BioBanker

Of course it does! And if you have one headlight that is brighter than the other, one side of the car accelerates slower than the other because it has a greater number of photons pushing against its forward motion.

I have disconnected my day time running lights for maximum forward performance. I turn my lights on to assist with braking!

In all seriousness, I think that the stock spoiler provides some downforce, but not tons. Im sure that you will be able to find exactly how much downforce a stock TT has via enough googling. The aerokit cars have more rear downforce and Porsche apparently had to put a bigger lip on the front to offset, and of course the GT2 has even more again. Many people report weird aerodynamic affects in 996TTs with GT2 wings on if they do not address the shortfall in front downforce. Ive never heard the same complaint with stock 996TTs with spoilers that dont extend, but Im sure there is a difference. You would just need to be going bloody fast to feel it, maybe even faster than the car can go. Just my uneducated $0.02. You can probably find the actual numbers if you look hard enough - whether they mean anything in real life is the bigger question. But of course a functioning spoiler is always better than one that doesnt work, simply because it works as it is supposed to.

TommyT

Honestly reading the instructions was harder than the actual install. Just do it!

champignon

Firstly, I'm not positing anything; I have no horse in this race. I simply would like to know, with some actual, empiric, observations, what the spoiler on this car does for its normal operation on public roads. If it turns out that the spoiler really needs to be the stock spoiler, and it really needs to go up and down, for drivability, safety, engine cooling, or whatever, I'm going to order one of those electric Ram kits and either install it myself or have it installed. I like cool stuff, and the spoiler going up and down is very cool, at least visually. You can bet that if I install it in my car, I will show it to everyone that I know.

As to theoretical underpinnings vs. empiric observations, that is a never-ending part of "reality testing." I have no doubt whatsoever that NASA and its contractors spent many times as much resources, time, and money designing the Space Shuttle, its rocket launchers, and its other features than Porsche ever spent designing the aerodynamics of the 996 Turbo, including its spoiler. I sincerely doubt that NASA would have sent the crew of the Space Shuttle Challenger up in 1986, which resulted in 7 astronaut deaths, had they thought this outcome would be likely. I also doubt they would have sent up the Space Shuttle Columbia in 2003, had they thought, from their extensive research, that this would result in the death of yet another 7 astronauts.

The bottom line is that there is theory, and there is practice. We have no access to the theory here (other than what Porsche has published which is very little), however we have great access to the practical results. And that is what I would like to know, and I bet that others reading this thread in the future would also like to know.

Thank you.

manimal

It sure seems that you do. No one is claiming that Porsche engineers are infallible. No one "admires" the problematic hydraulic spoiler, as you say in your OP. We're just pointing out that it's part of the system that Porsche engineered when they built the car.

Porsche has stated in many places that it's important for the rear wing to be operational, and that it's important for the front and rear aero to match (see: OEM aero kit documentation). I don't know why you would question this. The manufacturer says so, and it's also, quite frankly, common sense.

To use your questionable NASA analogy, consider how much R&D has been done via racing. You'd better believe guys have died racing Porsches. Literally, at the highest levels, these cars have been pushed to the max. Find a 911 race car that doesn't have a big rear wing, and corresponding front aero.

I think the theory is pretty obvious, and we have plenty of practical results to see. Google some photos of 911's in a wind tunnel.

If you're just asking what to do with your setup, well, that's a different question. If you're looking for some empirical evidence that your mixed-and-matched non-OEM setup is fine, well, I don't know what you're expecting to find.

My $0.02 is that if your rear wing resembles a GT2 rear wing, you should add some more downforce on the front. Maybe a GT2 front, or simply the Joe Toth splitter.

BioBanker

"To answer your questions, the 996TT has a coefficient of front lift of 0.02 and downforce of -0.01 in the rear. This means that the car is neutral at speeds of 125mph, close to zero lbs.

The 996GT3 with a protruding front lip and the aerofoil, has zero lift at 125mph in the front and close to 14 lbs of downforce. At 186mph, downforce in the rear becomes close to 30 lbs. I would think the 996TT aerokit to be similar.

