Maybe this will help...an article in SCC talked about effects of a 10# aluminum flywheel in a Focus with stock 22# fly...should be pretty similar for Contour.
I do not have the equation they gave but the deal is that flywheel weight is more of an issue at low rotational speeds and the benifits of lightening it are greatest in low gears and decrease in higher gears. You can calculate the net wheel HP gains (really decreased losses)...
1st gear ....equivalent to gaining 26 HP (you will feel that!)
2nd gear ...equival;ent to gaining about 9 HP
3rd................................about 5 HP
4th................................about 1 or 2 HP.
Now, when you dyno, it is in 4th gear...so it will look like little or no gain. But, if you can get traction in first with the extra power, you WILL be quicker. If you just spin wheels anyway, you will not.
What is the downside...
1) It will be harder to drive smoothly, esp off the line with more jerking. OEM carmakers do not want to build a car that makes it seem like you cannt drive!
2) faster dropping revs = good for race driver, bad for syncros (we are weak here BTW).. OEM would either need to put in stronger syncros or have a higher failure rate..neither is desireable.
3) Some strength is sacrificed. esp with aluminum. (using steel insert can make a strong al fly, just more $$)
4) More NVH
5) Less stored inertia for launch (more related to smoothness) but would require higher launch RPM to get same results in 60' times = more clutch/differential stress/wear.
Cost (in addition to smoothness) is probably part of the reason OEMs avoid light flies. But not so much cost of the flywheel (steel inserted al flies asside) Ford could have easily designed a cheap light nodualar iron fly that was even lighter than SVTs has for same money. But they would need to upgrade the clutch, differential, and syncros to meet the same durability goals. And if you buy such a fly, be prepared to do the same..ie. HD clutch, Quaife, bulldog box or late 2000+ syncros..
