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    Re: Rear spoiler lift mechanisms

    Speaking of rambling, except bbywu, no one has answered my orignial question - whether you can easily replace the hydraulic lift mechanisms from the cab into the coupe!! 

    But I have NO PROBLEMS listening to the views of other Rennteamers, be them serious or light-hearted. 


    --
    "I dream of a better tomorrow, where chickens can cross the road without being questioned about their intent"

    Re: Rear spoiler lift mechanisms

    Arshad...if you want to do it...I have a few pages from the service manual that I could send you...


    Re: Rear spoiler lift mechanisms

    intouch1:

    ......

    secondly, if the carrera wing provides enough downforce, it would be good enough for the turbo too.

    the wing on the turbo is to cosmetically differentiate the turbo from a standard fare carrera and more importantly to reduce rear lift and increase rear down force to make it safe for owners who are more likely to take this car to high spe

    Fixed it for you. Smiley

    >>>>>
    secondly, if the carrera wing provides enough downforce, it would be good enough for the turbo too.......
    the wing on the turbo is to cosmetically differentiate the turbo from a standard fare carrera
    >>>>>

    Based on what are you making these statements? Or is it just speculation? 

    I agree that a slow speed the difference is small. At high speed, say 150 mph or above, a speed easily achieved by owners of this car, it would be dangerous without the downforce and reduced lift, particularly the rear end.

    Esthetically, I don't disagree with you since it's a matter of taste. Functionally, let's not argue with facts please.

     


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    porsche has the engineering prowess to find a different solution...they don't cause they think the turbo must have a wing to seperate it from the lesser siblings.

    same as with the gt2. do you really think that it needs a wing zhe size it has. would not an even higher lifting turbo wing with a little more surface area done the same trick ?

    gt2 wing is so massive as to seperate it from the turbo.....cosmetically that is.....


    --
    Speed has never killed anyone, suddenly becoming stationary... That's what gets you.

    Re: Rear spoiler lift mechanisms

    bbywu:

    Arshad...if you want to do it...I have a few pages from the service manual that I could send you...

    Wow! Thanks!!  That would be lovely!!  Smiley  Then he could get an exact idea of what's in store for him if he decides to take up the job.  Smiley


    --
    "I dream of a better tomorrow, where chickens can cross the road without being questioned about their intent"


    Re: Rear spoiler lift mechanisms

    cannga:


     

    MMD, many of us are guilty of rambling on these forums, but is this endless, senseless rambling really necessary? Smiley  Your mission, should you choose to accept, is to google the words aerodynamic lift, drag, turbulence, Bernoulli's, and wing, and read ALL the articles before posting another post on this subject.  Frankly, I am surprised RC or Eunice has not  banned you yet.  

    Kidding aside, there are 2 issues here, aesthetics and function.
    Esthetically: "I don't like the wing, but I understand it's a matter of personal preference." That's one sentence; end of story. There is no need for your 400 posts on the subject, no? Smiley
     

     

     

    OUCH!  C'mon Buddy,  Smiley no problema.

    I like the idea of an optional detachable unit for when people take their turbos to the track. (see pic below).

    I got my turbo because I like Porsches and for it's straight line performance for passing on rural highways. Traded in my wingless 997S to get the extra HP/Tq. My car never reaches it's "cup car" limits, so why should I have equipment slapped onto it I don't need? 

    I think of Autobahn travel as the ideal use of *my* car. What is it..., 90 percent of Porsche buyers think the same way? The aerodynamics of   Autobahn travel must be simple and mild enough to get away with a retractable spoiler, no? Because it's good enough for the NA 997, I guess the compromise of the retractable spoiler would serve 90% of Turbo buyers too, the remainder can purchase a more effective, larger wing.

    As for the 400 posts? There's a whole bunch of guys here like me. They're interested in the subject, why not chime in when the subject comes up? The stuff I've heard before?  I ignore it while being happy other car guys are enjoying their cars too.

