When offered the chance to start up Project 997 TT, I jumped all over it. No, it's not my car and yes, I'm still enjoying my soon-to-be-slow-by-comparison Project M3. So let's get right to it.
One of the most popular Turbo upgrades is a new exhaust system. These flat-six motors have a unique tone, so who could blame owners for wanting to exploit that? And on a turbo-charged car, substantial horsepower gains can be had. To prove it, we contacted Fabspeed for its turbo-back exhaust system.Fabspeed's exhaust system for the 997 twin turbo is T304 stainless steel, complies (reportedly) with the original Porsche factory warranty, and is 50-state legal. It's offered in three different sound levels. We chose the quietest. With a change to high-flow catalytic converters and freer-flowing canisters (the 30-plus pound loss in weight is nice too), we expect significant gains. At $3,700, plus the optional $850 tips, there ought to be.
To plot accurate horsepower improvements, we must baseline the car first. Enter Imagine Auto of Lenexa, Kansas, the tuning and dyno facility we will use for our Project 997 TT testing, and official installer for this project. Its Mustang 500 SE dynamometer tests all driveline configurations and has a feature to simulate real-world engine loads for proper tuning. The company also specializes in Porsches. You may remember we recently featured two of IA's supercharged Boxsters and the owner's monster 996 Twin Turbo (ec, February and March '07).
Even though we could disconnect the front drive axles and test in rear-wheel-drive mode, all our testing will be done in all-wheel-drive mode for all-wheel horsepower (AWHP). IA usually reports a consistent five percent extra loss to the wheels when testing in all-wheel-drive mode, compared to testing for rear-wheel horsepower. Additionally, we'll be testing the car in overboost mode, a factory option that adds an extra 3 psi boost for up to 10 seconds at a time, but only up to 5500 rpm-thus affecting peak torque but not peak horsepower.
On the dyno, Project 997 TT shows a phenomenal powerband. Thanks to the new variable turbine geometry (VTG) technology, the turbos push the 3.6-liter engine's output to 300 lb-ft of torque at an astonishingly low 2800 rpm, which increases to a 440 lb-ft peak at 4000 rpm, never dropping below 350 all the way to redline. That adds up to 350 AWHP by just 4200 rpm and 429 peak AWHP at 6100 rpm. Such is the beauty of larger-displacement turbo engines-there's power everywhere. This is going to be fun.
Installing the Fabspeed exhaust is fairly straightforward, but the rear bumper must be removed. It takes IA's technicians about four hours. The car is then fired up. The new set-up provides a more aggressive tone at idle. Strapped to the dyno, at wide-open throttle, it's downright nasty (in a good way). It's not just noise, however. With no adjustments to engine software, power goes immediately up to an impressive 449 AWHP, a nice gain of 20 to 21 hp from 6200 rpm to redline. Torque improves with a 20 to 30 lb-ft gain from 2000 to 2500 rpm, and then between 10 to 17 lb-ft gains in the meat of its powerband from 4000 rpm to redline.
With an appreciable power hike from this modest upgrade, things are looking good. On the road, Fabspeed's 'quiet' system doesn't drone like some aftermarket exhausts. It's actually fairly quiet from inside the cabin and out, making it an upgrade worthy of serious consideration. On top of the power gains, there's a deeper tone at idle and the music at wide-open throttle is unique to the flat-six layout.
Now that Project 997 TT is under way, expect some drastic changes. The car will not only look different, it will sport a more exotic interior plus stupid-fast power that will really put the all-wheel-drive system to the test, starting with headers and software. Think this car is worthy of exotic car status now? Just wait.
Author's note: For those only interested in 'flywheel' or engine horsepower-forget about it. Don't waste time trying to figure it out. With Porsche's recent conservative engine horsepower claims (probably for insurance reasons) 'flywheel' or 'bhp' brake horsepower estimates are pure speculation. The important thing in this project will be to note actual improvements over our 429 AWHP baseline.