Can you confirm that 5L dry sump tank is big enough, as I have heard that I need a 9L tank? I would prefer a rectangular tank, why should I use a circular tank?
The Duratec requires a slightly bigger oil capacity in the tank than engines which have cam belts. The reason for this is that the area where the chain runs allows oil to accumulate in this area and under certain conditions you could actually accumulate as much as 1.5 litres in this area. Because the system we have developed with Titan is a twin scavenge with an extremely efficient pump both on pressure and scavenge, the oil is less able to accumulate in any sections of the engine, either when the engine is under braking or acceleration as the oil is then evacuated at the front or rear scavenge depending on conditions. If you were running a single scavenge system, the oil can only be extracted from either the front or rear of the engine. Normally the scavenge fitting is placed at the rear of the sump, which is fine when the engine is accelerating but not under braking and certain cornering conditions. This may be the reason why some people are recommending a huge capacity for oil. Steve can only assume that some systems are so bad, that vast amounts of oil are accumulating in the engine itself and not able to reach the single scavenge (or a low quality twin scavenge system). This way the tank slowly empties to the point where air can be drawn in to the oil system causing damage, so their solution is to fit a huge capacity tank. This creates many issues, the most important is that your engine under these conditions is effectively wading through a huge amount of oil, which could not only damage it, but is losing performance.
As far as using a circular tank is concerned, it is far more efficient for the returning air and oil mix to be spun around the wall of the round tank so the air separates out and only oil can then reach the bottom of the tank. A rectangular tank cannot work in the same way and the oil would simply bounce off the walls, carrying the air which is trapped in it to the bottom of the tank. So a 5 litre tank capacity we have found is sufficient even on our high specification engines. This does not mean that your oil system will not contain more oil, as this will depend on the length of your oil pipes, oil coolers, oil filter and any other components in the system. It simply means the tank itself will hold 5 litres and the oil should be checked on our tank with the engine running or immediately after stopping that the oil level is just below or level with the top baffle (and not above).