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Discussion Starter #1 (Edited)
I replaced my 987.1 Cayman with a 987.2 version this past year, and have been learning the new car this track season. Initially, I was vexed by the fact that I was about a second slower in the 987.2, despite its horsepower advantage. Also, I noticed that the brake pedal was going soft late in the day, a problem I had not had with the 987.1. And, during bleeding, the rear brakes had an unusual amount of air in the lines. This was all happening despite the fact that I was running the car with the PSM switched off. Some searching on this forum revealed that Porsche does not allow PSM to be completely disabled with the switch, and that totally disabling all nannies required unplugging the yaw sensor. So, prior to my last outing last Friday, I unplugged the sensor, held my breath, and headed out on track. I was nervous because I didn't know what other effects might show up (for example, the cruise control stops working--not that I use that on track).

The car felt just fine without the nannies on, and I think it was quicker, though a GPS problem prevented me from getting lap times. The ABS still worked fine, and the brakes did not go soft as they had before. And-- the car actually got a bit loose while coming out of the slowest hairpin on the track when I romped on the throttle, something I had not experienced before. This all leads me to conclude that, unbeknownst to me, the rear brakes were still intervening quite a bit even though I thought PSM was off.

Overall, it was a fine result. The only downside was the fact that the car has a hysterical electronic panic attack when the nannies are turned off--I get a bunch of dire messages at start up, like "PSM failure!" and "Driver assist failure!" in addition to the "Flat tyre!" message I already get since the inflation pressures of my track tires are outside the normal window. The flat tire message is especially annoying, because, even if you toggle through it, it reoccurs at random times during a run session--distracting and disconcerting when beginning to brake from top speed. The car ends up wth the entire dashboard lighting up, with bells and chimes signaling imminent doom. When the low fuel warning light came on, I almost missed it, since it was practically buried in the throngs of other warnings.

I'm hoping to find a way to reprogram the computer to get rid of all these extraneous warnings and error messages. If anyone knows of a way to do this, I'd appreciate it. I suspect most shops will be jittery about doing it, for liability reasons, but I'll happily sign a waiver acknowledging that I take full responsibility for making the car into a virtual deathtrap.

Terry
 

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Disabling the yaw sensor was one of the best upgrades I ever did, it stopped all the nervousness under hard cornering and best of all , all my brake problems disappeared.
I now have a switch on the ground wire to the yaw sensor so it can be on if I ever use the car on the road and always of when on track.
 

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Discussion Starter #3
Disabling the yaw sensor was one of the best upgrades I ever did, it stopped all the nervousness under hard cornering and best of all , all my brake problems disappeared.
I now have a switch on the ground wire to the yaw sensor so it can be on if I ever use the car on the road and always of when on track.
Do you just put up with all the warning lights when you drive? They drive me crazy!

Terry
 

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I don't notice the warning lights when on track :wink: and don't have any warning lights when on road as I switch the yaw sensor on.
 

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A middle-ground alternative to the yaw switch is to have someone with a PIWIS to program your Cayman to think it has carbon brakes. Doing so reduces the threshold for PSM to kick in when the PSM button is "off".
My recollection from other threads is that disabling the yaw sensor will affect other systems. May not be important at the track but you should be aware of them.
Bern
 

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A middle-ground alternative to the yaw switch is to have someone with a PIWIS to program your Cayman to think it has carbon brakes. Doing so reduces the threshold for PSM to kick in when the PSM button is "off".
My recollection from other threads is that disabling the yaw sensor will affect other systems. May not be important at the track but you should be aware of them.
Bern

These cars are so much better to drive without all the nanny-state electronics, so disabling the yaw sensor is great as it only leave ABS working :)
 

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Completely agree with disabling the yaw sensor. Before my first track day with my 987.2S I wired a switch for the ground so I could try it both ways. At first I tried with just the PSM off and the traction control light was still flashing all the time (even with a LSD) and you could feel the car being held back and intervening. Once I turned it all off, the car behaved as it should with the ability to rotate the car and get on the power without interruption. The car is so easy to control with everything turned off that it is somewhat annoying that Porsche won't let you turn off everything without rigging the yaw sensor. I can not image tracking this car without disabling the yaw sensor now.
 

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I definitely prefer the 987.1 brakes to the 987.2. To me the .1 brakes are very linear with better modulation and the .2 brakes almost feels like a pressure plate to me and just like my SIM.
 

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Biggest benefit from turning the Yaw sensor off when on track, apart from the better handling / driver control is:

Much less rear brake pad wear, especially the inside pads.
Less chance of overheating the rear calipers
Less chance of overheating the ABS pump.

Best part of turning all the driver aids of is that it become so much more rewarding to drive the car on track, you know it's you driving skills that get the lap times, not gadgets ;-)
 

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Terry, Nielsen33, 12pcar, and others that have seen large improvements with the yaw sensor pulled: is your car equipped with sport chrono plus?
No Sports Chrono on mine either so I can't compare. I have a 6Sp too if that matters. I'll also add that my shiny red brakes turned into dark maroon on all 4 corners (not just the rear) after 3 sessions at the track. Brake bias felt fine, if anything the car needs more downforce or tire on the front. I'm running DTC60 pads, stainless lines, Castrol SRF, titanium pad shims in the rear, GT3 front ducts and 997 turbo rear duct(don't think they do much). The brakes got hot but worked great every session.
 

