Wayne Smith

Bruce makes interesting points.

As I was making adjustments to the G Force table I was trying to compensate for the springs by adjusting the shocks. And I was wishing there were two tables ... One for compression and one for rebound. But There's only one table. The 991 shock has shock shaft velocity feedback that can be used as well but the 997 does not. This velocity does not include direction so my excessive rebound problem would not be resolved anyway.

The DSC doesn't actually know what the shock is doing or how it is responding. It only knows the G forces that the car is experiencing. So there are some limitations.

Back to spring vs shock. When negotiating a quick in and out curve you are using the shock more than the spring. A long sweeper gives more time for the suspension to settle and the spring dominates. My 2010 C4S has always been best in the quick in and out turns wherein the suspension doesn't have the opportunity to settle. The springs compress less so there's less stored energy to dissipate. On long sweepers there is a lot more suspension travel, a lot more stored energy in the springs, and the energy release causes rebound that becomes excessive. The same goes for bumpy roads vs extended dips (the later being where my rebound can be so bad that the rear pops off the pavement). So put a dip at the end of a long sweeper and do the math. It's even worse when you get on the throttle at the apex which further sinks the rear end and increases the suspension travel. Suddenly when you're counting on the rear to supply grip to complete the turn you find yourself without an ounce of contact patch!!!

Yep, ultimately this scenario is going to need some tuned springs. (Just musing ... Springs mounted to a hydraulic block that could be switched on and off to absorb the rebound energy). But the DSC gives you some easy cheap flexibility without needing to get wrenches and air hammers and spring compressors out all the time.

The DSC software does include time programming so you can maintain stiffness for an entry period. I know Tom reads these posts and maybe he can chime in here. It seems to me that we would be better served if these times were inverted for a soft period that then gets harder and harder with time so the initial response is soft for road surface compliance and gets stiffer to minimize spring compression and stored energy. Anyway, I sense I've gotten to the babbling phase of this conversation so I will pass it off to those more knowledgeable than I am.

Hindsight2010

I wonder if DSC controls compression, rebound, or both. Anyone know? I know most adjustable coilovers allow for rebound control only, unless you go for the REALLY expensive kind which can be 2 or 3 way adjustable.

I don't have a DSC controller but just put on Ohlins Road and Track coilovers. I have them set very soft and between those and GT3 front and rear sway bars, it's quite stiff..... not as nice on the city streets as I had hoped (not that I expected it to be softer than stock of course - just not quite this jarring), but it will be great on the track.

Bruce In Philly

Interesting..... now here is my no-compensation sales pitch for the DSC box. For about what now, $1K, you can put this thing in, dick with it, then decide if it is for you. If not, you can sell it for what I hear is the near price you paid. Total time spent dicking is just 1/2 hour for install and de-install. 0$ labor cost. Loss of money? Maybe 1 or 2 hundred dollars. Or, you can swap out your shocks, shocks and springs, or whatever for how much? Labor cost? Resale of the parts? Time spent? Cost of alignments and adjustments? Do the math.

Story: Around 2001, about 1 year after I purchased my loved 2000 Boxster S, I had an itch to tweak it (too much forum reading)..... to tweak meant new shocks, springs, alignment et al.... I considered the ROW 30 option and even stopped into a Porsche dealer in Berlin when I was over there thinking I could buy the parts cheaply and shove them in my luggage (OK, not such a bright idea). I figured at least the ROW 30 was sorted by Porsche engineers. Anywho, I talked to various folks... my indy who installed these various options all the time, customers of his who had done various options, and my indy let me ride in a customer's car he just finished with for the test drive. Barf! I hated what this other owner did. Further, everyone I talked to said the same thing... such as "total transformation", "so much better", "can;t believe it!". These comments scared me especially riding in and experiencing what was the most common setup of the day (sorry can't remember what it was). In short, I said "forget it" as it was just too much of a gamble. I just could not develop an understanding of what I really would be getting and, frankly, terrified if I didn't like it given the huge cost. So that is where I come from.

