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Old 01 Apr 2004, 01:56 am
Randolph
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Default Re: V-TEC/Non-V-TEC?

M C wrote:
<snip>

> Still, I think
> this is an awsome technology and doubtless increases preformance and
> usability. Does any other maker use similar technology?


Honda's VTEC uses several cam lobes as described earlier, each lobe
having a different timing and lift.
Toyota's VVT uses a different approach, where the cam shaft can be
shifted with respect to the sprocket, thus the timing is varied but the
lift is constant.

Honda's i-VTEC adds (over VTEC) the sprocket shifting that VVT uses
(which is not new and not invented by Toyota) and Toyota's VVT-i adds
(over VVT) the multiple cam lobes that VTEC uses. For all practical
purposes i-VTEC and VVT-i, are identical, even though a different
mechanism is used to select which cam lobe to use.

The original VVT had only two timing position, nothing in between. Both
VVT-i and i-VTEC has continuously variable timing.

BMW has had VANOS for years, it is a sprocket shifting mechanism similar
to VVT except that timing is continuously variable. Double VANOS is the
same, but applied to both the intake and the exhaust cams.

BMW now has valvetronic where the valve lift is continuously variable.
Valvetronic engines have no throttle, instead the amount of valve lift
is used to regulate the amount of air entering the cylinders.

Mitsubishi's MIVEC is similar to VTEC.
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Old 01 Apr 2004, 08:17 am
Stephen H. Westin
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Default Re: V-TEC/Non-V-TEC?

Randolph <trash@junkmail.com> writes:

> M C wrote:
> <snip>
>
> > Still, I think
> > this is an awsome technology and doubtless increases preformance and
> > usability. Does any other maker use similar technology?

>
> Honda's VTEC uses several cam lobes as described earlier, each lobe
> having a different timing and lift.
> Toyota's VVT uses a different approach, where the cam shaft can be
> shifted with respect to the sprocket, thus the timing is varied but the
> lift is constant.


<snip>

> BMW has had VANOS for years, it is a sprocket shifting mechanism similar
> to VVT except that timing is continuously variable. Double VANOS is the
> same, but applied to both the intake and the exhaust cams.


Ford has a similar system in at least some Zetec 4-cylinders. It was
designed to help get the Escort ZX2 into a lower emissions category,
as I recall. There are probably others.

> BMW now has valvetronic where the valve lift is continuously variable.
> Valvetronic engines have no throttle, instead the amount of valve lift
> is used to regulate the amount of air entering the cylinders.
>
> Mitsubishi's MIVEC is similar to VTEC.


--
-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.
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