[JimD]

Cost is probably a big reason but is not the point I want to make.

I googled for 1/4 mile calculators and 0-60 calculators. These are simple formulas that are empiracally derived (meaning they look at data from actual cars and develop a formula that matches the data). They are not extremely accurate but give you an idea. For both quarter mile times and 0-60, adding 50 hp to a 135i has almost exactly the same impact as dropping 500 lbs. For instance, the calculator predicts a 0-60 of 5.13 for a stock 135i and it drops to 4.57 with 350hp (with 3373 lbs) and 4.55 at 2873 lbs (with 300 hp).

Especially with a turbo motor you can reprogram, it seems to me a lot more feasible to add 50hp than drop 500 lbs. If you could achieve a similar effect dropping 200 lbs, I'd be more optomistic the M1 would be substantially lighter. The fact that you need 500 lbs to equal 50 hp make me think we may see a token weight change - an aluminum hood and/or carbon fiber roof - but the real change in performance will come from engine mods. An even simpler weight reduction we will hopefully see is lighter wheels and possibly tires.

Less weight would still be very desirable for handling benefits but it seems like the reasonably achievable weight loss will not affect acceleration a lot.

Jim