The 1M\’s Air Curtain in Detail

There were a couple of surprises earlier this week when BMW took the wraps off of the 1M. Two of them lie squarely in the air intake area. First the bad. No there are no functioning brake ducts. Instead M has routed the normal intake areas into two radiators to help cool the twin turbo inline six. Unquestionably this is a disappointing move but according to sources a necessary one given the engine ‘s need for cooling. However the same sources are also telling us that the extra intakes weren ‘t as necessary as they could have been given the brakes propensity to cool on their own given the design of the system and wheels.

The internally-vented, cross-drilled cast iron discs measure 14.2 inches (360mm) in diameter at the front and 13.8 inches (350mm) in the rear. In addition each disc is connected to a floating aluminum hub by cast-in stainless-steel pins which further helps to reduce thermal loads

Now the good. Somewhat surprisingly BMW is debuting it ‘s Air Curtain technology with the low volume 1M. We would have expected this to M to debut something like this on a higher volume car such as the M3 or even the M5. But instead M has used that technology to help define the look of the car with aggressive vertical slits just before each front wheel.

The air curtains improve air flow around the wheel arches with the benefit of significantly reduced turbulence. This feature consists of openings in the outer section of the lower front fascia that route high-pressure air through ducts at each front corner. The ducts are approximately 10 x 3 centimeters wide and are designed to channel air to openings at the front of each wheel arch, where it is discharged through a very narrow opening at high speed. The escaping air stream covers the side of the front wheels like a curtain, thereby reducing aerodynamically unfavorable turbulence around the rotating wheels.

Sources are telling us that this feature will play a key role in the development of future aerodynamic features on all BMWs. And of course this has all been possible with BMW ‘s new Environmental Testing Center (details here on BF last May).

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  • JonPD

    Interesting technology and very sad about the lack of brake cooling. While I do appreciate the technology of air current I have more concern over brake fade than a small gain in efficiency. I am sure the air current also plays a roll in the aerodynamics aiding the car to slip though the air. I do wonder how this will work with them trying to use the design of the brakes and wheels to cool the brakes with a boundary layer of air blocking wheels from biting the turbulent flow around the wheels to shed heat.

    No doubt it will be better than the condition of the E92 M3 with the much lighter weight but still a huge design shortcoming to me. Would love it if BMW would share some of their thermodynamic testing of the brake cooling with the air current. Guess once again I am going to have to hope somebody in the aftermarket comes up with something to address more of the short comings of the M1 spec design. Still not a reason to not buy the car but mark me as being disappointed.

  • lava

    I would guess that the smooth airflow across the face of the wheels would increase the disbursement of heated air around the brakes, not hinder it as you suggest. And if so it may accomplish much of what dedicated brake ducts do without aiding the overall aerodynamics as these vents do.

  • Micah

    Without real brake ducts, these brakes will fade at the track — serious oversight IMO. BMW claimed similar nonsense with the MINI GP, stating that the wheel design promoted brake cooling. GPs experience brake fade at the track, & I’m afraid without mods the 1M middle pedal will also get soft as the E9x M3 does. BMW enthusiasts have complained for years about their M cars being “underbraked”, and it’s amazing to me that BMW M engineers have not done more to address this valid criticism.

  • JonPD

    Lava you could be right, that is why I would love to see a thermodynamic image of the high curtain flow and heavy braking (IE typical track condition). Think of the bed of a truck where you have higher speed of flow over the cab and a lower flow area in the bed, you get a turbulent muddy flow in the bed of the truck. This will not be anywhere as bad but I would expect similar behavior. Sad to think a 25k Mini has something that a ///M does not. Maybe this car is more similar to the GP than I thought already. Can tell you about brake fade on that lol. Either way would love somebody to sit down and talk to Gabe or Michael to share some data on the air curtain and how it affects the standard “wheel design cools the brakes”.

  • lava

    That turbulent pocket behind the pickup truck cab as you describe, traps air there, where as the smooth air flow would take it away.

  • JonPD

    This would be true if tires didn’t have a second side with no smooth flow. Though to a much less degree there is also a turbulent flow behind the tire also. Will lay down a bet that we will see plenty of brake fade on the track.

  • Bimmer1

    I’m sure BMW was concerned about engine oil temp, as that was an issue for a while with the regular N54’s in warm climate areas. However, I know quite a few people who run their 135/335 at the track, some of them with a lot more power than the 1M is going to have and they have never had any oil temp problems. Myself included in my Dinan Stage II equipped 135i. Obviously, most of us know that any stock brake system on any car is going to fade with heavy use at the track. A lot of that has to do with the pad material as well, since the brakes on a production car have to work when they are bone cold as well. Wheel design has been a brake cooling aid for a long time now. It helps, but by no means does it eliminate brake fade. However we should assume that the 1M brakes will not overheat in any circumstance you would come across on the street. Even the E46 M3 comp package brakes fade after 20-30 min of hard driving at the track. And it’s even named the competition package!!!

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