Swamp, you went to a lot of trouble, but it was interesting reading.
It's probably fair to say that I too am skeptical that a non-S motor will be used. If that is the end result, M Division has deteriorated more and faster than I ever would have imagined possible. However, it is possible and we'll know sooner or later.
I'll throw the following out there for you and everyone who wishes to chew on.
The approach that I took was from a historical-generational-performance improvement over previous generation M3's.
NOTE: Weights and horsepower output numbers are those peculiar to the first motor offered within each generation.
E30 M3: 1,202 kg/220 hp = 5.46 kg/hp
E36 M3: 1,461 kg/286 hp = 5.11 kg/hp
Wt:HP ratio 5.11/5.46 = 0.94 (or a 6% decrease in the wt:hp ratio in the E36 in relation to the E30)
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E46 M3: 1,571 kg/343 hp = 4.58 kg/hp
Wt:HP ratio 4.58/5.11 = 0.90 (or a 10% decrease in the wt:hp ratio in the E46 in relation to the E36)
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E92 M3: 3.8 kg * 420 hp = 1,596 kg (Wt/hp source: Official BMW M3 International Launch information (Please see attachment page 17). Yes, the official “unladen” weight is 3704 or 1,683 kg which doesn’t quite mesh with the equally “official” 3.8kg-to-1hp.
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Wt:HP ratio 3.8 kg/4.58 kg = 0.83 (or a 17% decrease in the wt:hp ratio of E92 in relation to the E46)
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Over four generations the weight-to-horsepower ratio has been reduced by 6%, 10%, and 17% while horsepower has increased by 30%, 20%, and 22%. At the same time, weight has increased by 22%, 8%, and 2%.
It is probably a safe bet that the next generation M3 will follow tradition by being a better performer than the previous generation. Not knowing the extent to which performance improvement is targeted poses the greatest obstacle to getting a handle on this "puzzle". To wit: Will the next generation attempt to match the massive performance increase over a previous generation as was achieved with the E92M3 or will the performance increase be more akin to that of the E36M3 vis a vis the E30M3?
Scenarios
In order improve the kg/wt ratio of the 5th generation M3 at what would be a historical average – (6%+10%+17%) / 3 = 7.67%) – such would be achieved by increasing horsepower to 455 with no weight increase whatsoever would result in a “new” kg:hp ratio would be 3.51kg/hp.
If weight does increase as many suspect that it will, including myself, and let’s suppose the increase is a mere 25kg, an additional 17 horsepower would be needed to offset the weight increase while retaining a 7.67% decrease in weight to horsepower that results in the improved 3.51kg/hp.
On the other hand, if the design team of the next generation M3 targeted a replication of what was achieved with the E92 versus the E46 – a combination of minimal weight increase and massive power increase – the next generation would gain approximately 30 kg to weigh in at 1,628 kg (+2%) while power would increase by 92hp to 512hp (+22%), and that translates into a 3.18 kg/hp ratio.
Yeah, I don’t think that that’s going to happen either, but if it did, a lot of people would be signing up for a ride that would have little to fear from anything on the road. In the meantime, we have among us the E92M3 model which is the gold standard for performance advancement over previous generations. Matching its improvement specs would be something special, topping that set of improvement specs would make for a phenomenal fifth generation M3, IMHO of course.