Upgrading a 981 PDK Cayman

[ralphmusic]

Ha, I wondered whether I would catch up with the tuned UK Boxster. Glad to hear it's going well.

I'm off to Spa next week and at Castle Combe track day on 22nd.

Will you be at the Silverstone Classic?

Ralph

 

[gd61]

You sound to be busy ;-)

I will try to get to Castle Combe - need to call PCGB tomorrow to see if there are spaces left.

Best

Uffe

 

[ralphmusic]

Castle Combe is the 23rd, not 22nd as I wrote previously.

 

[ralphmusic]

Some recent suspension updates:

At the rear, we fitted Tarett monoball top mounts and 997GT3RS rear wishbones replacing the GT4 (offset) top mounts and stock wishbones (with Powerflex camber bushing) - this was to improve the rear wheels' clearance of the diagonal control arm.

Also, I replaced the OEM rear cross member with the GT4 part (981 331 071 80) - the GT4 part being more robust.

I've backed off camber and am now running negative 2:40 front and 2:30 rear, which seems to be working with the medium front and rear ARB settings. I did try hard setting on the rear ARB but it was a bit too lively for me through Eau Rouge/Raidillon.

As someone observed, when you start how do you stop? Anyway I'm looking to try TPC Racing's DSC V2 Controller, which replaces the PASM ecu. I've heard some positive reports of its performance on road and track so we'll see...

 

[ralphmusic]

I've bought a DSC V2 Controller from TPC and should have it in the car for Silverstone October 24th. We should get some structured empirical data with back to back runs with DSC installed versus running with stock PASM.

 

[ralphmusic]

The DSC controller was fitted in October and after testing, the set up was changed in March by Centre Gravity to run more camber to better suit DSC and Cup2 tyres. They also stiffened the ARBs which are now halfway between medium and hard settings front and rear (one side middle, the other side hard) which worked well on Silverstone GP circuit particularly though my favourite test of Maggotts/Becketts/Chapel.

 

[ralphmusic]

I recently decided to upgrade the brakes, having got fed up having to frequently clean out the holes which when blocked cause cracks in the discs.

The car had larger front 991 Carrera S 6 piston callipers and 340mm discs fitted in early 2015; the rears were left standard 299mm. Upgrade options included fitting Brembo GT kits, or standard PCCB callipers with aftermarket 350mm iron discs all round.

In the end I decided to retain the fitted callipers and fit larger slotted two piece Girodisc 350mm front and 325mm rear discs.

I went with Ferodo DS1.11 brake pads which are similar in type to Pagid's RS29 but are well regarded on Rennlist. Finally I changed the master cylinder to the GT3 part which has a larger 27mm barrel diameter v stock 25.4mm. I use Castrol SRF brake fluid but have not felt the need to change from stock brake lines.

Overall the new setup works well on the road, although recent weather has not yet allowed it to really be tested to the extreme.

 

[ralphmusic]

Further on the DSC suspension controller, I have written a number of maps which change the damper hardness range on both Normal and Sport settings and plan to test these out at Silverstone on March 19. It is a sessioned day with a 20 minute runs each hour so it works quite well forcing me to plan the testing and allowing time to reflect on the results with each setting. It is easy to change maps on the car using a laptop connected to the DSC box's USB port. I can also log damper behaviour in the context of G, speed and brake pedal pressure, although this data is nor presented in a particularly user-friendly way so it's best to review this after the track day.

On mapping, I have only changed damper settings, rather than any of the other several hundred parameters to limit the variables. Bilstein dampers normally work between 1500ma (full soft) and 500ma (hard) although staff on the Bilstein stand at Autosport told me they work down to near 0ma. The standard settings on the DSC box are front between 1500ma and 500ma with rears 1500ma and 600ma, rears being slightly softer. The DSC box allows ma to be set for each of 32 positions for each of the four dampers over the softest to hardest range. Happily one can enter the hardest and softest values for each damper and the software will pro-rata populate the other fields. The minimum change to really feel much difference is 150ma so I am starting with Normal and Sport maps that are significantly different and have others to try which hopefully will allow my "ranging" to identify an optimum map for Silverstone.

The DSC box replaces the PASM controller and sits on the CanBus. Depending on inputs (e.g. LongG, LatG, braking, throttle) it looks to the mapping and decides what ma goes to each damper (e.g. to give firmer front on braking, softer rear on acceleration, firmer loaded front on corner entry etc). The DSC box can respond to inputs in around 6ms but is somewhat constrained by Bilsteins (I have B16 coil-over damptronics) which would be an order of magnitude slower to respond and can't respond mid-stroke. Having said that, the DSC box has made a difference over the standard PASM which seems to use a narrower range of damper settings on the 981/991 platform.

 

[944Turbo]

Interesting stuff and I don't even have a cayman, thanks!

 

[JohnCRS]

Ralph, with all the suspension mods, are you still using standard 19" wheels and tyre sizes?

