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but I have to ask: What is with the rear fin/wing/aero bit.

I mean, these are front wheel drive cars, so not like down draft is needed.

So, just for looks or is there a purpose?
Robert
 

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The rear spoiler does change the aerodynamics of the vehicle a little, mostly by blocking/reducing the amount of turbulent wake which tends to climb up from behind the car onto the trunk lid behind the rear window. By doing this, it reduces drag a little. Also because of that it does reduce the aero lift at the rear of the car a little, but not because of it being a wing in that respect. Redirecting and smoothing the airflow over the top of the car and back, ie, reducing it's turbulence on the trunk lid which does the reduction.

The front lower spoiler also tends to reduce the drag a little by reducing the amount of air being rammed under the car, which if not blocked tends to cause excessive drag. This also tends to reduce the amount of front end lift. Basically, cars as generally designed tend to create lift which in turn creates an induced vehicle drag. Reduce the lift, and you reduce the drag.

Whether or not the car is front or rear wheel drive doesn't have anything to do with that phenomenon.

To quote the S Owners Manual, Alfa does say that the S aero fairing package does reduce drag and lift of the overall vehicle (I suspect slightly). They do show a pressure distribution side profile of the S, but not of the standard 164, alas. So, can't really compare, but I've seen many vehicle lift and drag test results to confirm it in my mind. Used to work compiling wind tunnel test results of aircraft and vehicle models, and once in a while, buildings models, even the Space Needle, and years before, Galloping Gertie, the infamous Tacoma Narrows bridge.

Vehicle aerodynamics is really fairly tricky, and manufacturers spend a ton of money to improve their products, often in very subtle ways. I do remember something from Alfa years ago, where they took a Sprint GT/GTV and tested it on the road while instrumented. First they tested the original as produced design to get baseline results, and then the added front and rear spoilers to various extents. They reported that while drag was reduced a little, the vehicle lift was significantly changed, 300 lbs less lift measured in the front suspension at 100 mph, and 150 lbs less in the rear. The original aftermarket Bobcor front spoiler for Sprint GT/GTV's was probably a copy of those Alfa spoilers, looking similar as I remember. I have this testing report somewhere, I'll have to search for it.

And yes, it is also for looks, lol. After all...

In that respect, these are not full race cars, where aero is all important and negative lift is achieved by much more involved appendages. Witness the ultimate, F1 cars, where different teams may have the same engine, but the aero designs can make much of the the difference between being a consistent winner and a consistent middle runner. Some teams figure out the aero characteristics of their chassis, some do not.

Finally, I put an S spoiler on the trunk lid of my LS in order to break up the look of that big bluff trunk lid. I just happen to think that unadorned lid looks a little big and bluff, esp in the light champagne color. Works for me, anyway.

And really finally, I like both cars. The S is a good around town and winding road car, and the LS is a great highway faster swervy roads car.
 

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Bling vs actual Aero affect...

I simply added a Zender 'knock off' rear spoiler on to my LS, and lowered the front a tad, mostly for visual, but some aerodynamic improvements were probably realized at the same time. For 'normal' road speeds ... not sure that there is really all that much affect .. Does anyone know when (at what speed) aerodynamic improvements really become a factor ?
 

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but I have to ask: What is with the rear fin/wing/aero bit.

I mean, these are front wheel drive cars, so not like down draft is needed.

So, just for looks or is there a purpose?
Robert
Purely looks. Aero effects don't even begin until the car is exceeding 80 mph.

Downforce is for cornering and is a disadvantage for speed. Fwd or rwd makes no difference to this effect.

Chin spoilers on road cars are there mainly to direct cooling air up into the radiator, they create a high pressure zone just above the lip (giving "downforce" as a by product at very high speeds when the primary function becomes a serious fuel eater, some cars use passive or active air blocking to reduce cooling airflow at speed).

Trunk lip spoilers are almost completely ineffective at inducing downforce unless, as for the Audi TT and the Porsche Cayman, the body shape is wrong to start with. Any sharp edge cut off tail induces the Kamm effect which in itself simply reduces skin drag rather than improving form drag. The lip spoiler increases form drag over a car not so equipped and is fitted to make a car look more sporty. A Kamm tail is more efficient than a long teardrop tail but only because skin drag of the "ideal" taper exceeds the reduction in form drag. Kamm tail effects do not work in higher drag fluids like water. I mean basically Kamm discovered that making the same car shorter reduced overall drag!

To actually induce rear downforce you need a Gurney flap ( named after Dan the man himself) which is brutally ugly. Dan discovered he could corner faster by fitting an essentially vertical plate on the back end of the car. However, he wasn't faster in a straight line. F1 DRS illustrates the trade off between downforce and speed very neatly and graphically. A Gurney flap makes you slower in top speed but quicker in the corners AND, bonus, makes anyone following you even slower in the corners.

