By on August 21, 2012
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This is a great video, and it showcases just how quickly things happen in a racing Porsche… including bad things.

While making my completely ignominious Canadian Touring Car Challenge at Mont-Tremblant a month ago (more on that later) I noticed this gorgeous 993 GT3 Cup running in the Porsche-only IMSA racing series with which we were sharing the track. Quite the looker and although I would conservatively estimate that 20% of all club-racing Porsches use the Gulf color scheme, all the way down to 924s, this one looked really sharp.

This morning, I saw that Jeff Lacina of TrackGuys had posted this video and I immediately recognized the driver: Dr. Bob Seitz. Dr. Bob has won plenty of races and he’s no rookie; still, it’s instructive to see how quickly a rear-engined Porsche can turn around on you.

It’s also important to note that rear-engined cars without swing axles understeer by default. Early Volkswagens and Porsches earned a reputation for “snap oversteer”. This happened because as the car leaned over in the turn, the suspension would suddenly change the angle of the tires on the road, drastically reducing the grip. Since a car leans over on its suspension at a rate determined by spring rate, it was therefore possible for a driver to enter a corner at a set speed and then experience sudden oversteer as the car settled onto the springs and pulled the wheel out from under him. That’s genuine snap oversteer, as opposed to the “snap oversteer” you hear about nowadays, which equates to “I managed to be a bigger idiot than my idiot-proofed car could predict.”

Modern Porsches don’t have drastic camber change in corners. The front end is lightly loaded and as a result steering input at the front end tends to be followed by the rear end after a slight but discernible pause. At the true, genuine cornering limit of the car, that time lag can cause problems with correction. I think that’s what happened here, although only Dr. Bob knows for sure.

PSM and the other Porsche stability aids are designed to address this behavior, which is why it’s not a good idea to turn them off on-track just to be cool. Learn the car using the blinking light as a guide to problematic inputs before you throw caution to the wind. Of course, for older cars like the one shown below, there’s no PSM, so as I found out this past weekend, it’s useful to have a coach with you on-track, even if he sits in the back seat.

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11 Comments on “Ever Wondered Just How Necessary PSM Might Be?...”


  • avatar
    Nick

    Did he take off his helmet or lose consciousness?

  • avatar
    TonyJZX

    that’s a 996 GT3, i can tell from some of the pixels and from seeing quite a few shops in my time

  • avatar
    dejal1

    Nice to see all the track workers come to his rescue.

    Did he have to call a tow truck himself to remove the car from the track?

  • avatar
    mitchw

    JB, how do you think about the limits of stability controls? We hear a lot about the laws of physics not being subject to lines of code.

  • avatar

    Dude, where’d you find a midget driving coach?

  • avatar
    Domestic Hearse

    I hope he’s on his back out of frustration and not injury. Holy smokes, is he okay?

  • avatar
    Robert.Walter

    I have no clue, even after watching the vid a few times, what happened to him…

    That he spun it and went off on the inside of the track I get, but I didn’t see any objects for him to hit, and I was thinking that another car (it seemed like there was one approaching just as he rolled off the tarmac) lost it and hit him (but this was not obvious in the vid shot as he climbed out of the car).

    So what happened? Did some kind of odd decel as he came into the sod snap his neck? (With all that gear, I would have thought he would also have neck support)…

    I’m baffled.

  • avatar
    Gone4Day

    He spins out then just before sliding to a stop, gets hit in the side by another car and knocked over the embankment. Obviously hurt, you can see damage to the rocker panel as he favors his left side climbing out of the car.

    Since he’s off track and nearly stopped when he gets hit, that suggests the other car was a few seconds behind and must have lost it on the same corner. Maybe oil on the track. Probably takes a minute or two to slow the field before its safe for track worker and EMS to get there. Unless you’re on fire of course. Hope the guy is OK.

    Nice contrast to Jack’s other video of the knuckle head crashing on a public road and walking away unhurt.

  • avatar

    As one who started with a rear engine, swing axle car, my sympathies go to anyone trying to hustle even a modern 911 around a race track. The mass of the engine at the end of the car is a disadvantage for everything but straight-line braking. If the tires are to do their best work, they want to be handling more or less equivalent masses at each corner. What a great illustration in this video.

  • avatar
    JohnTheDriver

    That 993 is a 996 ;-} Although I doubt it has PSM. PSM would not have gotten the job done in any case as it would undoubtedly be turned off on race day (funny how race car drivers don’t like stuff that hits the brakes for them.) A combination of PTV and PDCC would have probably prevented the need for that harsh steering input to begin with however. I love videos like this, I find it fascinating to try to sus out what initiated the “snap” (prior to the steering input obviously.)

  • avatar
    360joules

    My vote is oil but I have never driven a rear engine car at that speed. The engine sounded fabulous. Watching him suffer I was thinking, “Please don’t self extricate – please don’t self extricate.” I’ve seen bad things happen when disoriented and injured people stagger around after a collision; even in the weeds. I hope he’s ok. Good presence of mind to shut off the engine.


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