Crown

As a rule I don't put much stock in anything one vendor says about anothers product. They clearly have a negative bias. GMG is good stuff, and so is Techart and H&R. And the last time I checked Porsche was using H&R as their spring supplier on the GT2/3, so they must know what they are doing.

Doug

Houston, Texas USA 

997TT

As a rule I don't put much stock in anything one vendor says about anothers product. They clearly have a negative bias. GMG is good stuff, and so is Techart and H&R. And the last time I checked Porsche was using H&R as their spring supplier on the GT2/3, so they must know what they are doing.

Doug

Houston, Texas USA 

997TT

track vid

0-300kph

chasing a 997GT2

So far so good, about 10k miles, and my car had 20k on the odometer when I put 'em on.

The setup is phenominal at the track with R cmpd tires, I prefer cups to corsas having run both.

Very interesting read, thanks to exemag for checking in on the 'spring thing'. I can tell you my gmgs are stiffer than the HRs, but the Hrs do great on the track as well. There is something to the softer might be better theory, Remember the Ruf r Turbo conversion goes with a softer spring rate than stock, they say the car has better control esp on a irregular track surface.

c

Chris '07 997 TT Midnight on Sea

Farnbacher-Loles prepped!

hyper1:
bingo that is exactly what i was thinking, how can hr be softer then stock, and shorter, but what do i know i am just an engineer :) so are the hr springs actually shorter then sotck, or is this a anoter rumor!

Enclosed is a picture from an old Panorama article that shows the springs from different versions of the 996. My thinking is that lowering springs, if they are stiffer than stock, then they have to be shorter un-loaded. OTOH, if they are softer than stock, than they may or may not be shorter un-loaded.

Didn't mean to say which spring is better as far as GMG, H&R, or Techart, if I *have* to pick one, I might just go with GMG; just wanted to point out that the rumor of H&R might not be true, especially if it comes from a direct competitor.

Regarding Techart spring, "eclou" has this before switching to the Bilstein. You might want to check with him for his opinions.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Some more beginner's level info that hopefully will keep you informed. Please keep in mind this is not meant to turn anyone into a suspension tuner.

Enclosed is picture of shock dyno curves of the PSS10 version of the Bilstein shock absorber. I’ve been looking for it for a long time &only recently found it on Bilstein Germany's web site (duh). The PSS10 is the version that has a mechanical knob that allows you to select any one of 10 pre-set damping choices. Unlike the Damptronic version, it is not PASM compatible and obviously you need to get to the coilover to change its setting. In a way, it is BETTER than the Damptronic that everyone uses as it allows for more choices.

Horizontal axis is velocity – of the piston shaft, not the car -- in m/sec, and vertical axis is the damping force in Newton. Upper half is the rebound damping curve, lower half  the compression. Note here that the curves of the PSS10 are coupled – if you select the highest compression damping setting, you are "stuck" with the highest rebound damping setting. This coupling is a complicated issue that is beyond the cope of this discussion. Suffice it to say, not everyone agrees with this approach and there are more advanced level systems (eg Moton) that offers independent compression and rebound curve.

At the same time I should mention that I’ve ran across posts by experienced drivers seemingly never happy, forever searching for the *one* correct setting of their multi level adjustable advanced coilovers, so the limitation of the Bilstein could most definitely be an un-expected advantage especially when amateur drivers are involved. And of course, from my previously posted pictures, you already know who the test driver is for the Bilstein system is. Don’t think about arguing -- LOL.

Of course the “problem” with this curve is that no one here owns this version. We all have the Damptronic version that offers 2 levels only – Normal and Sport (Firm). The question is then: Which one of these 10 curves do those 2 settings correlate to? Let me check with my Deep Throat at Bilstein USA.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

can

i am assuing the pasm has a range just like the above chart, and adjustable bilstein, for e.g normal mode 1 to 5, sport 5 to 10 settings, i am also assuming this is varried by the pasm input to the shocks , with variable voltage ? unfurtunltely one has to depend on pasm making the decision verses fixed setting on the bilstein adjustable. if one would design the pasm perfectly then i would say pasm would be the optimal choice, but its not now. I think the pasm shock metallic fulid or someting that gets energized by variable voltage , not sure

