Originally Posted by verbs
Let's be clear, the F30 Alpina B3 only gains 10hp over the previous model with more or less the same engine/power delivery profile, and the car doesn't weigh substantially different from the previous version most likely. A low 5500rpm horsepower peak indicates boost is being tapered off at higher rpms. It does however get the 8 speed tranny which will help performance a tad no doubt.
There's only been a moderate hp gain because it seems that the new M3 will have almost no power gain as compared to the E9x M3 (rumours have it at between 430 - 450 hp). Alpina has to respect a certain power gap between their cars and the equivalent from the M GmbH - with a bigger turbo charger they could have gone far beyond the M3 power levels with the E9x already, but they were not allowed to do so. Same story for the F30.
Also, we don't know that it will be the same engine as the N54. No details about the engine have been released yet, but there are rumours that it is based on the F80 M3 engine which will most likely be a N54 with valvetronic and twin scroll, i.e. a mixture between the N54 and N55 engines. Alpina will certainly not re-use the N54, as this engine is not efficient enough any longer and fuel efficiency is something that Alpina is prioritizing due to marketing strategies. A straight six biturbo engine with valvetronic and twin scroll will be stronger than the N54 and have better fuel efficiency.
IMO it will probably boil down to a similar situation as we are already seeing right now with the M5 / B5 Biturbo, which are very similar in power but differentiate themselves mainly through suspension and clutch setups.
Originally Posted by verbs
The new F8x M3 will have a completely different engine setup and power delivery profile than the previous M3, not to mention they're targeting a noticeable weight reduction for the car. There's no reason this car can't come in 150-200lbs lighter than the Alpina.
I agree with you that it's a bit premature to compare the two cars as we don't have the final details about either. But forums are also there to speculate, and there is some proof from very similar situations in the most recent past (see above the M5 / B5 BT comparison).
I disagree with you that the new M3 F80 will be substantially lighter than the F30 Alpina. They will share the same chassis, and without heavy use of carbon fibre (which is excluded for cost reasons) a substantial weight reduction seems very unlikely for me to achieve. Granted, the new M3 biturbo engine will be lighter than the previous V8 (but also have to feature a water-to-air intercooler and other mechanics for the two turbos), and as previously they'll use a CF roof and lots of aluminium in the suspension. But that *might* gain 100lbs if compared to a 335i / Alpina B3, which in this weight class is negligble. Just look at the M3 CRT - even with the use of carbon fibre the weight reduction was almost non-existent.
I'd love to be pleasantly surprised, but the last few years have not given any indication that BMW sees weight reduction on mass-production cars as a priority (at present).