MayorAdamWest

I'm curious everyone's thoughts on traction control for the track? I'm relatively new to tracking, but I could definitely feel the car withholding power when I asked for it. I was driving in Sport+ (PDK in Manual) with the wing up.

simsgw

I agree completely.

As for traction control, Adam. I'd have to ask a Porsche field engineer, but I don't think it's possible to turn it off. We speak of "turning off PSM" but that really just lifts the threshold of engagement to allow experienced drivers more room to maneuver the car at extreme slip angles and rapid body rotations. It still kicks in to save our butt if we do something stupid, and some of the systems that PSM uses are independent and stay active at all times. For example, the anti-lock brake control.

I cannot assert it, but I believe that traction control is in that category. In the S models, we have a locking differential of course and that engages first to do its thing. But I'm pretty sure the traction control kicks in if you manage to spin the wheels despite the locking differential.

Incidentally, I've done a lot of driving without feeling the traction control. I wonder if it was something else causing that sensation you noticed?

Gary

Dr.Bill

As one of my coaches told me - leave it on. If it intervenes (particularly in Sport Plus mode) you did something wrong. If you can't figure out what it was on your own, grab an instructor.

STALKER99

As far as PSM, I think if you turn it off and engage the ABS, then the system turns back on.

I use to turn it off completely on my E90 M3, but I will def be leaving it on with the 991 till I learn and get comfortable with the cars dynamics, first 911 for me. I imagine it will take some time to get fully "in tune" with the car.

My plan for the upcoming track season is
1. Wheels and tires
2. Pagid RS29 pads
3. Castrol SRF brake fluid
4. Most importantly....get as much track time as I can.

Does anyone know the relative thresholds or slip angles the car allows in normal, sport and sport plus modes??? It would be good to know.

chuck911

As good as it is, these things can still cause problems every now and then. I'm thinking of the student who forgot instructions and we found ourselves spinning right down the middle of the straightaway. Any non-ABS car would have continued spinning in a straight line. But ABS does not like full lock-up. It releases then re-engages braking. Instead of spinning predictably, whichever wheel ABS manages to get braking traction becomes a pivot point that sends the car spinning off in a whole new direction. Racers and hardcore track guys will probably have seen, maybe even experienced this at some point. Let me tell you, you do NOT want to experience it! You go both feet in thinking you know where the car will go, then SURPRISE! it pivots violently off in another- random- direction! Instead of spinning harmlessly right down the middle of the track we veered off, changing both the overall direction of the car as well as the direction of rotation- TWICE - before finally backing into the Jersey barrier. Unless something has changed this is still a hazard, and powerful liability forces guarantee manufacturers will never provide a full deactivation mode. So this is just something to be aware of, to understand and hopefully avoid.

Related, if you do spin, with PDK, does anyone know do you have to manually select neutral or does the car protect itself automatically?

shizzle

PSM is a very different animal from the traction control in M cars. When the 991 is in sport plus, PSM is dialled way back. It's amazing how much slip angle you can generate with it. From my experience, PSM only kicks in when you really overcook it, whereas DSC in the M is very proactive (it loves turning on even before turn in). I don't find PSM intrusive at all, whereas it was a pain in the butt in my E92 M3. PSM cannot really be shut off, as it will reactivate if ABS kicks in, and Porsche Torque Vectoring in my mind is really another form of traction control as well and it's always on. I pretty much always have my car in sport plus mode (dampers as soft on street and hard on track), because I prefer the sharper throttle response, so I can't say how the different modes affect it.

MayorAdamWest

You might be right. It just felt a lot like the traction control in my Audi, where it would dial back the power. Maybe it was just a different sensation. I just didn't feel like I had full power during turn between 80-100 in 3rd.

simsgw

I've been thinking about this off and on this evening, trying put myself in that corner and imagine what could have caused that sensation. I honestly can't do it. I think it's one of the cases where you have to be there as it happens.

I can picture taking the sweeper at Fairplex. In my 991, I was taking it at about those speeds in the rain, which should be the perfect situation to feel what you did. The trouble is the car was still in break-in, so I was in manual mode forcing early shifts. I'll have to check tomorrow, but I'm pretty sure that shifting up at 4,000 rpm will have me in fourth gear at that point. We wouldn't expect the sensations to be the same.

I can't do this by analysis, but I can guarantee the next time I'm in a corner in mid-range third, I'll be trying memorize what it feels like. Maybe get back to you, Adam.

Gary

simsgw

Whoa. I've been getting vertigo just trying to picture that sensation, Chuck. Unpleasant doesn't begin to describe the situation. Just to inform our nightmares, can you give us some more details?

• What model and generation was the car? I'd like to figure out which generation of ABS was involved.
• Are you confident the student did it correctly? I have watched people do that without ABS. They don't have the courage of our convictions and whatever we tell them in chalk talks, they apply the brakes, but not hard enough to lock up all four. And of course, the whole idea is take away the directionality of the tires. Locked up, a tire doesn't care which direction it's moving, so it can't whip you around. But with the brakes merely applied, you get lateral forces as well as ones linear to the body but possibly lateral to the track. As your student discovered. If the student was not pressing hard enough to fully engage the ABS that would contribute to the control problem.

A spin without the brakes locked can be quite entertaining (to onlookers). It's always a crapshoot deciding which side to pass someone who spins right in front of your race car. Having a simple-minded ABS essentially creates that same situation.

I'm talking as an engineer you know, because my driver persona threw up his hands at this one. (And almost his lunch.) I am embarrassed to admit that I've only spun a car about four times in my life and three of those were intentionally set up by the instructors at different racing schools over the decades. I say 'about' because I only remember one actual spin and surely there was at least one other over the years.

