In a performance automotive world of conflicting technical opinions and myriad personal preferences, there's one thing that's indisputable: In the sixth-gen Corvette Z06, General Motors has given us one of the finest sports vehicles the world has ever known. With its fantastic 427ci engine, light weight, and supercar chassis dynamics, it's among the best out there-at any price. Sorry, foreign-car ans, but that's an indisputable fact.
What isn't a certainty is the best way to go about making insane amounts of horsepower with the car. The factory Z06 sticks with good, old natural aspiration-and 505hp is a sizeable amount to work with. But when looking to up the ante even further, is natural aspiration the best choice? Or perhaps nitrous injection should be in the cards. And then, of course, there's forced induction, but even this option offers the further choice of a roots- or screw-type blower, centrifugal supercharger, or turbocharger(s). The right choice depends not only on the intended use of the vehicle, but also on whom you happen to be talking to.
The base STS C6 twin-turbo...
The base STS C6 twin-turbo system is shown here. As we mentioned in our story, ECS uses different turbochargers and some other upgrades we'll discuss as we go along. If you're worried about larger turbos yielding turbo lag, fear not. All turbos used by STS and ECS are specifically sized to be rear-mounted and are internally quite different from your typical front-mount units. Thanks to this, boost response is said to rival that of an ordinary turbo system.
Cream Ridge, NJ-based East Coast Super-charging (ECS) offers one such option that's hard to beat. ECS has teamed with Squires Turbo Systems (STS) to create a rear-mounted, twin-turbocharger package that adds substantially to the LS7's already healthy horsepower while maintaining stock-type daily driveability. For the price of $14,749, ECS will convert your stock Z06 to a boost-huffing screamer-and this figure includes all parts, installation labor, and tuning. It's a 100 percent turnkey package.
ECS bases its package off of STS's twin-turbo system for the base LS2-equipped Vette. But for the larger-cube Z06, the shop takes the kit a few logical steps further and upgrades to stouter GT32 turbochargers as well as matching dual wastegates. In addition to LS7-specific fuel-system mods, ECS adds its own methanol-injection system to ensure safe operation on pump gas. Finally, the turbos and the stock exhaust manifolds are ceramic-coated for increased performance and durability.
Before we get to the installation overview and performance numbers, let's answer what is perhaps the most obvious question regarding the design of the STS system-why the rear mounting? This STS-patented turbo layout is all the rage right now, and it has been applied to everything from passenger cars to pickups. So a few words are probably in order for those who may not have heard much on the topic.
This photo shows the intake...
This photo shows the intake and exhaust tubing supplied by STS with the base C6 kit. Nearly all of it is used by ECS in its Z06 install. The tubing is so shiny because it's HPC-coated. Concerned about boost loss or delay through the intake pipes? STS says the post-turbo intake volume in its systems is similar to that of many conventional turbo systems running a front-mount intercooler, and it only takes about 0.05 seconds to compress that volume.
In a nutshell, rear-mount turbocharging isolates underhood components from the wire-frying heat typically given off by a turbocharger's turbine housing. In addition, the rear-mounting methodology means the turbos themselves run cooler, and the install is simpler and cleaner. Also, no piping downstream of the turbo means no backpressure whatsoever, thereby improving turbocharger performance.
The Z06 rear-mount twin-turbo kit is available exclusively through ECS on a per-customer basis. "We know what we need to do, and the install goes very smoothly," says ECS co-owner Doug Ring. "Just supply us with a Z06, and we'll take care of the rest."
As a sparingly paid freelance journalist, a new Z06 is only a glimmer in the eye of a daydream for me, and I only wish I could take Doug up on the offer. As for the rest of you, check out the accompanying photos and captions, which detail the kit's installation on ECS co-owner Chris Coriell's personal Z06. And if tech specs aren't your thing, don't worry. We've also included performance numbers and a gratuitous, VETTE-quality burnout shot.
The STS front-mount air-to-air intercooler is specially designed to fit just behind the sixth-gen Vette's grille. There is one rearward-facing inlet at each lower corner, and the two streams of air meet in the middle after being cooled by outside atmosphere. Factor in the heat-dissipating properties of the extra-long inlet tubing, and air exiting the intercooler can be chilled to a temperature just slightly above ambient.
Our starting point is the stock Z06 exhaust system. To begin the install, it is removed all the way back from the cylinder heads; however, essentially everything forward of the over-axle pipes will be reused. Note the large size of the factory mufflers-a big plus in this case, as it means there's plenty of room for a rear-mount turbo system.
