Nobody's going to argue that Corvettes are one of the best bang-for-the-buck performance vehicles on the road today. Going fast and looking good certainly has its appeal. But even the 300-or-so rear-wheel horsepower provided by a factory LS1 engine starts to get a little humdrum after a while, and some C5 owners develop a lust for more power. Long known for its line of Magna Charger blowers, Magnuson Products Inc., of Ventura, California, has come to market with an intercooled version of its Magna Charger blower for '97-'03 C5 and Z06 Corvettes.
We jumped at the opportunity to test one of these new units, and showed up at the Magnuson facility with our test vehicle, a bone-stock '01 C5 with 26,000 miles on the odometer. We immediately pulled onto the chassis dyno and made a series of pulls, the best of which netted 296.4 rear-wheel horsepower at 5,750 rpm and 292 lb-ft of grunt at 5,000 rpm. That's not bad, but we were eager to see what the blower would bring to the table.
The intercooled Magna Charger kit comes with absolutely everything you'll need to complete the installation, plus a bound, 44-page book of illustrated instructions. The whole job can probably be done in a weekend, provided you have a competent helper and a good supply of suitable beverages.
The hood was removed, the negative battery terminal was disconnected, and the coolant was drained. The car was placed on a lift and the front wheels and tires were removed to provide access to the steering components. We removed the front antisway bar, loosened the two bolts holding the power-steering cooler, and disconnected the power-steering high- and low-pressure lines from the rack-and-pinion, being careful not to mess up the seals on the line ends.
The rack-and-pinion was unbolted and the four nuts holding the crossmember to the frame were loosened enough so we could pry it down on the driver side and slide out the rack-and-pinion unit to gain access to the harmonic balancer.
The blower kit comes with an additional package that includes a stepped drill bit, a reamer, a drilling jig, and a new GM balancer bolt. We bolted the jig in place and drilled two holes; half of each hole created a groove in the crank snout and the other half grooved the balancer. These holes were reamed, and a pair of short pins was driven in with a drift punch to make sure the balancer wouldn't spin on the crank. The washer on the new crank bolt retains them. To install the intercooler, the center section of the front spoiler was removed, and we held the heat exchanger in position and marked and cut a 1-inch hole on the radiator shroud to accommodate a length of hose. Mounting brackets were installed on the heat exchanger using the supplied carriage bolts, then the exchanger was bolted up and the hose connections were made.
We assembled the new coolant pump and mounted it in position on top of the frame extension. We needed to modify the spoiler by removing the upper rubber portion along the top edge of the mounting bracket to ensure the heat exchanger would get enough air. The spoiler was reinstalled and we got busy with the electrical connections for the coolant pump. We went topside to the fuse/relay center on the passenger side of the engine compartment and removed the B+ terminal cover.
Pulling up the fuse/relay center revealed three wiring blocks on the bottom. We went to the white block and located a pair of gray wires. Different years have different wiring schemes. The smaller of the two wires was cut and the yellow wire from the heat-exchanger relay and wiring harness was spliced in with the supplied crimp/shrink connector. Just crimping the connection wasn't enough--we had to shrink the plastic covering, too. Then the black wire with the ring connector was routed down to the ground terminal under the battery. The rest of the wiring was worked forward following the factory path and the large red wire and fuse holder was attached to the B+ terminal with the ring connector.
The Magnuson supercharger's manifold comes with 42-pound injectors installed, so it was time to upgrade the fuel pump to make sure fuel delivery keeps up with the engine.
Installing the new fuel pump involved making sure the tank had no more than 1/8 inch of fuel left in the bottom and removing the right-side wheel and tire to access the stock unit. Four bolts were removed to release the end cap on the fuel-tank panels. Then we took off three fuel lines by pushing the connectors and squeezing the release triggers. We removed six more bolts and pulled the access cover and pump out of the tank about 6 inches and removed the fuel-level transmitter and eased out the pump assembly. Moving to a bench, the fuel-pump can was separated from the lid and the fuel line connection was removed, taking care not to damage the line. The electrical connector was unplugged and the new fuel pump was assembled and put back into the tank.
Installing the supercharger was about the same as removing and replacing the intake. But there were a few twists:
First, the plastic fuel-rail covers were set aside since they wouldn't be needed again. Then the fuel lines were disconnected using the supplied tool. From there, it was an exercise in removing the air-cleaner duct and mass airflow meter, unplugging the intake air temp connector, disconnecting and removing the EVAP-canister purge tube and the purge-canister solenoid from the throttle body. Next, the throttle-body coolant hoses were disconnected and clamped before pulling off the electrical connectors at the throttle body, the crankcase breather-vent tube, the electrical connectors on the fuel injectors, and the EVAP-canister purge-solenoid electrical connector.
