My 2008 C2S does not have a LSD. After searching multi threads, I find that some say Porsche believes PSM will mimic LSD functionality in this model year.

What are the facts here?

Has anyone tested LSD vs no LSD/PSM back to back on a track?
I turn respectable times at High Plains Raceway and have yet to break a rear inside wheel loose. Plus, I have never experienced a rear end wag under heavy braking. I run Michelin PCS. And it's ok to say, "..maybe you aren't pushing it enough..", but I don't think so .

I appreciate the feed back guys.

 

I have a Quaife Diff in my 06 C2S, it has improved my on track experience significantly.

Talk Matt from Guards (sponsor) he will set you up with the right unit. IMO these cars should have come with one, the open diff is limiting the performance.

 

I am interested in this as well although mine is an '09cs2 with pdk, no lsd. Is there any data that shows how a c4, c lsd, and c would perform for a given series of runs with a variety of curve conditions (constant smooth, pinched, tight to flare out, etc.) and with stability on or off? It would seem to me that P, M, BMW, etc. should be able to simulate these conditions both in s/w and on a track and have the data. Whether it would be available is anybody's guess but I would be interested.

 

I agree based upon several posts including this one

https://www.6speedonline.com/forums/...sd-buster.html

...however I am looking for how any testing on how PSM mimics the LSD vs a real LSD.

 

There is no way that PSM can mimic an LSD, this is all about physics and mechanics. When the load is lifted from one side of the car in a turn, an open diff will
always transfer the power to the wheel with the least resistance, this will create wheels
spin if the grip is limited do to a hard turn. The LSD will mechanically transfer the power to the wheel with the most grip, therefore giving a lot more power to the road.

PSM will not generate extra grip on the wheels with the most contact. I have done a number of track days with my car, both with the open diff, and with the Quaife.

 

I think (though I am not 100% certain at this moment without taking the book out of the shelf and re-reading it) that Paul Frère said on "The Porsche 911 Story" that PSM incorporates ABD or Automatic Brake Differential, up to 44 mph, by applying the brake to the tire that is spinning. This would make me believe that it brakes the tire that is spinning, but not that it would transfer the lost power to the tire with more grip or that isn't spinning - as in a real Limited Slip differential - thus not making the car have more traction and speed out of the corner, since the power that was making the tire spin would be taken care of by the brake on that tire without being sent to the other one. Am I correct? If I am, then PSM is not a substitute for a real limited slip diff. Does anyone else really know? I am thinking into installing one on my car and don't want it to have any issues with PSM.

 

Guys, please, I am not saying PSM is any substitute for a real LSD.

What I am after is, does PSM do as Cypergypsy state, apply Automatic Braking Differential at less then 44mph in such a manner to (try to) mimic an LSD? With any open differential, if you lock one wheel while applying power, the other wheel will get the power.

So just how effective is PSM in trying to mimic a LSD? I am just trying to understand the electronics.

 

Just found all this info, now that I know the magic words "Automatic Braking Differential".

http://www.auto-types.com/dictionary/abd-4.html

ABD
The Automatic Braking Differential (ABD) system was co-developed by Bosch and Porsche in order to counteract unnecessary wheel spin by one of the driving wheels. In essence, ABD is an electronic locking differential that uses the brakes and inputs from the Anti-lock Braking System sensors to simulate "the lock" of one of the wheels in case of hard acceleration or during a high-speed maneuver.

On most car models, the ABD does not substitute for a real locking differential, but is a supplementary system which provides better directional stability and more traction on less-than-ideal road surfaces by applying braking power to any slipping wheel during acceleration.

and

http://www.autozine.org/technical_sc...tion_other.htm

which calls it Artificial LSD : Bosch-Porsche ABD as an example.

Limited Slip Differential (LSD) can be artificially implemented by using ABS hardware with additional program.
When ABS sensor detected tyre slip in one wheel, ABD program will actuate the brake on that wheel. As the wheel locks up, differential will transfer torque to the other wheel which has traction, so the car can get out of trouble quickly.

and finally, I might have found my answer, as least from one unofficial test

http://www.caymanclub.net/cayman-cha...ck-report.html

Here's an excerpt:

"It isn't often that I'm proven wrong, at least I think that's the case. However, with respect to LSD I was proven very wrong today. If you go back and look at some things I said after Top Gear in the UK said that the Cayman S really needed a limited slip differential I believe I said that I didn't think so, that you could get around the track just fine without one. Well, I was wrong. The LSD totally transforms the Cayman, ok that's a strong statement, how about "significantly improves the performance of the Cayman" or "worth every penny" ? No, transforming the Cayman is what it does!

My lap times today were 2-1/2 to 3 seconds faster than before on a consistent basis. During the two tightest turns on the track I was able to put power down without wheel spin allowing me to increase subsequent speeds on the straights, as an example on place that I normally hit 109 or 110, I was hitting 113-115. This actually became a problem because my brakes went soft a few times due to the extra speed I had to scrub (brakes were later bled for some improvement but overall I think it may be the Hawk HPS pads, more on that later).

Acceleration was not the only improvement, the car was noticeably more stable in all areas of the track, particularly under high speed to hard/heavy braking, nothing squirming, nothing shifting around, etc."

The Porsche electronic LSD is called Automatic Brake Differential and is just like the one for the 135i, as far as I can tell. Neither car has a mechanical LSD - just applies brake to the spinning wheel and eventually cuts power from the engine if spins too much. I found it VERY annoying on my 2002 996 Carrera.

So maybe someone has done a more scientific before and after test?

Curious what is the installed budget and what will Porsche say about the install when the car is in warranty?

 

Guard builds the best LSDs. You might also consider upgrading your swaybars as they will help you with less roll keeping the right tires on the ground.

 

Neither was I (saying that PSM is a substitute for a limited slip diff)! I am just like tedean, trying to understand the electronics and finding a limited slip that would work seamlessly with PSM. Warranty will not be an issue for me in about 4 months' time anyways!

 

i asked at my P dealer if it was posible to retrofit a LSD to my 2006 997s, he told me it wasn't possible even though he didn't know why (shame).
when i ordered the car i couldn't take it because i chose to have pasm. only cars with the -20mm suspension could be delivered with an LSP.
so my question is, what does the pasm have to do with a lsd?