Impressions of GT3 (Manifold)
08-11-2015, 03:08 AM
#211
Rennlist Member
We've discussed car setup, etc. in various threads, so I thought post an update in this little 'journal' thread of mine.
I had an excellent track event this past weekend at Summit Point (main). Prior to this event, I had set my cambers back to the factory 1.5, instead of the 2.0 I've been running for all of my prior track days. After making the change to factory alignment, the car felt significantly better on the road, and I was pleased to find that it felt better on the track also. Tires may not last as long with this camber, but I don't really care at this point, the improved behavior of the car is worth it.
An even bigger step forward was Sunday morning, when I rode with a pro racer who drove my car for two laps. He's very familiar with the 991 GT3 and the nuances of tuning it, and is the person who advised me to go back to factory alignment. To my surprise, he advised leaving the buttons OFF for the sport exhaust, stiffer damping, and sport mode for the shifting, and also advised running the car in manual mode. I asked about tire pressures, he didn't think it mattered too much, so I set them to 31 hot (based on my wife coming off the track just prior), and he suggested trying a higher hot pressure. Watching him drive the car for those mere two laps was eye opening, to say the least. Next two sessions I went out and tried to incorporate much of what I observed into my own driving, and was able to drop my lap times ~1.5 s despite having a passenger in the car! Moreover, I didn't notice any of the PSM/ABS intervention I've whined about in the past, and by learning to use the frickin brake pedal better, I was able to eliminate nearly all of the instability in bumpy high-speed braking zones that I've been whining about. And by manually shifting on track, I rediscovered the pleasure of knowing what gear I'm in and controlling when shifts happen.
Much of the above differs from how others are setting up and using the car, and I'm just another guy posting stuff in a forum, so take with a grain of salt as you wish, but I offer it as data and food for thought.
The car now has over 10K miles and over 3K track miles on it, and I love the thing. Comfy on the road, and an exhilarating beast on the track. I've had many passengers in the car on track, and nearly all describe the car as 'amazing'.
I had an excellent track event this past weekend at Summit Point (main). Prior to this event, I had set my cambers back to the factory 1.5, instead of the 2.0 I've been running for all of my prior track days. After making the change to factory alignment, the car felt significantly better on the road, and I was pleased to find that it felt better on the track also. Tires may not last as long with this camber, but I don't really care at this point, the improved behavior of the car is worth it.
An even bigger step forward was Sunday morning, when I rode with a pro racer who drove my car for two laps. He's very familiar with the 991 GT3 and the nuances of tuning it, and is the person who advised me to go back to factory alignment. To my surprise, he advised leaving the buttons OFF for the sport exhaust, stiffer damping, and sport mode for the shifting, and also advised running the car in manual mode. I asked about tire pressures, he didn't think it mattered too much, so I set them to 31 hot (based on my wife coming off the track just prior), and he suggested trying a higher hot pressure. Watching him drive the car for those mere two laps was eye opening, to say the least. Next two sessions I went out and tried to incorporate much of what I observed into my own driving, and was able to drop my lap times ~1.5 s despite having a passenger in the car! Moreover, I didn't notice any of the PSM/ABS intervention I've whined about in the past, and by learning to use the frickin brake pedal better, I was able to eliminate nearly all of the instability in bumpy high-speed braking zones that I've been whining about. And by manually shifting on track, I rediscovered the pleasure of knowing what gear I'm in and controlling when shifts happen.
Much of the above differs from how others are setting up and using the car, and I'm just another guy posting stuff in a forum, so take with a grain of salt as you wish, but I offer it as data and food for thought.
The car now has over 10K miles and over 3K track miles on it, and I love the thing. Comfy on the road, and an exhilarating beast on the track. I've had many passengers in the car on track, and nearly all describe the car as 'amazing'.
I have my car booked to have the camber returned from -2.0 F+R on 19 August and have had this booked in for some time after careful consideration. I have just had new tyres fitted and have three track days scheduled for September so I am now really looking forward to them.
