Why both N54 and N55?
The answer is valvetronic. This is a variable valve system used in the N55 which continually varies intake valve lift to offering fuel efficiency gains. When varying the duration of the intake, the air/fuel ratio is affected to promote maximum efficiency along with shortening the duration of the intake reducing pumping losses. This all translates into fuel efficiency gains which are so important to a company that keeps shoving efficient dynamics down our throat. The thing is, in an M car, we don't car as much about efficient dynamics, we want the M to deliver the Motorsport experience. You want maximum valve lift in this application as the goal is WOT power not off boost and partial throttle efficiency.
Why can't we have both? Well, that is the tricky part. Valvetronic makes the tuning much more difficult. The change in focus to greater performance vs. efficiency has created some programming issues for BMW. With the car needing to come out fairly quickly due to the E82 1 series being at the end of its lifespan, BMW does not have tons of time to play with the valvetronic. The simplest solution would be to use the N55 block and turbo setup combined with N54 heads which do not have it. It is simply the neatest solution.
The N55 is going to be a part of BMW for a long time. The next generation M3 will use a variant of it, with valvetronic most likely. They have plenty of time to fine tune that application as that car is not due for a handful of years. There is no cushion on the 1 M coupe and fine tuning the valvetronic for the power goals just won't be possible. The 1 M coupe will offer a slight preview of the next gen M3 the difference being the M3 will have valvetronic and a different turbo with more boost for more power.
So what kind of performance can we expect?
The motor is going to be limited on purpose to not step on the toes of the M3. The M3 dynos in the 340-350 whp range. The N54 motors in the "is" cars are already in the low 300 whp range. BMW can only add so much hp and torque. We think another 20 whp on top of the N54is cars is about as far as they can go. This means the 1 M Coupe should have a crank rating of about 350 hp. This means it will still be enough below the M3 to not step on its toes but also allow it to challenge the TT-RS which it no doubt will be compared to. 1/4 mile times in the high 12's at just about 109 mph should be where it ends up.
Rumor is no DCT, why?
This is the rumor, which does not make sense. BMW is pushing DCT hard, so why now offer only a manual? Some people are saying it is to keep the car "pure." Well, is the implication then that all M cars that do not have manuals are not pure? This means the new M5, M6, and all future DCT M cars will not be pure? What kind of message does that send? Frankly, we think the lack of DCT, if it happens, will be to keep the costs down as well as not allowing the 1 M to close the gap with the M3 due to the faster shift speed and performance the DCT would offer. Even with less hp, if this car gets a DCT, due to its low weight and amount of torque down low, it will be very close to the M3. The manual will allow BMW to keep costs low, prevent model cannibalism, and maintain a mystique that the 1 M coupe is a drivers car. It will send a strange message that the rest of the M lineup is not "pure" if done though.
What about tuning it?
Well, we are all interested in this but BMW hates that we tune the cars. Get used to it BMW, we are going to do what we want with our vehicles. This should be the strongest factory 6 cylinder tuning platform. A single turbo means we should see large single turbo upgrades done in a much faster fashion than we witnessed on the N54 (and are still waiting for). The factor working against it is the production numbers are supposed to be kept low. This limits the investment of tuning companies. Regardless, 400 whp cars with exhausts, tunes, and meth will be the norm. It will be a nice power platform.
Will it be a success?
Of course, BMW has hyped this thing beyond belief. They will sell every single one, good for them. Does that mean we are in love with it? Not exactly, the suspension and brakes are just a parts bin carry over from the M3. The main criticism which BMW will alleviate should we be correct about the motor is that this will not just be a 135 with more boost and some M3 bits. If they make changes to the motor that can not be had anywhere else in the lineup, we will be getting a car that is at least somewhat unique and not just what should be labeled a 135is. We will see if BMW does enough to justify the M badge, considering the criticism M has faced lately, they better.