their problems.
What are the V-Four’s advantages? First, a 90-degree Vee engine can
easily be given perfect primary balance without resorting to balance
shafts. Second, a compact V-Four centralizes mass very well, as it is
the engine closest to being a cannonball. In your mind, compare the
ease of turning corners carrying a) a 12-foot ladder weighing 24
pounds or b) a 24-pound cannonball.
Ducati also has long experience with 90-degree Vee engines, both in
SBK, where they are Twins, and in MotoGP, where they are V-Fours. The
front cylinder of Ducati’s original, early 1970s’ V-Twin was only 15
degrees above the horizontal, so that long cylinder pushed the heavy
crank and crankcase rearward, giving that bike its long 60-inch
wheelbase and very low front tire loading. To get stability with so
little weight on the front, Ducati resorted to a 31-degree steering
rake angle and 4 1/2 inches of trail. Result? Very slow and rather
heavy steering.
Since then, Ducati has progressively raised the angle of the front
cylinder to allow the engine’s cg to move forward, allowing shorter
wheelbases and somewhat less-conservative steering geometry, but the
problem is not solved, only reduced. Every manufacturer picks a set of
compromises and works with it.
Now, comes the shock news that Honda is winning races with the very
same 90-degree Vee angle. How can this be? The drawing shows at least
three methods Honda has used to make its engine more compact, so it
can be moved forward enough to produce good performance, even on the
spec Bridgestone tires that have been such a problem for Ducati:
1) This engine has short connecting rods. Whereas Formula 1 racing
engines have a 2.5 rod ratio (center-to-center length divided by
stroke) and conventional race engines lie between 2.0 and 2.2, this
engine has a 1.8 ratio. One year at Daytona, John Britten reached into
his pocket and pulled out a titanium rod. “Cosworth is using a 1.8 rod
ratio, so that was good enough for me,” he said.
2) The wristpins in this engine’s extremely short pistons are as high
in the piston as they can possibly be. The outside diameter of the
con-rod’s small end barely clears the underside of the piston crown.
3) By making the exhaust valves shorter than the intakes, the cam
cover can be angled to give more cylinder-head-to-front-tire clearance
on the exhaust side (Ducati has also used this technique). Why not
shorten both? Long intake-valve stems allow the use of high-flowing,
nearly straight ports. These are not as essential on the exhaust side.
Yes, but maybe Ducati has already done all these things, right? Maybe
not. Think of how factory rider Andrea Dovizioso has recently
qualified a lot higher than he has finished. When I asked Ducati
MotoGP Project Manager Paolo Ciabatti about this, he said it is
because “our bike is quite physical to ride.” That is, it takes a lot
of muscle to heave it around. One or two fast laps in qualifying are
no problem, but 24 to 30 laps of racing are exhausting. This suggests
the Ducati still has the slower steering geometry required to
compensate for less-than-optimal weight on the front tire.
Another point is that we know Ducati’s general philosophy is to make
all the power that engineering can stuff into the engine, then use
electronics to make it rideable. Short rods are not preferred for the
highest power (greater rod angularity pushes the pistons harder
against the cylinder walls, generating extra friction), and Ducati
already has experience with the heat problem of high wristpin
location, causing lube breakdown and metal pickup on the pin.
Okay, maybe I’m building castles in the air, but the drawing is
suggestive. And the Ducatis are a second a lap slow. If Honda can do
it, Ducati, whose engineers are just as intelligent and well-educated,
should be able to do it, too. To add an element of crudity to the
discussion, an extra 30 million R&D dollars wouldn’t hurt, either.
MotoGP is not a contest of equals.