I am going to mothball my too delicate factory 20" wheels and 35 profile tyres (the rears are due for renewal anyway) and following your suggestion at Autosport and putting on simpler 19" rims and 40 profile tyres. I hope this will retain the overall balance but deal more effectively with our potholed roads. Whilst I do an occasional track day, most of my 15k miles per annum is road trips. Any suggestions would be helpful. Thanks.

 

[ralphmusic]

Hi John,

I stayed with 20" wheels but have moved to wider front and rears from Cargraphics. I perhaps should have gone to 19" but I have larger front callipers and wanted to use Cup2 tyres as specified for the GT4.

19" wheels are probably a better size for all round road and track use. I assume you have seen the approved list of tyres if you are maintaining warranty cover.

[link=https://www.porsche.com/uk/accessoriesandservice/porscheservice/vehicleinformation/tyreapproval/]https://www.porsche.com/uk/accessoriesandservice/porscheservice/vehicleinformation/tyreapproval/[/link]

This lists....

Goodyear Eagle F1 Asymmetric 2

Pirelli P-Zero N0 Pirelli P-Zero N1

Yokohama Advan Sport V105

For what it is worth, I had experience of 20" Pirelli OEM approved which came with the car. I found them quite poor and quickly replaced them with Michelin Pilot Super Sports (MPSS) which were miles better on the standard 20" wheels before going to Cup2 on the Cargraphics wheels. I have found Michelin to generally to be the better choice, but have not tried the Michelin Pilot Sport 4S (MPS4S) which followed on from the MPSS but others report 4S' better wet weather performance.

Ralph

 

[AndrewCS]

I use the 20" PS4S N0, have coped OK with a few potholes.

Have done 2,000 miles since January in all conditions ... can`t fault them []

 

[Brian_Innes]

I'll second that Andrew.

Michelin PS4S N0 are brilliant in the wet. Astonishing grip. The best wet weather tyre I have ever experienced.

Dry grip on the track yet to be fully tested, but looking very, very, promising.

Brian

 

[ralphmusic]

The LoT day on March 19 was cancelled due to snow and rearranged for April 9, the day before an already booked Goldtrack day there. Anyway it was wet most of April 9, just clearing up in the afternoon and there were 14 stoppages on the wet Goldtrack day, two due to fog...so back to Silverstone on May 10 with BookaTrack and Gary Marsh to see if I can complete testing DSC maps and my new brake set up.

I am then just going to Germany for a Nordschleife training course offered by the Nurburgring circuit and then moving the car on. It's been a great process getting the car really sorted but when it's done it's done, and I want to start a new project.

 

[Motorhead]

Seems a shame to part with it now Ralph since you've got it as you want it, but can understand your desire for a new challenge.

What's next? Maybe a 982 GT4 with PDK as a starting point?

Jeff

 

[ralphmusic]

Jeff,

Way back when I changed from the 911 GTS to the Cayman I posted that I thought maybe my next change would be to an older Porsche. I keep coming back to that thought but when something that appeals comes up, I'll know.

Ralph

 

[ralphmusic]

The Silverstone day was one of the best trackdays I've been on. The weather was great, I had a huge pit box all to myself, NO red flags, good driving standards and plenty of on-track time. Some interesting car on track including a race team pre-season checking some GT4 cars, a McLaren, Aston, KTM (amazing looking car) and Cayman Clubsport.

I got to a good (Sport) suspension setting for track, and (Normal) good compliance for the road. Gary Marsh was really helpful in teaching techniques for improving my braking style. The Girodiscs and Ferodo pads worked really well, pad wear was about 1.5mm which seems to be about what the rennlist guys report with the same pad/discs.

The new Silverstone surface is better than the old but for me the change was more noticeable in wet than in dry conditions. All the old bumps and undulations have gone, only to be replaced by new ones....

Anyway, the car was great both on track and cruising back and forth from Devon, it makes me wonder if I'll be able to replace it with something better.

 

[ralphmusic]

The new Silverstone surface is better than the old but for me the change was more noticeable in wet than in dry conditions. All the old bumps and undulations have gone, only to be replaced by new ones....

Just watching P1 Silverstone GP and Hamilton agrees with me, new bumps in the track (and I thought it was my suspension..)

 

[ralphmusic]

I've been talking to Ehresmann about fitting a PowerKit to the engine for another 35PS and a flatter and slightly higher torque band.

Really can't decide whether this is the way forward for this car, with next GT4 being manual only. PDK will handle the extra power based on USA experience, particularly BGB in high ambient race and track day conditions plus Ehresmann 50k km on a 3.8L Powerkit PDK Boxster.

 

[Motorhead]

Ralph,

Blasphemy maybe, but perhaps you should consider switching to turbo power to fulfil your desire for more power?

450PS and 406 lbf-ft from a 718S engine with Stage 2 tuning from Ehresmann. PDK's available, plus you get the latest chassis and steering updates.

Jeff