where is sport design ducktail package on the 991.2?
08-30-2016, 01:11 PM
#136
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08-30-2016, 01:16 PM
#137
11-12-2018, 03:03 PM
#138
Rennlist Member
Does the 991 ducktail actually generate downforce? If so, how much?
I want to repalce the moving spoiler on the GT3 Touring, which generates some downforce and has a sharper angle (20 degrees vs 15 degrees) than other 991s, plus the gurney flap.
I'm hoping the amount of downforce will be similar. What do you guys think? Any ways you can recommend I could do a CFD simulation?
I will go 150 - 200 MPH in this car regularly (it has already seen those speeds with the factory tail with no problem) - but I don't want to have problems! TIA!
I want to repalce the moving spoiler on the GT3 Touring, which generates some downforce and has a sharper angle (20 degrees vs 15 degrees) than other 991s, plus the gurney flap.
I'm hoping the amount of downforce will be similar. What do you guys think? Any ways you can recommend I could do a CFD simulation?
I will go 150 - 200 MPH in this car regularly (it has already seen those speeds with the factory tail with no problem) - but I don't want to have problems! TIA!
11-12-2018, 03:22 PM
#139
Rennlist Member
Does the 991 ducktail actually generate downforce? If so, how much?
I want to repalce the moving spoiler on the GT3 Touring, which generates some downforce and has a sharper angle (20 degrees vs 15 degrees) than other 991s, plus the gurney flap.
I'm hoping the amount of downforce will be similar. What do you guys think? Any ways you can recommend I could do a CFD simulation?
I will go 150 - 200 MPH in this car regularly (it has already seen those speeds with the factory tail with no problem) - but I don't want to have problems! TIA!
I want to repalce the moving spoiler on the GT3 Touring, which generates some downforce and has a sharper angle (20 degrees vs 15 degrees) than other 991s, plus the gurney flap.
I'm hoping the amount of downforce will be similar. What do you guys think? Any ways you can recommend I could do a CFD simulation?
I will go 150 - 200 MPH in this car regularly (it has already seen those speeds with the factory tail with no problem) - but I don't want to have problems! TIA!
as a package on the 991S'es etc ...
What they didnt do was test the duck on a GT3T ... and in the past PAG and PCNA have expressed concerns about owners who modify their cars, particularly those RS owners that insist on taking the
rear wing completely off.
I dont think that they publish figures for the efficiency of their aero such that you could confirm equivalence ... AFAIAK the ducktail only reduces lift but does not generate downforce (the distinction being the
difference in the weight over the axle at rest vs in motion, downforce increasing the weight in motion over that measured at rest, reducing lift makes the difference between the two test vs motion less than it
would be w/o the aero element present).
I'd be concerned about replacing the existing aero which as been tested as a system with another, especially if you expect it to function at high speed... balancing the forces can be tricky ... try taking the
front splitter off and going over 80mph ... front end gets v.light!!!
Also remember that the GT3 and Touring have the rear diffuser from the R that provides considerable d/f that the ducktail is not designed to operate with...
I hate to say it - but I would have probably just got a ("proper"
) "tailed" GT3 and taken advantage of its aero and ram air effects if I had planned high speed operation!I think the net of my advice/opinion, you can try it, (if you are certain that it will fit dimensionally on the Touring) but I would not paint it 1st, just in case the high speed handling is impaired ... then maybe
you can return it if it doesn't work out ... you paint it you own it!
and you will have to get a dealer to code out the moveable tail if you do replace permanently.
11-12-2018, 03:33 PM
#140
Rennlist Member
sirtom, here's a thread you might find interesting: https://rennlist.com/forums/991/1051030-how-important-is-the-991-rear-spoiler-for-stability-downforce.html
But my general take on this one is if you are planning on going 150-200 mph in a Porsche I wouldn't recommend fooling around with the balance Porsche designed into the car as it was configured from the factory. Remember that they coordinate the balance between the front and rear spoilers. Often if you change one you should change the other to maintain balanced stability front and rear. In the aerokits they won't allow a dealer to change one without changing the other to match (front and rear spoilers).
But my general take on this one is if you are planning on going 150-200 mph in a Porsche I wouldn't recommend fooling around with the balance Porsche designed into the car as it was configured from the factory. Remember that they coordinate the balance between the front and rear spoilers. Often if you change one you should change the other to maintain balanced stability front and rear. In the aerokits they won't allow a dealer to change one without changing the other to match (front and rear spoilers).
Last edited by StormRune; 11-12-2018 at 09:17 PM.
