Loosecayman

Hi guys,

Could some one help clarify how i could completely disable psm?

Ive been searching around the topic and theres been talk of disconnecting a brake sensor wire but the exact instructions are unclear.

Theres also feedback that this disables the sport function too.

Is there anyway to get complete control of the car? Many thanks. Appreciate it

Loosecayman

P.s this is for a 987 07 cayman s.

Thanks!

Tom Tweed

I don't have an answer for you, but I do have a question--why would you want to do this? Do you find the PSM too intrusive? I am a relative newbie to the Cayman and to the world of traction control, having owned nothing but "analog" sports cars previously, but I have tried the Cayman with PSM off at the limit, and my understanding is it only comes on again if you engage ABS or turn the car off. Why do you need it off completely?

TT

Hoopumpers

With my new 3.8L transplant in my Spyder, I definitely have to figure this out now too. Even with PSM off, the system is very intrusive under hard cornering. I want the car sideways, and I don't want any help.

I've seen a couple of threads that describe the process to build a switch which would disable PSM entirely. I will talk with Vision (who handles a ton of cayman race car prep) and let you know.

Loosecayman

Hi thanks for your feedback. I come from a background of race cars so would prefer to not have it on at all. Some might not find psm intrusive because they are rarely in the situation of which psm gets activated - there is a dimension of driving where you do find yourself sideways and having the choice of braking to trim your lines without spinning out helps greatly in being quick.

It does surprise me that this is remains somewhat of a taboo subject.

il pirata

Go here and scroll through the posts…looks like a solution cross posted from planet9…however it appears you may have an issue if you have PDK.

https://rennlist.com/forums/showthre...ferrerid=93689

Loosecayman

Thanks. As mentioned. there has been discussions but nothing clear. There is talk about disconnecting a certain wire off the brake sensor but its not clear which one or where this wire is located.

And as mentioned in my early post, the discussion isnt clear on whether this results in disabling sports mode too.

mschuster

Post #12 in this thread claims 987 PSM can be totally disabled by disconnecting a rotation rate sensor:
http://www.planet-9.com/987-cayman-b...-turn-off.html.
Mike

Tom Tweed

OK, I'm still confused. Maybe it's a semantic problem. What exactly do you mean by "sideways"? To me, sideways means the car is in an oversteering condition (ideal slip angle has been exceeded in the rear and it is sliding out due to loss of grip, requiring counter-steering). "Hard cornering" to me means driving a balanced car around a curve with all four tires at their ideal slip angle, generating maximum grip. The car is actually "crabbing" at 5-10 degrees in this situation, not going "sideways." Maybe we are talking about different things? Are you saying that the PSM interferes when you are at ideal slip angles, in a perfect 4-wheel drift?

I have had my Cayman for exactly one week, and run only one event in it (an autox, with speeds under ~70mph), so I will not pretend to be an expert in these modern mid-engine cars with their sophisticated electronics, but I have had 17 years of HPDE experience in cars with no electronic aids at all. I was very interested to see what was up with the "nannies," so I did try all the various modes to see how the car reacted. My CS is a PDK model with SC, LSD and PASM. In Sport+ mode, with PSM on, the car allowed all the yaw I needed to navigate a very tight course aggressively without intervention, including trail braking and throttle steering maneuvers. The parameters of the electronic systems seemed to be adequate to allow aggressive driving without shutting things down. I guess more explanation is needed about what interventions you are experiencing that are so bothersome, under what conditions.

From the other posts that have been referenced already, disconnecting the yaw sensor may be all you need to do if you have a manual Cayman, but that mod raises complications with PDK-equipped cars. If you do have PDK/SC/PASM, there are many other posts (and Porsche's own statements) that indicate that with Sports+ mode enabled, the PSM allows very aggressive driving without any intervention, and if you turn PSM off, it will not re-engage unless both front wheels lock and trigger the ABS system. So far, that's been my (limited) experience. I turned PSM off for one lap and overdrove the car, sliding it all over the place (but without invoking ABS under braking) and it never came back on. That lap was also a second slower than my smooth ones, though.

The fact of the matter is that PSM is a very complex system, with a number of interrelated components that "talk" to each other. It may be difficult to defeat completely, without inducing unforeseen and unwanted effects. These systems include:
ABD - Automatic Brake Differential
ASC - Automatic Slip Control
EDTC - Engine Drag Torque Control
DVC - Dynamic Vehicle Control
EBD - Electronic Brake force Distribution
ABS - Anti-lock Braking System

My understanding is that with PSM off, DVC and ASC are shut down, but ABS, ABD, EDTC and EBD are all still active. It will be interesting to hear what Vision has to say about your problem. From what I have read from Rick DeMan and John Tecce on this and other forums, PSM has not been a huge problem on their highly modified Caymans when driven smoothly.

