Perfect.

 

^^Thanks guys.
Revision to 997.2 Turbo's suspension below. Comparing it to this thread almost brings tears to my eyes.
You think someone at Stuttgart has been reading our complaints, or peeking at my interminable rambling & ranting on this thread?

A little surprise at the sway bar revision though (If you've done your homework and read through the incredibly boring posts, you'll know what that sway bar revision implies! LOL).

Regardless, those of us without the Bilstein, if this doesn't convince you... BTW, for the record, I still think you would still need Bilstein for 997.2. I suspect PAG's "marketing plan" for Turbo still hasn't changed and those astounding low 3 sec 0-60 acceleration times mean stiffer springs are even more critical to control front-rear weight transfer (squatting).

>>>>>>>>>>>>>>>>>>>>>>>>>>
http://www.caranddriver.com/reviews/...1_turbo_page_2
The overall suspension calibration has also been revised with stiffer front anti-roll bars, a softer rear bar, variable-rate rear springs that are now stiffer, and a revised calibration of the adjustable shock absorbers controlled by the Porsche Active Suspension Management (PASM) system. Basically, these changes have reduced rear suspension movement during hard driving, with the goal of improving handling stability at the limit without compromising ride quality.

 

1. Coilover versus Lowering Springs: The "suspension's heart" consists of 2 parts: a damper (aka shock absorber) and a spring. You could elect to change both at the same time, which is called "coilover" (spring over the shock absorber) or you could change just the spring, aka "lowering springs." It's called "lowering" because all of these Porsche 911 springs also lower the car 1 inch/24mm.

Coilover is considered the gold standard for a few reasons:
*it's a ideal solution where spring and shock absorber are designed to work with each other (as opposed to lowering springs, where the new springs are used with the old stock damper),
*the height is adjustable,
*possible to corner balance when used with adjustable drop links like Tarett's.
*the shock absorber is of much better quality and design than the stock shock absorber.

Lowering springs offer a simpler and less expensive alternative to coilover, and good ones such as GMG and Techart do get good reviews. There are various reasons that I chose coilover over lowering springs but for some one of the biggest problem with lowering spring is that you cannot adjust the ride height. All lowering springs on market that I know of lowers the car by 1 inch (24mm). For comparison my car is lowered 12mm and I think it's a little too much already for a daily driver because of the front lip scraping.

Second, lowering springs are better than stock because of the stiffer spring rates, but first, it still uses the not so good stock shock absorber, second, it is obviously not-adjustable (you are stuck with the one spring rate and if that is too stiff or too soft for you, you're stuck with it), and lastly, it tends to be designed by a third party, and for me anyway, does not give the peace of mind of something like Bilstein, designed and made by the same company that does the OEM shock. IMHO, coilover leads to less second guessing and buyer remorse.

As far as the rates of lowering springs, companies do not publish rates for the 3 most common lowering springs, GMG, TechArt, H&R, so you have no idea what you are buying. The (unconfirmed) rumor is that GMG is stiffer than TechArt, which is stiffer than H&R, and H&R might be SOFTER than stock. It should be noted that the lowering springs are progressive, meaning there are 2 rates, initial (softer) and final (stiffer), and we don't know which of these rates the above rumor refers to.

Historically, if you look at old posts and users reports, you will see several cases of people using lowering springs at first, then eventually switch to coilover; and *never* the other way around. So although I think lowering springs are better than stock, IMHO it is a much better idea to go straight to coilover from the beginning; you actually might save more money in the long run. A few users have also reported what sounds like wallowing, or a sense of loss of control or instability with lowering springs in high speed cornering. I do not know if this is true, just reporting what I've seen posted.

Bottom line: Lowering springs do work, is cheaper, and is simpler to install, but if you ask a competent tuner, you will be told that if you could spend the extra cash, a complete coilover replacement is overall a better solution and leaves no nagging questions, especially for the hard-core enthusiasts.