For the tyre pressures Ive come to believe in 33/36 F+R max hot during a session (following Michelin MPSC2 GT3 guidelines). This may be a personal thing but I found the 28F+32R thing others have preferred did not work for me. I find the sweet spot is around 32F+35R but enjoy the handling up to 33/36. 38 on the rear feels too greesy for me. My lap times confirm the 32/33F + 35/36R are faster for me on my local track. I find the tyres have given their best by around 60% tread wear F+R (5-6 track days approx) although they comfortably go another 2-3 track days and a whole fist full of road kms before they are technically at their wear limit.
Im very keen to try the factory camber settings as I only drove these in Europe on the roads and never on the track. With the mix of driving I do I should think the wear will remain fairly neutral.
Thanks again. Keep us informed how this all feels on your next track day...
08-11-2015, 09:35 AM
#212
Rennlist Member
Manifold - I've been watching your camber posts with interest. I started at 2.7 front and 2.5 rear with MPSC2s and didn't have a very good experience. Shredded my front wheel wells pretty quickly, mostly due to heavy compression on turn 12 at Road Atlanta - it didn't help that the original shop I worked with lowered the car too much. I was going to install the caster pucks but backed off camber to 2.5 front and 2.0 rear, raised the height a bit, and the car is driving better now, with minimal rubbing in front. I would consider going back to 1.5 all around but I just had my Trofeo R's mounted and understand they like more camber, so I'm going to stick with 2.5 front and 2.0 rear. Has anyone run Trofeo's with such a small amount of camber?
I'm also experiencing understeer on a high speed sweeping turn at AMP. It got better when I softened the front sway bar one notch (rear is at neutral factory setting), but there is still room for improvement. I've got the Crawford wing and the cup car splitter, so I've got other variables to consider as well. If I still see the understeer with the Trofeo Rs, I'm going to drive it with the stock wing to see if that makes a difference. If neither of those changes help, I'll give the stock settings a try.
I've tried different pressures as well. Everything from 29/31 to 34/36 hot with the MPSC2s. I've seen more tire wear with the lower pressures, and settled into 32/34 as a compromise. With the Trofeo Rs, it seems like 29-30 is the sweet spot, so that's what I'm planning to run at my next event. About the only thing I'm certain of is that the MPSC2s get greasy above 36!
I'm also experiencing understeer on a high speed sweeping turn at AMP. It got better when I softened the front sway bar one notch (rear is at neutral factory setting), but there is still room for improvement. I've got the Crawford wing and the cup car splitter, so I've got other variables to consider as well. If I still see the understeer with the Trofeo Rs, I'm going to drive it with the stock wing to see if that makes a difference. If neither of those changes help, I'll give the stock settings a try.
I've tried different pressures as well. Everything from 29/31 to 34/36 hot with the MPSC2s. I've seen more tire wear with the lower pressures, and settled into 32/34 as a compromise. With the Trofeo Rs, it seems like 29-30 is the sweet spot, so that's what I'm planning to run at my next event. About the only thing I'm certain of is that the MPSC2s get greasy above 36!
08-11-2015, 10:29 AM
#213
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^^
One thing to consider is that tires can get greasy because (a) the pressure is too high AND/OR (b) the tire temp is too high. Some of us, including me, may be thinking the pressure got too high, whereas it was actually the temp which was too high, thus giving a false indication of pressure being too high.
For example, this past weekend, my wife and I wound up sharing the GT3 because her Cayman had some issues. Her sessions were typically right before mine, so I got the car with fairly warm tires and drove it another 20+ minutes. Sometimes I noticed the pressure staying fairly constant, say 32, but the grip gradually falling off with each lap towards the end of my sessions. I could be wrong, but I suspect it was due to the tires getting too hot (and it was a warm weekend).
Considering all of this and my reduced cambers, at my next event, I plan to try higher hot pressures. But that's about all I want to tinker with as far as playing race car engineer, given that AP and his team at Porsche seem to know what they're doing, whereas guesswork by me or a shop without deep expertise is probably likely to make the car worse rather than better.