    Smiley

    1241279686425wing aerokit unbolt it small  copy.jpg

     

     

     


    --
    2007 997 Turbo


    Re: Rear spoiler lift mechanisms

    intouch1:

    porsche has the engineering prowess to find a different solution...they don't cause they think the turbo must have a wing to seperate it from the lesser siblings.

    same as with the gt2. do you really think that it needs a wing zhe size it has. **The wing reduces lift & increases down force, particularly at high speed and particularly important for the 911 shape and engine configuration. Do you need it? Uhhh.... depends on whether or not you want to visit the great great grand parents at 150 mph?** Smiley  would not an even higher lifting turbo wing with a little more surface area done the same trick ?

    gt2 wing is so massive as to seperate it from the turbo.....cosmetically that is..... Please quote one authoritative source who shares this opinion.


    1. The shape of the 911 (or any fastback car) is such that airspeed on top of roof is faster than at bottom of car. This causes a lift at the rear end -- the car is behaving like an airplane wing -- a particularly dangerous situation in the rear-engine 911. A rear wing acts to slow the airspeed on top and reduces this lift -- Bernoulli's principle http://en.wikipedia.org/wiki/Lift_(force) .

    2. But reduction of lift is not the only benefit of the wing, by angling the wing, downforce could be generated as well. The angle is adjustable on "serious" wings.

    3. So is the wing always good, and bigger is better? No. Disadvantages of the wing are both aero- and social-dynamic Smiley.  As the wing becomes larger it creates more drag (aerodynamically and socially LOL). In addition, no one would buy the Turbo if you slap a big huge cup wing on it. It's unnecessary downforce for the expected driving and is socially unacceptable.
    I have read that race teams in fact adjust the wing as dictated by the particular circuit, long straights versus multiple turns, etc. Meaning, like everything else, there are pluses and minuses.

    So let's review the 911's various wing shapes and sizes:
    *Cup car
    *GT2/GT3
    *Turbo
    *997S
    Do you see the pattern? The wings get bigger and taller as the anticipated driving aggressiveness and speed increase, no? I would call this "situational wings." Smiley At higher speed, the smaller and lower wing of the standard 997 is in fact a compromise and there is a reason the Turbo wing raises at speed and the Convertible's wing raises higher. Unless you could quote an authorative source, I would think twice about second guessing complicated aerodynamic work by PAG engineers.

    I can't be dragged into this endless rambling any further. Please help. Smiley


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    MMD:

    As for the 400 posts? There's a whole bunch of guys here like me. They're interested in the subject, why not chime in when the subject comes up? The stuff I've heard before?  I ignore it while being happy other car guys are enjoying their cars too.

    Smiley


    MMD, you got a good point. Plus I probably have been just as guilty of the "400 Syndrome." LOL.  Peace. Smiley


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    cannga....we all understand the need for downforce at the rear of the 911. even the audi TT was losing traction before thy added the wing.

    however, the standard carrera wing would certainly suffice in providing enough downforce to stabilize the turbo's rear.

    the reason for the 'add on' wing on the turbo and gt2/gt3 is cosmetic.


    --
    Speed has never killed anyone, suddenly becoming stationary... That's what gets you.

    Re: Rear spoiler lift mechanisms

    intouch1:

    cannga....we all understand the need for downforce at the rear of the 911.
    .....

    Thank you! Particularly at high speed.

    As for the cosmetic discussion, I respect your right to have an "opinion." Smiley I just want to make sure the interesting facts of the other side of the coin be shared with other readers.


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    intouch1:

    cannga....we all understand the need for downforce at the rear of the 911. even the audi TT was losing traction before thy added the wing.

    however, the standard carrera wing would certainly suffice in providing enough downforce to stabilize the turbo's rear.

    the reason for the 'add on' wing on the turbo and gt2/gt3 is cosmetic.

    The original Audi TT's problem before the rear wing was retrofitted was not a lack of traction, but a lack of high-speed stability. 

    The GT2's higher front and rear downforce values as compared with the Turbo have to, by definition, be bought at the cost of increased aerodynamic drag. They wouldn't have paid that "price" if it was not necessary to ensure the handling stability that the car needs at the speeds it is capable of.
    The GT2's rear wing isn't just cosmetic.


