Disabling TPMS

Since I can't fit TPMS sensors on my new wheels, I opted to just disable TPMS altogether. It's nice to have but ultimately it's more of an annoyance. Porsche configures the tire pressures based on stock tires and if you run something different that might require different pressures you can't change what your target tire pressures should be. I followed the steps in this Rennlist post which was pretty straightforward.

TPMS module exposed - 2-24-2019

The major difference is that on the Cayman the screws are just phillips head screws and not torx holding down the big plastic cover in the frunk. Once the TPMS module was exposed, I just had to remove the 11mm nut, then disconnect the wire going to the module. There shouldn't be any water getting into here but just in case I wrapped the connector in a small plastic bag.

Wire to TPMS module disconnected - 2-24-2019

I bought Durametric Pro a few months ago so I could code whatever I wanted on the car and so far I've only used it to disable the annoying seat belt chime. I'm glad I got it because it makes it really easy to disable TPMS from the system.

Uninstall TPMS from Instrument Cluster

Uninstalled TPMS from Gateway

A final reset of the instrument cluster and voila no more complaints about the disconnected TPMS module.

Advan GT Premium Wheels and Fresh RE-71Rs

Around November of last year I decided I wanted to get some wheels I really wanted. I liked the OZ Allegheritas but I think the car just looks better on wheels with fewer spokes. I fell in love with the Advan GT Premium forged wheels and placed an order with them from Vivid Racing during SEMA. They don't normally stock these wheels so they were effectively made to order and it took just a hair over 3 months to be made and get here from Japan.

New wheels and tires test fit - 2-23-2019

Since I bought the wheels before I decided to go to STU, they're actually B-Street spec at 18x8.5 +50 and 18x10 +40 5x130 bored for Porsche and specifically designed to run standard R14 conical bolts or wheel nuts. They weigh in at a very light 18.6 and 19.2 lbs respectively and are Racing Hyper Black in color.

Advan Racing GT Premium Wheel

Advan Racing GT Premium Wheel

Despite them being sized for B-Street, they're actually fine for STU since I decided to run 255/35/18 and 265/35/18 Bridgestone RE-71Rs. For sure, a 9" wide wheel up front would've been more ideal for a 255 tire but the tire is really barely pinched so it's fine. Heck, last year I ran 265s on the same width wheel!. I had the tires shipped to SJF Performance and took the wheels there to him today to have it all mounted and balanced. I had originally planned on running TPMS sensors but it turns out the shape of the front wheels just won't let that happen as the sensor interferes with the tire beading. Not a big deal, I'll just go ahead and disable TPMS and do what I've been doing for years...regularly check my tire pressures using an accurate gauge. I've been meaning to do this for some time now so this is a good excuse to actually do that. TPMS is extra annoying during autocross events anyway as it's constantly complaining that my tires are not at the recommended 37psi (in the warmer months) which is silly since I know what pressures these tires are supposed to run on.

Getting ready for tire mounting - SJF Performance - 2-23-2019

All tires mounted up and Advan center caps installed  - 2-23-2019

Although I knew the wheels would fit based on my experience with the OZs which are very similar in size and offset, I have much more camber now so the tops of the wheels are closer to the damper bodies. Anticipating I might need them, I picked up 5mm hub-centric spacers from Titan Wheel Accessories and I'm glad I did because these wheels with the 5mm spacers behind them is perfect fitment. NOTE: You need to run longer bolts to to use 5mm spacers but the Rennline wheel stud conversion we installed last year has enough thread to fit the 5mm spacers with no issues.

5mm hub centric wheel spacers

Wheel fitment of front wheel (top view)

Wheel fitment of rear wheel (top view)

The 255/265 tires are 0.5" and 1" shorter respectively than the stock 235/265 19" tires on the car so they don't fill the wheel well as much but they're certainly a lot better than the 285s I ran in the rear last year which were a whopping 1.5" shorter than stock. This will still give me good gearing while offering a tall enough 2nd gear for higher speed courses. The fronts are dropped about as low as I'd be ok with right now. The 19s just clear so these 18s have a more normal sized wheel gap. I had already planned on lower the rear another 10-15mm to get more rear rake and that rear wheel gap sure could use some work. It's not that bad though in real life though. The cell phone pic at closeup just makes the proportions look really out of whack.

