On Wed, 31 Mar 2004 17:22:47 -0800, "M C" <mcunix@swbell.net> wrote:

>>
>> 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.

That's what I thought when it first became an option but Honda claims there
has not been a single engine failure by or due to VTEC mechanisms.

> 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?

Yes there are other similar mechanisms, with similar effects but I haven't
looked to see how the actually work - I'd assume they were designed to
avoid patent issues with Honda. IIRC it was Rover which which developed a
completely variable lift mechanism - IOW not 2 or 3-stage - which was not
widely implemented, partly because the company descended into financial
ruin before it could be commercialized.

Rgds, George Macdonald

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