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wow... i seriously had no idea that the z32's had variable valve timing! a buddy of mine has a honda prelude with vtec and you can really hear it in the exhaust when it kicks on. never noticed such a drastic pitch change with my Z...

does it work similar? like does it kick in at a certain rpm or is it gradual?
 

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It's about the same, but VTEC has variable lifter height or something along those lines.

Most cars today have some form of variable valve timing, it's just named different things for different manufacturers.
 

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Honda's VTEC system has a hydraulically actuated cam that switches intake cam profiles entirely. It runs the "mild" profile at low-mid RPM and totally switches to the "hot" profile at a certain higher RPM value. It is an "on/off" system that runs one of two different intake cam profiles. The "hot" profile is a longer duration opening with a higher total lift.

Nissan's Variable Timing Control (VTC) system uses an intake cam that is rotated about 10 degrees advanced in the mid-range only. At a certain RPM (not precisely sure what it is) the VTC system is engaged and the entire intake cam is rotated on a helical gear, advancing timing about 10 degrees. At a certain higher RPM (again, not sure specifically what RPM) the VTC system is disabled and the cam returns to the standard position. That is why the '96 Z32 makes roughly the same peak power without the VTC, because at peak RPM the VTC isn't engaged on the older Z32s.

Honda's i-VTEC system incorporates both of these concepts, enabling timing advance/retardation along with a "hotter" cam profile at higher RPM. Toyota, Mitshubishi, BMW, Porsche and others have all developed similar systems and incorporate them into most newer vehicles. Honda = i-VTEC, Toyota = VVTi, Mitsubishi = MIVEC, BMW = VANOS, Porsche = VarioCam, etc.

Just thought that might help a little.



Post Edited (Jan 12, 10:36am)
 

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thanks guys! that's some really cool info.

i bet thats why my car gets better gas mileage going 80-85 @ ~3800 rpms than it does going 70 @ 3000 rpms. better torque in the mid range



Post Edited (Jan 12, 6:13pm)
 
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