HI Guys!...I have KWv3 on Cs2 -20mm spots chassis model, been having a bobbing problem. I totally love what the dampers are doing but the bobbing is driving me crash.
Have you ever come across this?
Scanners

 

You will have to provide your settings to get a good answer. Your dampening and rebound control maybe working against each other.

 

Thank you 997ttmeister.
Currently the front is -1 click from hard bump. I love the crisp steering.
Rebound is 8 open

Rear is 3 clicks from hard bump
13 from soft rebound

Spring rate front std
Rear spring reduced to 110nm from std 130nm. It was a bit harsh.
Car is lowered.
Thnx for your response
regards Scanners

 

Hi, welcome to 6speed; as mentioned in my PM 6speed is very active (world's best Porsche forum ) and I hope you'll find the answer here.

Best answer is to have a competent tuner look at your car; but short of that, to best of my knowledge and if I understand you correctly, bobbing is the same as the "porpoise" motion commonly associated with either a blown shock, an underdamped system, or the springs are too hard. The damper is there to prevent the spring from oscillation; when damping is not adequate, the spring does the kaboong/kaboong/kaboong thing like a dolphin.

I have a few questions please:
1. Has your car always had this problem, or is it recent development after you've changed something?
2. What are the manufacturer's basic recommended settings, as opposed to what you are now using? Have you tried going back to those settings yet, and if so, did it take care of the "bobbing"?
3. Could you please explain "8 open" and "13 from soft rebound"? How many clicks are there from one extreme to the other and where are you from the extremes at 8 and 13 above?
4. What did your tuner say?

 

Thnx Can
This car is a gen 1 997 with -20mm sports chassis. The USA missed out on this fantastic
Setup with its gt3 type suspension agility. Limited slip diff etc In a c2s.
Only problem was that it was harsh. So I bought the kw v3 after 5 years last year
And have been working with a tuner and wholesaler to get the feel I'm after.
Harshness is now gone and grip and balance is amazing but I have lost that edgie fun reactive driving experience around town. Hence I set the front recently to -1 click from full hard bump and its crispness returned. Ill also try yr toe out suggestions as well as camber. Thank you

8 open is 8 clicks counter clockwise from full clockwise which is full hard.

13 from soft is 13 clicks from fully open soft.

There are 18 clicks from hard to soft on these dampers.

The bobbing is an almost 2nd or 3rd reaction to 1 bounce in the road. It is only there at road speeds up to 35 mph. It's kind of annoying but only happens on certain bumps. I just had a turbo 997.2 for the week end. No such thing from it.

Cheers Scanners

 

Normally bobbing from a low speed depression, as Can mentioned, is due to faulty shocks. Unless you are bouncing off your spring rate on the return stroke, which could be not enough rebound control. You could try equalising your rebound with the dampening and start from there.

 

Hi, you are welcome and I agree with Geoff above. I believe the answer is the rebound damping needs to go higher. There are two ways to approach this IMHO: a. just start to increase rebound damping slowly one notch at a time from where you are now, or b. goes back to manufacturer's recommended settings (Just curious, did they give you a recommended settings and what are they?). It's not going to be easy as I could see the numerous permutations of the various combinations front and rear, but at least we could narrow it down to the rebound damping, I think.

However, suspension setting is known to be "black art," reserved for the best of tuners (not web "experts" like me for example LOL), and I suspect you might have to make some compromises as perfect handling *and* perfect comfort just don't exist in suspension trade-off. Some company advertises we could adjust so and so for comfort, so and so for handling, this is really an over-simplification, for the reasons that they are all inter-related and changing one parameter affects other parameters in both handling and comfort. (And oversteer/understeer behavior (!!) as well, but that's for another discussion.) For example, when you increase the rebound damping as mentioned here, what happens is that the spring is rebounding slower, slowed down by the higher rebound damping, meaning the wheel won't follow road imperfections once it compresses, wheel leaves road and your car will becomes harsh as well, IOW it's going to be a trade-off and there is no way around it.

I think I could guess what you are going after, the handling of that stock -20mm sport chassis (yes a great one and yes unfortunately not avail in US) with more comfort, but it might be that you won't be able to duplicate that handling again unless you take the discomfort as well. KW won't be able to perform magic here because this is just ride vs. handling trade-off, you could have one or the other, but never both.

