Quote:
Originally Posted by Pr0metheus
I think in order to meet the homologation rules (rules that state all parts of a car, think of it as an "as-built" bill of materials + sometimes production requirements to be allowed to compete) for FiA and such, they needed a production chassis that housed a v8 from the factory.
I believe that's why they switched to the Z4 GT3 race car after E90 M3 V8 (before E90 was E46 GTR v8) Homologation rules change, but I think they may have been just planning on this. M3/4 are street cars and euro emissions + USA (until the EPA is dead) make v8 street cars a bad idea, so they went for boosted 6-bangers to get the power & maintain fuel economy.
M6 is in a different category (giant beautiful grant touring) and gets v8 from the factory so it's easy(er) to slap some better guts the engine, add a roll cage in and a turbo on, etc and you got yourself a homologated chassis compliant for racing in a variety of series across the globe. You can also probably slap some factory BMW race engines in to speed it up if you don't get to start your GT3 design and build from blank paper.
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Pretty much this. I've explained in detail in the past here but i'll break it down again.
BMW hasn't raced with inline-sixes for almost two decades.
Beginning with the E46 era, the S54 (P54) just wasn't competitive in racing against the likes of Porsche.
BMW realized they could no longer be racing inline-sixes and expect to win so a V8 configuration was the only way they could stay competitive in GT category motorsports. This spawned the E46 GTR.
During the E9x generation, the fact that the "street" M3 was equipped with a V8 engine made it a no-brainer for homologation for motorsports. Remember, the E46 GTR was eventually "banned" from racing because the "street" E46 M3 wasn't sold with a V8, so this time, the E9x was conveniently equipped with a V8 in street form.
BMW homologated the M3 GT & GT2 and was later able to use a "loophole" that allowed the E89 Z4 to run a homologated version of the S65 (P65) engine in the GT category, even though no such Z4 was sold with an S65 engine (hence "loophole").
This time around, BMW has no more strings to pull. It is unlikely that BMW would be able to get away with homologating the S63 (P63) engine into a chassis like the F87 M2. On the other hand, homologating an N55 or S55 to race an M2 or M4 would be suicide.
Hence, the M6.
A longer wheelbase is a small price to pay for a [race]car that is already equipped with an engine that can be competitive given the company.