One thing to consider is that tires can get greasy because (a) the pressure is too high AND/OR (b) the tire temp is too high. Some of us, including me, may be thinking the pressure got too high, whereas it was actually the temp which was too high, thus giving a false indication of pressure being too high.
For example, this past weekend, my wife and I wound up sharing the GT3 because her Cayman had some issues. Her sessions were typically right before mine, so I got the car with fairly warm tires and drove it another 20+ minutes. Sometimes I noticed the pressure staying fairly constant, say 32, but the grip gradually falling off with each lap towards the end of my sessions. I could be wrong, but I suspect it was due to the tires getting too hot (and it was a warm weekend).
Considering all of this and my reduced cambers, at my next event, I plan to try higher hot pressures. But that's about all I want to tinker with as far as playing race car engineer, given that AP and his team at Porsche seem to know what they're doing, whereas guesswork by me or a shop without deep expertise is probably likely to make the car worse rather than better.
08-11-2015, 11:20 AM
#214
Drifting
Macca,
my experience completely concurs with your tire life and psi conclusion with cup2's
I believe the cup 2's are good for at least 2 more track days over the previous tire
what Manifold is stating about tire temp relative to grip makes sense
and have experienced that after long 45 min back to back sessions the grip gets greasy
and lap times start tanking even with psi constant 34-36
I figured it was my lack of endurance when things get pretty hot inside the car as well
car is still set up w/factory camber just opened the toe up
my experience completely concurs with your tire life and psi conclusion with cup2's
I believe the cup 2's are good for at least 2 more track days over the previous tire
what Manifold is stating about tire temp relative to grip makes sense
and have experienced that after long 45 min back to back sessions the grip gets greasy
and lap times start tanking even with psi constant 34-36
I figured it was my lack of endurance when things get pretty hot inside the car as well
car is still set up w/factory camber just opened the toe up
08-11-2015, 11:54 AM
#215
Rennlist Member
I always found just about with every tire that once you get them too hot, grip goes away.
PSI wont change it, it may help you find some grip back on less than smooth surface to run a little low but with heavy cars your fast lap will be lap 3-4-5 than its done even at the ideal pressure.
For winning your DE you must line up first, go FLATOUT (Its the only way I drive, FLATOUT) start a little higher PSI than you would like to be and gap the other drover enough that even with cooked tires you will podium in front of them. Your mirrors are only for going just fast enough to minimize the tire killing when you drive FLATOUT.
PSI wont change it, it may help you find some grip back on less than smooth surface to run a little low but with heavy cars your fast lap will be lap 3-4-5 than its done even at the ideal pressure.
For winning your DE you must line up first, go FLATOUT (Its the only way I drive, FLATOUT) start a little higher PSI than you would like to be and gap the other drover enough that even with cooked tires you will podium in front of them. Your mirrors are only for going just fast enough to minimize the tire killing when you drive FLATOUT.
08-11-2015, 12:19 PM
#216
Drifting
^^^^^
Excellent strategy input , must be added to the GT3 Drivers DE CUP Handbook
you know for guys like myself looking to win the day LOL
Excellent strategy input , must be added to the GT3 Drivers DE CUP Handbook
you know for guys like myself looking to win the day LOL
Last edited by R.Deacon; 08-11-2015 at 10:20 PM.
08-11-2015, 12:22 PM
#217
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For winning your DE you must line up first, go FLATOUT (Its the only way I drive, FLATOUT) start a little higher PSI than you would like to be and gap the other drover enough that even with cooked tires you will podium in front of them. Your mirrors are only for going just fast enough to minimize the tire killing when you drive FLATOUT.
09-20-2015, 09:39 PM
#219
Rennlist Member
Manifold. Could you provide some feedback on front OEM rotor life on your car? I have 8 track days (tracks are tight here, a few of them notoriously heavy on brakes) and 8000 road miles (at least 3000 of these are a significant pace including Autobahn work etc in Europe).
