What did you buy your 991 today thread
08-16-2017, 01:43 PM
#1696
I have a bit of Aeronautical Eng. background so perhaps I can provide some input. Yes, the balance will be off. The Vorsteiner wing was probably modeled to be a bit like the GT3-RS wing. However, the Vorsteiner wing has an angle of attack that is a bit different from the RS. Based on the pictures, it points down a bit more which would result in quite a bit more down force.
To compound the issue, the GT3 and GT3 RS cars have a different bumper that creates enough down force to achieve the force distribution that the Porsche engineers felt was appropriate. The non GT3/RS cars do not have that bumper. Even the Turbo has the front lip bumper that deploys at high speed to compensate for the effects of drag/down force. That is why Porsche doesn't want to sell the Aerokit wing without selling the matching front bumper. They don't even want to sell the sport spoiler lip to cars without Sport PASM!
To sum it all up, your front end does not have an adequate amount of down force to compensate for that wing. At high speed, your steering may be affected. Go even faster, and the car will do the acrobatic back flip that you see in some Indy/F1/etc races. At what speed I don't know, but at some point, the down force of that wing will surely cause most of the force to go toward the rear of the car.
For Joe Schmoes like me that only does spirited drives on the windy country back roads, probably no biggy. For guys that drive at speed, I would be very cautious/nervous.
To compound the issue, the GT3 and GT3 RS cars have a different bumper that creates enough down force to achieve the force distribution that the Porsche engineers felt was appropriate. The non GT3/RS cars do not have that bumper. Even the Turbo has the front lip bumper that deploys at high speed to compensate for the effects of drag/down force. That is why Porsche doesn't want to sell the Aerokit wing without selling the matching front bumper. They don't even want to sell the sport spoiler lip to cars without Sport PASM!
To sum it all up, your front end does not have an adequate amount of down force to compensate for that wing. At high speed, your steering may be affected. Go even faster, and the car will do the acrobatic back flip that you see in some Indy/F1/etc races. At what speed I don't know, but at some point, the down force of that wing will surely cause most of the force to go toward the rear of the car.
For Joe Schmoes like me that only does spirited drives on the windy country back roads, probably no biggy. For guys that drive at speed, I would be very cautious/nervous.
08-16-2017, 02:05 PM
#1697
Interesting! What do you think of the vorsteiner carbon baby duck lip paired with their carbon front lip spoiler? I figured since my car was originally PASM and the spoiler raises to a lesser angle that pairing these up would balance out. Car is lowered w techart but I assume all of this makes negligible difference
I don't think Vorsteiner would sell something that they think would make cars do back flips but I also doubt that they do any computer simulations or calculations.
08-16-2017, 02:42 PM
#1698
Rennlist Member
At high speed, your steering may be affected. Go even faster, and the car will do the acrobatic back flip that you see in some Indy/F1/etc races. At what speed I don't know, but at some point, the down force of that wing will surely cause most of the force to go toward the rear of the car.
For Joe Schmoes like me that only does spirited drives on the windy country back roads, probably no biggy. For guys that drive at speed, I would be very cautious/nervous.
For Joe Schmoes like me that only does spirited drives on the windy country back roads, probably no biggy. For guys that drive at speed, I would be very cautious/nervous.
08-16-2017, 02:56 PM
#1699
Burning Brakes
In the Seventies when Porsche first introduced a front spoiler and the ducktail, the factory instruction was to use never use the front spoiler without the ducktail for the above reason.
08-16-2017, 03:05 PM
#1700
Three Wheelin'
This is exactly backwards. If you add downforce to the front, then at high speed the front will be more planted than the rear and the car will oversteer. If you add downforce at the rear, you get the opposite effect and at 150 mph+ you'd rather have a bit more understeer than oversteer.
In the Seventies when Porsche first introduced a front spoiler and the ducktail, the factory instruction was to use never use the front spoiler without the ducktail for the above reason.
In the Seventies when Porsche first introduced a front spoiler and the ducktail, the factory instruction was to use never use the front spoiler without the ducktail for the above reason.
https://blackflag.jalopnik.com/sudde...y-v-1794984189
But ultimately....balanced is best.
08-16-2017, 03:40 PM
#1701
This is exactly backwards. If you add downforce to the front, then at high speed the front will be more planted than the rear and the car will oversteer. If you add downforce at the rear, you get the opposite effect and at 150 mph+ you'd rather have a bit more understeer than oversteer.
In the Seventies when Porsche first introduced a front spoiler and the ducktail, the factory instruction was to use never use the front spoiler without the ducktail for the above reason.
In the Seventies when Porsche first introduced a front spoiler and the ducktail, the factory instruction was to use never use the front spoiler without the ducktail for the above reason.
Here is a video, watch as the car goes over the hill, the front lifts up ever so slightly which results in dramatically reduced down force on the front end. I would rather have the rear wing fall off and have not enough downforce on the rear and spin out like in the Jalopnik video instead of the front losing the down force and flipping like in this video:
You are right, there needs to be balance, which is also what my entire first response was about and as an example, I mentioned that Porsche won't sell the aerokit wing without the accompanying bumper, or sell the sport lip without the car having SPASM, or how the turbo has a front lip that deploys with the back at high speed.
