What did you buy your 991 today thread
haha
08-17-2017, 02:34 PM
#1712
Thank you for this great input … this inspires me to read more about the subject.
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?
Here is an OVERSIMPLIFIED answer. The assumption the the airfoil (the wing) is relatively straight, which it isn't which makes the following result lower than it actually is.
Suppose the wing is 63" x 10" (total guess based on pictures) and is angled downwards at about 10 degrees. If you are travelling at 150 mph, there will be roughly 284 lbs exerted by the wing at the rear. At 165 mph, there will be approximately 337 lbs at the rear the rear. The weight distribution of the 991 is 38/62 front to rear, at 165 mph it would be 34/66 front to rear. To balance it out, the lip will need to generate the same amount of lift as the rear. Just eye balling the Vorsteiner front lip, I can't tell you if it is enough to balance it out, but the design will definitely cause some down force. If you look at the standard bumper, the sport design, and the GT3, you can see than the bumper and front lip extends further and further out to create more area to generate that down force. to balance the car.
Again, that was a very rudimentary, basic calculation. You can learn more about lift here: https://wright.nasa.gov/airplane/lifteq.html
Balance is a tough cookie to crack because it is speed dependent. I am willing to bet that when race cars are designed, they are made to have balance at a certain speed. 50/50 weight distribution at a stop doesn't mean as much when the car is moving at higher speeds.
08-18-2017, 09:38 AM
#1713
Rennlist Member
08-18-2017, 10:47 PM
#1714
Rennlist Member
The 911 has awesome dynamic weight balance. Under braking, the weight transfer to the front means all 4 wheels contribute to braking, unlike the typical FWD sedan (or even those perfect 50-50 cars). And under acceleration, the rear bias is dynamically enhanced so that most weight is on the drive wheels.
08-19-2017, 12:23 AM
#1715
Rennlist Member
Join Date: Nov 2015
Posts: 86
Likes: 0
Received 0 Likes
on
0 Posts
What did I buy my 991 today? I have a 2016 GTS.
I just installed the latest from Cobb, including the PDK tune. Wow. The new (for me, anyway) Stage1 93 v200 tune with the PDK COBB Sport v201 (NOT the COBB Aggressive tuning) is simply awesome. It smooths out all engine behavior and improves throttle response noticeably. The datalog shows -4.5 maximum ignition corrections across all cylinders. With the previous tune the ignition corrections were all over and some cylinders had as much as -16.9 degrees of correction. This is brilliant. Don't know if I even need the PDK aggressive tuning, but well, you know - Porsche.
Two comments, and I'll talk to Cobb about this. First, the car revs to 7808 on very aggressive driving, but I'm not sure if this is a problem - anyone care to chime in? Out of 18k+ data lines there were 2 points at 7808 and only 142 points where the revs exceeded 7400.
The second comment is that the new PDK tuning has the 2nd-to-3rd upshift very delayed. On aggressive driving, this is great, but around town, it stays in the lower gear too long for comfortable cruising. I needed to switch out of Sport Mode to get it to calm down.
Anybody else try these upgrades yet?
I just installed the latest from Cobb, including the PDK tune. Wow. The new (for me, anyway) Stage1 93 v200 tune with the PDK COBB Sport v201 (NOT the COBB Aggressive tuning) is simply awesome. It smooths out all engine behavior and improves throttle response noticeably. The datalog shows -4.5 maximum ignition corrections across all cylinders. With the previous tune the ignition corrections were all over and some cylinders had as much as -16.9 degrees of correction. This is brilliant. Don't know if I even need the PDK aggressive tuning, but well, you know - Porsche.
Two comments, and I'll talk to Cobb about this. First, the car revs to 7808 on very aggressive driving, but I'm not sure if this is a problem - anyone care to chime in? Out of 18k+ data lines there were 2 points at 7808 and only 142 points where the revs exceeded 7400.
The second comment is that the new PDK tuning has the 2nd-to-3rd upshift very delayed. On aggressive driving, this is great, but around town, it stays in the lower gear too long for comfortable cruising. I needed to switch out of Sport Mode to get it to calm down.
Anybody else try these upgrades yet?
08-22-2017, 02:21 AM
#1718
Rennlist Member
What did I buy my 991 today? I have a 2016 GTS.
I just installed the latest from Cobb, including the PDK tune. Wow. The new (for me, anyway) Stage1 93 v200 tune with the PDK COBB Sport v201 (NOT the COBB Aggressive tuning) is simply awesome. It smooths out all engine behavior and improves throttle response noticeably. The datalog shows -4.5 maximum ignition corrections across all cylinders. With the previous tune the ignition corrections were all over and some cylinders had as much as -16.9 degrees of correction. This is brilliant. Don't know if I even need the PDK aggressive tuning, but well, you know - Porsche.
Two comments, and I'll talk to Cobb about this. First, the car revs to 7808 on very aggressive driving, but I'm not sure if this is a problem - anyone care to chime in? Out of 18k+ data lines there were 2 points at 7808 and only 142 points where the revs exceeded 7400.
The second comment is that the new PDK tuning has the 2nd-to-3rd upshift very delayed. On aggressive driving, this is great, but around town, it stays in the lower gear too long for comfortable cruising. I needed to switch out of Sport Mode to get it to calm down.
Anybody else try these upgrades yet?