    --

    fritz


    Re: Rear spoiler lift mechanisms

    cannga:

    MMD, you got a good point. Plus I probably have been just as guilty of the "400 Syndrome." LOL.  Peace. Smiley

    Nah... . Smiley You did some nice work a few posts up when you ranked wing size.  It got clearer for me. Smiley I'm glad *you* have "400 Syndrome." Me? I totally admit I have a problem with the wing on my car. Smiley I may need psychiatric care.  My health insurance only covers inpatient services. Gotta find a few doctors willing to commit me. Smiley


    --
    2007 997 Turbo


    Re: Rear spoiler lift mechanisms

    MMD:

    Nah... . Smiley You did some nice work a few posts up when you ranked wing size.  It got clearer for me. Smiley I'm glad *you* have "400 Syndrome." Me? I totally admit I have a problem with the wing on my car. Smiley I may need psychiatric care.  My health insurance only covers inpatient services. Gotta find a few doctors willing to commit me. Smiley

     

    You know crazy people never think they are crazy right? Yep I think you are as sane as could be, maybe just a tad "nutty," a tad OCD, like a number of other Porsche owners whom I know. Smiley

    One interesting thing I've read is that, as opposed to a true gentle back slope like that of the Lamborghini Gallardo, a 30-35 degrees rear slope has particularly unstable airflow (any pro lurker here would like to chime in?). Well what do you think our 911 slope angle is?! The 911, as classic a shape as it is, is not exactly the best aerodynamic package.

    Second thing is downforce is proportional to the **square** of velocity, so it is particularly important at higher speed and at, say 150 mph plus, yes I would say it's a matter of life and death. The fact that it deploys at 70 mph or whatever it is should give us a clue as to what PAG engineers think when it is starting to be a factor. http://en.wikipedia.org/wiki/Downforce

    So IMO, you could mess with other things, but gotta to leave that wing alone.Smiley BTW, I am surprised as much anti-vent and slat as you are, you still have the stock wheel on your car. Just count them, 10 slats on each wheel! I think you might enjoy the car better if you change the wheels.


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    Some basic informatiion. http://www.autozine.org/technical_school/aero/tech_aero.htm
    I highlighted the discussion regarding the angle of the rear screen slope.

     

    Aerodynamics

     

      Drag and Lift

      Drag

      Aerodynamic efficiency of a car is determined by its Coefficient of Drag (Cd). Coefficient of drag is independent of area, it simply reflects the influence to aerodynamic drag by the shape of object. In theory, a circular flat plate has Cd 1.0, but after adding the turbulence effect around its edge, it becomes approximately 1.2. The most aerodynamic efficient shape is water drop, whose Cd is 0.05. However, we cannot make a car like this. A typical modern car is around 0.30.

      Drag is proportional to the drag coefficient, frontal area and the square of vehicle speed. You can see a car travelling at 120 mph has to fight with 4 times the drag of a car travelling at 60 mph. You can also see the influence of drag to top speed. If we need to raise the top speed of Ferrari Testarossa from 180 mph to 200 mph like Lamborghini Diablo, without altering its shape, we need to raise its power from 390 hp to 535 hp. If we would rather spend time and money in wind tunnel research, decreasing its Cd from 0.36 to 0.29 can do the same thing.

      Fastback

      In the 60s, motor racing engineers started to take aerodynamics seriously. They discovered that if they reduce the slope of the back of a car to 20 degrees or less, the air flow will follows the roof line smoothly and dramatically reduce the drag. They termed this design as "Fastback". As a result, many racing cars, such as the Porche 935 / 78 "Moby Dick" shown here, added an exaggerately long tail and lower the back.

      For a 3-box car, air flow leaves the car straightly at the end of roof line. The dramatic drop of rear screen creates a low pressure area around, this attracts some air flows back to complement, thus creates turbulence. Turbulence always deteriorates drag coefficient.

      However, this is still better than something between a 3-box and a fastback. If the rear screen angle is around 30 to 35 degrees, the air flow will be very unstable. It could greatly deteriorate the high speed stability. In the past, car makers had little knowledge about this and created many cars like this.

