997 gt3 4.0 rear suspension ?
06-20-2018, 06:29 PM
#76
Drifting
Thread Starter
^ lol sorry about that.
Further update: I have driven the car now for about ~700 miles. Holy F* . All this time I have been focusing on the front when the real place to focus should have been the rear, which in effect transformed the front !
Further update: I have driven the car now for about ~700 miles. Holy F* . All this time I have been focusing on the front when the real place to focus should have been the rear, which in effect transformed the front !
06-21-2018, 12:00 AM
#77
GT3 player par excellence
Lifetime Rennlist
Member
Lifetime Rennlist
Member
it is always the A** that matters.
***** are highly over rated.
***** are highly over rated.
06-21-2018, 03:26 PM
#78
Burning Brakes
Mooty must be channeling his inner Sir Mix A Lot ! 
Since the 4.0 was 997.2 based, seems this mod should work quite well on a 997.2 GT3.
If it could also cut down my commute time, it might be worth trying.
Since the 4.0 was 997.2 based, seems this mod should work quite well on a 997.2 GT3.
If it could also cut down my commute time, it might be worth trying.
06-25-2018, 12:06 PM
#79
Rennlist Member
F1,
Are you running the original DSC mapping or the stiffer Sport mode mapping I sent you?
And which mode feels better to you?
Thanks,
Tom
Are you running the original DSC mapping or the stiffer Sport mode mapping I sent you?
And which mode feels better to you?
Thanks,
Tom
02-05-2019, 11:29 PM
#80
Rennlist Member
GT3 RS 4.0 Spring Rates
Like F1CrazyDriver I am not entirely happy with the handling of my .1 GT3. Also like F1, in looking at what was available out there I made the decision to use the GT3 RS 4.0 as the blueprint for what to do. Based on what has been said and indeed written here, this set up seemed to be what I was looking for. It'll be a while before the snow disappears from us here in New England. So it'll be a while before I can post how this project turns out. To start this off I bought 997 GT3 4.0 front and rear springs along with the helper springs too. I asked Tom at TPC Racing if he could do a spring rate check to see what if anything was special about the springs on the 4.0... the result were surprising...
Front: 232
Rear: 576
Helpers: 20 ish
These figures are almost identical to the stock spring rates from a standard .1 GT3. They are also different than the 997 GT2 RS springs that F1 used. I'm as surprised as anyone based on what has been said about the RS 4.0 chassis. With that said Tom has some insight as to what Porsche did on the 4.0. I will let him chime in and tell you himself.
02-07-2019, 10:47 AM
#81
Rennlist Member
Mick,
Thank you for the rare opportunity of letting me check the factory 4.0 spring rates. I was surprised as well by the results. Frankly I expected higher numbers but these numbers are validated by two methods of testing, and the spring rate checker itself went through a series of QC test with known-rate springs to be accurate within +/- 1.5%.
So the 4.0 spring rates themselves using the standard test method of one-inch compression from free length(or free standing height) is 232/576 in-lb, which is slight higher than the 997.1 GT3 but lower than 997.2 GT3. This leads me to believe part of the firmer suspension characteristic of the 4.0 is from more aggressive dampers. The other part of the firmer characteristic is from the use of shorter free length springs; the spring rate itself is one way to evaluate stiffness, which is absolutely valid when comparing springs of the same free length. A shorter free length spring and/or narrower diameter spring of the same rate will ride stiffer due to the difference in frequency.
According to PET, the factory PASM controller for .2/RS and 4.0 supersedes to the same part #. This leads me to believe the secret recipe of the 4.0 suspension is pairing relatively softer and shorter springs with more aggressively valved dampers to the same PASM commands. For those who have swapped to 4.0 or GT2RS springs a DSC will "remap" the dampers to get the full performance potential out of the hardware combination.
Thank you for the rare opportunity of letting me check the factory 4.0 spring rates. I was surprised as well by the results. Frankly I expected higher numbers but these numbers are validated by two methods of testing, and the spring rate checker itself went through a series of QC test with known-rate springs to be accurate within +/- 1.5%.
So the 4.0 spring rates themselves using the standard test method of one-inch compression from free length(or free standing height) is 232/576 in-lb, which is slight higher than the 997.1 GT3 but lower than 997.2 GT3. This leads me to believe part of the firmer suspension characteristic of the 4.0 is from more aggressive dampers. The other part of the firmer characteristic is from the use of shorter free length springs; the spring rate itself is one way to evaluate stiffness, which is absolutely valid when comparing springs of the same free length. A shorter free length spring and/or narrower diameter spring of the same rate will ride stiffer due to the difference in frequency.
According to PET, the factory PASM controller for .2/RS and 4.0 supersedes to the same part #. This leads me to believe the secret recipe of the 4.0 suspension is pairing relatively softer and shorter springs with more aggressively valved dampers to the same PASM commands. For those who have swapped to 4.0 or GT2RS springs a DSC will "remap" the dampers to get the full performance potential out of the hardware combination.
02-07-2019, 10:58 AM
#82
Rennlist Member
Also want to added that there's no right or wrong way to configure suspension hardware(free length of spring, diameter of spring, the coil pitch of spring, damper valving, electronic damper commands, sway bar rate), it really comes down to how the decision maker(s) want a certain generation of car to perform for the targeted market.
As an example, on the DSC Sport/Tractive coilovers we typically use the tallest free length springs for the application with a softer rate and let the DSC actively commands the Tractive dampers to "exceed" the spring rates during moments of higher loads. This approach produces the widest dynamic range possible.