regards

Ronnie

hyper1:

can

i am assuing the pasm has a range just like the above chart, and adjustable bilstein, for e.g normal mode 1 to 5, sport 5 to 10 settings, i am also assuming this is varried by the pasm input to the shocks , with variable voltage ? unfurtunltely one has to depend on pasm making the decision verses fixed setting on the bilstein adjustable. if one would design the pasm perfectly then i would say pasm would be the optimal choice, but its not now. I think the pasm shock metallic fulid or someting that gets energized by variable voltage , not sure

regards

Ronnie

We are straying closer and closer to the limit of my limited knowledge. My understanding, or maybe speculating :
Internal valve is the basic mechanism. This is true in the stock Turbo coilover (supplied by Bilstein per web site), in the Bilstein Damptronic, and I suspect in other typical modern day shock absorbers at consumer level.

Damping force is adjusted by activation of a valve, nothing exotic. It is a bypass valve that opens in SOFT mode and closes in HARD mode. When the bypass valve is open, there is an additional "escape route" for the damping fluid to go through, therefore the damping force is reduced.

For Bilstein Damptronic: Nope, only 2 curves, and no automatic jumping between the curves. At least per my amateur level uderstanding of Bilstein US techs. (I believe that  that no other suspension company currently advertises such automatic adjustability. All require driver's input by button in cockpit or button on the shock absorber that activates a valve.)

I am well aware of Porsche's advertisement that there is some automatic (key word!!) adjustability/adaptability even WITHIN the 2 settings of  NORMAL and FIRM of PASM. I have my doubt that I will touch on later -- but for now I have a question to ask you (or anyone who wants to jump in):
Do you know if any other car manufacturer advertises the same capability? Driver's selection with a button is common place. But... what I am asking about is a car sensing road surface quality and AUTOMATICALLY changes damping force?

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Excmag,

I just read your 'book length' forum entry from 12/30 re suspension tuning on TT's. Very helpful and informative. I also didn't realized that the editor of Excellence lives in the Bay Area. One of the best spots on earth for sports cars.

The writeup comes at a perfect time in that, after reading some of the posts from Cannga,  I just indulged in a Damptronic/H&R (roll) upgrade for my 997S Cab, and am in the fine tuning phase - ride height, corner weighting and alignment. I'm sure for the experts, starting with a Cab as a base causes a raising of one or both eyebrows, but see previous comment about the Bay Area being a great place to drive an (open) sports car.

I'm just an amateur, and don't currently plan to track the car, but the changes are remarkably transformative, as Cannga notes. It's both softer and firmer at the same time. At first blush, I do worry that an even stiffer set of sway bars would be preferred, but I'm really looking forward to finalizing the setup after is all settles down. That said,  I'm already stunned that Porsche doesn't make the Damptronic either standard or optional components for the car. Like you (I think), I question the value of the PASM system. It's hard to believe that dynamic revalving can work with a single spring type - and so everything must be a compromise. But the PASM with Damptronic (both standard and firm) seem a much better solution than the stock one.

Anyway, thank you again, and any tips and recommendations on this setup would be appreciated.

Well, I took the input provided by a number of helpful forum members (across a number of Porsche-centric sites) and spent the better part of today lowering and balancing the car - as best I could - prior to getting the final work done at the alignment shop. Why? Because it's fun putting a wrench to such a great car.

By way of background, I've been reading and planning on improving the suspension of my 2005 997S Cab, and decided on the Damptronic coilovers and H&R sway bars. I decided that doing the install was beyond me, but the local garage, who does do work on many Porsche's and an eclectic collection of exotics did the install but spent no real time attending to any fine tuning. In addition, they found that the car needed new front rotors and pads, so I had them install a set of braided stainless brake lines while they had the patient open. After a few quick drives, I strongly endorse this low-cost mod.

I chose to lower the car about 18mm from stock and, from a practical perspective, that seems to be about the upper (well, lower actually) bound of driveability - making it up driveways, over speedbumbs and the like. In a few days, after driving and letting it all settle, I'll take one more set of measurements and, if it all measures as set today, I'll have it aligned.