Rear wheel gap on the 265/35/18 RE71R

Unfortunately all I could do was test fit today. I had to take them off and put the stock wheels back on since the temperatures still look to be below 40F for highs for the next week or two and I may still need to be able to drive her to places to sort out some final things.

Brake Service

The stock pads and rotors still seem to have a fair bit of life left. This is a clear sign that previous owners probably never really pushed the car very hard at all so I think I can pass on getting new pads and rotors this season. However, I like to change brake fluid every 2 years at most (once a year on any car that sees competition) since brake fluid is hygroscopic and one thing I don't mess with is stopping ability.

New stainless brake lines - 2-22-2019

I checked the service records previous owners had entered into the maintenance log and it looks like the brakes were last flushed at 20,000 miles which isn't that bad since it's only roughly 15,000 miles ago. The problem though is that was done back in 2013 so the brake fluid has been in there for almost 6 years now. That's no bueno in my book and certainly not when we're going to autocross it. Anytime I get an opportunity to get brakes serviced my first order of business is always to switch to stainless braided lines for extra safety and better pedal feel. I picked up a set of new Goodridge brake lines from Tire Rack as well as a bottle of ATE brake fluid. The bottle looks like it had been through a war but the fluid inside was all good.

ATE Type 200 Brake Fluid - 2-22-2019

You can certainly bleed brakes on a Cayman without anything fancy but to really flush the fluid you need a computer to actuate the ABS so you get all the fluid out. With March just around the corner, there was no time to waste so I dropped the car off with Lee at Hybrid Motors this morning so he could get this out of the way for me. The old fluid actually still came out pretty clean so that's a good thing but I can definitely feel a big improvement in brake feel after getting the car back. The pedal is nice and firm with no excessive travel. The number of items on the build sheet not marked as complete is approaching zero. I'm no longer waiting for any deliveries and there's just a few minor details left to take care of and I can fully mark her off as "Season Ready".

Stainless lines installed - 2-22-2019

Maintenance Updates:

Mileage: 34,557
- New Goodridge stainless braided brake lines
- Brake flush with ATE Type 200 Racing Quality DOT4 brake fluid

Cleaning Up Rear Shock Adjusters

The only way to get to the rear shock adjusters is by cutting a hole in the rear speaker panel. This is functional but detracts from the otherwise clean interior of the car.

Rubber trim installed - 2-16-2019

To clean this up a little, I bought some Trim-Lok Rubber Edge Guard from Amazon and the plastic edges of the hole slotted perfectly into the slits in the edge trim. I know it's such a minor thing but I'm really trying to make an effort to not ruin a perfectly fine Porsche just for sake of a bit of racing.

Dimensions of Edge Trim 

Fixing ECU and Dash USB ports and switches

Every since Bumblestook's first iteration of her BSP builds in 2013, we needed a clever way to place the momentary switches needed to operated the Racepak dash as well as USB ports to simplify connecting a laptop to either the ECU or the dash. This was done by putting them in a metal bracket and then placed inside the center console so it would be out of sight. This wasn't a high priority for the build so it was mostly just cobbled together and the switches were very flaky. It was also mostly held in place by a single self-tapping screw. This would often create all kinds of rattles and sometimes you wouldn't be able to connect to the ECU using these USB ports so you'd have to pull the console up to juggle the wires to make it reconnect.

Old ECU and Dash USB ports and dash switches

When we brought Bumblestook back to her current street-legal form last year, we replaced the momentary switches with better ones and tried to at last secure the bracket to the console using silicone so it would stop the rattling. There were so many other higher priority items we needed to get working, we knew this was just going to be a temporary solution until we could do this better.

New setup for ECU and Dash USB ports and switches

Today we finally got to address this once and for all. SJF created a new metal bracket that is now fully fastened to the console. We changed the configuration so that they attach vertically for a cleaner install and give me some of the center console space back. This allowed us to remove the 90-degree adapters that set behind the USB ports that were frequently the source of my connection issues. I just have to clean up the leftover silicone but I'm really happy about this new setup.

