Quote:- "However, critical to this is VVT agility which, given it is oil pressure derived, it is not!"
Having made this statement, I feel I must justify my reasons for making it.
The rebuilding of my Brera engine did not start immediately I wrecked the 159 engine. I purchased it at least some 18 months prior to that little escapade. So by the time the 159 failed, I had done a fair bit of research into it. And it was this engine which provoked the design of my C.L.L.S. It was quite clear there were serious restrictions within the block and the main timing chain tension-er was right at the end of the oil galleries, where it simply got what was left after all other services were catered for.
With the quantity of white metal shards, liberally scattered around the Brera block, oil ways included, it was obvious the galleries would need pulling through. But I was curious about the VVT's. More so, given there appeared to be shards in them too! How could this be? There are micro-mesh screens across all three of the VVT Solenoid Ports. It became clear the VVT Rotors would need disassembling and inspecting. That is not an exercise for the faint heart-ed.
Sure enough, white metal shards littered the voids of the rotors so it was clear, the screens were not keeping contamination out. On inspecting the VVT solenoids, it was seen, "Flats" are cut into the separating "Walls" of each port, "bridging" the oil pressure feed to them, with both the advance port and the retard port. The existence of these shards in the voids, confirmed oil indeed could circumvent the ports proper and enter the voids via these flats.
From this, it became clear, when oil was flowing to advance or retard valve timing, pressure was being lost as the flats allowed oil to pass straight to the solenoid drain and out into the cylinder head. So flow rate was being reduced, increasing the time it took for the valve timing to "Set", by rotating the rotors. Fundamentally, this affects the inlet camshaft advance and the exhaust camshaft retard much more so than the inlet retard and the exhaust advance, but non the less affects the rotors in both directions. (1)
The camshaft rotors have internal spring bias which rotates them back to their "Parked" positions. These are; inlet camshaft fully retarded and exhaust camshaft fully advanced. (2)
Because of the direction of rotation of the engine, inertia forces the inlet camshaft naturally in the retard position and as a consequence, the strength of the inlet rotor spring is weak and movement is substantially dictated by oil pressure.
However, because of the direction of rotation of the engine, inertia on the exhaust camshaft is also in the retard direction. As a consequence of this, the internal spring of the exhaust rotor is extremely strong, to keep it in the advanced position. Good - luck to anyone who attempts to disassemble these rotors and then put them back together!
When the engine is switched off, the inertia of the valve train, plus the internal spring, returns the inlet camshaft rotor to the fully retarded, "parked" position, where the internal "Pin" locks it into position. In the case of the internal spring of the exhaust camshaft rotor, it is sufficiently strong enough to rotate the camshaft to the fully advanced position - against the inertia of the valve train and the "Pin" locks it into position.
At tick - over, the ECU ensures the solenoid valve ports are set such that the inlet advance port is open to "Drain" and the exhaust retard port is open to "Drain". This ensures the "Pin" remains "In". Operationally, the pin is forced out by the oil feed from the solenoid valves and initiates the "Fill" of the rotor voids to start camshaft rotation. (3)
For this very reason, tick - over should always be a rock - steady 750 rpm.
From the above, it appears obvious to the author, the camshafts; due to the continuous feed - oil "Bleed to Drain" via the solenoid "Flats", the speed of the camshaft rotation is already predisposed to be longer than necessary which compounds the issue of failures of the camshaft positional sensors - particularly the rear bank exhaust camshaft. (4)
However at a time when the ECU has "Set" the valve timing and both the inlet solenoid advance and retard ports are closed, inertia, + the internal spring will cause oil to be forced across the flats bridging the ports, causing the inlet camshaft to retard - move away from the angle dictated by the ECU. (5)
Equally, at a time when the ECU has "Set" the valve timing and both the exhaust solenoid advance and retard ports are closed, the internal spring will cause oil to be forced across the flats bridging the ports, causing the exhaust camshaft to advance - move away from the angle dictated by the ECU. (6)
Thus, the valve timing is never properly "Set", insofar as the angle chosen by the ECU is never maintained. (7)
One extremely detrimental consequence of this is, the exhaust camshaft will always be moving away from any retard angle the ECU has predicted in the direction of advance. Perhaps one of the reasons why the front bank manifold Cat displays evidence of extreme temperature - heat corrosion? This is because, when the engine is making power, the exhaust camshafts will be retarded by the ECU. But with the internal spring forcing oil across the bridge, the exhaust camshaft will become advanced, causing the exhaust valves to open early and causing the cat, and the head, to overheat. (

Reading many posts on forums, there have been reports of coil packs burning out on a regular basis, high oil consumption and early degradation of oil. Plus the ubiquitous rear bank exhaust camshaft position sensor failure code. It is inconceivable that Alfa set out to combine so many weak elements in the redesign of the Holden V6.
So there must have be a common denominator to all these issues, surely? Oil pressure certainly has a great bearing on timing chain tension and inadequate pressure will result in poor mechanical timing between front and rear VVT rotors. Reduced oil pressure will also increase the delay in the camshafts setting time between banks (Hydraulic Timing). And a leaky VVT System which fails to "Hold" the correct valve timing angle chosen by the ECU will result in power loss, overheating of cylinder heads, manifold catalytic converters and early oil degradation.
It is all very well to think that the oil temperature gauge on the instrument panel of these vehicles is sitting at the ideal. But that is the temperature of oil in the sump. Research has shown that actual "Bearing Face Temperatures", particularly under load condition, can be as much as 45 degrees higher depending upon application.
This neglects the fact that the returning oil from the heads, exits the block, via huge drainage ports, clinging to their walls by skin effect, where rotating journals immediately pull it into windage, coating the hot, cavernous internal block and increasing the transit time for it to return to the sump.
Chrysler demonstrated that the engine oil of a V8 could be sucked into windage and rotated around the crank, with the sump being completely emptied.
This was at a time when they were experimenting with windage plates and subsequently scrapers. However, the windage plate in this engine did not exist in the original version and was only added later. But it does not extend the full length of the sump. With the latest incarnation of this engine - will run until 2026 - it does. Plus they have made extensive modifications to the block including increased sump capacity and baffle plates to prevent surge. And I am led to believe improvements in oil pressure an flow distribution.
Heavy going I know - sorry for that. But I felt the need to justify my comments.
P.S. It was only some 2 - 3 years later when considering speeding the VVT timing up further that I investigated other systems which use separate oil pumps to derive their oil pressure. The intention was to use two high pressure pumps from the BMW V 8/10/12 - Vanos system I believe. I subsequently bought a couple which I intend to fit at a later date, relieving the engine oil pump of this duty and using the Vanos for everything other than the crankshaft and timing chains.
However, when I came across BMW's solenoid valve, there were no "Flats bridging the ports and if my memory serves me correctly, they only have a screen over the oil pressure feed port. Certainly the screens across the Alfa solenoids will introduce a pressure drop. BMW however appear to protect their system by only having a screen over the inlet, given no oil can circumvent it.
Why did Alfa do what they did is a mystery to me!