2. 997.1 versus 997.2 Suspension: Going through the recent review in my favorite US car mag, Excellence Magazine, I couldn't help but notice that comments from Porsche engineers, and the changes to the 997.2 Turbo’s suspension, very much parallel the ideal of the suspension mods that a number of us have done to the first generation Turbo.
In summary, the changes are as followed:

1. Stiffer rear spring
2. Stiffer anti sway bar: Front bar only for cars without PTV, front AND rear for cars with PTV.
3. Stiffer rear bushing to "control lateral movement." Although I don't know which bushing they are talking about here. Reading this one almost brings tears to my eyes. I mean, this is deep into after-market US-style modding! This has got to involve the rear toe control arm here, I think.
4. PTV. Reduces understeer. I assume improve the rear end "rotation" into corners.
5. PTM: More gradual change and more rear bias; in essence the car behaves more like a RWD cars in corners. Yes the word “drift” was mentioned! (I have some misgiving about this particular change, reducing front traction in a daily driver with 500 hp. Faster at the track yes, but is it safer?)

Since my wife is preparing Thanksgiving meal soon, this post can’t be too detailed. I’ll have more quotes to add, but for now, I am glad that Porsche appears to be receptive to scathing reports on how soft 997.1 stock suspension was and how the stock alignment has too much understeer.

Judging from the numbers, the 997.2 Turbo appears to be right in between stock 997.1 and Bilstein as far as spring stiffness is concerned. Surprisingly, the rear spring is now progressive (Not sure I like this; but there are numerous other changes and I am not about to question Porsche engineers’ decision!). The car’s mission as primarily a daily driver with occasional track time is maintained.
If I have to take a guess based on reading alone, this would be my prediction: With respect to handling, the 997.2 Turbo has more oversteer (from PTV and PTM) and will feel a touch stiffer/tighter than stock 997.1 Turbo. It is however not quite at Bilstein Damptronic level and this mod is as critical for second generation as for first.

There is one major advantage to 997.2 suspension that should be mentioned: its generation 2 PASM system. 997.1 generation 1 PASM has a design flaw: Normal setting is way too soft, and Sport Setting is way too stiff, jittery, and un-useable for street driving. Porsche actually acknowledges this at the time of 997.2 release and true enough, 997.2 PASM is night and day better, particularly the Sport setting: it is much less jittery.

Happy Thanksgiving.

3. Spring Rates Summary: Spring rates are the heart and soul of the suspension system, they tell you the intention of the car/vendor: Is this going to be a street car or is this gonna be a track star :-)? Note that the damper also contributes significantly to how the car feel: a Bilstein PASM with 400/600 springs will feel completely different from a JRZ with 400/600 springs with adjustable bump/rebound settings. This is because the damping forces in the 2 coilovers are different, JRZ has damping forces designed for heavier springs and for more vigorous requirements of track use. Also other factors such as constructions are different; one example: Bilstein re-uses the stock's top mount/bearing which has rubber parts to soften the blow, JRZ to best of my knowledge does not - anyone pls correct me as needed. So although the spring rates give you some important idea, the bottom line is you won't know until you actually drive the car.
Source for spring rates below: Very extensive web research (ie no guarantee whatsoever of accuracy :-) ) and Excellence Magazine. GT3 rates are posted for comparison, and do keep in mind the GT3 is around 300 lbs lighter than Turbo, meaning if anything the Turbo's springs could/should be even stiffer than GT3's. Also, 997.2 Turbo's engine is lighter, making the increased spring rate noteworthy. Anyone with more info please correct as needed.
Spring Rate Unit conversion 100 lbf/in = 17.5 N/mm
Here are some technical data of Bilstein Damptronic coilover for anyone interested:
Front: Helper 80 lb/in spring rate, 60mm length; main 340 lb/in rate, 151.5 mm length; ID 70mm for both helper and main springs.
Rear: Helper 80 lb/in rate, 60mm length; main 565 lb/in rate, 200 mm length; ID 70mm for both helper & main.