As an example, on the DSC Sport/Tractive coilovers we typically use the tallest free length springs for the application with a softer rate and let the DSC actively commands the Tractive dampers to "exceed" the spring rates during moments of higher loads. This approach produces the widest dynamic range possible.
02-07-2019, 01:39 PM
#83
Rennlist Member
A quick shout out to Tom and TPC Racing. When I offered to pay for the spring rate test, Tom refused and said he was doing it for the benefit of the community. A hugely knowledgeable guy and a class act. Thank you for the knowledge and depth you bring to this forum.
02-07-2019, 11:27 PM
#84
Rennlist Member
I will second that. Tom has always been wonderful about answering my endless questions.
02-08-2019, 12:11 PM
#85
Mick,
Thank you for the rare opportunity of letting me check the factory 4.0 spring rates. I was surprised as well by the results. Frankly I expected higher numbers but these numbers are validated by two methods of testing, and the spring rate checker itself went through a series of QC test with known-rate springs to be accurate within +/- 1.5%.
So the 4.0 spring rates themselves using the standard test method of one-inch compression from free length(or free standing height) is 232/576 in-lb, which is slight higher than the 997.1 GT3 but lower than 997.2 GT3. This leads me to believe part of the firmer suspension characteristic of the 4.0 is from more aggressive dampers. The other part of the firmer characteristic is from the use of shorter free length springs; the spring rate itself is one way to evaluate stiffness, which is absolutely valid when comparing springs of the same free length. A shorter free length spring and/or narrower diameter spring of the same rate will ride stiffer due to the difference in frequency.
According to PET, the factory PASM controller for .2/RS and 4.0 supersedes to the same part #. This leads me to believe the secret recipe of the 4.0 suspension is pairing relatively softer and shorter springs with more aggressively valved dampers to the same PASM commands. For those who have swapped to 4.0 or GT2RS springs a DSC will "remap" the dampers to get the full performance potential out of the hardware combination.
Thank you for the rare opportunity of letting me check the factory 4.0 spring rates. I was surprised as well by the results. Frankly I expected higher numbers but these numbers are validated by two methods of testing, and the spring rate checker itself went through a series of QC test with known-rate springs to be accurate within +/- 1.5%.
So the 4.0 spring rates themselves using the standard test method of one-inch compression from free length(or free standing height) is 232/576 in-lb, which is slight higher than the 997.1 GT3 but lower than 997.2 GT3. This leads me to believe part of the firmer suspension characteristic of the 4.0 is from more aggressive dampers. The other part of the firmer characteristic is from the use of shorter free length springs; the spring rate itself is one way to evaluate stiffness, which is absolutely valid when comparing springs of the same free length. A shorter free length spring and/or narrower diameter spring of the same rate will ride stiffer due to the difference in frequency.
According to PET, the factory PASM controller for .2/RS and 4.0 supersedes to the same part #. This leads me to believe the secret recipe of the 4.0 suspension is pairing relatively softer and shorter springs with more aggressively valved dampers to the same PASM commands. For those who have swapped to 4.0 or GT2RS springs a DSC will "remap" the dampers to get the full performance potential out of the hardware combination.
02-08-2019, 01:03 PM
#86
Rennlist Member
They were linear. Fronts were 60mm ID flat tail at both ends. Rears were same as the GT2RS where the top was shaped to mate with OEM top mount, the bottom was 60mm ID flat tail. The rear bottom was intended for use with helper springs.
02-08-2019, 01:06 PM
#87
Rennlist Member
Linear. They are visually identical except for colour, red. (I've just seen that Tom beat me to it)
Last edited by The Mick; 02-08-2019 at 01:09 PM. Reason: Answered
02-08-2019, 02:13 PM
#88
Thanks for confirming. Just as a small point of interest, I have the DSC installed in the 4.0 and I have to say on the road running on the 'normal' setting, I didn't think I felt a lot of difference other than much less porpoising along an exceedingly annoying bit of road that approaches the main motorway out of my place. The car is more stable on track in the sport setting though especially on fast direction changes. Not sure how or if this might tie in with the differences in springing/more damping run on the OEM PASM as suspension is a bit of a black art beyond my comprehension unfortunately....
02-08-2019, 03:30 PM
#89
Rennlist Member
Thanks for confirming. Just as a small point of interest, I have the DSC installed in the 4.0 and I have to say on the road running on the 'normal' setting, I didn't think I felt a lot of difference other than much less porpoising along an exceedingly annoying bit of road that approaches the main motorway out of my place. The car is more stable on track in the sport setting though especially on fast direction changes. Not sure how or if this might tie in with the differences in springing/more damping run on the OEM PASM as suspension is a bit of a black art beyond my comprehension unfortunately....
02-12-2019, 02:04 PM
#90
Thank you for your feedback on the DSC. I don't personally know anyone who has a real 4.0 car using DSC. The standard DSC mapping was made on GT3's and RS's. After this spring testing exercise and my believe in how the factory 4.0 dampers are configured based on the spring rate test results I now can visualize how the DSC command for a GT3/RS dampers will have a slightly different outcome on 4.0 dampers; meaning that the minimum command of 5% stiffness in Normal mode on GT3/RS dampers may feel closer to the stiffness of 10% on 4.0 dampers. The higher percentage commands during aggressive/track doesn't matter because full stiff is just full stiff. My conclusion is that real 4.0 dampers have a narrower range by shorting the soft end of the range. I can rescale the DSC commands to make you a 4.0 calibration file to make the narrower damper range work better at the low end. Email me: tchan@tpcracing.com