And I'm embarrassed because I feel like I wasn't... no wait! I remember a second one! Okay, that's three intentional and two where I screwed up. Five! Sheez. Think how many tenths I've given up in qualifying laps in the last 48 years if a car has only managed to spin under me twice. Both of those were Formula Fords and one time was in the rain, so it almost doesn't count. I must be criminally cautious. For a race driver, that is.

I don't mean I haven't "lost it" regularly. Cindy loved to tell stories of a couple of exciting ones, but I always caught the car before it did more than 180 degrees of rotation and usually just 90-100 degrees which stops a car quickly. I've been turned around backward in the worst case, but that still makes a car easy to stop. Well, fairly easy. If your doctor ever complains you have low thyroid, I can recommend that evolution done at speed. Get backwards in a Formula Ford in the rain at 80-100 mph and it will perk up your adrenal glands a treat. That's an occasion I would have gone "both feet in" in better circumstances, but the car was pointed toward a drop-off when last under control. It snapped on me crossing an impromptu stream that formed between one lap and the next in a heavy rain. Letting it follow that trajectory toward the edge seemed unwise, so I kept steering and braked gently down to a speed I felt I could let it snap around forward again. Even in three layers of Nomex, I was cold in the rain until that happened. Formula Fords admit water like a colander. Odd though. I was sweating afterward.

I haven't the slightest idea. I've never been convinced you can damage anything but the tires with the car in gear in a spin, but the whole point of those training spins was to ingrain the habit of disengaging the clutch so I always find my left leg has done that automatically if the car gets any significant rotation on it. I would expect the PDK to protect itself against damaging levels of reverse torque, but I'm not convinced the tires can generate that much torque by sliding backward. If Porsche engineers have the same intuition, then the answer would be no, the PDK won't do anything to protect itself. What that means for car control is a different question. Fortunately, our current PDK is in a car that doesn't require us to go "both feet in".

One reason I asked about the generation of the car that did that to your student is that I doubt you can do that to a current generation ABS. The PSM system takes precedence, and with sensors to pick up body rotation rate and lateral/longitudinal g-loads, it will be selectively braking each wheel to prevent the spin. And if you managed to induce one by getting inside its control loop, I believe it would stop the spin promptly. That would be tough to do though. If paid enough to try, I suppose I would turn off PSM and try to avoid control movements that suggested a loss of control. Certainly, no heavy foot on the brakes. Probably avoid steering corrections, and ... Boy, I don't know. This system has almost a dozen sensors to recognize a situation that calls for PSM waking up, even when that button is pushed to "turn it off." It's very good at staying out of the way when we're doing intentional things, but I'm not sure I could fool it into thinking a spin was intentional.

[Incidentally, I would be hard pressed to see how any ordinary driver could even establish a spin on dry pavement with a 991. Asked to set up an instrumented test, I would create a region of zero-to-very-low traction on a test track so the car would be in full rotation before it slid past the region onto dry pavement that would let the PSM do its job. A landing aircraft can create a condition known as everted rubber hydroplaning that creates zero traction on dry pavement. It is theoretically possible to do in a car, but you couldn't pay me enough to try that.]

I'm tired and maybe not seeing something obvious. Anybody else have ideas about this? We know PSM stays out of the way when we're having fun, but is there any way a student in a current car would manage to get into a spin? I kinda think not, but as I say, I'm tired. I think I'm babbling.

Gary

SB

With so much rear traction in the back on 911, I highly doubt that PSM would be cutting in in third gear. To me, no matter how powerful of a car I drive on track, it starts to feel weaker the more time you spend at speed. Maybe that's what you are feeling?

Manifold

With the Cayman R, with PSM on, I've noticed that the car shakes a bit and feels sluggish when squeezing on a lot of throttle in tighter corners. Even though the PSM lights don't go on, I'm suspecting that the car is intermittently applying rear brakes to prevent too much power oversteer (sort of like brake-based torque vectoring). I don't know about the 991, but I hear that a similar thing happens with the 997 GT3 when PSM is on.

MayorAdamWest

Manifold, that may be what I was sensing. I've never driven a car with a rear differential like this one. Perhaps I'm mistaking the loss of torque for the differential doing its job to best apply power.

jdsc

Hey Gary,

When and where did you do your FF racing. You can pm me if you prefer.

Jim

certified_prime

This thread has some awesome insight into track days. I am particularly interested in the "novice" piece, and can't wait to have an instructor sitting in the passenger seat teaching me technique.

Two questions about tracking and DEs:

1) I saw a requirement for bolting a fire extinguisher "metal-to-metal" in the car. Does that require drilling holes into the floor? or is the harness bolted to something like the passenger seat frame?

2) Helmets. I know I would feel claustrophobic in a full face helmet. Are the open-face helmets allowed? Any drawbacks?

I am eagerly looking forward to getting this car on a track once the weather warms up. My understanding is that the fire extinguisher rule is waived the first time, and the track likely has helmets to borrow, but I'd like to know a bit more before throwing my hat in the ring.

chuckbdc

I don't think you will be required to have a fire extinguisher unless you have modified something to present a fire hazard- but if you do it needs to very very secure as it would be the most dangerous thing apart from your head in a whole variety of accidents if it came loose.

I don't actually know the local PCA policies, but feel that a full face helmet is well worth the added protection to the parts of faces that really hurt and look ugly if they hit anything. Re claustrophobic - with good instructors, I would guess that you will be so busy imbibing so much information that you can use in real time, be so focussed and be having so much fun that you won't have time to be. (I appreciate that like mileage, your adrenalin may vary, but I would bet the helmet would become a non issue fast).