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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Fri, Nov-21-2008, 05:56:14 AM   #1
Syndicate
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Default CSL Front Bumper vs Stock :: Brake Cooling

Hey all,

On the stock bumper we have the two air ducts that cool the brakes. I see that on the CSL there is only the duct on the driver's side. How did BMW address the cooling of the passenger side brakes? I know that the CSL has bigger rotors (better heat disappation), but still, is there another method for cooling this side?

Thanks.
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Old Fri, Nov-21-2008, 08:42:23 AM   #2
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On the stock bumper, we have 2 ducts like you said. The left one cools the brakes and the right one serves 2 purposes: cool the brakes and feed air into the airbox.

On the CSL's, the purpose of the duct is really for feeding air into the airbox.

CSL's were designed with track use in mind, and would likely have race pads when on the track. Simply put, the compound of a race pad works best when hot. When cool, they are actually very abbrassive and have minimal bite, and will chew up the rotors faster than when they are hot. In addition, stress cracks on slotted or crossdrilled rotors tend to develop when the rotors are repeatedly shocked by a wide range of temperatures (cold, hot, cold, hot, etc). As awkward as it sounds, for track use, cold brakes don't work well.

On the other hand, the streepads regular M3's generally have loose effectiveness when they get too hot since they have a much lower heat range. They're great when they're cool but can drop off rapidly as they reach their maximum operating temp range which *can* happen with spirited driving on the street. In addition, cooler temps with street pads prolongs pad and rotor life.
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Last edited by Got_S54?; Fri, Nov-21-2008 at 08:47:24 AM.
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Old Fri, Nov-21-2008, 09:47:10 AM   #3
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Originally Posted by Got_S54? View Post
On the stock bumper, we have 2 ducts like you said. The left one cools the brakes and the right one serves 2 purposes: cool the brakes and feed air into the airbox.

On the CSL's, the purpose of the duct is really for feeding air into the airbox.

CSL's were designed with track use in mind, and would likely have race pads when on the track. Simply put, the compound of a race pad works best when hot. When cool, they are actually very abbrassive and have minimal bite, and will chew up the rotors faster than when they are hot. In addition, stress cracks on slotted or crossdrilled rotors tend to develop when the rotors are repeatedly shocked by a wide range of temperatures (cold, hot, cold, hot, etc). As awkward as it sounds, for track use, cold brakes don't work well.

On the other hand, the streepads regular M3's generally have loose effectiveness when they get too hot since they have a much lower heat range. They're great when they're cool but can drop off rapidly as they reach their maximum operating temp range which *can* happen with spirited driving on the street. In addition, cooler temps with street pads prolongs pad and rotor life.
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Old Fri, Nov-21-2008, 12:55:17 PM   #4
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Quote:
Originally Posted by Got_S54? View Post
On the stock bumper, we have 2 ducts like you said. The left one cools the brakes and the right one serves 2 purposes: cool the brakes and feed air into the airbox.

On the CSL's, the purpose of the duct is really for feeding air into the airbox.

CSL's were designed with track use in mind, and would likely have race pads when on the track. Simply put, the compound of a race pad works best when hot. When cool, they are actually very abbrassive and have minimal bite, and will chew up the rotors faster than when they are hot. In addition, stress cracks on slotted or crossdrilled rotors tend to develop when the rotors are repeatedly shocked by a wide range of temperatures (cold, hot, cold, hot, etc). As awkward as it sounds, for track use, cold brakes don't work well.

On the other hand, the streepads regular M3's generally have loose effectiveness when they get too hot since they have a much lower heat range. They're great when they're cool but can drop off rapidly as they reach their maximum operating temp range which *can* happen with spirited driving on the street. In addition, cooler temps with street pads prolongs pad and rotor life.
Humm... Interesting. But what's up with track cars owners installing airducts that go directly to the rotor?
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Old Fri, Nov-21-2008, 02:45:56 PM   #5
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Thanks for the feed back. I'm torn between installing some Silver CF splitters that I purchased or just going with the OEM CSL front bumper. Is anyone here running the CSL bumper on the track with a stock or Euro rotors brake kit?