The 996GT2 has seen a few changes vs the 996TT to reduce front lift via the opening on the top of the front bumper, air flows through the front bumper and is extracted by the opening on top, reducing effectively lift and also improving drag. Front downforce on the GT2 at 125mph is about 5 lbs and rear downforce about 17-18lbs, climbing to about double those numbers at 186mph."

https://www.6speedonline.com/forums/...tt-anyone.html

Ive seen similar data from Porsche so I believe that the above is correct. Seems that the spoiler is required in the 996TT to counter the lift produced as the car nears top speed. The 996TT stock rear wing generates about 20lbs of downforce at 190mph, which is not much, but its enough to keep the car neutral at those speeds.

champignon

People mod cars all the time, even Porsches. This would cover everything from using non-recommended tires, to changing the wheels, to flashing the engine ECU software, to many other things not necessary to list. Most of the time, people get away with these things, whether or not we may consider the mods to be desirable.

Personally, I am not a modder. I usually avoid buying modded used cars, but I did make an exception in this particular case. I am not looking for some sort of validation from this forum or anybody regarding what has been done to my car in the past by previous owners. I am also not looking for any validation of anything that I might do to the car in the future. I make a point of not confusing my own self identity or worth, with my possessions.

I have not made any decisions about what I will do to my car in the future, other than that I am going to upgrade the stereo, and get the oil and filter changed again before winter.

I am, however, curious to know what other peoples' experiences are with inoperative and modified spoilers on these cars, and I think one will find that this thread will get a lot of activity, now and in the future, because I am not the only person curious to know more, about these things.

manimal

I'd like to know more, too, but asking people to "share their experiences" is inherently a subjective endeavor. I'm sure there are plenty of folks running GT2-style rear spoilers and stock front aero (because I see them for sale all the time, and they apparently haven't crashed yet) -- but that still doesn't prove that it's a good idea.

"02996ttx50

it goes up and down lol

believe that! i am beginning to detect a measure of "moveable wing envy" lol

interesting that you reference this, as i have often wondered if morton-thiokol was the supplier of the seals used in our spoilers. if they spent *more*? well, their results were far more catastrophic than our error messages and resultant loss of downforce reduction if our spoiler fails.

we don't NEED "access to the theory"! it's enough to understand why porsche and other mfg'rs of cars that factory race, employ aerodynamics as inherent features that are intrinsic to their designs! there IS science involved, regardless of whether or not WE fully understand it.

..and..i "bet" you're wrong but moving ( ahem ) forward(?) i'd advise you to simply eliminate "porsche" from your hypothetical query, as spoilers are, and have been for quite some time employed on many other types of cars upon which added downforce is sought, and have consequently been implemented as design features for the reasons stated ad nauseum here ( and elsewhere ).

so..is this for you.. ( as it is for me..) simply typing practice, thinly disguised as circular discourse, aka an online circle jerk? a rhetorical question, no doubt..and yet

i would never flip you the bird, and yet..this "wing" is for you.

racer959

OP, do you think the operation of the spoiler going up and down on a race course, has any affect on stability?

champignon

Firstly, I am the wrong guy to ask on this, because I do not claim to know anything about this subject, however . . . .

I am just now back from dinner with a friend, who has done many things in life including selling cars for a number of years (he is now a manager at a local landscaping company). I brought up this thread with him as a topic of some amusement, to get his take, and later I actually commented on the question that you posed, above.

I asked Randy (who used to sell Subaru STis, with their hideous huge wings) what he thought the effect of the wing was in normal, everyday driving, and his response was to laugh; he thought it was comical that I would even pose the question.

We then got to the question of performance at high speeds and on a race course. What I said (and I did pull this out of my ***, just to be clear), was that driving a car really fast involves a process laden with a lot of feedback between the car and the driver; the more stable you feel, the faster you are willing to risk going. And, any sort of racing activity, be it car racing, ski racing, whatever, typically has results where the winner is separated from the losers by fractions of a second. It almost goes without saying that if you are pushing a vehicle to the limit, the slightest bit of instability is going to make you back off of the throttle, take the turn more cautiously, whatever, because your survival instinct will kick in, and not very many people want to die or end up upside down in the ditch.