I havent been heat managing the discs (i.e. rolling the car back and forth at the end of a session) as I do with my 993 so this may explain some of the issues. I do run a long slow cool down lap. Ive also come in twice without cool down lap once red flag and once after spin to clean of much and both times did not favours to rotor longevity I suspect. I confess that unlike the tyres and the geo ive been a bit slack with heat managing the rotors. I did change pads three track days ago (2 weeks back) when I changed tyres and corrected geo to factory specs (very happy with that by the way). I now have brake judder under application. Plenty of meat on the disc (60% worn) and some 7-12 mm cracks all over but none joining or at the edge. I suspect warped rotor. I changed pads to Endless MX72 (street/track compound) but do not rate it as in three hard track days used up 60% of front pad. they dust less but they wear faster than OEM pad to which I will revert (I found them fine apart from the dust up).
Seems like they need replacing early as I expected 10-12 track days out of them even though my road mileage is higher than many. Im guessing my abuse of them hasn't helped. I do have passengers on many laps too.
Curious at to your experience and POV
P.S. our hardest track on brakes was last weekend - its the second time I've spent the day there and runs from Vmax 226 kmph in the GT3 to 55kmph within 200m!
I havent been heat managing the discs (i.e. rolling the car back and forth at the end of a session) as I do with my 993 so this may explain some of the issues. I do run a long slow cool down lap. Ive also come in twice without cool down lap once red flag and once after spin to clean of much and both times did not favours to rotor longevity I suspect. I confess that unlike the tyres and the geo ive been a bit slack with heat managing the rotors. I did change pads three track days ago (2 weeks back) when I changed tyres and corrected geo to factory specs (very happy with that by the way). I now have brake judder under application. Plenty of meat on the disc (60% worn) and some 7-12 mm cracks all over but none joining or at the edge. I suspect warped rotor. I changed pads to Endless MX72 (street/track compound) but do not rate it as in three hard track days used up 60% of front pad. they dust less but they wear faster than OEM pad to which I will revert (I found them fine apart from the dust up).
Seems like they need replacing early as I expected 10-12 track days out of them even though my road mileage is higher than many. Im guessing my abuse of them hasn't helped. I do have passengers on many laps too.
Curious at to your experience and POV
P.S. our hardest track on brakes was last weekend - its the second time I've spent the day there and runs from Vmax 226 kmph in the GT3 to 55kmph within 200m!
09-21-2015, 12:00 AM
#220
Nordschleife Master
I always found just about with every tire that once you get them too hot, grip goes away.
PSI wont change it, it may help you find some grip back on less than smooth surface to run a little low but with heavy cars your fast lap will be lap 3-4-5 than its done even at the ideal pressure.
PSI wont change it, it may help you find some grip back on less than smooth surface to run a little low but with heavy cars your fast lap will be lap 3-4-5 than its done even at the ideal pressure.
09-21-2015, 09:03 AM
#221
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Manifold. Could you provide some feedback on front OEM rotor life on your car? I have 8 track days (tracks are tight here, a few of them notoriously heavy on brakes) and 8000 road miles (at least 3000 of these are a significant pace including Autobahn work etc in Europe).
I havent been heat managing the discs (i.e. rolling the car back and forth at the end of a session) as I do with my 993 so this may explain some of the issues. I do run a long slow cool down lap. Ive also come in twice without cool down lap once red flag and once after spin to clean of much and both times did not favours to rotor longevity I suspect. I confess that unlike the tyres and the geo ive been a bit slack with heat managing the rotors. I did change pads three track days ago (2 weeks back) when I changed tyres and corrected geo to factory specs (very happy with that by the way). I now have brake judder under application. Plenty of meat on the disc (60% worn) and some 7-12 mm cracks all over but none joining or at the edge. I suspect warped rotor. I changed pads to Endless MX72 (street/track compound) but do not rate it as in three hard track days used up 60% of front pad. they dust less but they wear faster than OEM pad to which I will revert (I found them fine apart from the dust up).