The stock Z06 exhaust manifolds flow rather well, so ECS retains them on the twin-turbo kit. They have to come off the car temporarily to be coated with high-temp ceramic, which helps ensure that as much additional heat energy as possible is retained in the exhaust gases.
Though the standard C6 twin-turbo system includes T3/T04B Stage III Garrett turbos, bigger GT32 turbochargers are utilized by ECS for the Z06 system. Doug Ring believes these units can likely support 12 psi, so "more is in this kit," so to speak, if a customer wishes to build, say, a lower-compression forged engine. Note that the turbos' exhaust housings are ceramic-coated as well.
With the stock exhaust system (sans mufflers and over-axle pipes) reinstalled, the new over-axle pipes slip into the stock H-pipe, and the turbochargers are bolted onto the back of them. Notice the mounting flange for the wastegate just upstream of the turbine. This is where excess exhaust pressure will bleed off to keep the turbo spinning out just the right amount of boost.
Though the majority of the turbo system is located aft of the rear wheels, a few items go up front, and one of those is the air-to-air intercooler. Though many STS rear-mount turbo systems don't use an inter-cooler, STS and ECS felt it a necessity on these cars, thanks to their high-compression engines and partially concealed intake tubing (as you'll see shortly).
With all of the ducting attached to the turbos, the install at the rear of the vehicle is complete. While not readily visible from outside of the car, the twin turbochargers are truly a sight to behold if you take a peek beneath. One other advantage of the rear-mounted turbo setup is that the weight of the turbos is at the back of the car, meaning the Z06's near-perfect weight balance is not compromised. Note how the exhaust tips closely mimic the size and placement of the stock units, adding to the stealth factor and resulting in a truly clean install.
A close-up of one of the twin TiAL wastegates better shows how these units bypass the turbo and shoot exhaust straight out the back (through the outward-mounted tips). Though theoretically a single wastegate that spans the two exhaust pipes could be used, the decision was made to run duals to help eliminate any possibility of boost creep. Boost for this system is set to a conservative 5.5-6 psi, which is probably the safe limit for an internally stock LS7.
Don't be thrown by the fact that there are no mufflers back here-the turbos cut sound levels to near stock at part throttle. They do, however, add a distinctive, high-pitch turbo hiss that comes right out of the tailpipe. If you're curious as to where the air filters are located, they're up inside the rear fascia where it's cool and dry. From the turbo outlets, compressed-air tubing runs up into the rear fenders and over the rear wheels, so it isn't visible from underneath the car.
Up under the front of the car, the intake tubing carrying compressed air from the turbo runs safely over the rear wheels and inside the rocker panels (below the doors), finally emerging just aft of the front wheels. The pipes then run along the bottom of the front subframe and enter the intercooler mounted just ahead of the radiator and A/C condenser.
Worried about losing a Z06 Vette's already-sparse ground clearance? Fret not, for as you can see, the intake pipes are located up high to give plenty of space beneath. In fact, they don't sit any lower than anything on a stock vehicle. Plus, you can see that they are bolted securely to the frame. In the center-front of the subframe is mounted the STS electric oil pump. The pump is part of a patented system that scavenges the oil as it leaves the turbos and returns it to the engine, cooling it along the way.
Part of the ECS package is a pair of pillar-mount gauges showing readouts of boost and fuel pressure. Look closely, and you'll also see an LED. This lights up as a gentle reminder of when the ECS methanol system is flowing-though you'll probably be pushed too far back into your seat to care.
Another beauty of the remote-mount turbo is that very little changes under the subject vehicle's hood. As applied to the Z06, basically the only item altered is the polished aluminum pipe running from the intercooler to the throttle body. Note that the blade-type stock mass-air meter has been retained. Stock injectors are kept for fueling purposes, but ECS adds in a booster-pump unit to supply the required additional fuel.
With the install complete and the car on the ground, we can take a look at the rear. Can you see the turbo system here? Just barely! Complaints of low-hanging, rear-mount turbos should be nonexistent, at least on this vehicle.
The only other external cue to the vehicle's forced-induction configuration is the intercooler, which is just visible through the crosshatch Z06 grille.
When it comes to performance, onlookers will be left in a cloud of smoke to stare at two 325mm black stripes on the pavement. Horsepower went from 458 to 568 at the rear wheels after installation, with a corresponding increase in torque. As for numbers in the quarter-mile, "We tried some runs with the street tires, and it was just a joke-we couldn't hook," says ECS co-owner Doug Ring. "Our twin turbo-equipped Z06 feels like a 10-second car, and I'd be surprised if it wasn't. We'll see once we get some slicks on. What I can say is that the thing is a powerhouse!" Give ECS a call, and you can have one of your own.