11-12-2018, 04:40 PM
#141
Rennlist Member
sirtom, here's a thread you might find interesting: https://rennlist.com/forums/search.p...rchid=34281229
But my general take on this one is if you are planning on going 150-200 mph in a Porsche I wouldn't recommend fooling around with the balance Porsche designed into the car as it was configured from the factory. Remember that they coordinate the balance between the front and rear spoilers. Often if you change one you should change the other to maintain balanced stability front and rear. In the aerokits they won't allow a dealer to change one without changing the other to match (front and rear spoilers).
But my general take on this one is if you are planning on going 150-200 mph in a Porsche I wouldn't recommend fooling around with the balance Porsche designed into the car as it was configured from the factory. Remember that they coordinate the balance between the front and rear spoilers. Often if you change one you should change the other to maintain balanced stability front and rear. In the aerokits they won't allow a dealer to change one without changing the other to match (front and rear spoilers).
11-12-2018, 07:55 PM
#142
Rennlist Member
sirtom, here's a thread you might find interesting: https://rennlist.com/forums/search.p...rchid=34281229
But my general take on this one is if you are planning on going 150-200 mph in a Porsche I wouldn't recommend fooling around with the balance Porsche designed into the car as it was configured from the factory. Remember that they coordinate the balance between the front and rear spoilers. Often if you change one you should change the other to maintain balanced stability front and rear. In the aerokits they won't allow a dealer to change one without changing the other to match (front and rear spoilers).
But my general take on this one is if you are planning on going 150-200 mph in a Porsche I wouldn't recommend fooling around with the balance Porsche designed into the car as it was configured from the factory. Remember that they coordinate the balance between the front and rear spoilers. Often if you change one you should change the other to maintain balanced stability front and rear. In the aerokits they won't allow a dealer to change one without changing the other to match (front and rear spoilers).
I appreciate the very thoughtful comments and feedback - much to consider.
I was actually going 150+ without the front splitter on the other day and it was a bit wobbily but manageable. Kinda fun actually.
But I wouldn't want to remove rear downforce.
I'll look into designing a ducktail with some downforce or perhaps a gurney flap! Thanks guys.
11-12-2018, 09:17 PM
#143
Rennlist Member
Sorry for the bad link. It doesn't answer your particular question, but has some food for thought along that line.
Here's the correct one: https://rennlist.com/forums/991/1051...downforce.html
Here's the correct one: https://rennlist.com/forums/991/1051...downforce.html
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sirtom (01-23-2020)
03-03-2023, 02:55 PM
#145
That's exactly what I tried to recreate, modern '73 RS. It was always my favorite Porsche of all time growing up.
991.1 C4S w/ factory SportDesign pkg, and OEM Sport Classic (991's modern Fuchs wheels)
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Larry Cable (03-03-2023)
03-03-2023, 09:16 PM
#146
Burning Brakes
Duck tail is the way. I wish they could have kept it.
The following users liked this post:
Larry Cable (03-03-2023)
03-04-2023, 12:42 PM
#147
Rennlist Member
I think you can assume that PAG did all the necessary testing on the GT3T for safe operation (of the moving spoiler) at those speeds, and they undoubtedly did the same for the Sport Design aerokit
as a package on the 991S'es etc ...
What they didnt do was test the duck on a GT3T ... and in the past PAG and PCNA have expressed concerns about owners who modify their cars, particularly those RS owners that insist on taking the
rear wing completely off.
I dont think that they publish figures for the efficiency of their aero such that you could confirm equivalence ... AFAIAK the ducktail only reduces lift but does not generate downforce (the distinction being the
difference in the weight over the axle at rest vs in motion, downforce increasing the weight in motion over that measured at rest, reducing lift makes the difference between the two test vs motion less than it
would be w/o the aero element present).
I'd be concerned about replacing the existing aero which as been tested as a system with another, especially if you expect it to function at high speed... balancing the forces can be tricky ... try taking the
front splitter off and going over 80mph ... front end gets v.light!!!
Also remember that the GT3 and Touring have the rear diffuser from the R that provides considerable d/f that the ducktail is not designed to operate with...
I hate to say it - but I would have probably just got a ("proper" ) "tailed" GT3 and taken advantage of its aero and ram air effects if I had planned high speed operation!
I think the net of my advice/opinion, you can try it, (if you are certain that it will fit dimensionally on the Touring) but I would not paint it 1st, just in case the high speed handling is impaired ... then maybe
you can return it if it doesn't work out ... you paint it you own it!
and you will have to get a dealer to code out the moveable tail if you do replace permanently.
as a package on the 991S'es etc ...
What they didnt do was test the duck on a GT3T ... and in the past PAG and PCNA have expressed concerns about owners who modify their cars, particularly those RS owners that insist on taking the
rear wing completely off.