Examples on road cars include the aforesaid Cayman, the current F Type Jaguar, the McLaren MC12 and the new one and the Bugatti Veyron. On both the McLaren and the Bugatti these plate spoilers also act as air brakes. On both the car lowers itself significantly when the plate is deployed as a spoiler.

Any road car more than an inch or so off the ground needs no spoilers for aero effects. Undertrays yes, spoilers no. Smooth underbody airflow is known to be beneficial for both fuel economy and grip. The proper function of racing car spoilers is to create a vacuum under the car to reduce lift and active areo is banned for this reason. A road car cannot get close enough to the ground for this effect to work. My particular favourite styling spoiler at the moment is the front "splitter". Now those really are amusingly pointless with a ride height of three inches or more!
 

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I wish Alfa would have done something different with the Q looks wise. The LS is a great evolution from the L in my opinion. Alfa should have smoothed out the body on the Q and used a small spoiler. The S look is fine for the first gen 164 but looks out of place next to the LS.
 

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S compression ratio was 10:1 and base /L was 9.5:1.

Stated power was 200 bhp @ 5,800 rpm for the S and 183 @ 5,600 rpm for the L.

Torque was 195 lb ft @ 4,500 rpm for the S and 191 lb ft @4,400 rpm for the L.

No driver could tell the difference from driving either of those engines.
 

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S compression ratio was 10:1 and base /L was 9.5:1.

Stated power was 200 bhp @ 5,800 rpm for the S and 183 @ 5,600 rpm for the L.

Torque was 195 lb ft @ 4,500 rpm for the S and 191 lb ft @4,400 rpm for the L.

No driver could tell the difference from driving either of those engines.
Maybe not in the actual numbers of hp vs torque between the two but they accelerate very different from one another even with the very similar specs. I, like many here have owned them both at the same time and while my S was faster after lets says 70 I always felt my L pulled way harder up to that point. I never felt I needed as many revs in the L for most short power runs.
 

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"Aero effects don't even begin until the car is exceeding 80 mph"

Well, yes and no. The effect is there but is less the slower the speed, being a function of dynamic pressure, or Q (1/2 rho V squared). Nothing magic about 80 mph. Manufacturers have made body shape changes for the effects even at 60 mph in order to get that last small aero drag reduction. some older SAE reports have discussed this.

"Chin spoilers on road cars are there mainly to direct cooling air up into the radiator"

Yes, and no, actually they increase the air going through the radiator by lowering the ram pressure under the front of the car, inducing a higher flow higher up through the engine bay, and allowing that increased flow to escape down past the engine to under the car. Also to reduce the high pressure ram air under the car, in general. You do say this later on for race cars, but it is still there in lesser form for street cars.

"Trunk lip spoilers are almost completely ineffective at inducing downforce"

As designed for modern street cars, that is correct, but that's not their function, rather it is to block the fwd flow up over the trunk lid which causes separation behind the rear of the roof. Blocking that adverse flow enhances the Kamm effect as you note.

As Alfa states in the owners manual, their S fairing package does improve the aero characteristics (reduce drag?) slightly (well, they say that anyway, I'm sure it's not much). The previous testing by Alfa years ago did though demonstrate the effectiveness of proper spoiler design and body fairings on their Sprint GT/GTV design.

I'm sure we agree, as stated before, that the S fairing/spoiler/fin package is at least 90% show, not go, but it will have some effect at cruise speeds, just not much I'm sure.

I'm with Richard on the desirability/looks of the spoiler, regardless of effectivity.
 

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I think the drag coefficient for the was was higher than for the L.

Chin spoilers improve fuel economy on road cars, they're not their for downforce. They do reduce front end lifting at very high speeds, say over 100 mph, but not by much.

As far as the effect on cooling airflow I think Del and I are describing the same phenomenon from different perspectives. The higher pressure is induced above the chin spoiler and the main radiator inflow occurs just above that spoiler at speed. The exit for the airflow is improved by the lower pressure area immediately below and behind the chin spoiler.

I agree that a small trunk lid lip spoiler improves flow over the car roof, at the cost of very dirty tail lights in mucky conditions (ask me how I know this ) . The design of the rear spoiler on the S (and a similar shape on the SAAB 9000 Aero) are ill designed for this purpose. The current factory spoiler on my BRZ is particularly absurd in this regard.

This is why I say they are cosmetic devices. The function is minimal and inefficiently delivered to boot.
 

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If you were to choose an Alfa, other than a Spider, to race at Bonneville which one would you choose?
 
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