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Our ASP PDK Cayman is off to its new home near COTA, so time to start work on the new project. 997.1TT for SCCAs SSP. It already looks the part... had TPC swaybars, PSS10s on it. The car is heavy (3500+) in stock form, but will have lots of tire, power, and brakes, and is physically only an inch wider than the cayman.
First test event with just wheels, old tires, and alignment was not awful. It slalomed really well, but the previous track setup was pretty tight (pushy) on the slow corners. Power was solid, but some heat soak/lag would set in.
All can be fixed... Typical SP car setup from scratch - some bits from the 987 transfer over which helps.
- Engine drop to pin coolant pipes, fix leaks, and other 50k mi maint.
- New lightweight clutch and flywheel
- Rear diff mod/rebuild with Guard internals
- new exhaust
- new intercoolers
- tune
- re-barrel wheels - 18x12 or 18x13 rears
- rebuild shocks (used motons)
- replace battery
- replace all liquids
- replace brakes
- install race seats, harness bar, belts
- relearn how to drive with real torques again!
I predict winning all the practice starts at Pro Solo! I am hoping the initial selection of clutch will be adequate. One thing I am running into now is some of my tire fitment tricks on the 987 up front are complicated by the AWD geometry. Working on that first to be able to fit 295's without cutting like I had before.
In the rear, it is easy, 345/18's fit at ride height during the test event. Also another important thing learned was the AWD system (PTM) was not pissed off by the wide diameter variations - I tried 285/315s (3% difference in diameter) and 285/345s (over 5% difference) on multiple runs without issues.
Phase 1
Warthog (The new cars nickname - as in A10) is getting baselined now at Cobb Tuning Plano. Then the performance and reliability mods start. Coolant fittings will be pinned/welded and oil cooler elbows replaced. Normal 50k maintenance items will be addressed, belts, hoses, spark plugs, etc.
The baseline dyno was a surprise, we knew Warthog felt strong, but with a stock exhaust and no other indications of engine mods we were surprised to see 472/562. Looks like it still has a tune installed, but we will be improving on this.
For the drivetrain, we have proven parts in queue to help deliver the power. Aasco aluminum flywheel, a Sachs race clutch (764), Wevo engine mounts and a Guard LSD differential rebuild; we loved this combo in the 08 Cayman.
The power recipe is easy. We want to keep things lightweight, so budget friendly 997.2 units will be used. Injectors will be upgraded to handle E85, Silicone inlet pipes, and Warthog will find a voice with a Kline 3 inch GT2 race exhaust with titanium mufflers (thanks SamboTT@byDesign!). After that, a range of Cobb tunes for pump, race gas, and E85
It feels a bit strange having time to write about what we are doing because we usually too busy wrenching in our garage. For this first round, we are handing the keys off to Chris’s crew at Cobb Plano to do the heavy lifting (or engine drop in this case) and dyno tuning.
Phase II
Chassis and Suspension setup – this is where the real magic is for this kind of racing. It requires a stiff platform, top notch tunable damping, and lots of wheel and tire on the ground. We need to be able to pull 1.5Gs all the time or we will be too slow. Piglet the Cayman had 18x10.5F and 18x11R, running 295/315 Hoosiers, and Moton/Tarett suspension.
Warthog will have the same front setup, but we need more camber than the TPC camber plates can provide, and also caster adjustability. To keep the front driveshafts from ‘bottoming out’, we cannot ‘slam’ the top of the strut inward like we did on the cayman, so an eccentric lower arm bushing will be used to balance the driveshaft travel and camber setting.
Vorshlag, who are also nearby in Plano, TX, will be building some new 997 camber plates and delrin bushings to give us the adjustability we need. With their in house CNC machining capability, the new design will be ready to install in just a few days after measurements are taken.
A lucky ebay seach found a deal on a new Tarett blade adjustable front bar. This also comes with the extended length strut mounts to reduce the end link deflection angles. A GT2 swaybar will be used to balance this in the rear.
We also scored a used set of GT3 Moton club sports, which have been rebuilt locally by Maxcy Speed, who are former Moton USA techs. New C4/Turbo sleeves for the uprights and 2.25" spring perches have been ordered. We will start with the standard valving, which worked very well on the Cayman.