I dont think that they publish figures for the efficiency of their aero such that you could confirm equivalence ... AFAIAK the ducktail only reduces lift but does not generate downforce (the distinction being the
difference in the weight over the axle at rest vs in motion, downforce increasing the weight in motion over that measured at rest, reducing lift makes the difference between the two test vs motion less than it
would be w/o the aero element present).
I'd be concerned about replacing the existing aero which as been tested as a system with another, especially if you expect it to function at high speed... balancing the forces can be tricky ... try taking the
front splitter off and going over 80mph ... front end gets v.light!!!
Also remember that the GT3 and Touring have the rear diffuser from the R that provides considerable d/f that the ducktail is not designed to operate with...
I hate to say it - but I would have probably just got a ("proper"
) "tailed" GT3 and taken advantage of its aero and ram air effects if I had planned high speed operation!I think the net of my advice/opinion, you can try it, (if you are certain that it will fit dimensionally on the Touring) but I would not paint it 1st, just in case the high speed handling is impaired ... then maybe
you can return it if it doesn't work out ... you paint it you own it!
and you will have to get a dealer to code out the moveable tail if you do replace permanently.
In speaking with any number of Porsche engineers over the last 20~ years, my sense is they are more concerned about aero balance than downforce as it's critical to safety as well as confidence at high speeds…when both are most critical. The 911R was said to be a lot of fun while it ran away from the 991.1 GT3 from, say, 200kmh, but the latter was apparently a lot nicer to be driving on the last pull up to 300~. In speaking with them about the 991.2 GT3 Touring, it was interesting to hear about what they learned through the 911R project and incorporated in the Touring—and that the little Gurney on the back of the Touring makes a substantive difference.
So, little changes can make big differences to aero balance. See the angle of the rear spoilers on Carrera Cabriolets vs coupes, or even some coupes when the sunroof is open. PASM vs Sport PASM cars, too. Having added a Sport PASM lip to the front of my 991.2 Carrera, I've been meaning to get around to figuring out how to get the rear spoiler to do the SPASM/T thing…but I can't say its exactly a priority as my car rarely sees anything over 100-120mph here in CA. It isn't a track day car.
Also very important to consider re: 991.2 Carrera aero mods: Feeding & cooling the 3.0-liter engine and intercoolers. There was a LOT of detail work to get that done, and I'd imagine the hours and costs in the wind tunnel were pretty wild given they had to do it without a rear spoiler and no intakes on the side of the car. I asked the head of engine development what the biggest challenge with developing these cars was, and he answered instantly: Packaging and cooling, particularly with the narrow body cars. He was clearly very proud of the result—as he should have been…as even a base 991.2 Carrera can give a 991.2 or 992 GT3 a very hard time out of a 2nd gear turn yet we never hear about cooling problems with these cars. There's a lot of detail work to the way the intake and intercoolers are fed, and I understand the wing is very active in terms of angle when it comes to intake and cooling air alongside keeping the car safe at higher speeds.
if you are planning on going 150-200 mph in a Porsche I wouldn't recommend fooling around with the balance Porsche designed into the car as it was configured from the factory. Remember that they coordinate the balance between the front and rear spoilers. Often if you change one you should change the other to maintain balanced stability front and rear. In the aerokits they won't allow a dealer to change one without changing the other to match (front and rear spoilers).
But if someone wants to "wing it," I'll be curious to see how the 3.0 fares. I wouldn't take the chance with the engine in my car…
03-04-2023, 01:19 PM
#148
Rennlist Member
^ Yes to all of this logic.
In speaking with any number of Porsche engineers over the last 20~ years, my sense is they are more concerned about aero balance than downforce as it's critical to safety as well as confidence at high speeds…when both are most critical. The 911R was said to be a lot of fun while it ran away from the 991.1 GT3 from, say, 200kmh, but the latter was apparently a lot nicer to be driving on the last pull up to 300~. In speaking with them about the 991.2 GT3 Touring, it was interesting to hear about what they learned through the 911R project and incorporated in the Touring—and that the little Gurney on the back of the Touring makes a substantive difference.
So, little changes can make big differences to aero balance. See the angle of the rear spoilers on Carrera Cabriolets vs coupes, or even some coupes when the sunroof is open. PASM vs Sport PASM cars, too. Having added a Sport PASM lip to the front of my 991.2 Carrera, I've been meaning to get around to figuring out how to get the rear spoiler to do the SPASM/T thing…but I can't say its exactly a priority as my car rarely sees anything over 100-120mph here in CA. It isn't a track day car.
