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This car always did this.... on regular roads with undulations, the car will like.... hop... under hard acceleration and speed in corners and sweepers. I am not talking the old hops like my '70 Buick with the solid axle would do, but these lurches... or ... um.... like the car should have settled but takes an extra wiggle.
Opinions? (BTW... my 2000 Boxster S never did this.)
Peace
Bruce in Philly
BTW, I was driving through farm land in Delaware last night after taking my C2S to Bombay Hook where I did a bit of "off roading"... darn this thing sucks in the dirt... more air filters please. Great roads to enjoy your car and where I got annoyed with the car wiggle. I snapped this guy there... I love Porsches.... track cars as well as dune buggys.
There are a lot of rubber suspension bits in a stock 997 - strut tops, inner LCA mounts, dog bones, rear LCA pucks. Some hydraulic ones too - front LCA pucks and engine mounts. Stock alignment is rather mild for negative camber. Plus the stock sway bars are not that stiff. All in your stock setup is likely seeing camber changes from a mild starting position to something worse during hard turns causing the tire's contact patch to loose its grip for a second.
Start with tire pressure and alignment for more negative camber up front. After that it requires changing out stock parts. Motor mounts are a common upgrade. Then it all depends upon how much you want to trade off a daily driver with a track setup. Sways help. More negative camber up front would be next. Suspension mods get expensive real fast.
There are a lot of rubber suspension bits in a stock 997 - strut tops, inner LCA mounts, dog bones, rear LCA pucks. Some hydraulic ones too - front LCA pucks and engine mounts. Stock alignment is rather mild for negative camber. Plus the stock sway bars are not that stiff. All in your stock setup is likely seeing camber changes from a mild starting position to something worse during hard turns causing the tire's contact patch to loose its grip for a second.
Start with tire pressure and alignment for more negative camber up front. After that it requires changing out stock parts. Motor mounts are a common upgrade. Then it all depends upon how much you want to trade off a daily driver with a track setup. Sways help. More negative camber up front would be next. Suspension mods get expensive real fast.
Yikes.... so it is more than one thing... the sum eh? Hmmm.....
Honestly, I am a bit disappointed with the way this thing handles. It feels like it is alive or something. I have tracked before and know what under-oversteer feels like... but this is nothing like it. The car just seems to be jelly like.
99K miles, new shocks all around, newish sway links, newish lateral control arms in the rear, new lower control arms in the rear (the ones with three connections).
Michellin PSSs, tread is OK, maybe this summer is the last for them.... two - three years old.
It just does not feel like a tire issue.... the car just moves too much.
I've actually felt a hopping sensation at the track similar how you describe, where mid-corner to corner exit as I'm getting on the power, the rear feels like its gaining and losing grip slightly and oscillating between the two quite quickly, but neither understeering nor oversteering. Thing is, I went back a week later with different tires, and that sensation was gone. I've been to the same track with NT01's, R888's, PS2, Pzero, RS3's, and now Cup 2's. The RS3's were the only ones that gave me that feeling and it may have been a pressure or tire temperature issue. Are you feeling this on dry, smooth pavement?
I've actually felt a hopping sensation at the track similar how you describe, where mid-corner to corner exit as I'm getting on the power, the rear feels like its gaining and losing grip slightly and oscillating between the two quite quickly, but neither understeering nor oversteering. Thing is, I went back a week later with different tires, and that sensation was gone. I've been to the same track with NT01's, R888's, PS2, Pzero, RS3's, and now Cup 2's. The RS3's were the only ones that gave me that feeling and it may have been a pressure or tire temperature issue. Are you feeling this on dry, smooth pavement?
Yes,... maybe it is the tires.. To get this to happen, you really have to be on it.... brake-blip throttle...downshift... release on gas hard turn....... yeeeehaaa....
It has done this since new to me at 26K miles now 99K.... still behaves pretty much the same. I kinda think it is the "car".
Wow - great shot of that Indigo - what lens are you dragging around to be able to get a shot like that of such a small bird?
You are obviously a birder-brain to know this bird! Cheers!
All Canon... full frame 5DSr and the 500mm f/4 IS L (prior gen). Shot from my C2S window. I put the window up a few inches, throw a beenbag over, hang my 500mm log out the window and let fly. Gotta shut the car off as the vibration kill everything even with IS on.
The photo was still heavily cropped.
I am a bit of a joke with the bird-nerds I met over the years out there at Bombay Hook or Edwin Forsyth (near Atlantic City) as I am the only geek out there in a Porsche.... I think its hilarious. Fabulous sporting drive home up the coast through farmlands... curves and curves with plenty of visability and virtually no one around.
My car did that last year with the RS3 Hankooks or the V12. I think its the soft sidewalls. Going to a Bstone that has firm sidewalls and the back feels better.
My car did that last year with the RS3 Hankooks or the V12. I think its the soft sidewalls. Going to a Bstone that has firm sidewalls and the back feels better.
Yep, I think that plays a part. The MPSS is known to have soft sidewalls as well to promote rolling over onto the shoulder where the "grippier" compound is. The Cup 2 is similar but not quite as soft. I think this might be the reason why Porsche "stretches" the tires on their performance cars, i.e. a 12" wide rim for a 305 section Cup 2 tire on the GT3, to get the sidewall to be a bit stiffer through tension.
That said, I've experienced the rear end hopping on a hard straight-line acceleration. It was during a hard launch which jolts the rear end down, then I suppose the corresponding bounce upset the rear traction, which repeats the cycle since I was accelerating hard.
I suppose you could experiment with tire pressures as well as alignment. Perhaps taking a look at kinematic rear toe? But yea, maybe it's just a 911 thing. I know the 911 is known for wheel hop under acceleration in a straight line, but I haven't really heard/felt it much during cornering while getting on the power unless it was a really tight 1st gear corner?
Its the PSM. Same feeling you described. Turned it off, that feeling was gone.
My guess too. It's probably the PSM catching and releasing its control over the car. If you turn it off, you'll feel the rear start to move and continue to until you coutersteer into the drift to catch it again. I don't think your '09 is new enough to have torque vectoring (but maybe it is) so the car is applying a wheel brake to make it stop the yaw rotation you started and that's why you're getting this wandering feeling. Go to an open area, engage sport mode, disable PSM and recreate the same type of turn so you can feel the dynamics of the car but not have to worry about an unplanned off-road excursion if you can't catch it in time the first couple times.
Wow, PSM.... I never thought of that. Excellent, thanx... I will give it a try. So then it doesn't trip a dash light when engaged eh? I never noticed it coming on and I do drive pretty hard on occasion.
My wife's Lexus flashes like crazy at the slightest.
Wow, PSM.... I never thought of that. Excellent, thanx... I will give it a try. So then it doesn't trip a dash light when engaged eh? I never noticed it coming on and I do drive pretty hard on occasion.
My wife's Lexus flashes like crazy at the slightest.
Peace
Bruce in Philly
That's my theory and I don't think any light blinks when PSM is interceding as it does in some other cars, only when the system has a failure, and then it's a constant message.
06-13-2016, 10:43 AM
"Hopping" in turn and hard acceleration.