Seems like they need replacing early as I expected 10-12 track days out of them even though my road mileage is higher than many. Im guessing my abuse of them hasn't helped. I do have passengers on many laps too.
Curious at to your experience and POV
P.S. our hardest track on brakes was last weekend - its the second time I've spent the day there and runs from Vmax 226 kmph in the GT3 to 55kmph within 200m!
I havent been heat managing the discs (i.e. rolling the car back and forth at the end of a session) as I do with my 993 so this may explain some of the issues. I do run a long slow cool down lap. Ive also come in twice without cool down lap once red flag and once after spin to clean of much and both times did not favours to rotor longevity I suspect. I confess that unlike the tyres and the geo ive been a bit slack with heat managing the rotors. I did change pads three track days ago (2 weeks back) when I changed tyres and corrected geo to factory specs (very happy with that by the way). I now have brake judder under application. Plenty of meat on the disc (60% worn) and some 7-12 mm cracks all over but none joining or at the edge. I suspect warped rotor. I changed pads to Endless MX72 (street/track compound) but do not rate it as in three hard track days used up 60% of front pad. they dust less but they wear faster than OEM pad to which I will revert (I found them fine apart from the dust up).
Seems like they need replacing early as I expected 10-12 track days out of them even though my road mileage is higher than many. Im guessing my abuse of them hasn't helped. I do have passengers on many laps too.
Curious at to your experience and POV
P.S. our hardest track on brakes was last weekend - its the second time I've spent the day there and runs from Vmax 226 kmph in the GT3 to 55kmph within 200m!
I now have about 12K miles on the car, which includes about 4K track miles. During the break-in of close to 2K miles, my rotors had negligible cracking. I then started tracking the car with PFC 11 pads.
I'm still using the original OEM rear rotors (wow!), which have some cracking, but it's not bad enough that I feel the need to replace them yet.
After one track weekend, I switched from OEM to SRF brake fluid, and have stayed with that.
I replaced the front rotors when I felt the cracking was too much, which means cracks connecting between holes. Porsche would advise replacing them sooner, based on a shorter crack length, and others will use them longer than I did. Going from memory, I estimate that I replaced the front rotors at about 5K miles, which included about 1.5K track miles, so roughly a dozen track days. I'm now using AP racing front rotors, which have grooves, but no holes or slots, and it looks like they still have decent life left on them.
Once I finished a first set of PFC 11 pads, I switched to Ferodo DS 1.11 pads, and have been sticking with them. I find the brake feel to be better with the Ferodos, but am open to trying something else in search of even better pads.
I haven't done anything special for heat management, just a decent cool down lap at the end of sessions. I've had no brake judder or evidence of warped rotors. You may want to check into improper bedding as the source of judder with your brakes.
BTW, after all these miles on the car, my conclusion is still that the car is great (though not perfect). Some of the things I complained about regarding its track behavior have pretty much gone away as I've adapted to the car and learned to drive it better (especially better braking). And while I still don't get much enjoyment out of driving the car on the road at reasonable speeds, I continue to appreciate the relative comfort of the car on the road. I'm also glad that I went back to the factory alignment, and my tire wear seems fine by running a little higher pressure. Have had at least 20 passengers in the car, and all come out impressed, with many of them finding that the car exceeded their expectations. If the car doesn't run into mechanical issues, I see it being a long-term keeper, and the only thing that might lure me away is that the added safety and track focus of a proper race car.
09-25-2015, 01:21 PM
#223
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Smoother application, and smoother and better-timed release. I think mainly because of the PASM, the car doesn't respond well to hammering the brakes, particularly in bumpy high-speed braking zones. Nice side effect is that my braking technique is now better in all cars, not just the GT3.
09-25-2015, 04:37 PM
#225
Smoother application, and smoother and better-timed release. I think mainly because of the PASM, the car doesn't respond well to hammering the brakes, particularly in bumpy high-speed braking zones. Nice side effect is that my braking technique is now better in all cars, not just the GT3.