RE: Technical question: VANOS

[michael_kohlbrenner@xxxxxxxxxxx]

I don't think that either approach -- the cam profile switching
of VTEC or the variable cam timing of VANOS -- is necessarily
more or less complex than the other.

I don't think that there is a huge cost difference between the
two approaches.

There is also very little evidence that one approach or the other
produces more specific power (power/displacement) or a better
torque curve.

Both approaches also lend themselves to either the "only bolster
the low-end" objective or "increase peak power in a driveable
package" objective.  VTEC, in its SOHC implementations, provides
only modest peak power gains but with a widened torque curve.
It is the DOHC VTEC implementations that give both.  The same
goes for VANOS.  In the single VANOS implementations, which
work only on the intake side, there is primarily only widening
of the torque curve.  The Double-VANOS systems in the M engines
has the same objective as DOHC VTEC -- significantly improved
peak power with a wide torque band.  Interestingly enough, these
engine families are fairly close in their results as measured
by power/displacement, torque/displacement and shape of the
torque curve.

If you ask me, they are nearly equally effective ways to get
the job done.

Perhaps Toyota now has the best approach, which appears to be
to combine the two approaches.  The 1.8l in the new Celica GTS
makes 180 HP, which beats the same displacement in the Integra
GS-R by 10 HP.  They were also smart enough to give it a six
speed, which the Hondas sorely need.  (I don't know exactly how
this system is implemented, so take my statement with the
appropriate dose of sodium chloride crystals.)

Somebody is going to eventually solve the technical problems
associated with fully controllable valve actuation that doesn't
involve fixed cam profiles at all.  Then, we'll REALLY have
something!

Regards,
Mike Kohlbrenner

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