Even after just the initial drive, I think that the Damptronics/bars mod is the best price/performance enhancement you can make to the 997(s). As great a car as the 997 is, stock form it is pretty sloppy in 'normal' PASM mode (the nose bobbing, the yawing under hard cornering), and useless in 'firm' PASM mode (so firm that the tires seem to lose a lot of contact with the road). It's much different now. Driving impressions to come after a few days of familiarization.

Here are a few pics of today's fun:
1. The 'before' photo - with the new stainless brake line;
2. A low-cost digital micrometer made it easier to make the adjustments;
3. Every auto geek needs a lab notebook for their experiments
4. Someone gave me a tip to pre-load the driver seat with my weight before making the adjustments
5. The final (for now) look of the car.

If you need some auto-therapy, I highly recommend both the mods and taking a few things into your own hands. It was a great excuse to buy a few tools, a nice way to spend an afternoon (while watching the NFL playoffs), and the sense of bonding with your car having done a bit of tune-to-taste.

Verde

Wow congrats and I am in awe. I didn't know there is another handy man lurking. (You corner balance the car yourself?)

BTW, no raised eyebrow from me regarding having a Cabriolet. I had a 997S Cab, white also in fact -- in other words it's exactly like your car, as a loaner recently while my Turbo's clutch slave cylinder was being changed (Turbo owners NB: This could be a "design flaw" and I've seen a number of other cars with same problem.) and I must say that I ABSOLUTELY loved it! I didn't know driving top down -- 11 pm on 405 -- could be so much fun, and the car to me was as much a sport car as any other Porsche I've driven.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Alex_997TT:

I thought PASM adapts to the road type and driving style? If so the Damptronics are not just 2 settings...
............................
AM DBS and Nissan GT-R both use Damptronics I believe and they have a range of settings from the reports I have read. So I am sure the B16's in conjunction with PASM have more than 2 curves.
--

Interesting question that actually opens a can of worms. Yes Bilstein tech help in the US has told me on more than one occasion that there are 2 damping curves with the Damptronic and there is no ability to automatically adapt and jump between curves. In fact they appear puzzled when I read them the ad material from Porsche brochure (they offer an explanation that I will touch on later).

Which brings us back to the “adaptability” of stock PASM: I must admit on this I have more questions and no answer. But for the fun of it I will express my opinions. First let me make clear the distinction between the 2 features of stock PASM that we are talking about:
1. The cockpit button that selects between NORMAL and SPORT. I have no problem with this. Drives selects either soft or firm and an internal valve within the shock absorber opens or closes to change the characteristic of the damping curve. 2 curves in other words.
2. “PASM adapts to the road type and driving style.” Note that this is quite different from number 1. Here we are talking about an automatic (key word!!) adjustment and an ability to adapt.

Note that 1 is common in many car manufacturers, but 2 is extremely rare; in fact does anyone else claim this ability? I could be wrong but I don’t recall any manufacturer OTHER than Porsche claiming this. If you have time please read about the Aston Martin DBS again and see if I am wrong; as far as I could tell, it’s 1, and NOT 2.

It’s also interesting to compare what PAG ad writer writes in the brochure against what a driver actually feels.

From the brochure:
If Sport mode is selected, for example, the suspension is set to a harder damper rating. If the quality of the road surface falls below a certain threshold, the system immediately changes to a softer rating within the Sport range.

From my actual experience:
Sport mode was rock hard no matter how slow I drove. Likewise, Normal mode was irritatingly soft no matter how aggressive I drove. If PASM indeed adapts as Porsche says, I would expect the Sport mode to soften at SOME time – it never did. AND I wouldn’t have to change to Bilstein!
My experience parallels reviews in magazine and users experience IMO. We all do the "2 button dance" when we start the car: Sport on, PASM off. Why? Because the Sport setting is very hard and does not soften or adapts no? And I recall reading writers stating how stiff the Sport mode is. No one ever wrote about noticing the character of the suspension changing.

So I don’t know if I am right, but I have this suspicion:

1. If PASM does adapt to road surface as advertised, the effect is extremely subtle. At least, it’s never as large as jumping between the 2 curves.