Here is a neet article by Jason Fenske of Engineering Explained..... there is a ton of information to consume if you want to "improve" your suspension. So Wayne, maybe our springs are too stiff? (I still think our general ride quality is not good due to these stupid, childish, ricer, greasy kid stuff, low profile tires.)

https://www.roadandtrack.com/car-cul...ave-less-grip/

Peace
Bruce in Philly

Lastdragon

My thoughts on the DSC out of the box (installed last week) with my 997.1 CS:
1. It is amazing how flat the car handles on the back road while also being more compliant than the stock settings
2. The flat corning inspires great confidence on high-speed turns
3. The flat cornering feels a bit unnatural because it is too flat. It's fine for handling but I don't get the same engagement/feel when cornering because weight transfer is minimized.
4. The car absorbs bumps in the road better than stock
5. With DSC there is not much difference between the car being in sport or regular suspension mode on the street.

For context, before the addition of the DSC module, my car was bone stock with 80k miles. Up to this point I have replaced, trans mounts, engine mounts, and all four of my shocks with OEM units in the last 6mo. I have a new set of PS4s with under 3k miles on the car. I've tracked the car about 5 times in the same time frame

I will see about updating the algos to give more separation between stock and sport modes.

Taking the car to Laguna Seca tomorrow (if the track day is not canceled due to the fires) so I will see what it's like on track and give my impressions.

Petza914

To understand DSC, you first need to understand how the PASM system and dampeners work.

An excellent, yet simple explanation is from Total911.comIn ‘Sport’ mode the dampers stiffen, allowing greater cornering performance by maintaining the tyres’ contact with the road.

In order to affect this change, inside the damper body a special bypass channel is utilised to alter the suspension’s stiffness.

All hydraulic dampers work off the same principle: the damper body is filled with oil, which is compressed by a piston. In the PASM damper, the bypass channel is used to control the flow of oil.

In ‘Normal’ mode, the valves controlling the channel are open, allowing a greater flow of oil, resulting in a softer damper. However, when ‘Sport’ mode is activated, the bypass channel is closed. This increases the compression needed to force the oil through the damper body, creating a stiffer damper, and a more responsive Porsche.

So the current into the dampener opens or closes the bypass channel more or less allowing fluid to either flow though it faster and easier (softer for normal) or slower and harder (sport). The DSC controller automatically and dynamically changes the electrical inputs to the dampeners based on the g-forces experienced by the 3-axis accelerometer, so even in a very soft default setting, when the accelerometer senses high g-force loading in a direction, it automatically changes the signal to the dampeners receiving the high g-loads, siiffening those shocks by making the bypass channel inside the shock smaller and harder for the oil to pass through.

The real beauty of DSC is that each owner has the ability to completely customize it for their use case, hardware setup, driving situations, etc. For example, my car has a complete racing suspension on it - Bilstein Damptronics, RSS Tarmac Stage 2 everything, Tarret monoball top mounts, adjustable sway bars and drop links, toe steer kits, camber lock kits, etc. yet, because of what I can do with the DSC box, by Normal PASM setting is completely comfortable and I'll jump in the car for a 5 hour run to Nashville, 3 hours to Charlotte or Charleston, etc without a concern about the quality of the ride. When I'm doing high speed mountain work, a push of the PASM button puts it into sport mode where the shocks both start stiffer and go stiffer than they do in the normal mode.

I have my setups configured as follows: -
Normal - full soft of 1500 all the way up to 40% G-loading and incrementally moving to a stiffness of 850 at the end of the G-table
Sport - Starts at a stiffer initial setting of 1,350 and incrementally moves to full stiffness capability of the B16s of 500 at the end of the table (other shocks like TPC's own Tractive DDA can go to an even stiffer value and respond faster)
So, until I've reached 40% of the G-table load, the car is completely smooth and soft on the suspension. Once I hit an on-ramp or do heavy acceleration or braking, the correct portion of the suspension stiffen appropriately so the car handles that situation then automatically goes back to full comfort mode.

Owners of DSC that haven't played around with the customization options may be missing out on creating ride and handling dynamics for exactly what they want.

Tom@TPC Racing

The answer can be Yes or No depending on the interpretation of the question. Allow me to explain.