      Lift

      Another important aerodynamic factor is Lift. Since air flow above the car travels longer distance than air flow underneath the car, the former is faster than the latter. According to Bernoullis Principle, the speed difference will generate a net negative pressure acted on the upper surface, which we call "Lift".

      Like drag, lift is proportional to area (but surface area instead of frontal area), the square of vehicle speed and Lift Coefficient (Cl), which is determined by the shape. At high speed, lift may be increased to such an extent that the car becomes very unstable. Lift is particularly serious at the rear, you can easily understand, since a low pressure area exists around the rear screen. If the rear lift is not adequately counter, rear wheels will become easy to slip, and that is very dangerous for a car travelling at something like 160 mph.

      Fastback is particularly bad in this aspect, because it has a very big surface area in contact with air flow. It seems that good drag and good lift are mutually exclusive, you can't have both of them. However, as we did more research on aerodynamics, we found there are some solution to achieve both of them ....

     

      Aerodynamic Aid

      Wing (rear spoiler)

      In the early 60s, Ferrari's engineers discovered that by adding an air foil (we simply call "Wing") to the rear end, lift can be dramatically reduced or even generates net downforce. At the same time, drag is only slightly increased.

      The wing has the effect of directing the majority of air flow to leave the roof straightly without going to the back, this reduce lift. (If we increase the wing angle, a hundred kilograms of downforce may even be available.) There is still a little bit air flow follows the back and leave the tail under the wing. This avoid turbulence that appears in non-fastback car, thus remain drag-efficient. Since there is too little air follows this route, its contribution to the lift can be easily cancelled by the wing.
       
      Wing must be installed high in order to be benefited from the majority air flow. Escort RS Cosworth is right .... Cougar, well, seems to use wing as decoration only.
       
      The first wing car was Ferrari 246SP endurance racer in 1962. Just one year later, 250GTO road car incorporated a small duck tail rear wing, a first for road car of course. However, wing did not get popular until Porsche launched its 911 RS 2.7 in 1972, whose big duck tail reduced lift by 75% at high speed. Just one year later, 911 RS 3.0 used a "Whale tail" wing which completely eliminated lift. It became a trademark for the later 911s.

      Porsche's new 996 Carrera offers us some useful data :

     

      Front lift (at 157mph) Rear lift (at 157mph)
    Wing down 64 kg 136 kg
    Wing up 5 kg 14 kg

     

       

      Spoiler

      Spoiler is the aerodynamic kit that alter the air flows underneath the car. We call those installed at the bottom edge of front bumper as "Chin Spoiler" or "Air Dam", and those installed at the bottom edge of the car's sides as "Skirt". To understand its principle, we must first talk about underside air flow.

      Air flows underneath the car is always undesirable. There are many components, such as engine, gearbox, driving shaft, differential etc, exposed in the bottom of the car. They will obstruct the air flow, not only cause turbulence which increase drag, but also slow down the air flow thus increase lift. (Remember Bernoullis's Principle ?).

      Spoiler is used to reduce underside air flow by encouraging air to pass either side of the car. As a result, drag and lift caused by underside air flow could be reduced. Generally speaking, the lower the spoiler locates, the better result obtain. Therefore you can see endurance racing cars having spoilers nearly touching the ground. Of course road cars cannot do so.
       
       

      Smooth Undertray

     

    We can also reduce the influence of underside airflow by covering the car's bottom by a smooth undertray, as shown in this Ferrari F355. This avoid turbulence and lift. 

     

      Ground Effect

      To motor racing engineers, wing might be a good solution to lift, but still far away from what they really want. A typical formula one racing car corners at around 4g lateral acceleration, that requires substantial downforce to keep the tyres firmly on track. Install a huge wing with high angle can satisfy this requirement, but also deteriorates the drag coefficient.
      In the 70s, Collin Chapman (again) invented a completely new concept to provide downforce without altering drag - Ground Effect. He incorporated an air channel into the bottom of his Lotus 72 racer. The channel is relatively narrow in front and expand towards the tail. Since the bottom is nearly touching the ground, the combination of channel and ground forms virtually a closed tunnel. When the car is running, air enters the tunnel in the nose and then expands linearly towards the tail. Apparently, air pressure is reducing towards the tail so that downforce will be generated.

