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posted November 03, 2006 04:58 AM
Kawasaki Brings Variable Valve Timing to the Mainstream with the Concours 14 From Motorcycle Daily
By Alex Edge
When I last discussed variable valve timing and lift technology, I was writing about the future of sportbike engine development (see http://www.motorcycledaily.com/07february06_cams.htm). It came as something of a surprise, then, when I heard the rumors that the first application of TRUE variable valve timing in a mass-produced motorcycle would be a sport-tourer - specifically, Kawasaki's 2007 Concours 14.
It does make sense, however. For all its terrific top-end rush, the 1352cc inline four found in the 2006 ZX-14 does respond somewhat sluggishly in the lower rpm range, a problem that will only be exacerbated by the greater weight of the new Concours. For those of you who have been reading up on the ZX-14, you know that the soft low-end power can be remedied by removing the restrictive butterflies in the intake tract, but it is likely that this change would also increase the emissions below 7,000rpm (above which the butterflies are fully open).
For Kawasaki's engineers, using a variable valve timing system is a much more elegant solution. We don't know yet what form of variable timing will be used, but rumors suggest that rather than a two-valve/four-valve switchover (like Honda's Interceptor), it will be a true variable valve timing system. This will allow the Concours 14 to effectively use a smaller camshaft at lower RPM, which will boost low-end power and torque, while at the same time offering improved fuel economy and lower emissions.
I find it unlikely that the Concours motor will use a multiple-profile system (like Honda's VTEC automobiles), which would give a pronounced step in the power output at the change-over point. This could be a safety issue in such a powerful machine, as the jump in power might cause the rear wheel to break traction at an inopportune time. Instead, I suspect the Concours will feature a variable timing system that can advance or retard one or both of the camshafts by means of some sort of motor on the end of the cam. This would allow the cams to have less overlap at low RPM, which, as I said, will increase power and torque while reducing emissions and increasing fuel economy. At higher RPM, the cams can offer more overlap to sustain a healthy power curve.
Of course, it's much more complicated than that - most automobiles that use such systems also take into account throttle position and engine load (in addition to RPM) in selecting camshaft timing, which means the ECU can optimize for mileage under light-throttle, highway cruising conditions, and also optimize for power at heavy throttle openings.
As I said in my article about camshaft design, variable valve timing carries a host of benefits for any powerful motorcycle which is intended to be used over a broad RPM range (i.e. a STREETbike). The Concours 14 should show that it's usefulness extends beyond sportbikes to motorcycles of any type, and it's only a matter of time before other manufacturers follow in Kawasaki's footsteps.
posted November 30, 2006 08:07 AM
part of that sluggishness
is a direct result of the 14 being neutered
in 5 out of 6 gears
a quasi form of traction
more to the point "stupid control"
in the context of a sport tourer
where most of the time is spent on the hi-way
cruising between 45....75mph
any engineer can design build & accomplish a 150hp
180hp ..... a 200hp sport tourer thats ridable
evwen the usual passing a car......semi etc
variable valve timing will scarely be noticed
certainly NOT necessary
drop 1 ...2 gears
get it done......get a grin
go back to stealth mode
variable valve timing will offer NO Performance
advantages for the upper HP & torque ranges that cant be designed in
built correctly & tuned properly
without the complexity...... repair/reliabilty issues
bikes today have more than twice(2x) the HP & torque(except HD) of
comparable bikes 10-15 years ago that motivated quite well
within their designated parameters
this is a new entry in an expanding market for KHI
1 that willl take them a while to discern
one in which they will have to get away from hi HP & speed
to more miles & stealth
the 14Concours offers more by leaps & bounds over the previous model
some might have to Wowed by gadgets....gimcraks.... bells & whistles
with some leds & lcds thrown in for flava
just to loosen the purse strings to participate
nothing was wrong with the old Concours
it would eat up interstate with the best of them
utilitarian.......cheaper......reliably
that was the most impresive thing about an otherwise
bland outdated bike
the new 1 will cost more than twice as much
it aint twice the bike
it wont do twice as much
it wont be twice as good
it very well may end up being twice as complicated
never a good thing
____________
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or break your ass...!!
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posted November 03, 2006 04:58 AM
