As I'm sure you've heard before, the internal combustion engine is nothing more than an air pump-the more air the pump can process/move, the more power it can make. While this basic theory holds water, other contributing factors are to be considered, such as engine displacement, camshaft profile, valve size, and so on.
In many cases, the first, easiest and most cost-effective modification performed to a virgin automobile in order to produce power gains is the air filter/induction system. With a plethora of options in the aftermarket, a single air filter or cold-air induction system can net decent power gains, but is it due to the higher rate of airflow into the engine? Some may argue yes, and some no-the larger amount of air into the engine helps, but in some cases the vehicle's electronic control properties are centered on the stock filtration system.
By changing to a higher-flowing unit, the air-fuel mixture is essentially leaned out, causing an increase in power (leaner is meaner). Most vehicles are tuned conservatively from the factory, so leaning the mixture out doesn't generally cause an engine-damaging condition. But be aware of what you're doing.
At the other end of the spectrum, what goes in must come out, which leads us to the exhaust system. Spent exhaust gases are expelled from the engine via the exhaust valves, through the exhaust ports in the cylinder heads, then the exhaust manifolds/headers, one or more catalytic converters, several bends in the exhaust tubing, the mufflers-finally reaching the atmosphere via the tailpipe(s).
That leaves us with many avenues for restrictions. Engineered restrictions are necessary to produce a certain amount of backpressure, although some think manufacturers add additional restrictions to detune the car.
But keep in mind that your favorite car company has to meet stringent noise restrictions (both corporate and government mandated), safety and fuel economy standards, and emissions regulations. As hot rodders, we look at all of the potential power gains achieved by applying aftermarket components to reduce the factory road blocks in your engine.
Additional factors that will increase the "in and out" effect are throttle plate/body size, intake manifold port diameter and runner length, camshaft lift and duration, intake and exhaust valve sizes and cylinder head port volumes. When taking an engine to the extreme via extensive modifications, it is necessary to consider additional factors such as injector size and custom tuning to the engine management system, which can become very costly, never mind turning your ride into a gas-guzzling beast that won't pass an emissions test and who knows about the drivability thereafter.
For this particular installation/test we'll leave the actual engine alone, installing an air-induction system from Motorsport Technologies in Houston; long tube headers and mid-pipe with catalysts from American Racing Headers in Amityville, New York; and a trick-looking quad-tipped muffler system from GHL Motorsports in Mesa, Arizona.
The specimen being utilized is none other than an LS2-powered 2006 C6 Corvette automatic with paddle shifters. To perform the installation duties and custom tuning, we called upon Chris Corriell, Doug Ring and the crew of East Coast Supercharging in Cream Ridge, New Jersey. ECS specializes in LSX-powered vehicles, especially the Corvette, so we were more than comfortable being surrounded by the professional staff, as well as the stout machinery being modified at its facility.
ECS Technician John Romano got the nod to perform the installation. John began by removing the fasteners for the mid-pipe at both the catalytic converter and toward the rear attaching to the muffler assembly. Once all the fasteners were removed, the midsection was simply taken from the vehicle.
To facilitate easy removal of the muffler assemblies, John needed to remove the rear sway bar mounting brackets in order to move the bar to a lower position. This step holds true for both the C5 and C6 models. Beyond removal of the sway bar, John took off the rubber muffler hangers with a prybar and carefully removed the mufflers from beneath.
At this time, John installed the new muffler assembly from GHL Motorsports. The four-tip unit features a nice throaty sound, comfortable at low speeds, but more like a raped ape when laying into the throttle. Each unit is handcrafted, using T-304 stainless steel and completed with a beautiful polished finish.
John moved to the front of the C6 to remove the catalytic converter assemblies, gaining access to the exhaust manifolds. Once the manifolds are removed, be sure that the cylinder head surface is clean before installing the header gaskets and headers.
Pictured are the stock manifold and the new American Racing Headers piece. All ARH products are manufactured utilizing the highest quality 304 stainless steel available and come with race-inspired merge collectors with scavenger spikes. John installed the headers from the bottom of the C6-unbelievably with no problems. Part of the reason is the header design. And the C6 doesn't have kickouts on the oil pan like the C5, thus creating even more room.
Once the headers were reinstalled, the spark plugs and ignition cables were returned to working order. The header on the passenger side interfered slightly with the body pinch weld. The instruction manual says this may need to be trimmed. About 1/8-inch was taken off in a simple fashion-by using a cut off wheel.
Next, John assembled the S/S X-pipe with high-flowing catalytic converters to the connection tubes, which will eventually mate to the muffler assembly. All ARH systems include Grade 8 hardware and heavy-duty S/S band clamps. Once installed into the vehicle, the pictured oxygen sensor harness extensions must be used because of the new sensor locations. Be sure to tuck all sensor harness wiring away from heat and in a secure fashion to prevent future problems.
Our C6 exhaust system fits together without hassle. For future reference, the oil filter and starter can easily be worked on without removal of the headers. Once all of the band clamps are tightened, John gave each clamp a spot weld to ensure it stays in place (optional step that's a matter of preference).
Next we moved back to the front of the C6 to begin installation of the XCelerator Air Induction System from Motorsport Technologies. John began the process by removing the stock induction system and the air deflector that will be modified. MTI supplied a template to aid in drilling the proper holes required, as well as the necessary cutout needed in the air deflector. John employed an air-powered saw for cutting.
Next John installed the baseplate for the filter housing via rivets supplied with the XCelerator kit. The air deflector is then reinstalled and the washable, high-flow air filter is installed. John can then install the remainder of the air intake system, which maintains a rather stock look with an advertised 36 percent increase in airflow. The XCelerator is molded from the highest-quality ABS plastic to ensure years of service.
The air induction and exhaust system are now complete. The C6 was started and checked for any possible leaks. None were found. Doug Ring took over by connecting his laptop-containing tuning software from HP Tuners-to the Corvette's diagnostic port. Doug then took the car on extensive road tests to tune the car for drivability under real-world conditions; once he was satisfied with the tune, the C6 was returned to the dyno for verification and to check potential horsepower and torque gains.
The after-dyno results were more than pleasing. The C6 pumped out a whopping 361 hp with 349.8 lb-ft of torque, and that's a gain of almost 37 rear-wheel horsepower and 28 lb-ft of torque. Estimated flywheel horsepower is now in the neighborhood of 450 hp, that's up 50 from stock. Not bad for an exhaust system and air induction kit, although maximum numbers don't mean diddly. How is the drivability you ask? Phenomenal. Throttle response was quicker, mid-range power is seat-planting and wide-open throttle snaps your head back hard. In all, the system installed flawlessly.