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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Sat, Apr-03-2010, 02:58:13 PM   #11
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Unless the spoiler rises above the roof line, there's very minimal downforce. Unfortunately for street driven car, you'll be labeled a r|cer with a usable wing.
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Old Sat, Apr-03-2010, 07:11:12 PM   #12
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I love you, Slickfast. Great info.
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Old Sat, Apr-03-2010, 09:28:12 PM   #13
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Originally Posted by M3n00b View Post
Unless the spoiler rises above the roof line, there's very minimal downforce. Unfortunately for street driven car, you'll be labeled a r|cer with a usable wing.


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I love you, Slickfast. Great info.
Thanks man. Nice cage btw, that must be a fun toy!
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Old Sat, Apr-03-2010, 09:51:02 PM   #14
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A spoiler by its very nature does not clean up airflow; rather, it makes it worse.
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it is called a spoiler because it spoils the airflow causing it to get "dirty" (creating a wake behind it) and increasing drag

PS, the E30 M3's rear glass is more aerodynamic (teardrop shaped like the Corvette whose C5 ad C6 generations are very pronounced) than the E36's .....plus on the E30 M3, the rear glass area is structural
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Old Sat, Apr-03-2010, 10:37:39 PM   #15
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As I understood it, the rear spoiler has nothing to do with downforce, that would be the job of a wing, not a spoiler.

The spoiler was put there to decrease the turbulent low pressure area from the rear of the roof to the rear edge of the trunk caused by the sloping back of the E36, which causes turbulence, drag and instability at high speeds.

This holds true for most cars.

By adding a spoiler, it makes the air flow take a longer route to the back of the car, allowing for less air flow separation, better stability, less drag, better fuel economy, and it helps keep the rear window clean.

I have read and heard reports from people who have driven the E36 M3 on racetracks with and without the rear spoiler, and the comments were generally the same, at high speeds, the car with the spoiler was more stable than the one without the spoiler.

From that, take what you wish.

Sometimes just because you can't feel something while driving to work doesn't mean it has no useful purpose.
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Old Sat, Apr-03-2010, 11:47:50 PM   #16
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Unless the spoiler rises above the roof line, there's very minimal downforce. Unfortunately for street driven car, you'll be labeled a r|cer with a usable wing.
Absolutely positively incorrect. See the duck tail spoiler on a 911RS, the whale tail spoiler etc. as well as the spoiler on a 924 v 944.

which makes me again ask this question - if that gigundo fugly spoiler on the LTW does increase downforce on the rear wheels, what is done to compensate for the lift in the front?

remember the chaparral and how it sucked itself to the ground? remember the vacuum cars that were banned. downforce is good, and a spoiler wing (you can argue the minutia) is supposed to increase it.

while you guys bench race the merits of a rear spoiler, dont forget the soft white underbelly of a car and the drag that causes.
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Old Sat, Apr-03-2010, 11:53:13 PM   #17
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which makes me again ask this question - if that gigundo fugly spoiler on the LTW does increase downforce on the rear wheels, what is done to compensate for the lift in the front?

remember the chaparral and how it sucked itself to the ground? remember the vacuum cars that were banned. downforce is good, and a spoiler wing (you can argue the minutia) is supposed to increase it.
I guess you've never seen the fully adjustable large undertray that comes standard on the LTW's... Ant has one on his car and its quite a piece
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Old Sun, Apr-04-2010, 01:32:25 AM   #18
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As I understood it, the rear spoiler has nothing to do with downforce, that would be the job of a wing, not a spoiler.

The spoiler was put there to decrease the turbulent low pressure area from the rear of the roof to the rear edge of the trunk caused by the sloping back of the E36, which causes turbulence, drag and instability at high speeds.

This holds true for most cars.

By adding a spoiler, it makes the air flow take a longer route to the back of the car, allowing for less air flow separation, better stability, less drag, better fuel economy, and it helps keep the rear window clean.

I have read and heard reports from people who have driven the E36 M3 on racetracks with and without the rear spoiler, and the comments were generally the same, at high speeds, the car with the spoiler was more stable than the one without the spoiler.

From that, take what you wish.