      Ground Effect is so superior than wing that it was soon banned in Formual One. In 1978, Brabham's Gordon Murray tried again with different means - instead of expansion channel, he used a powerful fan to create low pressure near the tail. Of course FIA banned it again.

      Ground effect is not too suitable for road cars. It requires the bottom to be very close to the ground to form a closed tunnel. For racing car, this is no problem. But road cars should have much higher ground clearance to suit different rough roads, up hill and down hill etc. This greatly reduce the effectiveness of Ground Effect. McLaren F1 road car followed Brabham's trick by using 2 electric fans to create ground effect, but honestly speaking, no tester had ever praised its down force. Dauer 962, a so-called "road car" but it is actually a road-legal Porsche 962 endurance racing car, use conventional air-channel ground effect as the race car. Adjustable ride height allow it to run in rough road (slowly) and make good use of Ground Effect in Germany's Autobahn. Nevertheless, it can barely generate 40% downforce of the racing car.

     

      Cd World Record

     

    Cd Year Model Remark
    0.137 1986 Ford Probe V Concept car 
    0.19 1996 GM EV1 Electric car
    0.25 1999 Honda Insight Hybrid car
    0.25 2000 Lexus LS430 --
    0.25 2000 Audi A2 "3-litre" --
    0.26 1989 Opel Calibra 2.0i base model
    0.26 2000 Mercedes C180 --
    0.27 1996 Mercedes E230 --
    0.27 1997 VW Passat --
    0.27 1997 Lexus LS400 --
    0.27 1998 BMW 318i --
    0.27 2000 Mercedes C-class C200 up to C320

      

    Copyright© 1998-2000 by Mark WanAutoZine Technical SchoolReturn to AutoZine home page
    --
     

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    Great post cannga, thanks.


    Re: Rear spoiler lift mechanisms

    Eunice, you're welcome. For me what's neat about the article is after reading about what's particularly bad (3 box, 30-35 degree rear screen), you look at the Audi TT with its little wing and think to yourself, wow, there's immediate evidence.

    I don't know which gen Audi TT fritz and intouch are talking about but the enclosed pic is of a 2002 Audi TT.

    audi.jpg


    --
     

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    cannga:

    I don't know which gen Audi TT fritz and intouch are talking about but the enclosed pic is of a 2002 Audi TT.

    I was referring to the very first Audi TT built in 1998, which was initially delivered without a rear spoiler. It was prone to snap-oversteer when cornered at its high limits and, after several spectacular accidents had been reported in the press, Audi was forced to offer to retrofit a rear spoiler and to change the suspension set-up free-of-charge.
    The company also offered to retrofit an ESP system, but owners were expected to pay part of the cost of that.

     


    --

    fritz


    Re: Rear spoiler lift mechanisms

    Very nice read cannga, I always like technical articles that make hard stuff easy to understand, or at least give you the feeling that you understand it partially.

    I'd like to make two additions:

    In this picture:

     

    You see the effect of the turbulence behind the rear window. This is because a low air pressur exists behind the rear window, and the airflow is curved toward that low air pressure. The same phenomenon also takes place behind the rear of the car. To me, it seems that the cougar and the Audi TT try to solve that problem by adding the tiny wing at the aft edge of the car: the little wing forces the air to stop trying to follow the shape of the car.

    Additionally, it is mentioned that a venturi for the ground effect doesn't add to the drag... This is not entirely true: you create a vacuum (relatively low air pressure) at the aft underside of the car. As much as the car is "sucked down" by this vacuum, it is also being "sucked backward", because it increases the vacuum behind the car.

    Often, aerodynamics may be illustrated by comparing it to hydrodynamics: Air tends to behave like a fluid in many cases. Picture a heavy, square boat travelling pretty fast. You'll see all those whirls and currents behind the hull, slowing the boat down dramatically. Same goes for cars with a very square/high rear shape.


    --

    Porsche, seperates LeMans from LeBoys

    Re: Rear spoiler lift mechanisms

    I notice the spy pics of the 991 look a lot more fastback!


