While some can only dream of owning a $70,000 supercar such as the LS7-powered Corvette Z06, some followed their purchase with envy of the new ZR1's output and the means to do something about it. Thankfully the Australian company Air Power Systems (APS) makes a twin-turbo kit with OEM-quality fit and finish that will transform the already potent 427-cube Gen IV into a fire-breathing dragon, and satisfy even the most hard-to-please Corvette owner. With their recent release to the U.S. market and a limited amount of U.S. retailers and distributors, we had only seen a few installed kits on GTOs and F-bodies. All seemed to look and perform marvelously, though, with one of the most complete, well thought out, and high-quality designs out there. When we happened to get wind of an upcoming install at APS retailer and installer Redline Motorsports in Schenectady, NY, I jumped at the chance to get this exciting new product onto the pages of GMHTP and Editor Jensen was happy to comply.
Like all of its late model GM kits, the APS C6 Z06 Twin Turbo Kit comes with two cutting edge Garrett water-cooled turbos, heavy-duty cast manifolds, high efficiency bar and plate air-to-air intercoolers, hot and cold plumbing, a higher capacity MAF housing, twin APS blow-off valves, and TiAl wastegates. For the hungry 427 LS7, APS supplies Garrett GT3582R ball bearing turbos with Inconel turbine wheels that efficiently produce up to 1200 horses at only 18psi knowing that with a few modifications-such as forged pistons-these engines can certainly handle it. Big turbos, though, need big wastegates, so cleverly packaged TiAl 44mm units are tucked under the floor pan. This particular kit also comes with a larger oil cooler (to replace the smaller factory piece), a stainless steel after-cat exhaust, and the necessary fuel system upgrades including high flow fuel rails, injectors, and dual in-tank pumps.
Our '06 test car is Redline's official guinea pig, which owner Howard Tanner had previously had a set of Kooks long-tube headers, B&B exhaust, and a centrifugal blower enhancing the stock motor. He had planned to use the APS kit to eventually make up to 1,000 rear wheel horsepower, so the first order of business was to replace the stock LS7 with a low compression 427 using Diamond forged pistons, as well as a heavy-duty set of rods and a crank, and a re-sleeved block from Race Engine Development. He even decided to have West Coast Cylinder Heads port a set of LS7 heads and put in a larger boost cam. That being said, we expected that even at 6psi dyno pulls would be healthier than a boosted stock LS7. (APS claims 625 horses at the wheels in that configuration.) The added benefit of having the fortified motor is that Howard had no problem cranking up the boost to 9psi on pump gas to give us an idea of what this kit was really capable of, where the stock hypereutectic pistons and lightweight titanium rods might have called it quits.
The APS C6 Z06 Twin Turbo kit is definitely not the cheapest out there, but with OEM-quality pieces throughout, you can see the quality. The thick cast manifolds have little chance of cracking, the twin ball-bearing Garrett GT turbos are water-cooled and some of the best on the market, the 10x11x4-inch, air-to-air intercoolers cause less than 1.0psi drop in boost and keep intake air temperature 15 degrees below ambient at any vehicle speed above 50mph, and the fit and finish on the kit is top notch. It even comes with an after-cat exhaust, larger oil cooler, and all necessary fuel system upgrades. A complete kit is $13,995 plus shipping. | 
To begin assembling the turbo system, the factory-like heat shields are bent around the manifolds then bolted and clamped down with the supplied hardware. Redline prefers to coat the manifolds (as seen here) for appearance, heat transfer for the turbos, and to reduce underhood temperatures. Extra heat shielding is also provided to shield the underbody and starter from the high temperatures emitted from the turbos themselves, and extra heat wrap for a few wires including the ground and power to the starter is a must. | 
Some assembly is required with the turbos, including bolting up the oil feed line via a banjo bolt. Since these turbos are water-cooled, there are also coolant feed lines that tap into the factory freeze plugs on the block. |
Studs are screwed into the flange on the manifolds,... | 
...then the turbo is mounted. High-temp copper RTV sealant is used to prevent leaks. Brass locking nuts and washers secure the turbos to the manifolds, which techs Jon Bettini and Tony Madia found easier with the oil feed lines removed. | 
High quality hinge clamps, and copper RTV,... |