So, if you were racing really fast, and the spoiler did not deploy and you lost a small bit of that "planted on the ground" feeling, the tiny bit that you back off the throttle or are tentative in the turns, will be what causes you to lose the race. At this level of performance, there is really very little margin for error, and I would bet a lot of money that the spoiler in the 996TT earns its cost in those high speed situations.

This says nothing about the functionality of the spoiler on the car in the way that most people will drive the car, on public roadways.

champignon

I love the car; is it for sale?

champignon

Could you please give me a list of things discussed on this forum that is not subjective?

"02996ttx50

she's a beaut! no doubt. i'd *gift* it to you but am told the owner is living in it.

but i'd like to further add to the obvious, which given your recent anecdotal with your subie buddy might ( or not ) further add to the discussion..

it's fairly obvious, that fixed wings are a bit ( ahem ) "over the top" on "street cars" as evidenced by my supplied pic, as well as your friends reported "chortle"..in that no one here would dispute that added downforce is needed unless one merely needs added plumage while parked at the local cars n coffee event ( you'd be amazed i imagine, to find how many of those types there are here lol ) with wings aloft but again, i digress..

so, while ours is a "street" car with a max speed of 195+ ( provided of course the wind is at ( and over ) your back? the spoiler still exists as an example ( if i may borrow an architectural phase? ) of "form following function".

so irrespective of whether or not you'll "feel" the difference btw having it "up"or "down" at speed? i would proffer that the car, will.

also, on a somewhat tangential yet related point,..i realize you may be "new" to 911's? but you haven't lived until you've had the *** end of this car swing out wildly, only to snap back quickly.. and while admittedly the spoiler wont help that peculiarity of this rear engined behemoth,.. any added stability at speed one can muster,. is good.

but i have two words for you. ( three, actually )

tail wag. cheers.

champignon

I have heard but never experienced this. It is no doubt a given that the 911 started out off a bad design premise, and ever since the company has been trying to deal with that decision. The Cayman/S is often described as an inherently sportier car than the 911, that was designed right, from the start. This is why, when I got down to actually buying a used Porsche, I made it a 911 vs. Cayman S choice rather than a straight 911 choice. The TT part only came later after driving a number of 911's and 911S's, and finding them, ahem, boring (at least the 996 and 997.1 versions).

But bad design premises can make for cool, and interesting cars. No one wants to drive a Yugo, but I'd bet that the Camry is one of the best-designed vehicles of all time, and I would not take one as a gift.

"02996ttx50

bad design premise?!? a *given, my ***!*. care to venture a guess as to how many 911's have been sold since 64/65?

these cars have been getting me laid since 69! so no design flaw here/there or anywhere lol. seriously though, i have no idea about that. its not like i've ever run off a 1000 ft canyon in the last 50 years, and lord knows I've tried lol..so perhaps rear engine driving is an acquired taste/habit. but it's not like this is a corvair.

so aside from the 5 911's i have been driving since i was an adolescent, and the 914 i almost self immolated inside in '75, ( while scrambling out the open top )..i have engaged in tailwag at nearly every opportunity since. whether intended to not.

so what i suggest you do to experience this infamous "taillwag", to have a more visceral understanding, and feel for the car; would be.. to mod the car as best you can, with some bolt on's, and remove the front diff, and make sure you have an lsd ( of one type or another ) and get on full boost around a tight right hander, punch it, and make sure the wheels pointed hard left, and cry baby cry..

this btw, is an example in which the spoiler in whatever position is completely unnecessary. because it doesn't help if and or when you are sideways.

for again, as rufus thomas so eloquently once put it: "if you don't know how to do it? i'll show you how to wag the dog".

but if you don't do any of that? you definitely don't, and possibly won't ever need a spoiler, working, fixed or not. but then i would then understand your questioning ( as i understand you? ) the necessity of a spoiler at all. unless of course you pass those cpl cars again at 100 mph