 A Cartuning kit retains stock...  A Cartuning kit retains stock exhaust manifolds and mates them to the turbo by way of a custom stainless steel crossover assembly. Ceramic-coating is available at additional cost. |
 A Cartuning air-to-air intercooler...  A Cartuning air-to-air intercooler mounts behind the front bumper cover just ahead of the radiator. Charge cooling drops air temperature to within 50 degrees of ambient. |
 A Turbonetics wastegate mounts...  A Turbonetics wastegate mounts between the engine and firewall and is adjustable. Beyer usually runs between 11 and 17 psi, the latter being enough to put any 3800-powered GP into the 11s. |
So what about this kit? Cartuning, a Canadian firm, spent about 18 months developing a turbo kit for 3800-powered W-bodies that is flexible enough to give the buyer some options, yet is by no means a trouble-prone "cafeteria plan." Various turbo upgrades and an intercooler kit are available for those who want to build a full competition setup.
The kit has already produced some impressive results. Development was conducted on a stock L36-powered Grand Prix. With a baseline of 160 wheel horsepower (195-200 SAE net depending on year), Cartuning claimed its Performance Stage 1 Turbo Kit made 280 hp and over 300 lb-ft of torque to the wheels. That equates to about 350 hp at the crank. The company adds that the Stage 1 kit is completely streetable and suitable for customers who want to bolt-on a turbo kit to a stock L36 vehicle. The Stage 1's turbo is good for up to 425 crank horsepower with additional supportive mods.
Putting The Kit To The Test
In Beyer's case, his kit as installed in the Comp G uses a larger Precision PT 60-1 turbo (a T04-B P trim Garrett is standard), which will support 700 hp, if he dares. He also opted for the Cartuning air-to-air intercooler. The basic kit also uses a stainless steel ducting from the turbo compressor to the throttle body, a Turbonetics EVO wastegate, a Monza blow-off valve (BOV), and a custom-made stainless steel exhaust crossover assembly that mates perfectly to the stock exhaust manifolds. Also included are new flow-matched Lucas/Delphi 65-lb/hr fuel injectors, a custom reprogrammed PCM, hardware, gaskets, hoses, instructions, and so on.
This kit was designed around the stock cast-iron exhaust manifolds, which were retained for their durability, resistance to leaks, and the exhaust velocity they generate. To those who believe headers are the only way to go, rest assured, you'll be able to make more than enough power to grenade the transaxle without them.
The exhaust side is finished off with a custom stainless steel crossover assembly, specific mandrel bent, TIG-welded, 2.5-inch stainless steel downpipe with a U-bend removal and a CarSound high-flow catalytic converter. Happily, the outlet bolts directly to the stock exhaust system or Borla, DynoMax , or SLP systems to greatly simplify installation.
Since Beyer's car was a supercharged GTP, he was left with the task of choosing an intake manifold, which he handled cleverly and inexpensively. "I've seen guys spend over a grand on a custom sheetmetal intake manifold, but I'm not one to throw around money like that," he says. "I just took the impellers out of the stock M90 and used Cartuning's optional L67 adapter kit, which blocks off the open end with an aluminum plate. That way the throttle body and injectors are left in their stock locations. It works great."