 

yes I also agree the rebound, but im suspecting the rear spring too. The "factory" suggestion for the car was..
front bump 7 open
front rebound 9 open

rear bump 5 open
rear rebound 9 open

open being the amount o=f clicks from fully closed clockwise hard.

yes im hoping i was going to get the best of both worlds like the turbo series2 or the gt2 etc. hmmmmm....ill keep you guys updated i have the tuner doing my alignment to your and gt2 spec on moinday, that sounds like fun. I noticed on the std spec alignment for me car 0 toe was its min position anyway.
cheers
Scanners

 

Part of the reason why I mentioned that damper setting is black art/black magic not to be taken lightly. Unfortunately I do not remember where I got this from but it's a good diagram for you to keep in mind as you adjust your suspension, the point being that the point of max traction may not coincide with the point of subjective control, nor the best comfort. Frequently you need both good tuners and very experienced driver to set it "perfect," and even then perfect is not absolute with all parameters.

Second chart is how damper's setting affects understeer/oversteer.

It is from these 2 charts that my opinion is best to start with manufacturer's recommendations, and unless you are very advanced driver with advanced tuner, do not stray too far from recommendations. Extreme settings (lowering, camber, damper, etc.) are almost never good in suspension tuning for *street* cars - moderation is the key IMHO.

I would probably go back to recommended settings, if you still have bobbing there, then it's problematic, because now it could be your replacement spring. Unfortunately, I would not ruling out going back to the Porsche suspension either if that handling is what you miss. This is for the same reason that I don't think GT3/GT2 suspension should be modded. In the Turbo, it's a luxury suspension and it's a simple matter to firm it up and improve it. In your car/GT2/GT3, Porsche has gone all out for handling and you are going to lose handling if you alter it for comfort.

 

You are so right in ref to Black Art.
I have been on a fierce learning curve with this over the last 12mnths and have definitely considered returning to the original suspension to recalibrate my intentions/memory after such a journey.
I understand the emotional perspective of this as well and wonder if im chasing something that ends up being my own myth .

Those charts are great thanks so much!

I guess when i read your Bilstein report on your suspension it rang bells in my head and i agreed with so much of it incl the sharpness and fun factor around town, i missed it in the KW, but not the harshness, hence running the bump comp full hard last mnth.... it came to life.
Now Ill Play with toe/camber, rotation of the rear to get the front oversteer reduced this sounds good as i never can get the rear to let go in spirited driving.

If I go back to the OEM suspension Ill really know what im gaining now and ive learnt so much more about it as well as tyre pressures. mps2 and mpSS. I have both on porsche mags for fast swaps.

Onwards and Upwards!

 

This isn't good news for me. I just ordered a set of KW V3s to try out in hope that the adjustability will result in a "better" setting than the already excellent PASM TECHARTS. Hope you get your car sorted and I'm keeping my fingers crossed for mine.

 

I would be interested in your findings, you may not be going for the same
feeling as me, cheers Scanners

 

They arrive in a week or so, so I'll keep you updated on my progress.

 

Yes, I understand perfectly what you are talking about, having taken the suspension "journey" :-) myself. In the words of JR Tolkien, we have been "there and back again" .
Some of my suspension experiments (the ones I don't talk about LOL) have not ended well and some were costly. But in the end the journey is as important as the end result and even now, with 100% hindsight, I still would not have traded what I have learned for anything else.

Regarding spring rates, is the rear spring rate 130 Newton/mm = 750 lbs/inch? That's race-oriented spring rate, would be harsh for street driving, and I understand why you bought it down. Do you happen to know what the KW front spring rate is?

Porsche OEM suspensions and Porsche tuners tend to use spring rates in the range of 300 front/500 rear for street cars, or 400/600 & 600/800 for more race oriented cars. I wonder if KW uses this same scheme, and if not, that may explain some of the difficulties I've seen with KW in the Turbo. It seems like KW is a very stiff suspension set up more for the track based on the spring rates I've seen so far.

 

:-) yes agreed Can. 100% hindsight :-)
Ive sent a question to KW about front spring rate, I know my OEM rear is Progressive 60-90nm!! I suspect my OEM dampers on the rear were very hard.