In my experience...
BMW pedal travel is longer than Porsche pedal travel, but shorter than Asian imports (I've had experience with Nissan, Subaru, and Hyundai on track) with better modulation on stock systems. Modified systems, all bets are off. The WORST is 'Mercan cars, unless they're equipped with large, multi-piston fixed calipers (Challenger SRT-8) from the factory.
If you've got excessive pedal travel before brakes will engage, it's likely there's air trapped in the line or you've got mis-matching slave cylinder area to master cylinder ratio. What I've also noticed, on the MZ4 especially, it MUST share the same brake master cylinder design as the E36 M3, because it's got that same issue that once you get air in the lines, and you crack it open to bleed/flush, you will NEVER get the same feel back. I don't know what it is. Never had that problem on the E46, didn't have that problem with the Z4 3.0i when I tracked it heavily...The MZ4 Coupe, after the first bleed, didn't quite feel the same with the brake pedal engagement.
With the RacingBrake 4 piston front, 2 piston rear fixed calipers though, it's got that quick engagement back. At least compared to what else I drive regularly now in the garage (the 335D and the Fiat 500e). Can't really compare it to the i3 because I rarely use the brake pedal on the i3.