I just installed the latest from Cobb, including the PDK tune. Wow. The new (for me, anyway) Stage1 93 v200 tune with the PDK COBB Sport v201 (NOT the COBB Aggressive tuning) is simply awesome. It smooths out all engine behavior and improves throttle response noticeably. The datalog shows -4.5 maximum ignition corrections across all cylinders. With the previous tune the ignition corrections were all over and some cylinders had as much as -16.9 degrees of correction. This is brilliant. Don't know if I even need the PDK aggressive tuning, but well, you know - Porsche.
Two comments, and I'll talk to Cobb about this. First, the car revs to 7808 on very aggressive driving, but I'm not sure if this is a problem - anyone care to chime in? Out of 18k+ data lines there were 2 points at 7808 and only 142 points where the revs exceeded 7400.
The second comment is that the new PDK tuning has the 2nd-to-3rd upshift very delayed. On aggressive driving, this is great, but around town, it stays in the lower gear too long for comfortable cruising. I needed to switch out of Sport Mode to get it to calm down.
Anybody else try these upgrades yet?
Any measurable improvements on the butt dyno?
08-22-2017, 04:13 AM
#1719
Rennlist Member
Join Date: Nov 2015
Posts: 86
Likes: 0
Received 0 Likes
on
0 Posts
The ECU tune is noticeably better - maybe the same improvement over the previous (was it V101?) as that one was over stock, so now maybe +50 hp? I didn't look closely at Cobb's charts so I don't know what they're claiming. It seems to run a little smoother, too. With a manual, the new V200 ECU tune is definitely worth doing. Coupled with the PDK aggressiveness (and I'm NOT using their "Aggressive" PDK tune) the car is bordering on scary. No bad thing. Yay.
08-22-2017, 10:52 AM
#1720
Banned
Thread Starter
Join Date: Jan 2016
Location: Where aspirations are natural
Posts: 4,389
Likes: 0
Received 41 Likes
on
32 Posts
Yes I had to reprogram the spoiler motor to a fixed wing mode via PIWIS. Then the rest is a plug and play.
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.
I will look into the front lip spoiler…
yes … the big wing is easily removable and just leave the deck lid spoiler in place.
Thank you for this great input … this inspires me to read more about the subject.
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?
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.
I will look into the front lip spoiler…
yes … the big wing is easily removable and just leave the deck lid spoiler in place.
Thank you for this great input … this inspires me to read more about the subject.
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?
Yes a very aggressive front lip could balance it out but there is no way to test or really know without some experimentation and computer modelling.
Here is an OVERSIMPLIFIED answer. The assumption the the airfoil (the wing) is relatively straight, which it isn't which makes the following result lower than it actually is.
Suppose the wing is 63" x 10" (total guess based on pictures) and is angled downwards at about 10 degrees. If you are travelling at 150 mph, there will be roughly 284 lbs exerted by the wing at the rear. At 165 mph, there will be approximately 337 lbs at the rear the rear. The weight distribution of the 991 is 38/62 front to rear, at 165 mph it would be 34/66 front to rear. To balance it out, the lip will need to generate the same amount of lift as the rear. Just eye balling the Vorsteiner front lip, I can't tell you if it is enough to balance it out, but the design will definitely cause some down force. If you look at the standard bumper, the sport design, and the GT3, you can see than the bumper and front lip extends further and further out to create more area to generate that down force. to balance the car.
Again, that was a very rudimentary, basic calculation. You can learn more about lift here: https://wright.nasa.gov/airplane/lifteq.html
Balance is a tough cookie to crack because it is speed dependent. I am willing to bet that when race cars are designed, they are made to have balance at a certain speed. 50/50 weight distribution at a stop doesn't mean as much when the car is moving at higher speeds.
Here is an OVERSIMPLIFIED answer. The assumption the the airfoil (the wing) is relatively straight, which it isn't which makes the following result lower than it actually is.
Suppose the wing is 63" x 10" (total guess based on pictures) and is angled downwards at about 10 degrees. If you are travelling at 150 mph, there will be roughly 284 lbs exerted by the wing at the rear. At 165 mph, there will be approximately 337 lbs at the rear the rear. The weight distribution of the 991 is 38/62 front to rear, at 165 mph it would be 34/66 front to rear. To balance it out, the lip will need to generate the same amount of lift as the rear. Just eye balling the Vorsteiner front lip, I can't tell you if it is enough to balance it out, but the design will definitely cause some down force. If you look at the standard bumper, the sport design, and the GT3, you can see than the bumper and front lip extends further and further out to create more area to generate that down force. to balance the car.
Again, that was a very rudimentary, basic calculation. You can learn more about lift here: https://wright.nasa.gov/airplane/lifteq.html
Balance is a tough cookie to crack because it is speed dependent. I am willing to bet that when race cars are designed, they are made to have balance at a certain speed. 50/50 weight distribution at a stop doesn't mean as much when the car is moving at higher speeds.
You need a wind tunnel and about 10K an hour to test it unfortunately. The Porsche OEM parts have some data but mostly my comment was related to balancing out the aesthetics. I simply bolted on a SPASM lip to my Cab which SPASM from the factory was not an option. Porschofiles in the know recognize the better lip. Nobody else even cares
08-22-2017, 10:55 AM
#1721
Rennlist Member
Bit the bullet and got some ZunSports
08-24-2017, 07:46 PM
#1723
08-24-2017, 11:20 PM
#1724
