VVT
#2
02-17-2008 | 04:35 PM
Senior Member
Joined: Dec 2004
Posts: 960
RE: VVT
Mazdas sequential valve timing is a lot different than hondas v-tec
great link for vvt
http://www.mazda6tech.com/index.php?...4&Itemid=1
"Because camshafts are optimized for a single RPM, it would be beneficial if an engine could use two camshafts- one optimized for low RPMs, and the other optimized for high RPMs. Somewhere in-between, the engine would switch from one cam to the other.
This, in essence, is what Honda's VTEC does. VTEC allows two different cam profiles on the same shaft to switch nearly instantly, giving two very distinct timings. At higher RPMs, the valves open longer, faster, and higher for better breathing. At lower RPMs, the shorter valve openings keep the charge of incoming air at high velocity. The intake and exhaust valve opening times will overlap as RPMs rise, recycling some of the charge the outgoing air creates.
Mazda's engines are not quite so sophisticated. Mazda uses a static camshaft, however the shaft is attached to a cog that can advance or retard its rotation. The valves can open sooner or later, but never longer, faster, or higher. The cog is controlled by a precision oil pump, called the oil control valve (OCV). The car's computer tells the OCV how much to advance or retard the intake timing based on a number of input parameters, such as pedal pressure, engine temp, and more."
great link for vvt
http://www.mazda6tech.com/index.php?...4&Itemid=1
"Because camshafts are optimized for a single RPM, it would be beneficial if an engine could use two camshafts- one optimized for low RPMs, and the other optimized for high RPMs. Somewhere in-between, the engine would switch from one cam to the other.
This, in essence, is what Honda's VTEC does. VTEC allows two different cam profiles on the same shaft to switch nearly instantly, giving two very distinct timings. At higher RPMs, the valves open longer, faster, and higher for better breathing. At lower RPMs, the shorter valve openings keep the charge of incoming air at high velocity. The intake and exhaust valve opening times will overlap as RPMs rise, recycling some of the charge the outgoing air creates.
Mazda's engines are not quite so sophisticated. Mazda uses a static camshaft, however the shaft is attached to a cog that can advance or retard its rotation. The valves can open sooner or later, but never longer, faster, or higher. The cog is controlled by a precision oil pump, called the oil control valve (OCV). The car's computer tells the OCV how much to advance or retard the intake timing based on a number of input parameters, such as pedal pressure, engine temp, and more."
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