VVT-i and BEAMS are generally used to make the torque curve more flat. Rather than switching to radically timed cams that emphasize high RPM, Toyota has chosen to make the engine more flexible with good acceleration available even at low engine RPMs.
If you want to learn more about variable valve timing systems, go here:
http://www.fortunecity.com/silverstone/lancia/58/technical_school/engine/vvt_1.htm
Note that the Celica 2ZZ-GE engine was co-developped with Yamaha engineering. Toyota probably cannot apply VVTL-i to any of their (other) engines unless they work out an arrangement with Yamaha.
2ZZ-GE info:
http://www.corollaperformance.com/TechInfo/2ZZGE.html http://www.hinterland.com.au/November99/celicakit.htm#17
"High Lift, Long Duration: Toyota's variable valve lift system operates on the inlet and
exhaust valves. The Toyota 2ZZ-GE engine switches to the high-lift camshaft settings
at 6000rpm. The high-lift cam lobes increase intake lift by 54 percent to 11.2 mm and
exhaust lift by 38 percent to 10.0mm.
The high-lift cam profiles have the effect of increasing valve-opening duration, and
therefore the range of inlet timing variation.
Valve overlap can vary between 4 degrees (full-retard inlet setting and low-speed lift
settings) and 94 degrees (full advance inlet and high- speed lift settings).
A valve overlap of 94 degrees would normally be associated with full race engines.
For comparison, superseded Celica's 5S-FE engine had six degrees of valve overlap
and the sports two-litre 3S-GE engine in the first front-drive Celica model had 14
degrees of overlap.
Inlet camshaft timing is varied according to engine revolutions, throttle position, inlet
camshaft angle, engine coolant temperature and intake air volume.
Variable Timing Activation:
Toyota Celica's VVTi is a computer controlled and oil-pressure activated push-push
type system, using the engine oil.
The engine ECU can command the system to advance or retard the inlet camshaft
timing, thereby providing for faster response.
The hardware is a camshaft timing oil control valve (mounted adjacent to the inlet
camshaft gear wheel) and a VVTi controller mechanism built onto the inlet camshaft
timing gear.
The camshaft timing oil control valve is a spool valve, controlled via a coil and plunger
by the engine ECU.
It can signal advance, hold or retard.
The VVTi controller consists of a housing on the front of the timing wheel, driven from
the timing chain, and a four-bladed vane coupled with the intake camshaft.
When the engine ECU requires a change in inlet timing, it signals the oil control valve
to provide oil pressure to either the advance or retard side of the four vane chambers.
Inlet cam timing is set to the maximum retard position for engine start-up, operation at
low engine temperature, idle and engine shut-down.
A locking pin in the controller locks the camshaft timing in the maximum retard
position for engine start-up and immediately after start-up (until oil pressure is
established) to prevent any knocking noise.
Celica's VVTi system can vary inlet camshaft timing over a range of 43 degrees relative
to crankshaft angle.
However, the variable lift system has the effect of increasing valve opening duration, so
the full range of inlet timing variation is 68 degrees.
(Taken from the maximum retard intake valve opening in the low-medium engine speed
range at minus 10 degrees BTDC to the maximum advance intake valve opening in
high engine speed range at 58 degrees BTDC.)
Variable Lift Activation:
Toyota's intelligent variable valve lift system uses a cam change-over mechanism to
increase the
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