hollus wrote: ↑06 May 2017, 17:33
I think this was discussed at some point in the past ~30000 posts, but I'll put it out there again:
Would there be any possible benefits to running only 4 cylinders? Would it even be legal?
I m thinking along the lines that a 4 cyl engine is often more efficient than a 6 cyl engine, so maybe a 4 cyl engine with 1.067 L effective capacity might have some merit to it, but this is sooooo far from my zone of comfort!
In particular I am thinking of benefits from having 2 "fake cylinders", which do not need the same space, structural integrity and cooling as the others, or maybe of running only 4 of the 6 cylinders at any time, but cycling so that each cylinder only fires in 2 of each 3 opportunities, with the third one left mostly for cooling/venting purposes.
This might even interact with some rumors of engines purposely revving much higher than 12000 rpm (or trying to).
Let's look at it another way. What if the formula was 100 kg/hr max fuel flow etc but no stipulation of engine displacement - only the displacement per cylinder. Would 6 cylinders (ie 1.6 litres) be the magic number? I doubt it. In fact your 4 cyl, 1.067 L is probably a lot closer to the money. Less friction, less combustion surface area (heat loss). Whether it could be done (fully implemented I mean, with only 4 pistons moving) without infringing the rules I doubt very much.
As far as cycling cylinders, they almost certainly do that already - for part load operation. Which begs the question - why not do it at full load if it increased efficiency? The friction benefit would not be there but any combustion benefit?? would.