Originally Posted by Uli_HH
You are totally right ... it is impossible for an car build on the F30 chassis
But none says that the next M3 would be build on the (steel) F30 chassis ... it would be build on the F80 chassis and its High-Strange-Steel + Carbon-Compount material matrix ... it has little to do with the AG F30 except the overall-look of the car and its dimensions!
And if you think about the carbonparts of the F80, you shouldn´t think at carbonroofs like the old M3 or the new M6 ... I guess little or nothing of this parts would be visible because they consist of parts such as shaft drive / transmission tunnel, lock-makers, engine and luggage compartment rear wall, crash boxes and wheel mounts and axle stools. All parts that must be structurally strong and solid and so are relatively heavy in steel.
If you now imagine that this parts are produced of very light and relatively favorable industry-carbon composite (two layers of carbon with a layer of cardboard / paper in between) , you can easily imagine the weight savings in these dimensions.
The produced in relatively small quantities F80M3/F82M4 will be the first application of this design before getting it in the next 7-way into the AG mass production.
So ~3.200lbs seems not impossible!
You are right in the sense that CF will be used more. Not necessarily solely with the cardboard as you mentioned- high strength areas require an Aramid core if going the dual layer sandwich route. Certain areas of the car can not be changed from the F30 because of homologation. The CF cardboard can be used in areas like the seat backs, center console etc. CF is also not the only solution to weight- there are ways to make stronger lighter plastics for interior uses and E-Glass for parts like the trunk lid and such.
Combining CF and the unibody is more than likely a no go as well, considering the cost of repairs and the needed retooling at the factory, that would be an entire extra step to unite via adhesive the clips and that is not cost effective or practical. When the E60/61/63 were being made they were all made on the same line because of this added step of bonding the then aluminum to the steel. That is why BMW has moved on... not cost effective. BMWi is different as the chassis and passenger cell are separate then joined in a process that was designed to be that way from the get go and will be assembled in its own manner. If M develops its own chassis completely the cost per unit would be in the stratosphere- M numbers are not even remotely practical to do that with unless you are talking halo car. If (and I have no indication they will from my connections) I would be blown away and at the same time sad because each car would either be out of reach for me or being sold at a loss....
Garching is not capable of building M3s in a large volume so that is out of the question, it will be built on the regular line outside of special editions.
The drive shaft and half shafts will be much lighter than now (more on that in the future), as will the rear diff, wheels and suspension components. Decreasing unsprung weight as has been mentioned before will be a huge target and the new designs of the CF roof.
Sure if pricing was no object they could build something unthinkable but they have a hard number to hit and that will be in line with current market expectations and still be revolutionary.
BMW M and parts suppliers have been working closely on some of the developments with this car... some of the tech is not new but the effective use of the tech has been adapted for use in a daily driver. Other components are already in competitors products.
The engine will feature some great additions that people are still debating but just remember that performance and efficiency must improve. There are some sacred parts of this car that must be made more efficient in terms of emissions and fuel economy (not always the same issues).