These days, the German autobahnen are so chock full of traffic, it's hard to find a long, clear stretch where you can safely run up to and hold near 200-mph speeds for even a few seconds. Today, however, it looked like lady luck was with us as I dropped onto the autobahn from a slip road and found the asphalt clear as far as the eye could see.
With no hesitation, I maxed the bright yellow Turbo in third and fourth gears, and was well into fifth at an indicated 185 mph (near 300km/h), with the engine still pulling hard, when I saw a cluster of slow traffic in the distance. I could not resist holding the throttle down just a couple of seconds longer before moving my right foot over to the middle pedal. Progressively and firmly applying the brakes, I watched as I swooped down on the traffic ahead with a closing speed of around 100 mph (160km/h).
The standard 911 Turbo brakes have far more stopping capacity than the factory-installed 420 bhp can overcome, so they rapidly and confidently washed off a huge chunk of the speed I was carrying. By the time I was almost level with the slower moving traffic, I was able to drift pass on constant throttle with a 20-mph speed differential-certainly enough safety margin to brake if somebody were to pull out without looking.
This yellow 540-bhp monster Porsche is PSI Motorsport's demonstrator. Owner Christian Schumacher purchased the base Turbo from one of his clients, who had ordered it in Speed Yellow with GT3 Recaro seats and the rear seat deleted. The original owner had ordered up this spec so that PSI could modify it for him, but by the time he found out that Porsche was about to launch the GT2, it was too late and he was about to take delivery of the Turbo.
Coincidentally, PSI was looking for a Turbo to use as a demonstrator, so it happily bought the car from him. But once its client had taken delivery of his GT2 and drove it back-to-back with his old car, which PSI had by now modified, he was sick as a parrot. The obvious superiority of the PSI 540 left the client full of regret for his hasty decision, and he even made an offer to buy his old Turbo back, but to no avail.
The full spectrum of modifications included removing the front differential, uprating the suspension, fitting new wheels and tires, new rear engine cover with fixed wing and the 540-bhp engine kit. All this came in well under the difference between the price of the factory-standard Turbo and the GT2.
The heart of the engine conversion is a pair of KKK K24 turbochargers. They flow a lot more air than the stock Turbo's K16s, and are complemented by a new fuel-pressure regulator running at 5.0 bar as opposed to the standard unit's 3.8 bar. This supplies the extra fuel required for combustion and cooling duties. At the other end of the motor, PSI's sports exhaust incorporates four small free-flow metal sports catalytic convertors, welded together to make up one long U-shaped tube configuration.
I had access to the engine dyno plots of the engine before and after the modifications, which made for an interesting comparison. Porsche claims 420 bhp at 6000 rpm for the standard Turbo motor. On the dyno, it showed an impressive 429 bhp at 6600 rpm.
As good a showing as this was, it paled beside the numbers achieved after the modifications were carried out, which included a re-programmed ECU with fuel and ignition maps unique to this car. Power leaped to a heady 540 bhp at 6640 rpm, accompanied by 459 lb-ft (622Nm) of torque at 4700 rpm. The standard Turbo has 413 lb-ft (560Nm) of torque between 2700 rpm and 4600 rpm. As the 540-bhp conversion also applies to the GT2 motor, the comparative numbers for a standard GT2 are 462 bhp at 5700 rpm and 457 lb-ft (620Nm) between 3500 and 4500 rpm.
In bald acceleration terms, as torque gives you acceleration, the PSI car works out a fraction faster than the GT2 through the gears and is only significantly faster at the top end. Where it is most noticeably quicker, though, is in in-gear acceleration and flexibility.
Accelerating from 80 to 120 km/h in sixth gear takes 6.863 sec., compared to 7.174 sec. for the Turbo and 8.092 sec. for the GT2, which suffers slightly at low crankshaft speeds because of the shape of its torque curve.
The same increment in third gear, when all three are on boost, takes 3.298, 3.772 and 3.421 sec., respectively, which shows the relative power advantages of the GT2 and PSI 540 at their best. Over the wider 100- to 200km/h speed range, the three cars take 8.541, 10.051 and 8.812 sec., respectively. The numbers are conclusive and proportional to their outputs.