Thanks again.
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Old Fri, Nov-21-2008, 04:02:42 PM   #6
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Humm... Interesting. But what's up with track cars owners installing airducts that go directly to the rotor?
For tracks located where the ambient temp is very high during the summer season (ie AZ, NM, NV, etc) or if the track layout is brake intensive (tighter, smaller tracks). For high speed courses, ie the 'ring, there is no benefit to having aftermarket brake airducts.

In fact, even though our non-csl bumpers have the airducts, they are actually plugged. You have to pop off the covers if you want the air to flow to the brakes. What that does though is reduce the amount of air that goes into the airbox on the drivers' side, because instead of the air being rammed up the pipe into the airbox, it's now flowing straight through to the brakes. Oh and yeah - Vorsteiner's CSL bumper that has no hole = not good.
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Old Fri, Nov-21-2008, 04:12:25 PM   #7
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Quote:
Originally Posted by Got_S54? View Post
On the stock bumper, we have 2 ducts like you said. The left one cools the brakes and the right one serves 2 purposes: cool the brakes and feed air into the airbox.

On the CSL's, the purpose of the duct is really for feeding air into the airbox.

CSL's were designed with track use in mind, and would likely have race pads when on the track. Simply put, the compound of a race pad works best when hot. When cool, they are actually very abbrassive and have minimal bite, and will chew up the rotors faster than when they are hot. In addition, stress cracks on slotted or crossdrilled rotors tend to develop when the rotors are repeatedly shocked by a wide range of temperatures (cold, hot, cold, hot, etc). As awkward as it sounds, for track use, cold brakes don't work well.

On the other hand, the streepads regular M3's generally have loose effectiveness when they get too hot since they have a much lower heat range. They're great when they're cool but can drop off rapidly as they reach their maximum operating temp range which *can* happen with spirited driving on the street. In addition, cooler temps with street pads prolongs pad and rotor life.
Good info. I was actually wondering the same thing recently. Guess I have my answer.
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Old Fri, Nov-21-2008, 04:23:24 PM   #8
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Originally Posted by Got_S54? View Post
For tracks located where the ambient temp is very high during the summer season (ie AZ, NM, NV, etc) or if the track layout is brake intensive (tighter, smaller tracks). For high speed courses, ie the 'ring, there is no benefit to having aftermarket brake airducts.

In fact, even though our non-csl bumpers have the airducts, they are actually plugged. You have to pop off the covers if you want the air to flow to the brakes. What that does though is reduce the amount of air that goes into the airbox on the drivers' side, because instead of the air being rammed up the pipe into the airbox, it's now flowing straight through to the brakes. Oh and yeah - Vorsteiner's CSL bumper that has no hole = not good.
Are you serious or are you kidding me? Just about every BMW track/D.E junkie has aftermarket brake cooling ducts. The BMW ones are pretty much useless once you really start moving on the track. They serve a vital purpose to cool the rotors that could easily warp at the temperatures demanded of them after numerous 130mph stops (well over 1200 degrees) and these temperatures without the ducts literally bakes race pads if used constantly at those temperatures. If I did not have brake cooling ducts I would go through a set of Performance Friction race pads in a days time. The ducts cool the temperatures so the pads can work at optimum temperature, just like any other race cars ducts. If I didn't have them, the pads would work great but I would get no life what so ever out of them
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Old Fri, Nov-21-2008, 04:53:17 PM   #9
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Are you serious or are you kidding me? Just about every BMW track/D.E junkie has aftermarket brake cooling ducts. The BMW ones are pretty much useless once you really start moving on the track. They serve a vital purpose to cool the rotors that could easily warp at the temperatures demanded of them after numerous 130mph stops (well over 1200 degrees) and these temperatures without the ducts literally bakes race pads if used constantly at those temperatures. If I did not have brake cooling ducts I would go through a set of Performance Friction race pads in a days time. The ducts cool the temperatures so the pads can work at optimum temperature, just like any other race cars ducts. If I didn't have them, the pads would work great but I would get no life what so ever out of them
i agree
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Old Fri, Nov-21-2008, 05:13:47 PM   #10
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+1, and remember, the e46 is a very heavy car so yes, you DO NEED BRAKE COOLING DUCTS for track driven M3, even with racepads.
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Discussing CSL Front Bumper vs Stock :: Brake Cooling in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)