mark_schnell

I think nobody except the engineers at the factory have taken the time to actually wind-tunnel test various spoiler designs. I looked into it, and hit dead ends without contacts. Whenever someone (even a supposedly-knowledgeable tech) says something that sounds like an absolute, it makes me doubt and wonder where they got this info.


I don't think I can agree that a wing provides "no improvement".


Lambo's new Hurican Performante managed the fastest lap time at Nurburgring using "Active aero". Sure, that only accounted for a few seconds' better lap time in several miles of race-speed driving, so it's a safe bet that there is "little" noticeable effect. Anything you put on as a wing short of a parachute might have "little" noticeable effect, but car enthusiasts and racers might be the most sensitive to little changes of any group of drivers. Like the "Princess and the pea" story.


The Porsche factory designers put the big GT2 and GT3 wings up high for lots of downforce to get better lap times, so I'd say that big/high wings probably do SOMETHING, even at sharp corner speeds of sub-100mph. Otherwise, they wouldn't bother adding the weight.


So I'm not sure I'd jump to say the techs were cool just because they sounded like they knew something for sure.

autobonrun

Mark, you are spot on. There are some important words in the techs statements; and some key words left out of it. When they say "no improvement", the word missing is discernible; "no discernible improvement". They further bracket their statement by using the term "reasonable speeds". Reasonable means speeds that the typical buyer obeying speed limits or occacionally exceeding them would see.

If anyone expected a technician to say a Porsche becomes unsafe if the spoiler doesn't go up at 75 mph, they don't understand design. No engineer, and I mean none set maximum operating conditions and maximum design conditions at the same number. Does anyone think if an elevator says maximum capacity of 11, and the 12th person steps on its going to crash down? Or if a bridge says maximum capacity 10 tons and a 12 ton truck crosses, it will fail? The answer is no. When Porsche says 75mph, it does not mean it becomes unsafe with no wing deployed above that speed. And it does not mean the laws of physics suddenly change at the figure. Yes, increased airflow over a wing or spoiler will have some affect. Engineers typically put a 50% to 100% design factor between maximum design and maximum operating figures. So I would expect the car to remain safe at speeds in excess of the figure published and blessed by Porsche attorneys. For legal reasons, I won't attempt to guess what that figure is, but you can bet Porsche knows and you can bet it's in excess of 75mph.

Functionally, I've personally tested three different spoiler designs in my years of ownership. I bought my SC with no spoiler front or rear. At 120 mph, the front became light. Meaning if I centered it on the white line, it would drift left and right and my steering input had substantially reduced impact. I added a lip to the front and whale tail on the rear and it was rock steady at the same speed. The car actually responded to steering input at that speed.

My 993 also has a spoiler, although retractable, and it serves the same function; to reduce lift.

The TT and GT2 take the aerodynamic design one step further by adding a wing. Possibly more important than the height of the wing is the shape. When down, the design functions as a spoiler. At higher speeds, when more downforce will prove helpful, the wing extends. Now, in addition to reducing lift, it actually creates down force. Raise your TT wing and actually look at the shape of it. The section facing into the air is thick, the trailing end is thin, just like an airplane wing. However it's inverted with the convex section on the bottom and the flat/concave section on the top; opposite of an airplane. So its forces are generated downward, not up. Yes there is an impact, that's why I would add the word "discernible" to the tech's statement. The techs would have you believe an airplane goes from 0 to 100% lift instantly if they define impact as only the moment when your a$$ realizes the plane is off the ground. In actuality, lift is increasing as the plane picks up speed. So does downforce on the TT.

There is also a reason why newly designed planes bend the tips of the wings up, to increase the efficiency of the wings by reducing vortices from impacting the lift. Notice that the GT2 wing tips are bent downward; for the same reason, to improve the efficiency of the wing. The wing doesn't have to be as large.

if interested:
https://aviation.stackexchange.com/q...aft-performanc


The above statements are my opinion and are not intended to imply fact; not from the "horse's mouth" so to speak.

champignon

I don't have any disagreement with any of this. And this is not the first thing in my life as an "enthusiast" for various things I have been interested in over the years, where there is a discernible benefit to something which is however somewhat limited and subject to other operating variables.

The next question then becomes, "in comparison, to what?" So, by way of example, you could take the difference in grip between any number of tire models and brands available to the public which could be put on the car, everything from a Kumho POS to a street racer from any of the best brands, and everything in between. And there would be definite differences, and in some cases these would be rather large.

And then you drill down further and you try to quantify the incremental value of this or that, divided by the amount of your usage as relates to percentage of usage in what conditions, at what speed, etc.

So how much is 35% better performance, or grip, or control worth during 1.5% of our potential usage of the vehicle? This is the sort of question you need to ask yourself, assuming that there is 1.5% of your mileage to be driven that would require this better control or grip. Do you need that set of tires that costs $2000, or can you get by on the set that costs $950?

These are not questions that get the same answers from all the people you would ask. And I don't actually at this point know what my answers would be.

Plus the moving spoiler is very cool,mesmerizing in fact; how much is that worth to you? It's not zero, but what it is worth will vary by the individual.

Thanks.

BioBanker

If there is one certainty in life it's that big wings provide downforce at speed. Bigger the wing, slower you need to go before it starts to work. Stock 996TT wings are tiny.

I put a big wing on my old track rat NSX and I can tell you it worked. It's simple math. You can't deny physics but it also means you need to deal with the front end.

http://www.nsxprime.com/forum/showthread.php/111272-Taitec-GT500-wing-with-Deck-Lid-Spoiler

808Bill

You do know you're trying to reason with a pigeon right?

FRUNKenstein

OK, you gotta warn me next time before you post another one like that - just shot soda pop right outta my nose