12-09-2013, 09:05 AM
(11-09-2013, 08:30 PM)Dum-Dum Wrote: On the intake flow subject Im pretty sure that the 2.2 is a pair of 30mm valves and the 8v is a 36mm both with 6mm stems so the 2.2 16v will flow more at the valves (if a very quick mental estimate is right)
Think for a second WHY Peugeot went for the 16v head... To use TWO sets of valves to be able to have higher gas velocity all the time to give a stronger swirl (that's also why they had swirl flaps - so they can cut off a valve per cylinder at lower RPMs for stronger swirl) - it's PURELY down to emissions..
Exact same reason the 2.1 12v has an extra 2 inlet valves - two pipes with a smaller bore will result in the same amount of airflow, but higher velocity in them... But also causes more restriction - since the swirl effect uses energy to be generated...
Your gains of having a 2.2 engine are negligible, on the basis that you could quite happily get to the point where more boost doesn't equal more air in the cylinders because the head is the restriction - once you get to that point, whether you have a 2.2 litre engine or a 2.0 litre engine or even you could put that cylinder head on a 1.6 litre engine, you've reached the limits of the head - I would put money that the 1.6 litre engine would give as good results as a 2.2 litre with the same head... That's a disadvantage of turbocharged engines - but also an advantage... Displacement is heavilly masked by turbocharging...
Look at that 1.5 ish litre Supercharged XU some chap on the GTi6 forum did, 230hp with the same hardware as the usual low boost engines - that's all because the head flows well, therefore you don't need the displacement, since the forced induction is doing a great job of that for you!
If however you make the cylinder head flow better, then fair enough, but I guarantee you'll run into other problems before you need the extra displacement to help you out... Again, therefore, the 2.2 litre is a pointless upgrade.