Then the vacuum hose was disconnected from the brake booster, and the knock-sensor wire-harness connector was removed from the PCV tube and the connector was unplugged. The PCV tube assembly was then removed and the MAP sensor electrical connector and vacuum line were disconnected. The 10 intake bolts were pulled using an 8mm socket, and the manifold assembly was lifted off the engine.
A Shop-Vac was used to clean the dirt and debris away from the intake ports, then the coolant vent pipe was removed. The intake ports were taped shut and the serpentine belt was removed and discarded. The power-steering reservoir and its bracket were removed from the driver-side head and the bracket was separated from the reservoir. The bolts were reinstalled into the head and torqued to 37 lb-ft. The line was disconnected from the reservoir and the fluid was discarded. The reservoir line was rerouted under the top radiator hose and over to the passenger side where the reservoir will be permanently attached later on a new bracket.
A new front coolant vent pipe was installed using the stock bolts, making sure the O-rings were in place. The two rubber knock-sensor covers were removed from the engine valley cover and their electrical connectors were disconnected. The knock sensors were removed before removing the engine-valley cover. The original gasket can be removed, but the bolts will be replaced. The new engine-valley cover from the kit was installed with flathead bolts. Finally, six O-rings were placed in the recesses in the cover.
This was a great time to replace our old knock sensors with new ones since we had some doubt about their efficacy. Their wires were routed through channels milled into the new valley cover for this purpose and held down with small dabs of silicone adhesive.
Work moved to the bench where components were swapped from the stock manifold assembly to the blower unit. The MAP sensor and seal, throttle body, new power-steering-reservoir bracket, fuel-pressure regulator, and other components were installed. Protective tape was removed from the engine's intake ports and the area was sprayed with silicone lubricant before the supercharger assembly was lowered onto the engine and bolted in place with new, shorter bolts supplied in the kit.
Once the new manifold bolts were started finger-tight, the MAP sensor electrical connector was plugged into the rear of the new manifold, and the manifold was torqued to 89 lb-in. A new, longer, serpentine belt was routed and installed according to the diagram in the instructions.
A new piece of coolant hose was attached to the driver side of the throttle body and the original hose on the passenger side was reused. The EVAP hose and solenoid were reattached, the fuel-injector connections were snapped into place, and the stock fuel line was pushed onto the fittings on the new manifold. A new, 10-inch piece of hose was attached to the power-steering reservoir and it was slipped onto its new bracket. Then the IAT's split loom was shucked back and the wiring was rerouted to connect the plug to the sensor; a new piece of split loom was installed. The rest of the components were installed according to the instructions, using new hoses and wiring from the kit as required. A new air duct from the kit was put in place between the throttle body and MAF meter, and the K&N filter element from the kit was slipped into place.
The new intercooler reservoir was temporarily slipped into place on top of the battery and a notch was cut into the rubber strip along the top of the partition to accommodate a hose that will attach to the reservoir. Then a 1-inch hole was cut near the fuse/relay center so the other hose could pass through to the reservoir. Then lengths of supplied 5/8-inch hose were cut to length and run to fittings on the blower manifold, which was then filled with a mixture of water and Red Line WaterWetter. The radiator was refilled with coolant, the battery was reconnected, and the ignition switch was keyed on several times to fill the new fuel rails so we could check for leaks.
The only thing left to do was tune the vehicle's PCM so everything would run as it should. Magna Charger supercharger kits come with a Micro Tuner 2001 unit from Superchips Inc., into which the vehicle's VIN-specific parameters are downloaded. It's as simple as plugging the unit into the connector under the dash and uploading the new tune-up to the car. The original specifications are retained in the Micro Tuner in case of a need to swap back for some reason. And, if the dealer flashes the PCM back to a stock tune-up, your vehicle's specifications are kept on file according to the VIN so they can be retrieved. The Magnuson tune-up can be further tweaked using LS1Edit or similar software, although the company doesn't necessarily recommend doing so. Magnuson also recommends staying with the pulley that comes with your supercharger, which will provide between 6.5 and 7 pounds of boost.
After the car was run for a while to check for leaks, Magnuson R&D calibration guru John Germanson strapped the car back down to the dyno and let 'er rip. The first pull was a little rich with an 11:1 air/fuel ratio, and the car posted 437 rwhp at 6,000 rpm and 409 lb-ft of torque at 3,500 rpm.
A short cool-down period was followed with a session on the computer, tweaking the A/F ratio closer to the desired 12:1. The second pull got the car closer--an 11.7:1 A/F ratio netted 437.2 rwhp at 6,000 rpm and 424.7 lb-ft of torque at 3,500 rpm.
Another couple of tweaks and the final pull netted 443 rwhp at 6,000 rpm and 416.9 lb-ft at 3,250 rpm. That's 146.6 rwhp and 124.1 lb-ft of twist over stock. More impressive was the torque curve--it was flat enough across the entire powerband to make your ears bleed when you mash the throttle. And that's what having a supercharged Corvette is all about.