2. Or it could be Porsche ad writer going wild and was simply writing about an inherent character in all shock absorbers and makes it sound like something exotic: The change of Damping Force (Y axis on the curve) as Piston Shaft Velocity varies (X axis). (This actually was not really my opinion but was suggested by someone with some knowledge of suspension systems.)

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Verde,

Well, I gotta live somewhere, and I'm with you: it's hard to beat the roads and weather mix here in Northern California. Plus, I'm from here and am fairly determined to stay here.

That's a great looking Cab! I've had some very good drives in 911 Cabrios over the years on both road and track (yep...), and the "real-world" performance hit on the street is ridiculously small --- and more than offset by the experience. If anything, there is a small dynamic advantage that goes to modern Cabs in terms of "911ness" because of where the extra weight is. I first discovered this while driving 996 C2 coupes and cabrios back to back at Infineon. No one really talks about this, but I've felt it again since. Very hard to measure, and you're approaching the limits when it is most obvious. It's in the *way* the rear transitions. Thankfully, I find 997 Cabs a lot more appealing visually than 996 Cabs... I still prefer 911 coupes in terms of looks and I have a vintage open Porsche to do the "let it all in" thing, but I think a lot of people miss a great time to be had in the 911 cabrios for that reason alone, and the (misplaced?) idea that the coupe's performance advantage is really worthwhile for how they'll use the car.

But I digress. Kind of. 

As for tips, I'm not sure anyone can give you good ones over the internet without driving your car, or at least getting VERY detailed impressions with re: to what you're feeling and what you want to change. Then there's the old "what I like" thing with regards to suspension. Gets back to the black art aspect.

My experiences tell me that, more often than not, S Car Go racing gets damper tuning better than most. But there are plenty of other shops with good experience, too. I am not comfortable "endorsing" any of them, though I know the above could be taken as such.

As for Porsche offering Damptronics, well, I think PASM Gen 1 was a learning experience. Remember that engineers were quoted in our magazine as saying they were still tweaking the programming right up to the very last minute. Some of my experiences suggest that PASM programming (esp. in the GT3) was tweaked IN production, but we'll probably never know/get confirmation. As with early 997S rear suspension bushings, superceded is a good but mysterious word. 

 PASM Gen 2 is very impressive in my experiences thus far. I think I still like fixed dampers for fast backroad work, but I am now questioning that. The lastest PASM is far more transparent, and some of the brilliance I've long associated with Porsche damping is certainly back. As for Damptronic from the factory, I think that's called Sport PASM... ;) A test between two identical 2009 997Ss with Sport PASM and Damptronic would be very interesting. But I suspect very difficult to put together and do right.

 Best,

 pete 

Pete,

Once again thanks for the many insightful comments, such as the one on PASM development.

I am into high-end audio & we are into comparison. A review of component A makes more sense when it is compared against a competitor, component B, especially if B is a well known "standard." For some component review, such as interconnects (yes that's correct, interconnects ) it is almost meaningless -- to me anyway -- to review an interconnect without some sort of comparison.
What I am trying to get at is I wish to see more such type of articles in your magazine. Imagine how cool it would have been had you driven the GMG Turbo as well and compared it against the Champion Werks1Turbo? How about Bilstein versus KW? Another interesting article would be a comparison of different exhaust systems. If anyone manages to pull these types of articles off, I think it would be Excellence. You are in the heart of USA Porsche country -- California .

As for the Turbo for orthodontist observation -- LOL & thanks for the chuckle. I "resemble" that remark. It is a complete puzzle to me why an option for a more sporty suspension is not offered for the Turbo, and who at Stuttgart has made the decision to make 997 (& 996) Turbo so soft and comfortable. Goes to tell you, it's all about the $.

I also was in mild state of shock (and amuse) when I saw your remark on the chrome Turbo badge. Bingo! So I am not the only one so bothered by the chrome badge. What on earth is that all about?! Fortunately, http://www.bumperplugs.com/BPindex.html does come to the rescue and because of that: --- hah!

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Thank you Cannga. I try, feeble as my rookie attempts may be. But factually speaking, as best I understand what corner weighting is, I don't have the tools to do a proper corner weighting.