No(sort of), if you are referring to setting static compression and static rebound in the manner as using manually-adjusted dials on conventional fully-mechanical dampers. I said "sort of" because if you were to edit all the cells in the DSC software G-Force table to a fixed value to up/down vertical g-force you could sort of achieve that.

Yes, if you are referring to whether DSC can command varying damping output for the downward travel and upward travel on electro-mechanical dampers to real time changes. Basically a downward travel stroke is the "compression" of the suspension and an upward travel stroke is the "rebound". But instead of thinking of statically setting the damping output with manually-adjusted dials, DSC sets the damping output for either travel direction to real time driver inputs in a multi-dimensional way. We just don't use the phrases Compression and Rebound often because the traditional context of these two phrases is for static management and not so much for dynamic management.

Using automotive fuel system as an analogy, static damper setting is to swapping jet size in a carburetor to change the ARF curve for the highest predicted load, whereas DSC dynamic damper tuning is to electronic fuel injection system monitoring inputs in real time.

Side note-
This is not applicable for 997 cars, but for cars that come with factory equipped with four hi-speed ride height sensors(such as Porsche 991/981, Ford GT350/GT500, Chevy C7 Corvette and G6 Camaro), DSC uses suspension Travel Velocity, defined as Hi-speed, Med-speed, Low-speed Compression and Rebound Travel to offset individual damper commands. Again, DSC uses Travel Velocity to dynamically offset to real time changing input,it is not the absolute value that is often thought of in a static system. Using the fuel system for analogy again, think of the DSC offset function as the engine ECU compensating(offsetting) for temperature/altitude change.




The DSC system is more of a hybrid between Skyhook and Groundhook system as the original objective of the Skyhook theory leans more to comfort. The initial body roll from DSC control adds grip.

I had pro race car driver Mike Skeen drive my 997 with DSC + Tractive. When he got of the car he said "This car feels really soft but it has a lot of grip. It turns in very good and doesn't get loose any where."

Wayne Smith

Edit: Three posts occurred as I wrote this. Sorry for any repetition, etc.

Just a few random thoughts ...

As for skyhook suspension you can tune that out. All you need to do is go to the G Force Table and program the same shock values on both sides of the car for all different G Force values. You can turn this into an effectively single channel system if you want. Or two channel splitting front and back. You can still program front to rear G forces to minimize brake dive and or acceleration squat, or not.

So program Comfort mode that way for the street if you want. And then program Sport mode for ideal handling. DSC gives you these options.

The DSC doesn't know which direction the shocks are moving. Well, I don't think it does. A 3 axis accelerometer is used for sensing so I could be wrong. But I believe the system reads the accelerometer and reads from G Force Table to decide what to do regardless of compression or rebound. That table does not include the Z axis so I don't know if there's some other magic in the algorithms or not.

My feeling is that our springs are not adequately progressive ... Soft start quickly collapsing the soft part and transitioning to the hard part. You could kind of soften the springs if you could set the DSC to be progressive ... That is soft for .25 seconds and then ramping up to the programmed stiffness. Or maybe just a controllable programmable ramping table.

The DSC software does have some time settings that I haven't played with yet. Maybe I can do that. Maybe that will help. There are two specific test corners I still need to test on. Both require significantly high speeds. One is just over a hundred miles away. The other is 300 miles.

Coming out of a corner induces rebound. It also reduces G loads and that transitions you into the comfort box in the G Force table. That's unfortunate since the sudden transition to soft that is implied by that comfort box allows extra rebound. That creates instability. I would like to see a two second (or programmable) delay when re-entering that comfort box before enabling the reductions that box allows. Just musing.

But my car is becoming more and more an appliance ... Taken out to be used only occasionally. Between not commuting to work and Shelter In Place it mostly sits these days. Add in the fires and smoke in the San Francisco Bay Area and the road stays out there without me. My failure to use this car more than I have been is criminal really.

Bottom line is that I can make changes but it could be a while before I can report on them.

And since my last changes, at least for the roads I tested on, I don't see a need to make adjustments. Once we get out on the road more my feelings might change. Or I may get bored and decide to blindly experiment.