Suspension and Limited Slip Differential

One STU legal mod that I had been debating on whether or not to add to the car was a mechanical limited slip differential (LSD). Having had a proper LSD in Bumblestook for years, I know how much they transform the car for the better but I was venturing into new territory doing this on a Porsche. The most important detail of course was finding the right shop to install it. This sits inside the transaxle so unlike the S2000 where I could easily ship a spare diff carrier to a well known diff installer somewhere in the country, I was more hesitant to do so with a Cayman transmission. After speaking with Jonathan Lugod (congrats by the way on winning SCCA driver of the year) at OSGiken, I was referred to Speedsport Tuning (SST) in Danbury, CT, one of their east coast vendors.

Kay getting ready for corner balance and alignment
Speedsport Tuning - Danbury, CT - 2-7-2019

I had some very good back and forth emails with Bryan Schute at SST and he was very helpful in answering all my questions and concerns (I had a lot of them). They had done a number of OSGiken installs on Caymans before which made me comfortable that I wasn't going to be the guinea pig. Jonathan shipped me an OSGiken Super Lock LSD that had been given some special sauce treatment by Lugod himself for autocross applications. Last week I dropped the car off at the shop to finish this phase of the build. Since I live in NYC and the car was going to have to be in the shop in CT for a week anyway, I figured it was in my best interest to have them also put in all the suspension pieces that had been piling up in the garage for this build. I normally would've wanted to do this myself with SJF in his garage so I could get my hands dirty and get more intimate with the suspension but I'm running out of time. Getting all the suspension bits on now in one shot means that I have more time for the springs to settle and make tweaks before racing season begins. I'd also be able to start breaking in the diff and hopefully do another fluid flush before the first event.

OSGiken diff and Motul Competition Gear FF 75W140 fluid

Speaking of suspension, as much as I love having PASM on the car, without being able to do a DSC upgrade, it just wasn't going to be good enough to be competitive in STU. This car is already going to be an underdog in the class and I needed every advantage I could get to try and close the gap. I was chatting with Bryan Karwan at Karcepts back in December when Motion Control Suspension (MCS) announced they were going to release dampers for the 987.1 and had him order a set of MCS 2-Way non-remote dampers, MCS front and rear spherical top mounts, Hypercoil 600lb/700lb 2.25" ID 6" springs and Hypercoil 4" helper springs which conveniently arrived in mid-January. For reference, the stock PASM spring rates are 174lb/297lb so this is quite a bit of an increase in spring rate.

MCS 2WNR Dampers

MCS 2WNR Dampers

To get proper camber up front, I had also picked up GT3 lower control arms. To match the GT3 front sway bar, I got a GT3 rear sway bar and Tarett Engineering drop links. This is important so I have adjustment in the rear bar as well. To make sure I was going to get the rear toe back in line after dropping the ride height, I also got Elephant Racing rear toe control arm eccentric bushings since adjustable toe arms with spherical bearings, the most common way to do this correctly, aren't legal in STU.

GT3 front lower control arms

Rear toe arm eccentric bushing installed

Since the rear suspension was already coming out, it was easy enough for them to just remove the axle and lower the transmission to install the diff. I had them put in new diff carrier bearings and everything was shimmed back to spec then the transmission was filled with the new Motul Competition fluid.

OSGiken diff getting installed

To get to the rear suspension, you have to remove a lot of the interior panels. Since the rear damper is so close to the headers, I guess MCS felt having that part of the damper wrapped in heat reflecting tape was a good idea.

Interior panels removed for rear damper installation

OEM rear damper / springs vs
MCS rear damper + Hypercoil springs

Rear dampers installed

The GT3 rear sway bar and Tarret Engineering drop links were also installed and set to full soft per my request. The spare rear speaker panels that I had painted were then cut to give me access to the rear adjusters. I think I'm going to add some kind of weather stripping to clean up the look a little. I then added the stickers MCS provides to remind myself how to adjust them. It's too easy to get confused when making changes during competition.

