<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:<hr /><font size="1" face="Verdana, Helvetica, sans-serif">Originally posted by Scott McI:
<strong>Ahhh - so the variator is a thing that does stuff to the valves to open or close more at different revs. I think I'll see if I can get a job writing the Haynes manual for a GTV then!
Are there 2 parts - variator belt & the actual variator? If so, is the variator a bit like a gear wheel engaging the cam?
</strong><hr /></blockquote><font size="1" face="Verdana, Helvetica, sans-serif">I found this article that explains the 'thingy' on our engines:
The twin overhead cams, driven by a double chain, act directly on the valves set in a tight Vee configuration (46o).
The timing of the valve train is not fixed as in most present day engines, but can be adjusted by a patented device conceived and produced by Alfa Romeo, the timing variator.
This is an electro-hydraulic actuator keyed onto the gear that drives the camshaft acting on the intake valves. This actuator enables the camshaft to be shifted into two different angular positions and to modify the intake valve opening durations. Its operation is controlled by the electronic control box of the integrated ignition and fuel injection system.
Valve timing actuator logic is predetermined so that overlap - i.e. that fraction of the engine's operating cycle when both the exhaust and the intake valves are open simultaneously - is shorter at low revs and with lighter loads, and longer at higher engine speeds when extra power is required.
This offers the following advantages: at high and medium-high engine speeds or whenever additional power has to be provided (normal timing) cylinder filling is optimal, maximising power output and torque; at low and medium-low revs and lighter loads (delayed timing), fluctuation-free operation is ensured combined with a reduction in specific consumption; at all engine speeds, noxious emissions are minimised.
I hope all this manages to confuse you a bit more!!!!