PDX991

On my commute to work every day, I have to make a sharp 90 degree turn to the left at speed on an off-camber road. My 987.2 would kick it's rear end out if I gave some throttle and it was always fun to induce a little slide. And I'm not talking about high speeds, it's a 30 -35 mph turn going uphill in my 987.2.

Well with my 991 C4S, it's only given me straight tracking with slight understeer every time despite how much throttle I give and how fast I take the turn. So this morning with no traffic on the road, I thought I would try to turn with PSM off. I took it at 20 mph to be safe. The rear end came around with barely any throttle and I did a 180! Ended up in the other lane facing the right direction 5 ft from a guardrail and nearly s*&ting my pants.

I have no experience driving a pre 997 911 and I assume this is the normal behavior of our 911's without PSM. I just didn't think it could happen at such low speeds. Granted it was wet, 46 degrees out and I have the PZeros on, but still.

I'm impressed with how much the PSM corrects the physics of the car. But also completely intimidated by it. And now that I've recovered, I wouldn't mind learning how to do that in a safe environment.

I'm sure a lot of you are going to think I'm a total idiot, and I totally feel that way. I've read about all the instances where people lose control of their old 911's because of throttle lift off but I always assumed that was with much more throttle. I was in 3rd at 20 mph and not accelerating.

NoGaBiker

Glad you're safe! Glad you didn't bend your car!

PSM-Off is a great setting once you've gotten used to it. But sounds like you might want to take the car out to the local high school parking lot in the evening or something and find out how to control the progressive break-away of those rear tires. I love doing exactly what you are describing. In fact, my daily commute involves leaving the office, travelling west for 200 feet to the light, then doing a 180 degree u-turn to travel east on the main road home. For 12 years I've been doing that, in a variety of Porsches. I almost always turn off PSM so I can intentionally break the rear loose, countersteer, and put on a little Chris Harris show before straightening her back up and traveling sedately home like a good citizen. (Note -- I only do this, of course, when there aren't cars around).

I will also note this is the fastest way to make that turn and get up to speed, at least in a RWD Porsche. PSM cuts throttle too aggressively if left turned on.

CSK 911 C4S

PDX991 what mode were you in. Econo, Sport or Sport Plus?

I was thinking even with PSM on and lets say in Sport Plus mode it will let the car get a bit upset without the spin.

Jay-S

The only time I've really had an oh-$#%! moment was under similar circumstances - 45 degrees, wet, 90 degree turn. I gave it gas too early, went an extra 90 degress before PSM saved my bacon. It completely corrected the oversteer and sent my on my way. That was in a Cayman though.

I have driven both the 997 and 991 with PSM off on a wet skid pad. I did not find the oversteer to be that different between the two...pretty fun in both.

Grunty

I expect that warmer and dry conditions would have been different. The pzeros have little mercy in cold.

LexVan

PSM= please save me.

Wet. 46 degrees.
Had a lot to do with it too.

I wonder with PSM off, does torque vectoring also go bye bye??

lunarx

I drive w/ PSM off a lot, but not in rain.
Problem with PSM is it reinforces bad driving habits.
Then when you turn it off and make the same mistakes you find out what was supposed to happen.

Better to drive with it off and get a feel for how the car responds.
Do an AX w PSM off and get a good feel for how to control the car.

chuck911

Thank you so much for this post!

You are not a total idiot, merely another normal guy lulled into complacency by some of the most deceptively effective driver aids on earth. Several times now I have mentioned how the 991 (great machine that it is) is actually making it a lot harder for people to learn to drive. The car just does so much for you, so unobtrusively, it creates the false impression you can do no wrong. Even when people wear out rear brake pads faster than fronts (an obvious indication the systems are saving you!) everyone is all no, no, no, that can't be it, you don't know what you're talking about.

You are right about wanting to learn how to handle this in a safe environment. What you need though is a lot more than a parking lot. What you need is a lot of re-education about driving. You're not the only one by the way. Nobody I've ever met learned the first thing about driving until they took a class. PCA, BMWCCA, Bondurant, Barber, Porsche, doesn't matter they all teach the same thing. Everyone needs it. I needed it. Everyone.

What you will learn, for starters, its all about controlling weight transfer. Its the weight of the car pushing the tire onto the road that determines how much traction you have. Your inputs (steering, throttle, brake) control weight transfer, which in turn determines traction available at the four wheels.

Notice how completely different this is than the usual understanding that steering determines where the car goes. Did steering determine where the car went for you?

Next thing is, mass distribution. This is one of those times when we have to get a little geeky and distinguish between mass, which has inertia, and weight, the fuzzy common sense idea of a force pressing down. Your 987 handled the way it did because of its even mass distribution. It has what we call a low polar moment of inertia- a very low and balanced resistance to change of direction. You hit the throttle, the rear slips and the car slides quickly yet controllably because the main mass is in the center of the car.

991, different story. Most of the time, because so much weight is over the rears, if you hit the throttle the rears have so much traction all it does is push the front out. But, if you go in a little fast, so you have transferred weight off the rears onto the fronts, then your throttle could make the rear wheels spin and give you oversteer. In this case however, while the weight has transferred forward the mass is still all in back- and once that mass starts moving it acquires a very hair-raisingly scary inertia very quickly. If you don't catch it immediately you never will. As you found out.