In corner weighting, I'm told that you set the height of each corner coilover so that the weight of the f/l wheel + r/r wheel = f/r wheel + r/l wheel. That is, the sum of the tire weight of the diagonals are equal. I don't have scales or other weight measurement devices to do this. Or I'd be all over it.

It may be that getting the relative heights very very close to the original minus the lowering amount (accounting for the driver weight) would be an excellent approximation, but it's a surrogate measurement.

If I'm wrong on this, I'd love to know. I'm considering paying for corner weighting (even though it's superfluous) when all of this is done. If I've already done it, that would save $300 or so.

Thanks,

Verde

http://autopianviews.blogspot.com/

Wow congrats and I am in awe. I didn't know there is another handy man lurking. (You corner balance the car yourself?)

BTW, no raised eyebrow from me regarding having a Cabriolet. I had a 997S Cab, white also in fact -- in other words it's exactly like your car, as a loaner recently while my Turbo's clutch slave cylinder was being changed (Turbo owners NB: This could be a "design flaw" and I've seen a number of other cars with same problem.) and I must say that I ABSOLUTELY loved it! I didn't know driving top down -- 11 pm on 405 -- could be so much fun, and the car to me was as much a sport car as any other Porsche I've driven.

--

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Oh, and BTW, I didn't think you were being critical of the Cab. It's just generally viewed as a lesser 'drivers' car. And in theory, it is. There is, even in the 997 series, a bit of windshield frame shake (evidenced in the rear view mirror) and a tiny bit of creaking in the door frames. Now exacerbated by the Damptronics' firmness.

But the feeling of driving an open topped version of the Porsche makes it feel even faster and more competent than it likely is. Someday, maybe a supercharger to put it completely over the top. For now, it's just an excellent car.

Thanks again.

In case you are curious how the shock dyno curves correlate with your driving, and to understand how coilovers differ, some more amateur level info:

Remember that similar to having stiffer spring, higher compression damping causes more overall stiffness (this is how stock PASM increases stiffness). In other words, as you increase the spring rate in your car, you actually might want to decrease compression damping for same overall level of subjective stiffness.
As mentioned several times, setting suspension is black art, reserved for the best of professionals and I merely mention this for “fun” reading, not for anyone of us to turn this into a DIY project. LOL.

The horizontal axis is the speed of the piston shaft. Events such as acceleration, cornering and braking cause slow compression of the spring/shaft, as your car squats, leans, or dives. This is referred to as low speed bump (bump = compression, not a bump on the road). To my thinking, this is related to the "good" effect of stiffer suspension -- the sporty handling.

OTOH, when you hit a curb or pothole, the spring and piston shaft is compressed at high speed, also known as, of course, high speed bump. This is related to the bad effect of stiffer spring -- the harsh ride.

http://www.pca.org/panorama/sample_article_3.html
I've marked the graph using values from this excellent article -- written by, of all people, an anesthesiologist and a radiologist. 

The KW Variant 3 coilover for example, allows one to adjust low speed bump; whereas a 4 Way Adjustable Moton allows adjustments of low speed bump, high speed bump, low speed rebound, and high speed rebound. From my reading of past postings, simply spending mega $ for a sophisticated 4 way Moton definitely does not guarantee happiness. It should be reserved for experienced & very advanced level drivers and tuners. I believe that for a majority of amateur drivers, the simple Damptronic might actually be the best solution.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

+1. I'm actually relieved that there are few coilover options available that preserve the PASM function. The more I research this, and measure/modify/balance - then 'rinse and repeat', it's very clear that having fewer degrees of freedom is an asset for this amateur. Moreover, I suspect that the number of true amateurs is larger than people perceive.

The skills required to deal with high/low speed damping and compression likely exceeds the analytical and sensory skills of most owners. Even if you have a great shop as a partner, the owner has to be able to convey the sensory input that a given collection of settings provide, so that improvements can be made.

Nonetheless, if I had my druthers about configuring my 'S' from the factory, I'd prefer to omit the PASM, and purchase the car with a set of coilovers that are optimized for, aggressive street driving but still have 10 'clicks' or so to allow experimentation. More variety than the binary PASM settings, but no comprimises in the default setting.