For the rear, we are super sizing to 18x13 and 345 Hoosiers in the rear, as the tire is a bit pinched on the 18x12 rim - 3pc CCW’s win here for making the size changes easy. Also in queue will be solid subframe bushings like the GT cars, and a delrin or urethane inner control arm bushing to match the front ones. No changes to the other rear links yet. SCCA rules do not allow heim jointed links, so we have to be careful not to make any bushing changes that would bind up the kinematics.
We should have the full TPC suspension ready for sale here in about a month to help rebuild the checking account
562 ft*lb seems like an assload, any idea what your Cayman put down? A quick Google shows Porsche factory specs were 251 lb*ft at the crank. Hell, a 996 + X50 was rated at 455 ft*lb at the crank. That has got to be a wild ride as is, on E85 with SSP weight reduction I bet it'll be terrifying.
So, uh, how much do I have to sweet talk for a ride along on the Lincoln practice course this year?
EDIT: Ok, really putting things in perspective - the 7.0L C6 Z06 motor is rated at a measly 470lb*ft, peak, at the crank. And you measured 562 on an all-wheel dyno? On some off the shelf canned tune? WTF.
The target numbers are in the 600's for whp/tq. We will be 300lbs heavier than the Corvettes, so I need some 'margin' in my favor The ASP Cayman put down 293/257 on the same dyno. That was after $$$ in intake and exhaust hardware and tuning, with maybe only 10% more left on the table. It was pretty easy man math once I looked at the numbers that were possible.
Weight
Touchy subject for sure - The baseline weight was recorded on Cobb’s setup rack. This is with stock exhaust, seats, battery, Nav and CD changer, rubber floormats etc. and about ¼ tank of fuel. It is better than we expected, spec weight for a 997.1 Turbo is 3495lbs, so we are close at 3508lbs.
Cross weights were also very good, someone had set this up nicely before.
We have at least 100lbs of weight reductions coming to help here, with some removals (stereo) and lighter exhaust, flywheel, seats, and battery,
Camber
The TPC(?) camber plates on the car now are maxed out at around 3 degrees (actually a good thing given the warning below) That worked for our first test , but we will need more adjustment range.
On the 997TT, we found you cannot move the strut too far inboard without risking ‘bottoming’ out the front CV joints. So an offset lower arm bushing will be used to balance the driveshaft travel and camber setting. Why not use GT3 style arms? The SCCA SP rules allow only one method of camber adjustment – adjustable lower arms OR camber plates. But bushing changes are legal – go figure.
Vorshlag Motorpsorts, who are also nearby in Plano, TX, did some forensic work with our front control arm bushing to determine the rubber to metal volume. SCCA rules require the replacement bushing to have the same or less metal % than the original.
Then they ordered in this trick powerflex adjustable offset bushing, measured it, and confirmed it satisfied our metal % requirement.
Vorshlag will be building some new 997 camber plates to give us more range for camber adjustment, and true caster adjustment. They should be similar to this design, and with their in house CNC machining capability, the new plate design will be ready to install in just a few days after measurements are taken.
The other key component for big front tire fitment is a very short, small diameter, spring package – 4” x2.25” main springs and low rate tenders. This moves the perch and spring further away from the wheel and tire, so that it can be pulled further inboard. This is the spring stack on the Cayman below, you can see at the red arrow how high up the perch is on the strut body. We will setup the GT3 front struts the same, with the same 18x10.5 wheel, with 295/30/18 Hoosier A7.
Vorshlag will be building some new 997 camber plates to give us more range for camber adjustment, and true caster adjustment. They should be similar to this design, and with their in house CNC machining capability, the new plate design will be ready to install in just a few days after measurements are taken.
I've got Paul's C2 in here this week. Looks like I'll use a design similar to the EVO-X or our E46 style where the caster is adjusted in steps using the countersunk flatheads and the camber is adjusted by the outer studs.
12-03-2015, 07:13 PM
Someone had to try this! 997TT build
The ASP Cayman put down 293/257 on the same dyno. That was after $$$ in intake and exhaust hardware and tuning, with maybe only 10% more left on the table. It was pretty easy man math once I looked at the numbers that were possible.