    --


    Click for bigger picture!


    Re: Rear spoiler lift mechanisms

    cannga:

    http://www.autozine.org/technical_school/aero/tech_aero.htm
    Porsche's new 996 Carrera offers us some useful data : 

      Front lift (at 157mph) Rear lift (at 157mph)
    Wing down 64 kg 136 kg
    Wing up 5 kg 14 kg

     

    Joost, good points & explanation.  I hope MMD is still reading this thread? (just teasing Smiley)

    I also notice the above. Somehow it seems odd to me that the REAR wing also reduces FRONT lift. Someone likes to explain this? It's not a typo?

     

     


    --
     

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Rear spoiler lift mechanisms

    cannga:
    cannga:

    http://www.autozine.org/technical_school/aero/tech_aero.htm
    Porsche's new 996 Carrera offers us some useful data : 

      Front lift (at 157mph) Rear lift (at 157mph)
    Wing down 64 kg 136 kg
    Wing up 5 kg 14 kg

     

    Joost, good points & explanation.  I hope MMD is still reading this thread? (just teasing Smiley)

    I also notice the above. Somehow it seems odd to me that the REAR wing also reduces FRONT lift. Someone likes to explain this? It's not a typo?

     

     

     

    Just guessing here: 
    Raised rear wing causes lower air pressure low down behind the rear bumper, which in turn draws air out from below the car's floor, in turn reducing lift or  - in some cars  - increasing downforce.

    Since pressure is reduced to a lesser or greater extent over the whole length of the undertray, lift is reduced or downforce increased even at the front of the car.

    Edit: Have just read Joost's post above.
    In spite of not specifically mentioning the air flowing under the car, it effectively supports this explanation.
    --

    fritz


    Re: Rear spoiler lift mechanisms

    Thanks for the compliments guys!

    I am by no means an aerodynamics expert, but both through my lifetime hobbies (glider flying and paragliding) and my work (engineer for an aerospace company), I tend to put much interest in the subject.

    Fritz' comments definately make some sense. Additionally, it is perfectly possible that a wing at the back of the car influences the entire shape of the airflow over the car, thus also reducing lift on the front. For example, I have been working on a gurney flap lately, which works in the same way as the gurney on the GT3 (see picture).

    Gurney.jpg

    This is a very small addition on a wing or a car, greatly influencing the global aerodynamic flow over the wing profile, thus creating more lift/downforce, without adding a lot of drag.
    More on gurneys and aerodynamics: en.wikipedia.org/wiki/Gurney_flap


    --

    Porsche, seperates LeMans from LeBoys

    Re: Rear spoiler lift mechanisms

    cannga:
    cannga:

    http://www.autozine.org/technical_school/aero/tech_aero.htm
    Porsche's new 996 Carrera offers us some useful data : 

      Front lift (at 157mph) Rear lift (at 157mph)
    Wing down 64 kg 136 kg
    Wing up 5 kg 14 kg

     

    Joost, good points & explanation.  I hope MMD is still reading this thread? (just teasing Smiley)

     

     


    Yes!  Assuming reducing lift is the same as adding downforce, now I know I can strap approximately 136 kg of premixed concrete or cat litter  to the wing/luggage rack for transport home without breaking it .

    Smiley

    Unfortunately they're probably not the same. Smiley

    --
    2007 997 Turbo


    Re: Rear spoiler lift mechanisms

    MMD, you know, that so called 'ugly' wing on the back of your car probably looks more elegant than 130kg of concrete :)


    Re: Rear spoiler lift mechanisms

    Whoopsy:

    MMD, you know, that so called 'ugly' wing on the back of your car probably looks more elegant than 130kg of concrete :)

    Yes..., you are correct, sir. Smiley 

    It's true and as cannga has well-explained, there's no losing that wing.

    But a guy can still have his dreams can't he:   Smiley

    1242073667696TT wing wingless comp.jpg

     


    --
    2007 997 Turbo

    Re: Rear spoiler lift mechanisms

    MMD:

    Yes!  Assuming reducing lift is the same as adding downforce, now I know I can strap approximately 136 kg of premixed concrete or cat litter  to the wing/luggage rack for transport home without breaking it .