That said, it's a great upgrade and I thank you (Cannga) for having taken the time to detail the process and results. It allowed me to come up to speed on this topic more quickly than if I had just scanned all of the less analytical forum entries. It's also why I've tried to 'pay if forward' by adding some more detail in my blog. Hopefully, many others will benefit.

You are welcome, Verde.  Yes the bump and rebound setup clearly involves a lot more than just "is this stiff enough, is this too stiff, etc."  For example, one must think that the relative front to rear suspension compression/rebound settings have major effect on tire grips front to rear and therefore car's behavior in corners. I remember reading how motorcycle riders set the rebound damping by observing how their bike behaves during turns; gives me a headache just to think what's involved in setting up a car.

 I previously mentioned how PASM works and why I was somewhat critical of it, at least as currently implemented; the Bilstein curve now gives a graphic explanation (or speculation ) of what's involved when one pushes that PASM button.  As mentioned on page whatever LOL of this thread, one could increase overall stiffness by changing to a stiffer spring, or, by increasing compression damping. The former is in general the conventional route, the latter is how all cars with cockpit button do it. In case of stock Porsche PASM, I am thinking the stock spring is so soft that to compensate, the compression damping must have been increased to a level that is simply too high to be of use.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Verde:
Cannga, are you sure that the chart you posted (above) represents Damptronics curve's or are they the settings for the non-PASM version of the shock? It just seems odd that there are discreet 'level' in the Damptronics that match the number of 'click settings' of the non-PASM unit.

Hi Verde,

Never mind about the Bilstein, I just now realize (duh) that is the great Ford GT in your avatar, we must talk about it first! I *LOVE* that car; even went on ebay to look at it. How about a comparison between handling traits of Porsche versus Ford GT? How much are they selling for nowadays? Any problem as far as reliability? Why do you get a Porsche in additiion to the GT?

Did you know I wrote the following about your Ford GT?  Was I close with my evaluation or do you think it's all BS? 
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
http://www.rennteam.com/forum/thread/462492/Re_Bilstein_PSS10_Damptronics_A_Must_For_The_Tur/page5.html#462492

Over the weekend I participated in an event organized by Road & Track which allows me to drive 6 cars in succession: Lambo Gallardo, Ferrari F430, Ford GT40, Porsche Stock Turbo, Corvette Z06, and Dodge Viper.

I had deliberately set up the drive to follow my major recent mods, Bilstein suspension, GMG sway bar, and Cargraphic exhaust change. The goal is dual: One, to "calibrate" my modded car against a stock Turbo in order to confirm the changes are beneficial, and two, to compare it against other world class sports cars. 

Ford GT40: I absolutely LOVE everything about this car. I like the styling inside and out; the thing screams "race car"! Steering is heavier than Porsche Turbo, lighter than Lambo, overall so nicely weighted and with fantastic feedback; this is my favorite of the day. Car feels wonderfully stable going through corners, again the best of all the cars for me. The Ford GT does have some lag in engine response and does lack the nimbleness and agile feel of some of the competitors. It's also very stiff, cumbersome to get in and out, and obviously will not function as a daily driver. The reverse light was on the whole time I was driving the car, a sign of things (reliability, gremlins, etc.) to come? It would not surprise me if the price will go up from here and the car will be a collector item in the future.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Oh btw, yes you've done your homework: the curves are for the Bilstein PSS10, not the Damptronic. I am using this here because this is the ONLY shock dyno I've found of any Turbo after-market coilover (these things are very rare, no kidding). The Damptronic uses 2 of those curves. UNOFFICIALLY, I've been told the top and bottom curves are used in the Damptronic. But this is from the help desk of Bilstein USA, not officially document from Bilstein Germany.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

cannga:

For those following this thread and new to suspension mods, let me summarize what I've learned in case you are interested. There are 4 common mods that people have added to the Turbo, with number 4 probably the least frequent:

1. Front camber adjustment to reduce push/understeer. Stock is -.4 or so, a common target is about -1.3.

2. Lowering and stiffening the car. 2 ways to do this: With coilover such as Bilstein, or lowering springs...

3. Stiffer Anti-Roll Bar (the drop links that connect the anti-roll bar to the suspension are sometimes also replaced).

When I posted the above 7 months ago, someone (Alex) asked the very valid question that, which of the top 2 changes, Bilstein versus alignment changes, is responsible for the dramatic improvement in the Turbo’s behavior. At the time, I said Bilstein, which now seems to me like the wrong answer, or at least the wrong way to approach that very good question.