Stock 997.1 Turbo:
Front: 206 lbf/in
Rear: 457 Linear

Stock 997.2 Turbo
Front: 206
Rear: 514 Progressive (342 initial, 514 final)

Bilstein Damptronic For 997 Turbo
Front: 340 Linear
Rear: 565 Linear
Helper springs (no contribution towards rate) 115 front, 145 rear

Bilstein Damptronic in my baby, 997.1 Turbo (stiffer springs than Bilstein OEM)
Front: 392
Rear: 600

Ohlins Road & Track For 997 Turbo
Front: 400
Rear: 685

TPC Tractive DDA for 997 Turbo
1. Road & Track version with 343/628 (60/110 n/mm) springs
2. Intermediate version with 457/742 (80/130 n/mm) springs
3. Extreme track version with 571/857 (100/150 n/mm) springs

KW V3 For 997 Turbo
Front: Progressive, unknown final rate, possibly around 300
Rear: 970
For 997 GT3: 285 front/ 970 rear
For 997 C2S: 230 front /740 rear

Moton/JRZ For 997 Turbo (starting min. rates, stiffer if needed)
Front: 500-600
Rear: 700-800

Stock 996 GT3:
Front: 225 Linear
Rear: 550 Progressive

Stock 997 GT3:
Front: 257
Rear: 600

Moton for 997 Turbo from poster Webspoke
Front 750
Rear 1000

JRZ Pro for 996 Turbo from poster pwdrhound
Front 1400
Rear 1500

2018 GT3 RS (the one that beats the 918 at the 'Ring)
Front 570 lbs/in
Rear 915 lbs/in

 

Really interesting analysis THANKS Can!

 

Alex, thanks.

BTW, your excellent review of the 997.2 Turbo mirrors very closely what the numbers and Porsche engineers are indicating: More oversteer for the facelift car, and a little tighter than stock but not quite Bilstein level.

 

Great review. I am wondering if you have driven a 997 GT3 mk1. If so, how do the two cards differ in terms of handling?

 

The car I drove was the GT2, which has an improved suspension system over GT3 997.1 (front components revision). The changes I've done (Bilstein, stiffer GMG anti-sway bar, more front negative camber and front toe out) bring my Turbo much closer to GT2, compared to stock Turbo, but the gap is still there. Turbo is a better street car and GT2 a better track car, clearly one of best in the world.

I could narrow the gap closer with Moton, etc. But I don't want to because it would be too stiff for my intended use.

For Turbo versus GT3, you are not going to find the "perfect" car for everything and will have to "pick your poison," or "set your priority."
If you are to track the car or only use it for weekend canyon runs, then clearly GT3 is the way to go because you won't have to mod much and because of the lighter weight of the car and linear response of the engine.
If you are into taking drives with the wife, drive the car to work, take long distance cruise, then Turbo.
If low end torque and straightline speed are important to you, then Turbo hands down. It's not even close.

The GT3 has to be a "second car" in the garage unless you are masochistic, or very very young . You are not going to drive it daily unless you run out of money and can't afford a daily-driver. The Turbo could function as the only car you have, unless if you live in the snow country.

Incidentally, of the cars I've driven, Porsche GT2, F430, Lambo Gallardo, Ford GT, Corvette Z06, and (old) Viper, the car that the Turbo comes closest to "overall" feel, like stiffness and feedback, but not the mid-engine handling, is the F430. The only thing about F430 is that from the perspective of a Turbo owner, it has very little torque below, like it's missing in action. I ran the F430 at 5000 rpm plus the whole time of my 15 mile or so drive and still felt like the torque was missing. It's an utterly amazing car otherwise, but I actually prefer the Lambo's V10 when it comes to engine response. The lesson for me, again: There is not a single best car for everything.

A stock Turbo is a boring car. However, modded with Bilstein and alignment change, a good exhaust, and a good ECU tune, it could take on an extremely aggressive nature and remains the best dual purpose car in the world, by far. (And of course, there is no free ride; as your gain "aggressiveness," you will lose the "gentleness" of stock. That's why I love it that my GIAC ECU tune could be turned off when I am not "in the mood.") Whatever decision you make, good luck and have fun.

 

Fantastic thread. I just read the whole thing.

Is this suspension set up noisy? Like clunks, etc?

 

David, drive mine sometime, stiffer but not noisy at all.
c

 

Can, if you are ever interested in getting them hotrodded, we only need the fronts and your PASM box. Let me know

 

I'd love to!

 

David, glad you are enjoying reading the thread. As TTSurgeon mentioned: Stiffer, no noise. Some people have a clunking noise at low speed and extreme steering angle (one that you will never see while actually driving); I almost want to call it "normal finding."