Sometimes just because you can't feel something while driving to work doesn't mean it has no useful purpose.
Unfortunately for your understanding, and I don't mean to be derogatory here, but it is nearly all incorrect. I'm not someone that's just calling you out because I don't like you or something (on the contrary actually, I really enoy your posts about track time, driving technique, etc), I'm just educated in aerodynamics and hate seeing misinformation spread like wildfire. Here's some response to what you said:

First point: The spoiler is indeed exactly a wing. The only difference between it and an airplane's wing is that it is inverted, creating lift towards the ground. A roof spoiler actually increases the low pressure area between the rear of the roof and the trunk lid, so go tell whoever told you the opposite that they're completely incorrect. Or get me in touch with them, I'd be happy to explain it. What you are describing is again the effect that a vortex generator would have, which increases energy in the boundary layer to keep airflow from separating (HUGE drag increase if this happens).

Second point: it all depends on the spoiler and it's location. Some are more effective than others... this is not a black and white issue. For the most part, street car spoilers do very little to increase downforce. Now, do I think any of our stock spoilers do a thing for downforce? Not anything I'd notice. Even the LTW high-rise is well below where I believe really useful air would be, but I wouldn't know until I did some analysis.

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Absolutely positively incorrect. See the duck tail spoiler on a 911RS, the whale tail spoiler etc. as well as the spoiler on a 924 v 944.

which makes me again ask this question - if that gigundo fugly spoiler on the LTW does increase downforce on the rear wheels, what is done to compensate for the lift in the front?

remember the chaparral and how it sucked itself to the ground? remember the vacuum cars that were banned. downforce is good, and a spoiler wing (you can argue the minutia) is supposed to increase it.

while you guys bench race the merits of a rear spoiler, dont forget the soft white underbelly of a car and the drag that causes.
The M3Noob is still correct. The duck tail is a VERY different scenario, Tom. The boxiness of the E36 has no comparison to the very aerodynamic 911 profile. I'd be much more confident that the spoiler would have more of an effect if we were talking p-cars. But we're not, we're talking about an extremely boxy body, where airflow separation is much more of a problem.

(if you can't tell, p-cars make aero engineers happy )

As for the downforce, the imbalance of pressure that the LTW undertray creates is effective at creating downforce in the front, so there's your answer. Sure, a non-flat underbody with no rear diffuser would do much more, but the tray is effective in itself.



Also, I thought of a good way of conveying this whole disagreement that a street car spoiler is useless for the most part. Go for a drive, get on the highway, and put your hand out the window. Put it behind the mirror (even like a foot and a half behind), and feel the amount of drag as opposed to how it feels when you raise your hand above the wake of the mirror. There is a very real difference between the two.
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Old Sun, Apr-04-2010, 04:16:48 AM   #19
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Well the understanding I had on the topic was from previous discussions I've had with people who also claimed to be educated on the topic, but I can make no such claims..

I do however notice that Wikipedia supports what I posted, but I suppose the accuracy of Wikipedia can be called into question.

The article I read and the comments I've had in person from people who have done a track test on the spoiler vs no spoiler in the e36 M3 are true though, so I expect the truth lies somewhere in the middle.

I still believe the spoiler is generally not for downforce on most production cars, and that it has more to do with changing the airflow over the car - that just makes sense to me. I don't doubt your education, but I would very much like to hear from someone who designs the spoilers and is privy to the wind tunnel / airflow measuring that went on when this was being done.
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Last edited by M3Works4Me; Sun, Apr-04-2010 at 04:21:02 AM.
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Old Sun, Apr-04-2010, 04:51:52 AM   #20
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I guess you've never seen the fully adjustable large undertray that comes standard on the LTW's... Ant has one on his car and its quite a piece
i asked the question about three times and each time people on this forum posted that there was nothing needed, or nothing done to the front of the car to counter the downforce. so yu are correct that i've never seen the LTWs undertray, and in fact, based on statements made by some self proclaimed experts here did not know one existed.

now that I know, i know i will not but one of those fugly gigunco ltw spoilers on my car without also putting the undertray on.

thanks for setting the record straight.
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Discussing Admiring BMW's aerodynamics (question inside) in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)