 |
 |
 |
|
| The ¾-inch hoses are connected to the Magnuson-supplied coolant reservoir and pump that are mounted in the engine compartment. From the top, all you really see is the OE-like reservoir tank, but the coolant circulation pump is below it on the business end. Juice to turn the pump is sourced from the main fuse box via a Fuse-Tap and some careful wire manicuring. | |
10 THINGS ABOUT SUPERCHARGERS1. Increasing the amount of air that will pass through the engine will generally increase power. 2. This is called boost or positive manifold pressure, expressed most commonly in pounds per square inch (psi) 3. There are three types of superchargers in common use: Roots, screw, and centrifugal 4. Modern variants (mega-OE supplier Eaton used Magnuson, The Blower Shop, Weiand, Blower Drive Service, etc., in the aftermarket) are of the Roots-type and descended from the GMC diesel predecessors. The two 3-lobe rotors with a 60-degree helix inside the Magnuson case don’t compress the air within it. Rather, compression of the inlet charge takes place in the cylinders, so the Roots-type is referred to as an external compression blower. 5. Examples of the screw-type supercharger are manufactured by Kenne-Bell, Whipple, and others. Though similar in appearance to the Roots, the screw blower uses two rotors that are set with very close tolerances in order to compress the air inside the case before it reaches the cylinders. 6. The centrifugal supercharger, such as those produced by Vortech, ATI Pro-Charger, Rotrex, and Powerdyne, are round, compact, mounted at the front of the engine, and often mistaken for a turbocharger. Like the other two types, the centrifugal blower is driven by a belt connected to the crankshaft. A step-up drive inside the supercharger allows it to spin phenomenally fast. For this reason, most ultimate street blower engines use this type of supercharger. 7. If driven judiciously, the supercharged can actually increase fuel mileage due to the scavenging effect the forced air has on the contents of the combustion chamber. 8. Though the ECU is peppered with electronic safeguards to squash detonation, using premium fuel is a primary rule (91 octane minimum). 9. With normal throttle input, the supercharger doesn’t make any noise. Get rambunctious, though, and the thing sounds off with its own special whine. 10. When you add a supercharger, it’s always advisable to include a charge-air cooler (intercooler) between the exhaust discharge and the intake side, the most common types being air-to-air and air-to-liquid. A non-intercooled engine heat-sinks rapidly after the initial full-throttle application, thus diluting performance markedly, so an intercooler is mandatory to reduce the charge air temperature for repeatable performance. |
Though we applied this system to a truck, there’s no reason why a similar conversion couldn’t grace any 4.8, 5.3, or 6.0L Gen-3 engine in any body style you choose. Remember that 5.3’s are built in a 2-to-1 ratio compared to the others and that total production surpassed the one-million mark months ago. The boneyards await.
Trucks built from ’04-up require a new in-tank fuel pump, but our ’03 needs only an auxiliary Walbro (GSL 394) pump mounted in close proximity to the new fuel filter (not supplied) on the frame rail.
Since the Radix is designed to compliment a stock engine, programming the ECM to accept the change is not a big deal, but when you throw non-stock camshaft events, more fuel, and revised cylinder heads against it, the story gets a lot more interesting. For the final trim, the engine was seeing 6.5psi boost, 50 percent injector sizing, 10 percent increase in initial timing (19 degrees), and a 5 percent power enrichment. The last two values were set via a Crane hand-held tuner, not the Super Chips programmer included in the kit.
A new belt tensioner bracket relocates the original pulleys to accommodate a longer drive belt, a 90mm idler pulley, and inherent spacing problems.
Fuel enrichment is not activated until the throttle is wide open. Roese: “Ideally, you should have stayed with the stock camshaft as the Crane is wildly un-stock. The overlap siphons off a little too much cylinder pressure, but then, 450hp at the asphalt isn’t bad, is it?” For the sake of brevity, we’ll concern ourselves with the Radix’s main system upgrades and equipment rather than a step-by-step installation.
How’s this work in the real world? Mileage in-town and flogging the gas at will, the Silverado knocked down an okay 15.4mpg. In cruise mode, however, the blower shuts down (Magnuson claims parasitic loss of only 1/3hp at 60 miles per hour) and air is channeled through an internal bypass valve, so the engine thinks it’s normally aspirated. Indeed, a steady state 75mph cruise confirmed this. The big, boxy truck still recorded 19.5mpg (equaling the best we ever got before installing the AFR heads and shorty headers).