Short of driving a 964 or earlier 911 I really don't know how anyone stands any chance of experiencing the reality of what I'm talking about. That's why its so important to find a good program and get yourself as much quality instructor time as you can.

drcollie

I used to have my students turn off stability management on track days when I was Instructing them, back when cars first came with that option. And I always used to turn it off on my cars on track days. But as the years piled on, I realized that almost none of my students were used to driving cars without that engaged and quickly got into spins and the like, so now I no longer ask them to disable it. If I'm really hustling a car around a track, I can go faster with it turned off, it gets to do the nanny thing when I've got two wheels up on the track berm and puts on the brakes or cuts off the fuel a little (depending on the car).

I've had 911's since the 70s'. Yep, I wound up back-asswards more than once. Look at old photos of 911's (esp. Turbos) single car wrecks from the 70's-80's-90's. Almost all have their rear end smacked because they lifted and spun it into something. 911's are inherently unstable with that engine out back, so you best not lift in a turn if you have the electronic babysitters disengaged. But that also makes then go 'round the corners like BO Diddley Squat if you stay on the gas. That rear engine layout also makes them stop quicker than just about any other car around when you really get into the brake.

Do a wet skidpad exercise sometime and turn the electrics off. Your Porsche will behave entirely different and with each spin-out you'll laugh and say 'how'd that happen?"

mrhebert

A few years ago,11-12, when lapping Road Atlanta during the early years of the Porsche Driving Experience, Hurley Haywood, our chief instructor, told us in all the classes with experienced and rookie drivers, the only time someone kissed the wall was when they decided to over ride the PSM. So we all took his advice with no crashes. I switched mine off on my 996 C4S during a high speed autocross, and switched ends so fast, I couldn't believe it happened.

Larry Cable

Dont forget that on the Carerra's PSM is NEVER fully off, even when you think its turned off, there are conditions under which it will kick back in (unlike the GT cars where off is off)

Larry Cable

+1 964 RS America and the gen 1 996 GT3 are GREAT cars because they teach you how to extract the most from a 911 platform w/o driver aids its all
about balance and smoothness ...

VIC_50th

Apart from the obvious (wet, cold), the <off-camber> is extremely important to take into consideration.
Agree with everything Chuck911 and drcollie said.
I have the great fortune to have been instructed by Ross Bentley on a number of occasions - read everything you can he writes!

Glad you're safe and your car is OK!

chuck911

Imagine the picture this paints for those like me and the doc who've been around long enough to have seen how far the 911 has come. Okay I can't speak for Duane. But for me…

The 996 was I believe the first 911 with PSM. It also had a much more advanced suspension than the 993. Those early 911's not only required drivers who could actually drive in order to go fast, they required drivers who could actually drive in order to survive going fast! And yet, if we subtract out the vast majority who never got instruction (which, remember, everyone needs) and only look at those who did get instruction, I doubt if accidents or spins are any more likely with a 911 than any other car. In my experience for example I had one student spin a 911, one spin a Boxster, that's it, a draw.

But now look where we are 15 years after the introduction of PSM in the 996. The car has seen three generations of suspension improvement. With the 991 not only was the suspension improved, the whole car was redesigned with wider front track, longer wheel base, and a significant reduction in rear mass bias from relocating the rear axle further back relative to the engine. Every single one of these improved stability and handling, again, over and above the significant improvements made with the LSA (Light, Stable, Agile) suspension philosophy.

And yet, for all that, guys showing up at the track are spinning so much instructors like Duane are giving up on even having them try.

I can't by the way help but think this is in some way related to the videos that get posted on here showing the most atrocious track driving, literally makes me cringe, and yet everyone thinks its great, even though the last one for example destroyed a wheel and tire he was driving so bad.

I guess because nobody can see it. When you never learned what its like when its done right its awful hard to see when its done wrong.

The new cars make it hard, but not impossible, to learn. Its well worth the effort. Not only will you be able to avoid wrecking your car like the OP almost did, but as anyone who's done it will tell you, the better you drive the more you appreciate your 911.

drcollie

I agree with you, Chuck.

The problem with teaching PSM 'off' in a car like someone's $ 100,000 991 is that by the time we can demonstrate the characteristics of trailing throttle oversteer inherent in the chassis we are carrying so much speed that the spin out / catch is way too fast to be comfortable. Back when I had my 1970 911E the car had 155 HP on 2,250 lbs. The 991S is 400 HP and another 1,000 lbs. Cars have become heavier and faster, and I find it far more difficult to instruct in a fast car than a light and slower one. I sure don't want to be the guy that gets a student to ball up his Porsche into the Armco because I was trying to show him how the car would behave when the electrics were disengaged. And I don't want to get maimed in the car either, as going backwards into a solid object at 60 mph is apt to do. So we leave the driver's aides on these days, and I don't think many turn them off as owners. The only time I do is at autocross (if I remember to do it!). If a student wants to try it, I like to take them over the wet skidpad to experiment if its operating that day. That way we can play around at 30 mph instead of 80 or 90.

But its all good. An old 911 is hard to drive fast and well, you always have to be on your game It was a lot of work to hustle one, it wasn't a natural driver like the BMW E36 M3 of 20 years ago. There was a car that anyone could drive fast, it had no bad habits and was delightfully neutral with just a touch of understeer. Porsche has done a remarkable job taming out the bad habits of the rear-engined 911 over the decades and each generation gets better and easier to drive. Truth be told I think a Boxster/Cayman is the superior handling platform for 10/10th's track driving, its just more manageable and neutral with the mid-engine layouot. But the 911 is the Franchise and they will always have it in the lineup.