Anyway, back to the original point of this thread, with the ability to play with the values in the DSC I fail to see any reason to not install it. You can always mimic OEM operation (or improve on that in any way you'd like) in the Comfort mode program. Then make anything your heart desires in the Sport mode. And it's easy to do!!!

Brian Cheung

I loved it on my 997.2 C4S and transferred it to the 997.2 Turbo. Transformed it completely in a better way. On the original dampers and Techart springs, after downloading the "stiffer" map the car was less floaty and much more planted on undulating and fast corners. On the 997.2 turbo, i swapped to B16 dampers (comfort) version and did find the original map a bit stiff for my roads. However, i started playing around with the G-maps, speed maps, damper rates etc and it is now super comformtable in normal mode and stiff enough yet not back breaking (like the original sport map), but i have to say its not a track car, stiff does not mean faster car. Original normal mode was too floaty, sport mode is too harsh and skippy.

Recommend this product for sure, and the team will support you.

Hindsight2010

This really sounds like a smart approach to a car that logs a lot of street miles with some track or at least canyon-carving miles. It will be interesting to see how I like my Ohlins long-term. I'm definitely giving up some street comfort for them - though the same can be said about the GT3 sway bars which are obviously not dynamic. I was really sold on the Ohlins based on people I have run with on the track who have them on a variety of cars. They just seem to blow away everything else - absorbing small and big pumps and keeping the car vary planted and stable. But I'm going to have to do a lot of track time to make up for the loss in street comfort. It would be different if I lived somewhere with nice roads, but Atlanta is pretty awful.

Petza914

I was one of the early adopters of the DSC box - even had one one of the 3 mode boxes with flashing PASM light originally. I had done all my other suspension work previously. I went with the Bilstein B16 Damptronics because they were the only option compatible (other than GT3 versions) with the cargraphic AirLift noselift kit I was also installing. I needed this to protect my RUF front bumper that doesn't have a replaceable lip and also project forward more than any of the OEM bumpers, so even more difficult to clear driveways and humps. The point to the story is that I installed all the suspension components including the coilovers before I did the DSC install and I could tell immediately how much better the coilovers worked compared to the stock PASM dampeners. The rear end wallowing up and down over long undulations at higher speeds was gone, everything felt more planted and precise and the ride was firmer, but actually better - less abrupt jolting on sharp bumps. Adding the DSC box as the final step just made things that much better and being able to make it more compliant for street driving but with automatic stiffening when needed (on ramps, avoidance maneuvers, etc) made it perfect.

I believe you'll really like what the Ohlins do for the car's feel and handling on the track, but what you'll lose is the ability to make the setup more streetable for longer range comfortable cruising. With my configuration, I feel like I have the perfect setup for how I use the car and can have razor sharp handling without compromising comfort when I want that.

Hindsight2010

Do you ever track yours? Or is it just a mix of high performance street and regular street driving?

Petza914

Other than parade laps at Road Atlanta, I actually don't. It's too rare and valuable and haven't wanted to pony up for the special track insurance. So it's used for spirited street driving only, but would be an absolute blast on a track.

Hindsight2010

Sounds very wise. Yes I hear you about track day expense.... Between the HPDE fees ($400) plus track insurance ($400) plus temporary track wrap paint protection for the rock-chip prone areas ($100), that's almost a grand, and that doesn't count consumables like expensive R-compound tires, brake pads, and doing an oil change with Motul after each session.

Brian Cheung

I don't track. As a 911 owner i don't pamper my car, i drive it fast, i drive it hard and i have family days in my car. But it handles excellent now - comfort = compliant, sport = stiffened up and still driveable.
After some fine tuning it is possible to find your own "optimum" setting.

Zakowsky

Noob question: I've been driving my 997.1 turbo for a few weeks now and it is pure awesome, but once while driving in city traffic, sport mode off and PASM off, I had to hit the brakes full on and the front valence scraped on the road. The car is totally stock - is this to be expected? Or is it a sign of weak shocks up front? I assume the DSC controller would work to reduce the dive and so I am now thinking about getting one, but wondering if that would be just masking a shock/suspension problem. Thanks.