In retrospect, the simplistic answer I gave, that Bilstein was the "star" of the show, was partially wrong for the following reason: you can’t really compare the 2 modifications because they affect 2 different aspects of a car’s handling, which are, a. overall body/chassis control (Bilstein), and b. cornering and turn-in behavior (alignment changes). As always, I don’t claim to be a professional, just sharing amateur-level experience here:
Bilstein: When you accelerate, the stock Turbo’s squats; when you brake, it dives; in corners, it leans and its rear end has vertical & lateral motions. The Bilstein helps to control these motions, which to my thinking are related to the car’s body controls, in corners obviously, but majority of the times, it involves “straight line” behavior.
Alignment Changes: To me, alignment changes affect more or less the car’s behavior in corners. How the front of the car turns in corner (understeer), how the front responds to steering input (turn-in response), and how the rear end rotates.

If you are new to this and have some trouble understand what I am talking about, I encourage you to take test drives in the C2, or any RWD Porsche. (I love comparison drives; they have been critical to my learning.) I think your experience would match my observations below:
1. The Turbo, as set up from the factory, understeers. It is beyond the scope of this post to explain in nit picking details, but basically if you approach a corner at speed, the nose wants to go straight. To me, the Turbo does this more than both the C2S and the GT2 that I’ve driven.
2. Turn-in behavior: The steering of the Turbo is stubbornly straight. The good thing: Great & solid center feel. The bad thing: If you move from center, it wants to go back straight. This is different, in a bad way IMHO, from both the C2S and the GT2 that I’ve driven.
3. Rear end rotation: It is extremely hard, actually impossible, to get the rear end to rotate in stock form. The car just wants to go straight. It is safe behavior and I understand why Porsche set up the car this way, but personally I would prefer more rear end rotation. 

The 2 alignment changes that I have made to my car are: increasing negative front camber to minus 1.2 degree, and change the front toe setting from toe-in to slight toe-out at minus 0.02 degree. The first change (front negative camber) is common among enthusiasts, but the second (front toe out) I’ve only seen in race/GT3 forum, and is used for selected drivers by (at least) some very well known tuners here in Southern California, including mine. My tuner (a great and very careful one) was hesitant to do the toe-out for me, probably because I don't track and I am only a beginner level driver, but I "pushed" him towards it because I was curious and wanted to learn, with the idea that I will set the toe back to factory level eventually. As it turns out, there are pluses and minuses, but I am now having second thoughts about going back to the factory toe level at all and I do "get" what the tuners and track guys are trying to do with this setting.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Table (thanks Alex) to show better the alignment changes in my car . Very simple really, both changes are in the front only: more front negative camber, and front toe-out, a negative number (stock is toe-in, which is positive). Watch the unit, some are in minute, some in degree.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

cannga:

(I love comparison drives; they have been critical to my learning.) I think your experience would match my observations below:
1. The Turbo, as set up from the factory, understeers. It is beyond the scope of this post to explain in nit picking details, but basically if you approach a corner at speed, the nose wants to go straight. To me, the Turbo does this more than both the C2S and the GT2 that I’ve driven.
2. Turn-in behavior: The steering of the Turbo is stubbornly straight. The good thing: Great & solid center feel. The bad thing: If you move from center, it wants to go back straight. This is different, in a bad way IMHO, from both the C2S and the GT2 that I’ve driven.
3. Rear end rotation: It is extremely hard, actually impossible, to get the rear end to rotate in stock form. The car just wants to go straight. It is safe behavior and I understand why Porsche set up the car this way, but personally I would prefer more rear end rotation. 

