On Fri, 9 Apr 2004 20:26:01 -0400, "Steve W." <me@homer.org> wrote:

>"M C" <mcunix@swbell.net> wrote in message
>news:106mkgcb8hdi616@corp.supernews.com...
>> >
>> > Your explanations are very confusing. In this post, you make it
>sound as
>> if
>> > VTEC can change the valve timing continuously. The cam has only two
>> > profiles and it switches between the two when the engine deems it
>needed.
>> > It rides on two for economy and rides on the third one (locking all
>three
>> > together) for performance. As far as I understand, a non-VTEC
>engine
>> can't
>> > really be adjusted, the profile would have to be ground on the cam.
>You
>> > make it sound as if adjusting the valves will give you a different
>cam
>> > profile to adjust the power band.
>> >
>> > Also, as I understand it, the engine uses different length runners
>to help
>> > boost torque at low engine speeds and shorter runners to boost the
>top
>> end.
>> > Once the engine reaches a certain speed, the runners are activated
>(I
>> > believe it's butterfly valves) and the short runners come into play.
>> >
>> > -Bruce
>> >
>> >
>>
>> I knew about VTEC for a long time but never really read about it. I
>think it
>> is a brilliant design for getting the best of 2 worlds of valve
>timing. I do
>> wonder a about the reliability issue. More parts means more stuff to
>wear
>> out and fail. Also, the high RPM lobe actuates double duty for the
>other 2
>> when it is used. I'm sure honda accounted for this with extra lube if
>> needed. Also, most cars don't run at high RPM all the time. Still, I
>think
>> this is an awsome technology and doubtless increases preformance and
>> usability. Does any other maker use similar technology?
>>
>>
>Considering how long this technology has been in use I wonder why Honda
>claims it as theirs? The Corliss valves used on old steam engines was a
>mechanically controlled variable valve system that varied valve action
>based on engine speed, that was in 19th century.

Hardly the same "technology" as I see it. In a steam engine, the "intake"
valve stays open on the power stroke so, in fact, varying the valve open
time is a method for controlling the duration of the power stroke and
therefore speed of the engine... not the contrary. Those are also rotary
valves which do not need any variation in "lift" amplitude.

I'm not sure what Honda actually claims nor what similar automotive systems
might have preceded their system but theirs was certainly innovative when
first introduced... in F1 IIRC.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??