    Smiley

    Unfortunately they're probably not the same. Smiley

    If you are really interested, downforce is in fact negative lift.
    When aerodynamic lift is reduced (by using such sensible measures as spoilers) to a value below zero, then it starts to distance itself from its nasty reputation for destabilizing cars at high speed by calling itself downforce.

    136kg of kitty litter has the undesirable side-effect of increasing the car's inertia. As well as the desired increase of the load on the tire contact patches, it would also surely increase the car's aerodynamic drag. I wouldn't like to predict its influence on aerodynamic downforce when transported on the rear wing  without first seeing the results of a windtunnel test.

    I would therefore recommend you transport the kitty litter in your car's front trunk. I have only ever transported three 20kg sacks at any time, having just one reasonably continent cat, so cannot confirm whether or not you will have to make 2 trips to the store to be able to bring home your whole shipment of 136 kg.

    --

    fritz


    Re: Rear spoiler lift mechanisms

    MMD:
    Whoopsy:

    MMD, you know, that so called 'ugly' wing on the back of your car probably looks more elegant than 130kg of concrete :)

    Yes..., you are correct, sir. Smiley 

    It's true and as cannga has well-explained, there's no losing that wing.

    But a guy can still have his dreams can't he:   Smiley

    1242073667696TT wing wingless comp.jpg

     


    What you really want is something like the 996 C4S, which looks exactly like the 996 Turbo sans wings and side inlets. Too bad the 997 C4S doesn't look like the 997 Turbo.

    With such a body, have someone souped up the engine to at least Turbo spec and you will be in heaven.


    Re: Rear spoiler lift mechanisms

    fritz:

    If you are really interested, downforce is in fact negative lift.
    When aerodynamic lift is reduced (by using such sensible measures as spoilers) to a value below zero, then it starts to distance itself from its nasty reputation for destabilizing cars at high speed by calling itself downforce.

    --

    fritz

    Hmm, when you keep in mind that in fact the whole car acts like a wing profile (flat underside, curved upper side -> Air travelling over the car has a longer path than under the car -> Air density above the car lower than under the car -> Net result is lift), you'll realize that you'll probably need a whole lot of wings to absolutely reduce the total lift to subzero... (will result in something like an F1-car, which in fact is able to drive upside down at topspeed). Luckily, there's gravity keeping our cars on the ground too... :-)


    --

    Porsche, seperates LeMans from LeBoys

    Re: Rear spoiler lift mechanisms

    Joost:
    fritz:

    If you are really interested, downforce is in fact negative lift.
    When aerodynamic lift is reduced (by using such sensible measures as spoilers) to a value below zero, then it starts to distance itself from its nasty reputation for destabilizing cars at high speed by calling itself downforce.

    --

    fritz

    Hmm, when you keep in mind that in fact the whole car acts like a wing profile (flat underside, curved upper side -> Air travelling over the car has a longer path than under the car -> Air density above the car lower than under the car -> Net result is lift), you'll realize that you'll probably need a whole lot of wings to absolutely reduce the total lift to subzero... (will result in something like an F1-car, which in fact is able to drive upside down at topspeed). Luckily, there's gravity keeping our cars on the ground too... :-)

    In fact, a handful of road cars like, for instance, the Porsche 996 and 997 GT2 models, have aerodynamic downforce (= negative lift) in spite of not having wings as large or pronounced as an F1 car. Smiley


    --

    fritz


    Re: Rear spoiler lift mechanisms

    Whoopsy:

     

     


    What you really want is something like the 996 C4S, which looks exactly like the 996 Turbo sans wings and side inlets. Too bad the 997 C4S doesn't look like the 997 Turbo.

    With such a body, have someone souped up the engine to at least Turbo spec and you will be in heaven.

    HAHA! Good idea; but how will other Turbo owners know I'm "cool?" Smiley (kidding)

    You make a good observation though. Perhaps the 997T wing is needed even more because the intercooler vents add additional upward aerodynamic forces?!

    Hummmm..., I feel better now if that's true. 


    --
    2007 997 Turbo

     
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