Subjectively, the result of 1-3 above is that the Turbo feels un-natural and a little "dead"  when it enters a curve. It doesn't follow the curve, instead wanting to go straight, and perhaps as result, it leans a lot. In addition, when you apply throttle coming out of a curve, the rear end doesn't rotate so it's so much harder to perform a power slide (am sort of kidding with this last one).

The car now feels "alive" , when you move the steering wheel, it responds and turns quickly, and has more willingness to turn, and the car's body & rear end rotates nicely to follow the curve. (BTW, another very noticeable effect is the steering wheel effort now feels much lighter.) IMHO the alignment change makes the car much more similar to the GT2 when it comes to turn-in response (very quick and responsive in the GT2) and corner behavior. It is now so much more fun on twisty roads and feels very fast and responsive. True also, as it feels more sporty, it also has become more edgy: There are 2 curves, a 43 mph and a 71 mph one, that I've done hundreds of times as they are on my way to work; I am now perhaps faster in the 43 curve because the car appears to lean less but slower in the 71 just because, like the GT2, it feels like you have to pay attention at the edge or the thing is going to give, and I get scared easily.

I should also add that it's now a little hard for me to tell which one does what as far as front negative camber AND front toe-out alignment change, but it seems the front camber change reduces understeer, while the front toe out is what causes the steering to become so much more fun & responsive.

I am definitely coming towards the end of modding my suspension; from now on it's more or less tinkering about for the sake of playing around as the key work has been done. As you could tell, despite of much "talking," the changes I've made are rather conservative and minimal -- the 3 small steps to Nirvana LOL. In return what I have is a car that is still close in spirit to the original Turbo, yet night and day more aggressive in nature: A ferociously fast beast with a nuclear power plant for an engine, and handling and chassis dynamics to match.  I know my adventure has been successful because I do miss my car very much every couple days that I don't drive it.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Sorry for the delayed response, but have been on some biz travel. Finally got a chance to catch up. First things first:

I now proclaim the suspension upgrade for my C2S (Cab) complete.  I've taken a minimalist approach (for now) going only with Damptronics and sway (H&R) bars. By the way, I don't know whether it's because I chose H&R (versus GMG) or it's an 'S' and not a 'TT', but the bars I received had no adjustments in the front, and only three settings in the rear. In some respects, it simplifies life in that there are fewer setting combinatorics to play with, but I would have wanted more adjustment options. I've tried to follow Cannga's guidance to the letter, with the coilovers, stiffest sway bar setting in the rear (nothing to adjust in the front) and a GT3-like alignment. This was the last step so a few added comments re this phase. On my 'S', I was only able to squeeze about -1.0 degree of camber our of the hardware. I did not choose to upgrade the shock tower components to give me more adjustability so that's about it for now. And for an early poster, it is certainly not true that the alignment provides 75% of the value of these changes. Just the other way around. The new coilovers are 'the thing', the bars likely have some value (I could not do the before/after experiment here), and the alignment certainly helps in improving with turn-in (or dynamic instability if you're in to another line of machinery), but nothing breathtaking.

So, my findings are much like Cannga's. This basic mod is a must-have. I do not know what incremental value new drop links, et al would provide though I suspect it's diminshing returns. And this is not a track car. Just an aggressive driver. Further, although the ride is a bit firmer, I don't think that this aspect should sway (sorry, bad pun) anyone from going with it. The ride is just fine, immerses the driver in the experience, does create more road noise - especially tire noise - likely for the reason Cannga cites, and the handling is night and day. Now that I've been driving it a bit, I do wish the Damptronics had some manual adjustments. Though I have no formal experience in this aspect of car mods, it feels like it could use yet more rebound damping to expunge the last of the P-car nose bob. It's mostly gone, but not thoroughly. So, for those who are still considering the change, and they want to get it 'just right', and are willing to defeat their PASM system, Moton's or alternative Bilstein's, Penske's, etc., might be the way to go. OTOH, I have no first-hand knowledge re the ride quality trade-off with these others, so caveat emptor.

Finally, I had a bit of a grin on my face when the fellow doing the alignment (at TCDesign - very nice folks) measured and found that I got the ride height to +/- 1.5 mm. He said that it was near impossible to do - and totally unnecessary for a street car! :) So I guess the techniques cited on my blog worked.