James Gunn

What I want to know is, if Schumacher or Senna were driving a Boxster S would it be faster with or without PSM?

TIA

NJ-GT

PSM will always be slower for auto-x unless it is snowing.

Z-man

I agree with NJ-GT: PSM will slow you down at an autocross. You want a little wheel spin to carry your momentum through a corner. PSM will just bog you down, no matter who the driver is!

I am in instructor within NNJR - PCA's autocross program. I was given the opportunity to drive a student's car: a Ferrari 360 Modena F1. Understandably, the owner of the car said to keep the Ferrari traction control on. The traction control significantly reduced my exit speeds coming out of the slow corners. In the end, I was about 4 seconds quicker in my 944S2 than I was with the Ferrari.

For DE's, I have heard this is a good way to go: Turn PSM off in the dry, but run with it in the wet as a safety net.

Of course, YMMV,
-Z.

James Gunn

My assumption is that everyone would be running with PSM turned off, but that other feature it provides is still needed to have a smoking run.

The one key feature is the simulation of a limited slip -- called ABD which applies brake forces to the unloaded (slipping) tire.

True or not true?

James

cgomez

True. IMO. THe ABD is much needed in the Boxster S. However, I never driven an S without PSM, but I driven a regular Boxter without it and the wheelspin is annoying and slows down the car on tight corner exit. It should be a bigger factor in the torquier S.
Should also work for Schumi or Montoya (Senna can't do much now) as their arms are not long enough to pull them out the window and stop that spinning rear wheel! nor they have tractor brake controls to brake each wheel independently!

Leeds Gulick

ABD is still enabled when PSM is switched off.

cgomez

Exactly, that's why PSM is good. With PSM off with you get "sort of a LSD". Nost as good as the real thing but better than nothing.

BTW, is a shame that you need to buy a GTX version in a Prosche to get a real limited slip.

FlipE

I have heard that ABD burns up your rear brakes if you are autocrossing. True or false?

My car is a 2011 Cayman, 987.2 with PDK and Sport Chrono.

Have not put fresh tires on it yet. Came to me a couple of days ago with RE-11 tires, well-worn, but evenly. At the autocross, it oversteered everywhere. I have two events left this season, so I plan to disconnect the rear sway bar. Start fresh with new tires in the spring, maybe put stock rear bar back on and get a stiffer front bar. Window sticker agrees that the wheels on it now came that way new: "18' Cayman S II Wheel"

Auto_Werks 3.6

RE-11 tires have been discontinued for a while now, so the fact that they are well worn probably means they are pretty old. Probably not a good set of tires to make any setup choices with. I agree that you could disconnect the rear bar to try to milk them for the rest of the season. Start with your current setup in the spring with new tires and then decide what you want to do with the hardware.

I just watched the video of the BS 987 that won at nationals last week. That car has a front sway bar and still has a wheelspin problem. We have a 981S that we run with base suspension, 6spd, and a GT4 rear bar. We don't have wheel spin or oversteer problems.

FlipE

Front tires are DOT 2014 and rears are 2015.

Not making choices that require investment until new tires in the spring. Disconnecting the rear bar is free.

I would never consider using any kind of rear sway bar on my Elise…

But my interest in this thread is the ABD. I had no wheelspin on my test event but I don’t know how much that wore the rear brakes. ABD is on the window sticker.

Z3papa

When I first bought my car, the car was crazy loose oversteer with lots of wheel spin with the old Stones. Since then I've had the car aligned with more toe, transitioned to better tires, and have a FSB on my 718 which is set on soft and have virtually no inside wheel spin or oversteer, but I can induce controlled mid-apex rotation if I want. I'd definitely vote getting better tires. Tuning a car around old compromised RE71R's is a recipe for headaches.

FlipE

Can you share your alignment settings?

My Elise is at zero toe and minus 3 degrees camber both front and rear. I don’t expect I will go that aggressive with the Cayman 2.9.

Z3papa

I'll look for them as it seems everything I could easily put my hands on has disappeared during a recent move. I can tell you front max was ~1.4 camber zero toe/rear 2.0 with 3/16 toe. Caster I'm not sure.

saxonite

For the first event and a half I ran by 997.1 with PSM on, hoping the ABD would help act like a LSD but I seemed much slower than normal when comparing pax times. In my previous car I was almost always top 10 out of 80-100 drivers for the past several seasons. I turned off PSM and instantly dropped 1.6 seconds on a 45 second course. The car felt more neutral to slight oversteer vs understeering everywhere.

FlipE

I think the ABD works all the time whether or not you have the PSM on. I have never had wheelspin cornering on an autocross course in the Cayman. I assume the ABD is working. A bit more front sway bar seems indicated, and I think that will reduce how much the ABD is called for.

A TorSen diff would be a better solution IMHO, but I never went to that expense on my Elise and don't expect that I will on the Cayman as I'm now in autox for fun, not competition points. The days of me turning FTD are behind me.