Re: V-TEC/Non-V-TEC?
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?? |
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