The Monza blow-off valve vents...
The Monza blow-off valve vents excess pressure away from the compressor when the throttle is closed. Otherwise, it would cause a rapid drop in compressor speed, which could stress or bend the blades.
The Cartuning 3800 turbo kit...
The Cartuning 3800 turbo kit comes as a completely engineered kit, down to the high-capacity catalytic converter, making for a simple, effective modification that yields big power increases. Optional equipment, such as the intercooler, can boost power even further and reduce octane requirements. An F-body version is also in the works.
Talk about a sleeper! Though...
Talk about a sleeper! Though the Grand Prix GTPs have a good reputation for performance, this particular car is capable of running with Z06 Corvettes and Dodge Vipers-all the result of a turbo upgrade, which can be added to any 3800-powered Grand Prix.
Beyer says the performance increase was huge, knocking more than 2 seconds off the Comp G's e.t. and adding over 15 mph to the trap speed. Our seat time in the Grand Prix confirmed that, even with the boost down from 17 to 12 psi, this car was an absolute rocket, yet it idled and otherwise behaved like a stocker. From a 15-mph roll, the V-6 was able to easily overpower the tires, and while torque steer was present, it wasn't enough to cause any concern. The GP zipped up to 100 mph at least as quickly as a Z06 Corvette, almost too quietly to realize just how fast this car really was. When the throttle was let off, the BOV let out a loud hiss and the 3800 quietly coasted back to legal speed.
As quick as the GTP is, we were astounded to find out later that it was running with a damaged turbo. An air filter was accidentally left off during a visit to a quickie oil-change emporium and some debris was able to enter, damaging the compressor. Beyer noticed the torn blades while at the racetrack and decided to run anyway, as the compressor turned freely, though it wasn't grabbing air like it was intended to. Still, he managed to make quite a showing.
"My first pass when I drove in was a 13.2 at 110 mph," Beyer says. "I paid my money at the gate and got in line with all the stuff in the trunk and with street tires. Once it started hitting 12s, things got fun as people kept coming to the pits to see what just beat them. I took out a few Mustangs, which was easy, and an E55 AMG Mercedes-just barely, though. Even with the slicks, it couldn't hold traction.
"I didn't see the damage to the compressor wheel until I was at the track prepping it. But I basically said, 'Screw it, we're already here, so let's see what happens.' We got stuck at 12.1. I tried giving it more boost, but it didn't run faster. Evidently, the damaged turbo was at its limit. All the later runs were between 12.1 and 12.4 and around 114-117 mph."
The results, while not perfect, were still spectacular. With a fully functional turbo, this car would have been well into the 11s-it was nearly there to begin with. The Cartuning kit, as Beyer installed it, cost just under $4,500. Granted, that's a pretty stout chunk of change, but if you add up the cost of the ported heads, the cam, the headers, the oversized throttle body, and the nitrous system, you're most likely money ahead. Best of all, the turbo kit can be moved from car to car a lot easier than the aforementioned mods.
In this age of "trick of the week" hop-ups and frequently spending hundreds, if not thousands, of dollars for single-digit horsepower increases in late-model performance engines, the viability of turbocharging becomes more and more relevant. It remains one of the most effective power-producing modifications available and also one of the most cost-effective. Seventeen pounds of boost is definitely our idea of "displacement on demand."