YMMV,
TT

Tom Tweed

Please define "sideways" for me (see my post above). I must not be understanding you correctly, because if I hear about driving "sideways" at the limit, I am thinking oversteer, and the correction would be counter-steering and getting on the gas gently to transfer weight to the rear to get the tires hooked back up. Braking (or even lifting) under those conditions would transfer weight forward and almost insure a spin, not "trim your line." We must be having a "failure to communicate," as Cool Hand Luke would say...

I don't perceive any "taboo" around the subject--I see it discussed in multiple forums. What there doesn't seem to be is any consensus on the necessity of disabling PSM to drive fast.

TT

Hoopumpers

Aw geez. Ya know. I try and drive my track car fast (no nannies btw). I want to drive my Spyder FUN. And that means no systems "helping" me. I want to feel the natural balance of the car. At and beyond the limit. I was in tight mountain roads, trail braking and then trying to induce oversteer. PSM off didn't like that and kept "aiding" me. I honestly never noticed the intervention on track or canyon before the 3.8L, so either the extra power is exacerbating the issue or some ECU coding went wrong.

Lose all the acronyms and give me a car that doesn't try to drive for me. I suppose I just need an older car for the road.

sjfehr

I long felt PSM was helping me, as it seemed mostly to be turning any big mistakes I'd make into small mistakes, and I could toss the car with 11/10ths and it'd do 1-wheel braking and other magic to spit out 10/10ths performance, and didn't seem to get in the way much at all on most autocross courses. But then a friend of mine codrove with me and wired by 986S all up with his racekeeper gear (way better than what I usually use), and beat my by a half second in my own car. Poring through the wealth of data, it was clear that the two of us were holding virtually identical times in most segments (despite my friend being unfamiliar with the car), and he was really only cutting the time out in one particular corner where, unbeknownst to me, PSM was slowing me down. The data also showed that the acceleration curves were different with PSM on vs of; When we were driving with PSM off, the acceleration curves looked like ^, with a sharp peak when we got off the gas and immediately onto the brake. But with PSM on, it looked more like an inverted U; turned out PSM modulates the brake and e-gas to smooth out inputs, even before the car gets wiggly, and that modulation translates directly into lost time. Now, could be different for the 987/981, but I betcha it's the same.

Anyhow, I started autocrossing exclusively with PSM off after that. I do leave PSM on for track time trials, though; the confidence it inspires far outweighs the performance hit, at least for me.

Tom Tweed

Did it do the same thing with PSM on? Were you in Sport+ mode?

There ain't nuthin' "natural" about these modern cars, just a lotta CYA engineering catering to the lowest common denominator. I think you can still "drive around" most of it and have fun, though, but I may be wrong--I've only got a few miles on mine so far.
TT

Loosecayman

Wow. thanks for all your replies. I appreciate it. While googling the topic i repeatedly find reponses to the same questions of attempts to turn psm off - "why would you want to do that?". I'd repeat again that i find my self in situations of which i would appreciate complete control of the car. This would include not having to turn psm off each time i start the car.

I lothe to enter a discussion of whether it would be faster (or not) because that becomes an entirely subjective question which brings driver ability, style, objective and ego into the picture. As it has been correctly pointed out, PSM gets reactivated when you reach a certain yaw angle coupled with the application of brakes. As a side hobby i also own a cagged drift car which i use on weekends - and as explained earlier there are situations where one can trim the lines on the car to close in on the apex while being sideways (or oversteer, whichever the terminology).

But that is beyond the scope of this scope or my request (plea!?) for assistance. I hope to keep this thread objective.

1. Are there exact instructions on how i can disable PSM i.e which wires to disconnect and where they are located?

2. Would this disable sport mode as well?

3. Is there a way to achieve my end objective? (perhaps its impossible, as some have mentioned, all systems are interlinked - would a reflash help?)

There have been discussions on this on planet 9 - but as i've mentioned before, the threads ended abruptly. Thanks in advance

Supagoat

I autocrossed my Spyder yesterday and got into a half-spin on a sweeper just fine with PSM off and sport mode on.

I've heard on the Miata that you can disable it by holding the stability control button off for 10 seconds as you turn the ignition... Frankly, I don't see the need as I can step the back out just fine with it in whatever mode turning it off is. I don't feel feel like software is really holding me back...