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Motorsports & Track Forum by BimmerWorld
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Old 06-23-2008, 09:31 AM   #1
NightRunner
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Any significant downforce from the CSL trunk?

Have a quick, pretty simple question that i absolutely couldn't find any information on it, either on any forum, or online at all.

But is there any "Significant" down force generated by the csl trunk integrated spoiler at speed? I'm not looking for people saying "I totally felt it on the highway going 60!" but actual track experience. I'm at the point where I'm wanting to work on my aerodynamics, and was thinking about a functioning front lip, diffuser, spoiler. Basically I'm trying to figure out if the csl "spoiler" would provide enough down force so that when i'm braking hard from 100+ coming into a turn, with the front spoiler adding even more weight on the front end, the rear end has enough force on it so that it stays planted and doesn't get squirrely. I'd rather stay away from a huge rear wing, and as i understand from talking to other racers, if the csl spoiler does indeed provide some down force, that coupled with a proper rear diffuser should have me good to go.

Anyone have any insight?
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Old 06-23-2008, 09:33 AM   #2
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are you tracking your car?
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Old 06-23-2008, 09:36 AM   #3
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That's the reason i've asked about "Track experience"
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Old 06-23-2008, 10:05 AM   #4
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Quote:
Originally Posted by NightRunner View Post
That's the reason i've asked about "Track experience"
Most track guys I know wouldn't bother with the CSL trunk, they get an adjustable wing. Bimmerworld has an ALMS style wing that should provide all the downforce you could ever need.

Weight wise, the OEM CSL trunk is actually pretty heavy compared to aftermarket copies.
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Old 06-23-2008, 10:07 AM   #5
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That's the reason i've asked about "Track experience"
that doesn't answer the question.
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Old 06-23-2008, 10:58 AM   #6
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While I don't have any experience with the CSL trunk, I do have a background in aerodynamics. Trunk spoilers don't really provide downforce. They can help eliminate lift but they won't really provide any downforce. To get down force of the magnitude you are talking about (ie, to actually load the suspension) you're going to have to add a wing as pei330ci has mentioned.
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Old 06-23-2008, 11:43 AM   #7
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ok. cool. thats what i was thinking in the back of my mind but wanted to see if i could get away from it. thanks
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Old 06-23-2008, 12:09 PM   #8
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You mentioned braking from 100+. What speeds are you starting from and how much speed are you carrying through the turn?
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Old 06-23-2008, 06:23 PM   #9
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I do have track experience but not with a bmw. I track my civic and i use aero and it has helped me significantly that i can feel it through most corners. Iv gone down sweepers at 80+mph and down straights at about 115; with a splitter/rear gt wing and the car felt solid and firm, while doing the same course i didn't run a front splitter or a gt wing and the car was quite wiggly and lifted at high speeds from the front. The CSL trunk is used to smooth out air flow/turbulence and not used for downforce like what your looking for. Get a GT wing and you'll be set. But remember, if you do use a gt wing, your going to need something to compensate for the rears downforce and equal it out with a front splitter/undertray.

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Old 08-05-2008, 03:26 PM   #10
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I can't remember the reference, but I remember reading the combination of the CSL trunk and front bumper were good for a swing from around 50lbs of lift for standard M3 bumper/decklid spoiler to about 50lbs of downforce for the CSL setup at around 120 mph.
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Old 08-07-2008, 03:42 AM   #11
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I found this on a German car forum:

Quote:
M3 E46
Wind channel
Lift Force at 200 Km/h (160mph) : 18kg (39.6lb) at rear axis
cW Value: 0,32

M3 CSL
Wind channel
Lift Force at 200Km/h (160mph) : -10kg (-22lb) at rear axis
cW Value: 0,33
So the CSL produces 61.6lb more downforce at 160mph than the standard M3.
Note that this is the complete car, but since it's measured at the rear axis, you can estimate that the majority of this is produced by the trunk lid.
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Old 08-07-2008, 03:44 AM   #12
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i notice the difference but only at very high speeds
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Old 08-07-2008, 03:55 AM   #13
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Doesn't the real CSL feature a flat bottom back end and a diffuser?
I think your better off cleaning up airflow under the car and adding a diffuser rather than a big wing. Also if you want significant downforce from high speed braking, look into a active rear wing, ala carrera gt, boxster, mclaren F1 and such. Just a thought. But if you can eliminate air pockets behind the reae wheels and in the bump, then you will have better results. Look at pics of the M3 GTR, besides the large wing, it features, flat bottom, diffuser, splitters and stupid aggresive front spoiler.
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Old 08-07-2008, 04:10 AM   #14
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The M3 CSL only has the standard "diffuser frame" that everyone if buying because it looks better around the exhaust pipes. There is no underbody diffuser.
At least I have found no info on this, and my two 1:18 model CSL's (each from a different brand, one original BMW) don't have it either.

There is, however, this: http://forum.e46fanatics.com/showthread.php?t=597369
Note the underbody panels hanging on the wall.
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Old 08-07-2008, 04:14 AM   #15
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Ah, I see. But still, it'll probably be the most effective way to eliminate lift.
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Old 08-07-2008, 04:17 AM   #16
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Ah, I see. But still, it'll probably be the most effective way to eliminate lift.
Well... If it's good enough for the CSL (which is more or less the perfect E46), then it should be good enough for our cars.

Note: I would also install the front CSL flaps with the rear trunk, since I think those flaps "scoop" some of the air that would go under the car and lift it to produce even more downforce.
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