Journalists constantly struggle to find new ways to describe how a car feels. For example, comparing an engine revving to redline with a pack of rabid Himalayan badgers chasing a fast-moving dinner. The boundaries of good taste are slammed back and forth like the pistons in said engine. It becomes even more complicated trying to describe a tuned car, having to express what it feels like now and how that relates to a stock version. Superlatives dance with analogies as metaphors reverberate with words not commonly used in conversation, like cacophony or crescendo.
VF Engineering has made my job easier with its recently updated supercharger kits. Yes, they're powerful, but when it comes to how they make the car feel, well, they feel stock. It feels just like the factory normally aspirated engine, there's just more of it. If you look at the dyno graphs, the new curves follow the stock curves point for point, just higher up on the page. There's no sledgehammer to the lumbar, just a smooth shove, something akin to a hydraulic press. Sometimes similes just happen.
VFE spent hundreds of hours developing the kit to the level it's at now. They didn't cut any corners either. It probably could have been made cheaper, but descriptions like "cheaper" and "almost as good" really shouldn't be associated with a Porsche now should they?
When VFE begins a design, the engine bay and hard points crucial to fitting the kit are digitized into a CAD program utilizing a three-dimensional digitizing arm. Think of a robotic arm that you see in car factories, but instead of moving on its own to weld something, it's holding a ruby-tipped probe that allows the user to set points in virtual space. It's a long way from an erector set and Play-Doh for judging fitment.
Once the area is digitized, the components are fitted virtually before all the mounting harware and plumbing is modeled. Those components are then stress tested digitally to make sure failures will never occur on the road due to fatigue or lack of strength. Flow throughout the intake system is then optimized through the use of CFD software and verified in real-world flowbench testing. The results of all this testing can be seen in the compressor inlet tube. Right before the inlet on the supercharger, the entire tube flares out to equalize flow around the opening. Apparently a constant diameter during the 90-degree bend caused starvation on the far side of the inlet. That flair, resembling a muffin top on the inlet, cured the problem.
The result of all the extra effort in construction becomes immediately obvious on the road. On startup, there's no evidence of aftermarket equipment except for slight gear chatter from the supercharger itself. Owners familiar with air-cooled 911s will likely welcome the extra bit of mechanical noise coming from the engine bay. The idle is smooth and feels completely stock. That's the whole idea according to Nik Saran, VFE's head of R&D. He doesn't want something with a big, lumpy idle, or worse, no idle at all. Factory functionality is always the main goal.
Once on the road, that factory-like driveability doesn't stop. It is, however, overshadowed by the extra thrust from the supercharger. At speed, the blower's chatter disappears and is replaced by a whooshing intake noise. Again, air-cooled 911 drivers will think someone has put a fan back in their engine compartment. It's strange how much you miss mechanical noises absent in modern cars. Manufacturers do so much work to eliminate noise that cars no longer sound like machines.
VFE had two different supercharged cars for us to sample, a rather fast 3.6-liter Carrera 2 and an even faster 3.8-liter Carrera S. Both kits run at between 5 and 6 psi. The relatively low level of boost means the factory compression ratio is still utilized, so off-idle performance remains intact. The supercharged Carrera 2 really comes to life, the blower waking the low end up and making driving it easier than ever. The chassis is already extremely competent and from the factory the 3.6 feels almost underpowered. The extra boost doesn't sound like much, but it's definitely noticeable on the road.
The Carrera S, while fast from the factory, feels elevated to GT3-like acceleration. At low- and mid-range rpm it pulls like you're in a gear lower than you actually are. At high rpm it pulls like you have two more cylinders. The linear power delivery is the most impressive part. There's no big jump in the powerband so coming off corners is smooth and controlled. In turbo cars you sometimes feel like you're lighting a fuse and waiting for it to blow all at once, while the supercharger gradually feed the power in.
Short of increasing displacement, we don't know of another way to add this kind of seamless power to an already well-developed engine like the Porsche flat six. The VFE kits start around $10,000 for 996 models and about $12,000 for 997s. That may sound steep, but we've seen aftermarket exhausts that cost half as much deliver only a tenth the power. The only downside is that if the dealer sees one on your car, your warranty is in jeopardy. The kit is completely reversible though, so if you happen to pull the pin on your motor, everything can be taken off before it finds its way back to the service department.
If it were ours, we'd look into a few other upgrades to compliment the supercharger. Both cars will benefit from an aftermarket exhaust to deal with the higher flow rates. A standard Carrera will be a better candidate for more power with some slight suspension and brake upgrades. Other than that, get a helmet, book some track days and learn how to drive.
2009 Porsche 911Carrera S
3.8-liter flat six, AWE headers and cats, VFE Supercharger kit
Peak Power: 456 hp @ 7200 rpm
Peak Torque: 339 lb-ft @ 6100 rpm
0-60mph: 4.1 sec.
Top Speed: 185+ mph (est.)
*measured at the wheels, VFE data
2008 Porsche 911 Carrera
3.6-liter flat six, VFE supercharger kit
Peak Power: 399 hp @ 7400 rpm
Peak Torque: 302 lb-ft @ 6400 rpm
0-60mph: 4.2 sec.
Top Speed: 180+ mph (est.)
*measured at the wheels, VFE data
VFE supercharger kit
* Let's look at the anatomy of the kit. It's centered around a V3 centrifugal supercharger, the newest offering from Vortech. The V3 is based on the proven V2 unit, but updated with a new internal oiling system. The new oiling system allows for a quicker and easier installation without extra oil lines cluttering up your engine bay. It uses a proprietary oil blend that can be drained and replaced without having to remove the supercharger from the car.
A liquid-to-air charge cooler is present to cool the pressurized intake air. The cooler is mounted in the engine bay, while up front the roto-molded water reservoir, Bosch 3psi pump and a GT3 radiator keep the whole system cool. All the lines supplied in the kit are by Goodyear and once installed look completely OEM.
The kit also includes higher flow rate Bosch injectors, a MAF housing and a longer belt for the drive pulley. VFE's attention to detail is apparent again in the belt routing. All the factory accessories still spin the same direction and even utilize the same swept area on the pulleys as the factory setup. The list of hardware is rounded out with factory bumper inserts for the air ducting and various fasteners and wiring to complete the install.
Engine management is handled by software from GIAC. It isn't possible to add boost through programming when using a supercharger. That's determined by the blower's revolutions, which are mechanically determined by the size of the drive pulley. It is possible, however, to control engine timing, which can be optimized to driving conditions and, more importantly, fuel octane levels. Like most GIAC software, a handheld switcher is available to change programs through the OBD-II port. Owners can choose from pump and race gas programs, as well as valet mode. There's even a kill switch.
The first iteration of this kit was released in 2003. Since then, more than 300 kits have been installed on cars the world over. The newest version appears to be the best and easiest to use yet, but with five years experience already in the bag, you know the product is thoroughly tested.