Casey, thanks. Very tempting but no plan for now since I don't track the car. Amazing job you guys did hacking into the suspension program (first in the industry!).
For those interested -- and I would recommend for anyone tracking the car to consider TPC's revised Bilstein http://www.tpcracing.com/products/Da...overs-for-997/ :
1. The PASM computer box is easy to remove? Is it similar to how we remove the engine DME?
2. Turnover is how long once I send in my front coilover and PASM box?
3. What's the cost of upgrading?
4. Think you guys could hack into the PTM program that controls the 4WD function? I think people might be interested.

 

you detail was incredible

 

I found this totally cool table http://en.wikipedia.org/wiki/Automobile_handling


Just looking at each scenario and trying to find the explanation is itself a complete basic education in car's handling :-). And check the part of the table that shows you could use tire pressure (within reasons of course!) to change understeer/oversteer behavior: front low pressure, rear high pressure, just like the anti-sway bar's stiffness, to reduce understeer.

I struggle to understand this concept at first and still do :-) but the key word is RELATIVE GRIP: Understeer/oversteer behavior is determined by the relative grip of tire, of the front relative to the rear tires. Let's use one example, how to decrease understeer: more grip in front RELATIVE to rear will decrease understeer/increase oversteer. It has to do with slip angle, more grip = less slip angle = less understeer. Now that you understand that, then know the other way around, more grip in rear relative to front, increases understeer/decrease oversteer.

Understeer is the front having not enough grip, RELATIVE to the rear. It kinda makes sense if you break down the word, under = less, steer = steering action of the front wheel, therefore understeer means the front is not doing the steering that it is supposed to do, from having less grip relative to rear. In a curve, an understeer car, with *under* *steering*, wants to go straight. An oversteer car wants to "steer" the front and swings the rear around. I hope I don't give everyone a headache here.

FWD and 4WD cars tend to understeer (because power applied to the front wheel increases slip angle, causing understeer), RWD cars tend to oversteer. Our Turbo is 4WD, hence it tends to understeer. I should add that while professional drivers tend to prefer either neutral or oversteer, understeer is in general safer for amateur drivers like me/us, and at amateur level it's anybody's guess whether each one of us is faster with understeer or oversteer (you have to test yourself at the track). In fact an oversteering rear engine car, like the 911, could be deadly dangerous. For years and years the 911 oversteers too much with the rear wanting to swing around (has to do with center of gravity of the 911 being towards the rear - this increases oversteer); Porsche engineers always try to reduce this and they finally succeeded in 2007, and I believe the 997 Turbo is the first 911 that actually understeers "too much," as come from factory. There are people who think Porsche overdid and dialed in too much understeer with our 997 Turbo.

I have become increasingly fond of the safety that our understeer 4WD Turbo provides. 2WD 911 such as GT3 and GT2 could feel "eerie" in the curves, same thing with my M3; powerful RWD cars with less understeer could feel, and be, very twitchy and temperamental, where the rear want to swing around and go in front of you :-). Anyway, I am not expert by any stretch of imagination :-), but above is how I understand this concept; anyone feel to correct me as needed.

So to summarize, what could you reasonably do to decrease understeer?
1. More front camber (Simple, effective, works! everyone should do this: increase front camber in stock Turbo to minus 1.2)
2. Softer front sway bar setting relative to rear
3. Softer front spring and shock absorber relative to rear
4. Softer front tire pressure relative to rear
5. Wider front tire
6. Front toe in

Alignment Numbers for GT2

GT2 "street" alignment spec
Front camber -1.3 degree
Front toe +0.7mm (or +5')
Rear camber -1.35 degree
Rear toe +1.7mm (or +13')


GT2 "intermediate track"
Front camber -2.0 degree
Front toe 0
Rear camber -1.5 degree
Rear toe +2.0mm (or +14')


GT2 "full track"
Front camber -2.7 degree
Front toe -1.0mm (or -7')
Rear camber -2.2 degree
Rear toe +2.0mm (or 14')

 

Can-your reviews are absolutely amazing to read and quite interesting. i have a 09tt stock and use it as a DD and was wondering what to do to make the car more exciting and you seem to have very informative answers. The porsche dealer here in hawaii discouraged adding bilsteins and ecu tuning saying that Porsche does it right and there is no need for that stuff.
Where do you notice the big difference in handling with the bilsteins, on highway driving? How does the GIAC tune go from stock to tune and back?