Why the Duck?
09-13-2017, 12:48 PM
#17
Spoilers and wings on street cars are for decoration and cause huge drag in a straight line. I did some instrumented testing on fitting spoilers and wings to a BMW M3 and was stunned at how much they slowed the car down above 110 mph. A small trunk spoiler cost 3 - 4 mph and wing around 6 - 8 mph at max speed.
Sure, they are great at the track if you have a race suspension and slicks or R-Comps to take advantage of the stick in the corners and now you can go 'round the corners like nobody's business, but a street car at an HPDE can't take advantage of the downforce because your suspension and tires are not up to it for the majority of owners. So if you want to spend money on your street ride and slow your car down - by all means put one on.
The rear pop-up spoilers that come up at speed help keep the rear from lifting on cars that tend to do so which is why your Porsche has it. First generation Audi TT's became unstable over 110 mph causing many severe crashes (and five deaths) were attributed to that lift so that started the real trend of activated spoilers in the German cars that routinely hit those speeds on the Autobahns.
Sure, they are great at the track if you have a race suspension and slicks or R-Comps to take advantage of the stick in the corners and now you can go 'round the corners like nobody's business, but a street car at an HPDE can't take advantage of the downforce because your suspension and tires are not up to it for the majority of owners. So if you want to spend money on your street ride and slow your car down - by all means put one on.
The rear pop-up spoilers that come up at speed help keep the rear from lifting on cars that tend to do so which is why your Porsche has it. First generation Audi TT's became unstable over 110 mph causing many severe crashes (and five deaths) were attributed to that lift so that started the real trend of activated spoilers in the German cars that routinely hit those speeds on the Autobahns.
09-13-2017, 12:54 PM
#18
I may be wrong about this. But recalling what I learned back in the day in my fluid dynamics class, the sloped back of the car could cause the airflow to develop something called boundary layer separation and create an area of low pressure behind the car, thus higher aerodynamic drag. The duck tail could induce a turbulent flow and thus eliminate the boundary layer separation, just like the dimples on a golf ***** that make them travel farther.
09-13-2017, 12:59 PM
#19
Rocky Mountain High
Rennlist Member
Rennlist Member
Wait a minute, does this mean that the rear wing on my 1984 Pontiac Firebird slowed me down? That baby had a V8, rated for 145 HP. Nothing could slow it down!
09-13-2017, 01:23 PM
#20
I always liked how Singer put a small lip or baby duck on the motorized spoiler of the 964. I thought the vorsteiner baby duck was similar and nice that's in carbon.
if you don't want the full duck but want something a bit more the baby duck is a nice in between.
The rear spoiler still raises with it on there, and actually looks much more aggressive with it up.
09-13-2017, 01:26 PM
#21
Three Wheelin'
I had that vorsteiner baby duck on my last 911. It looked great from a distance, but had poor fitment issues and it looked very non OEM when up close. It ended up falling off during a track day...
09-13-2017, 01:57 PM
#22
did you try getting a replacement?
09-13-2017, 02:41 PM
#23
Three Wheelin'
I had one with similar issues and I took a photo and sent it to vorsteiner through Eric at supreme power. They promptly sent a replacement with much better fit and finish. I'm not sure what the issue was the first time but the replacement came within 2 days and I was satisfied with the fit. No issues with high speed and I've had the car well over 100 mph with it on and it handled the recent monsoon just fine.
did you try getting a replacement?
did you try getting a replacement?
I ended up selling the 911 it was on back to the dealership and picked up a 991.1 GTS to replace it with. GTS is in the shop now for OEM duck tail install...I couldn't do the vorsteiner again. I prefer a more OEM look.
09-13-2017, 11:27 PM
#25
Rennlist Member
I prefer the clean look the pop-up spoiler allows. And from this forum, I have learned that I should never, ever leave it up while parked. It's never even put up in the privacy of my own garage. Happy that it is planting the car's butt to the road at fast-ball speeds though. Pure function, and it gets put away when not needed. 
09-14-2017, 04:19 AM
#26
09-15-2017, 09:51 AM
#27
Rennlist Member
I may be wrong about this. But recalling what I learned back in the day in my fluid dynamics class, the sloped back of the car could cause the airflow to develop something called boundary layer separation and create an area of low pressure behind the car, thus higher aerodynamic drag. The duck tail could induce a turbulent flow and thus eliminate the boundary layer separation, just like the dimples on a golf ***** that make them travel farther.
Porsche discovered this back in the 80's in the Bonneville salt flats performing absolute speed tests. They discovered that the rear wheels were spinning a little at very high speeds, the resultant fix was the wing which evolved into the classic whale tail. True to German engineering this 'design feature' started with a functional purpose.
Today they can measure these effects in wind tunnels which is why; a) the wing deploys at 75 mph, and b) it further deploys if you have the sunroof open. The duck and the fixed wing provide the same aerodynamic effect without the complication of an active wing.
09-15-2017, 11:52 AM
#29
Burning Brakes
Great story. I assume the test drivers brought extra underpants for these situations
"They discovered that the rear wheels were spinning a little at very high speeds"
my old BMW 540 6-speed RWD daily driver did this in the rain. I promptly got introduced to the jersey barrier. Never purchased a RWD BMW again(90% sure it was driver error)
"They discovered that the rear wheels were spinning a little at very high speeds"
my old BMW 540 6-speed RWD daily driver did this in the rain. I promptly got introduced to the jersey barrier. Never purchased a RWD BMW again(90% sure it was driver error)
09-15-2017, 11:54 PM
#30
Three Wheelin'