Also very important to consider re: 991.2 Carrera aero mods: Feeding & cooling the 3.0-liter engine and intercoolers. There was a LOT of detail work to get that done, and I'd imagine the hours and costs in the wind tunnel were pretty wild given they had to do it without a rear spoiler and no intakes on the side of the car. I asked the head of engine development what the biggest challenge with developing these cars was, and he answered instantly: Packaging and cooling, particularly with the narrow body cars. He was clearly very proud of the result—as he should have been…as even a base 991.2 Carrera can give a 991.2 or 992 GT3 a very hard time out of a 2nd gear turn yet we never hear about cooling problems with these cars. There's a lot of detail work to the way the intake and intercoolers are fed, and I understand the wing is very active in terms of angle when it comes to intake and cooling air alongside keeping the car safe at higher speeds.
+1
^ Your 991.1 looks great! The rendering of the 991.2 with the green wheels and graphics looks very cool, to the point I'd mull it if it was possible (particularly on a white car!), but is sadly unrealistic. No way to get those wheel offsets on a 991.2 (and I doubt flatter ones would look that good), but realizing that ducktail with proper cooling/intake/aero balance would be a project for serious wind tunnel time + tens of thousands of miles of heavily instrumented testing.
But if someone wants to "wing it," I'll be curious to see how the 3.0 fares. I wouldn't take the chance with the engine in my car…
In speaking with any number of Porsche engineers over the last 20~ years, my sense is they are more concerned about aero balance than downforce as it's critical to safety as well as confidence at high speeds…when both are most critical. The 911R was said to be a lot of fun while it ran away from the 991.1 GT3 from, say, 200kmh, but the latter was apparently a lot nicer to be driving on the last pull up to 300~. In speaking with them about the 991.2 GT3 Touring, it was interesting to hear about what they learned through the 911R project and incorporated in the Touring—and that the little Gurney on the back of the Touring makes a substantive difference.
So, little changes can make big differences to aero balance. See the angle of the rear spoilers on Carrera Cabriolets vs coupes, or even some coupes when the sunroof is open. PASM vs Sport PASM cars, too. Having added a Sport PASM lip to the front of my 991.2 Carrera, I've been meaning to get around to figuring out how to get the rear spoiler to do the SPASM/T thing…but I can't say its exactly a priority as my car rarely sees anything over 100-120mph here in CA. It isn't a track day car.
Also very important to consider re: 991.2 Carrera aero mods: Feeding & cooling the 3.0-liter engine and intercoolers. There was a LOT of detail work to get that done, and I'd imagine the hours and costs in the wind tunnel were pretty wild given they had to do it without a rear spoiler and no intakes on the side of the car. I asked the head of engine development what the biggest challenge with developing these cars was, and he answered instantly: Packaging and cooling, particularly with the narrow body cars. He was clearly very proud of the result—as he should have been…as even a base 991.2 Carrera can give a 991.2 or 992 GT3 a very hard time out of a 2nd gear turn yet we never hear about cooling problems with these cars. There's a lot of detail work to the way the intake and intercoolers are fed, and I understand the wing is very active in terms of angle when it comes to intake and cooling air alongside keeping the car safe at higher speeds.
+1
^ Your 991.1 looks great! The rendering of the 991.2 with the green wheels and graphics looks very cool, to the point I'd mull it if it was possible (particularly on a white car!), but is sadly unrealistic. No way to get those wheel offsets on a 991.2 (and I doubt flatter ones would look that good), but realizing that ducktail with proper cooling/intake/aero balance would be a project for serious wind tunnel time + tens of thousands of miles of heavily instrumented testing.
But if someone wants to "wing it," I'll be curious to see how the 3.0 fares. I wouldn't take the chance with the engine in my car…
03-04-2023, 03:30 PM
#149
Rennlist Member
The exchange of data/knowledge/concepts/ideas is a big part of what makes this hobby fun imo.
03-04-2023, 03:39 PM
#150
Rennlist Member
Yep, and I just remembered a late-night run from the Ring > Stuttgart in a 991.2 GT3 & 911R. I remember being happy that I ended up in the one with the wing for that run (a lot of time at 270+) while the 911R driver kept up but was a little frayed as we pulled into the museum garage.
I also recall back in '05 while back home in Scotland in my 996.2 GT3 w/the RS wing and a cup front splitter I ripped the cup splitter off of the car at around 120mph (I took off over a bump and landed heavily) the car was not at all stable/happy w/o the splitter to balance out the rear wing.
frankly I personally would never either:
- remove factory aero because I wanted my car to be "less conspicuous" ...
- or replace it with aftermarket components, *unless* the manufacturer of them had demonstrated that they had performed either CAD modeling and/or wind tunnel testing
my 991.2 GT has the Manthey wing and cup front splitter ... which I am happy with and confident that MR have the experience to develop these components accordingly.