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....if anything the car needs more downforce or tire on the front....
True story. I added a splitter and the car was much more compliant under braking. Then went from a 245 last season to a 285 this season in the front, what a friggin difference. The wider front tire is absolutely amazing for the brakes on these cars (well.....generally any car really.) Stuff as much as you can under there (for what its worth, I fit 255's RS3's with stock coach work a few years back.)
 

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True story. I added a splitter and the car was much more compliant under braking. Then went from a 245 last season to a 285 this season in the front, what a friggin difference. The wider front tire is absolutely amazing for the brakes on these cars (well.....generally any car really.) Stuff as much as you can under there (for what its worth, I fit 255's RS3's with stock coach work a few years back.)
I'm trying to keep the car street-able so a lot of the splitters available are too low. I added the R front splitters but don't they they add much. Did you notice much with your dive planes? I wish someone made an oem GT4 type splitter that would bolt up to a 987.2.

I'm on 245/275 NT01's which work well but they don't make a 255. May go to the R888 next in a 255/275 setup.
 

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Discussion Starter #15 (Edited)
I definitely prefer the 987.1 brakes to the 987.2. To me the .1 brakes are very linear with better modulation and the .2 brakes almost feels like a pressure plate to me and just like my SIM.
I didn't like the 987.2 brakes either, so I added the GT3 master cylinder. Huge difference in feel and ability to modulate.

My car is just about perfect now. All it needs is a roll bar, race seats and harnesses, JRZs, and another 100 hp.:hilarious:

Terry
 

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I'm trying to keep the car street-able so a lot of the splitters available are too low. I added the R front splitters but don't they they add much. Did you notice much with your dive planes? I wish someone made an oem GT4 type splitter that would bolt up to a 987.2.

I'm on 245/275 NT01's which work well but they don't make a 255. May go to the R888 next in a 255/275 setup.
Honestly no I didn't notice. That said, I was still learning the car after pulling a ton of weight, different setup, tires, etc. Plus the fact that I like my car a little on the tight side (for racing,) so all of that combined I didn't notice much of a difference but again there was so much change that who the hell knows.

I ran that exact setup (888's) 3 years ago before converting my car. I didn't like the 275's as much as the 285's (could have probably done more with the suspension to dial it in, but whatever.) I'm of the opinion that you run as much tire as humanly possible so long as you can get temp in them. Our cars turn lap times through braking and lateral g's, not through straight line performance. So I don't believe that smaller tires are better for lap times (which runs contrary to many ITC & GTB1 racers.) To each their own....just my experience and driving style.
 

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I asked about Sport Chrono, because I do have it on my 2010 Boxster S and my experience regarding PSM is significantly different than yours. Sport Chrono opens the PSM engagement window such that it ceases getting in the way, and the other wizardry packaged with PSM, like dynamic brake bias adjustment, becomes a HUGE asset on the track, enabling much more aggressive corner entries, and faster lap times. It's a completely different car on the track in Sport+ vs normal.

I'm no national champion, but I am a 5-time state autocross champion and locally highly competitive in time trials and can attest that my 987.2S is fastest with SC in Sport+ and PSM left on. I think it may be a bit dangerous to be encouraging people to pull yaw sensors when what you really need is a SC retrofit (about $1k through a dealer, cheaper through an indie.)
 

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Honestly no I didn't notice. That said, I was still learning the car after pulling a ton of weight, different setup, tires, etc. Plus the fact that I like my car a little on the tight side (for racing,) so all of that combined I didn't notice much of a difference but again there was so much change that who the hell knows.

I ran that exact setup (888's) 3 years ago before converting my car. I didn't like the 275's as much as the 285's (could have probably done more with the suspension to dial it in, but whatever.) I'm of the opinion that you run as much tire as humanly possible so long as you can get temp in them. Our cars turn lap times through braking and lateral g's, not through straight line performance. So I don't believe that smaller tires are better for lap times (which runs contrary to many ITC & GTB1 racers.) To each their own....just my experience and driving style.
The smaller diameter tires help close up the gear ratios which improves acceleration. The smaller diameter tires also allow a much higher top speed. The trick is to get the wider tires in 17" and get the best of both, wider tread and smaller diameter. The smaller diameter rim also negates any need for a big brake kit. Big brake kits are needed for larger diameter wheels because the tire/ 19" or 20" wheel has more leverage against the rotor compared to the 17" wheel with the wider tires
 

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Discussion Starter #20
I asked about Sport Chrono, because I do have it on my 2010 Boxster S and my experience regarding PSM is significantly different than yours. Sport Chrono opens the PSM engagement window such that it ceases getting in the way, and the other wizardry packaged with PSM, like dynamic brake bias adjustment, becomes a HUGE asset on the track, enabling much more aggressive corner entries, and faster lap times. It's a completely different car on the track in Sport+ vs normal.

I'm no national champion, but I am a 5-time state autocross champion and locally highly competitive in time trials and can attest that my 987.2S is fastest with SC in Sport+ and PSM left on. I think it may be a bit dangerous to be encouraging people to pull yaw sensors when what you really need is a SC retrofit (about $1k through a dealer, cheaper through an indie.)
I hope my thread was not interpreted as encouraging everyone to pull their yaw sensors. I'm just relaying what happened when I did mine. For sure, people should not perform this modification unless they have the experience and ability to control the car, and are willing to take the risk of a bad result. I did my first 15 years of track driving in a 944 that had no driver aids beyond ABS, so I felt confident enough to give it a try on the Cayman, but, even still, I took it easy until I was sure there would be no ugly surprises.

Please, everyone--be careful out there.

Terry
 
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