Rear completely done

Access to rear adjuster knobs

The fronts were slightly easier because the front panels come out pretty easily. However, the GT3 LCAs are a bit fiddly since you have to use shims to set the alignment so a little bit of the undertray needed some trimming to get to the bolts for the adjusters. Once the suspension work was done, the PASM module had to be disconnected and the ECU reprogrammed to remove the feature so it doesn't complain that the OEM dampers are missing.

Front dampers and springs in

Trimmed underpanel to get to shims and nuts

I asked that they lower the car only 25mm all around for now since I wanted to give time for the springs to settle. On Bumblestook I've seen springs settle as much as half an inch before so I didn't want to set it too low for now and find out I can't even get up the driveway later. I had them corner balance the car and align it. Obviously once all the springs settle and I finish with the weight reduction, I'll readjust the ride height, alignment and corner balance but setting it to a known quantity now is going to make that process a bit easier later. It'll also let me sort out any clearance issues and help me decide if I want to lower the car further. I think I plan on lower the rear another 10mm before the next alignment. Bryan advised me that the car likes some reverse rake and that seems like a sound plan. I also picked up 5mm wheel spacers and I'm glad I did because with the increased negative camber the wheels are getting awfully close to the springs. I'll have to see how it all clears when my new wheels arrive later this month.

Alignment and corner balancing

Alignment Specs:
Front:
-3.5 camber
0.06" toe out total
max caster

Rear:
-2.5 camber
0.06" toe in total

With 9 Gallons of fuel, a 175lb driver ballast (flattering but quite a bit off haha) and OEM 19" wheels with 235/265 Continental DSW tires the weight was 3,256 lbs. That's going to be close to her competition weight since the additional weight savings I have planned for the car is approximately the difference between the ballast and my actual weight.

Cross weights - 2-9-2019

When I picked the car up, I asked Bryan if we could get it on a lift so he could show me the work and explain anything I needed to know. He gladly obliged and also noted that all the bolts they touched were marked to note that they had been torqued to factory spec. I can appreciate that level of attention to detail. I had given them a rather detailed checklist of what I wanted done when I dropped it off and we made sure everything was done to my liking.

After I got the car, I figured I'd finish off some of the interior things I wanted to get done. Since I already have a few splashes of yellow in the interior from the steering wheel and 6-pt harness, I decided I'd also continue this theme a little bit more and installed a new shift boot with yellow stitching and yellow strap door pulls. The interior was looking a bit drab and a splash of color helps it out a bit I think.

Adding a bit of yellow on the inside - 2-9-2019

Adding a bit of yellow on the inside - 2-9-2019

Driving Impressions:

I put on about 140 miles today (note: current mileage at pickup is now 34,256). The first leg was from the shop to my storage to drop off all the parts taken off the car. That was a bit interesting because the car was full of boxes and I had asked the shop to set the dampers to one click from full soft all around for both rebound and compression so while the ride was fine, if I hit dips or bumps let's just say the car was quite underdamped. Once I had dumped the stuff out of the car. I went around and started tweaking the shocks by setting the compression to 4 and rebound to 8 as the instructions for the MCS dampers say should be the initial settings. That was night and day. She started driving like a proper German car again and I think this is a good starting point for tuning. I took her to some nice twisties and hot damn...this is how the car should've left the factory. So many smiles per gallon and definitely sparks joy!

The diff is super smooth. No diff / gear whine or annoying low speed clunking when doing tight turns. I obviously didn't push it that hard since I'm still breaking it in and it was 25F so I wasn't about to be the next Internet meme of a car wrapped around a tree but so far this is all very promising.

Great day for picking her up - 2-9-2019

I want to thank Bryan and the race team over at Speedsport Tuning for doing a great job and getting the car back to me on time. When I dropped the car off last week they were at Sebring racing a bunch of their race cars and they had just gotten back this week and worked on my car. The communication throughout this entire process was superb and I got the car back with a flash stick with a bunch of photos from the build and additional data relevant to me.

That concludes the major parts of Kay's STU build. We've got some added lightness on the way and a few tweaks here and there but we should be ready for the March season opener.