Last edited by Capt_and; 08-16-2017 at 04:31 PM.
08-16-2017, 03:53 PM
#1702
Banned
Join Date: Jan 2013
Location: Chicagoland Area
Posts: 26,141
Likes: 0
Received 5,406 Likes
on
2,513 Posts
We leaned a couple days ago, to off-set the b i g a s s wing in the back, all you have to do is this:
08-16-2017, 08:16 PM
#1703
Originally Posted by Philip Goughary
Love them. Common practice is to align them so that the bottom of the Porsche emblem points towards the valve stem covers.
08-16-2017, 08:28 PM
#1704
Burning Brakes
It's not backwards, we are just talking about two different things. You are talking about oversteer/understeer. I am just talking about lift. Yes, they play hand in hand in 3 dimensions but I was simplifying it into 2d. I was just saying it is much easier to flip a car backwards than forward and given the choice, I would overload the front with down force instead of the rear.
With excessive rear downforce, the car will be very stable and tend to go nice and straight--up until the point that it flips.
P.S. I don't think you have to worry much about flipping a street car.
08-16-2017, 08:43 PM
#1705
I point mine towards the valve stems for the fun of tradition (I should add not on 991s. I'm a Cayenne driving troll.. ...for now).
Last edited by Philip Goughary; 08-17-2017 at 09:38 AM.
08-16-2017, 08:48 PM
#1706
Instructor
08-16-2017, 08:58 PM
#1707
Drifting
08-16-2017, 08:59 PM
#1708
Banned
Join Date: Jan 2013
Location: Chicagoland Area
Posts: 26,141
Likes: 0
Received 5,406 Likes
on
2,513 Posts
Originally Posted by feh
I pointed mine towards the wheel lock, since it's harder to find than the stem.
08-17-2017, 04:26 AM
#1710
Intermediate
Join Date: Aug 2014
Location: Abu Dhabi
Posts: 46
Likes: 0
Received 0 Likes
on
0 Posts
One thing I have to mention is that my car came with SD ( ducktail spoiler ) XAT option, so I had to change the mounting bracket and install a retractable spoiler mounting bracket which comes with a motor. Then the Vorsteiner deck lid spoiler sits on the mounting bracket. Also, I had to cut the welded screws, which are onto the bracket surface, and use the ones provided by Vorsteiner to attach spoiler to the bracket. I have to say Vorsteiner instructions were not clear enough about how to attach the spoiler with those welded screws so I chose what I did.
As a future mod, I am looking into a way to have a manual switch where I can just switch the motor on/off (without using PIWIS) thus I can have access to the spoiler mounting bracket.
yes … the big wing is easily removable and just leave the deck lid spoiler in place.
I have a bit of Aeronautical Eng. background so perhaps I can provide some input. Yes, the balance will be off. The Vorsteiner wing was probably modeled to be a bit like the GT3-RS wing. However, the Vorsteiner wing has an angle of attack that is a bit different from the RS. Based on the pictures, it points down a bit more which would result in quite a bit more down force.
To compound the issue, the GT3 and GT3 RS cars have a different bumper that creates enough down force to achieve the force distribution that the Porsche engineers felt was appropriate. The non GT3/RS cars do not have that bumper. Even the Turbo has the front lip bumper that deploys at high speed to compensate for the effects of drag/down force. That is why Porsche doesn't want to sell the Aerokit wing without selling the matching front bumper. They don't even want to sell the sport spoiler lip to cars without Sport PASM!
To sum it all up, your front end does not have an adequate amount of down force to compensate for that wing. At high speed, your steering may be affected. Go even faster, and the car will do the acrobatic back flip that you see in some Indy/F1/etc races. At what speed I don't know, but at some point, the down force of that wing will surely cause most of the force to go toward the rear of the car.
For Joe Schmoes like me that only does spirited drives on the windy country back roads, probably no biggy. For guys that drive at speed, I would be very cautious/nervous.
To compound the issue, the GT3 and GT3 RS cars have a different bumper that creates enough down force to achieve the force distribution that the Porsche engineers felt was appropriate. The non GT3/RS cars do not have that bumper. Even the Turbo has the front lip bumper that deploys at high speed to compensate for the effects of drag/down force. That is why Porsche doesn't want to sell the Aerokit wing without selling the matching front bumper. They don't even want to sell the sport spoiler lip to cars without Sport PASM!
To sum it all up, your front end does not have an adequate amount of down force to compensate for that wing. At high speed, your steering may be affected. Go even faster, and the car will do the acrobatic back flip that you see in some Indy/F1/etc races. At what speed I don't know, but at some point, the down force of that wing will surely cause most of the force to go toward the rear of the car.
For Joe Schmoes like me that only does spirited drives on the windy country back roads, probably no biggy. For guys that drive at speed, I would be very cautious/nervous.
R_Rated and Johnny5Alive pointed out that using a more aggressive front lip could balance it out .. do you think it will improve the balance for a track driving ? and how would I test it ? any indicators beside the back flip?