Supercharging a Fox Body Mustang
The Fox Body world is no different, with competing offerings from Vortech and Procharger ready to be installed in your Fox’s engine bay. Now, there are several different types of superchargers (Roots, positive displacement, twin-screw, centrifugal) but due to Ford’s pushrod 5.0 setup and packaging, centrifugal superchargers are the predominant choice. Before we go through each respective manufacturer’s offerings, let us delve into the science of a supercharger.
Types of Superchargers For Fox Body Mustangs
As mentioned, there are multiple types of superchargers. Their end goal is all the same (to pack as much air into the cylinder as possible, via creating a positive pressure) but how each type goes about it may differ. The focus of this article is on the centrifugal type, which also happens to be not only the easiest to install, but the most efficient type as well.
Without getting too complicated, the way a centrifugal supercharger works is as follows. First and foremost, any supercharger is powered by the engine itself – meaning it is coupled to the engine via a belt and pulley, thereby as long as the engine is running, the supercharger is spinning. As the supercharger spins, an impeller draws in air via an inlet (the hub). As the air is drawn in through the intake side (commonly called the ‘fill’ side), the centrifugal force causes the air to radiate outward (recall: centrifugal means to move away from a center). At this point, the air is moving very fast, but with little pressure. A set of stationary vanes behind the impeller slows the air down as the air molecules collide with the vanes, creating lower speed but higher pressure (think of a traffic jam, going from 2 lanes to one lane and how traffic is affected). The air is then pushed out of the discharge side and into the combustion chamber at a positive pressure (in relation to atmospheric pressure) called boost. How much boost is made depends on how fast the supercharger is spinning and in conjunction with that pulley setup. Boost is directly proportional to engine RPM, so more RPM’s will give more boost. This also leads to the fact that maximum boost with a supercharger is achieved at engine redline.
That last sentence brings up an interesting point about superchargers. Seeing that superchargers run directly off the crankshaft pulley, it must mean that like an alternator or any other accessory, they consume power to be driven. If you were thinking this, you are indeed 100% correct. Just like any other accessory, a supercharger does place a parasitic draw on the engine. The cool part? Despite using up some power to spin the charger, a charger is so efficient at what it does that it will not only make up what power it draws, but exceed it. How can something give more than it takes? Luckily for us, we need not ponder that philosophy but rather can just enjoy the major boost in power a centrifugal charger gives.
Selecting a Supercharger For a Fox Mustang
As mentioned, there are two major players in the Foxbody supercharger world. Vortech and ProCharger are the big dogs, and both companies offer great centrifugal kits.
Vortech: Vortech has two offerings. Their entry level ‘Street Boost’ kit features their V-3 self-lubricating supercharger, capable of 5-6 PSI of boost. Included with the kit is a fuel management unit and mounting hardware. If you’re looking for bigger power, consider their next level up, featuring their V-2 SQ Si trim charger, ribbed to produce between 8-10 PSI at wide open throttle. This kit also includes a fuel management unit with a high flow fuel pump, as well as a digitial MSD ignition box to help prevent pinging. On a stock engine, the basic Street Boost kit is good for a gain of 50 HP and 75 ft-lbs of torque. The V-2 kit will net in the neighborhood of 100 HP. These numbers don’t sound like much, but keep in mind they are for a STOCK engine. Expect bigger gains if your engine has been modified to breathe better (ex: cylinder heads, intake, camshaft).
It is interesting to note that Vortech says their Street Boost kit does not need an intercooler, nor will adding one net any additional power. Furthermore, Vortech states that a standard bypass valve is necessary for systems that exceed 6 PSI of boost and a MaxFlo racing bypass valve for 10 PSI and more.
ProCharger: Like the competition, ProCharger offers two kits. Both kits feature their P1-SC self-contained supercharger, a 2-core air-to-air intercooler, bypass valve and high capacity fuel pump. Of course the mounting hardware is included too! Their first kit comes with an 8-rib pulley whereas the more expensive second level is equipped with a 12-rib pulley.
A great feature that both companies offer is that some of their units are self-contained, meaning there is no need to tap your oil pan and run a line to the supercharger – they are self-lubricated.
Supercharger Pulley Sizing
Something else to note is pulley size in relation to boost production. Changing a supercharger’s pulley set (to a different ratio) can decrease or increase the boost, depending on which way you want to go. For instance, say you are making 8 PSI of boost but wish to make 10 PSI, you don’t need to purchase a new charger. Instead, changing the pulley ratio (with different sized pulleys) will give you the increase (if you recall, the crankshaft pulley is connected to the supercharger, thus varying the ratio between the two can increase or decrease the speed of the impeller, which effects the pressure produced).
When running a car with forced induction, fuel delivery and ignition timing become especially important to prevent detonation. For Fox platforms, the stock EEC-IV does not have the capacity to properly manage a supercharged engine. It is recommended to get an aftermarket computer chip and tune.
Furthermore, as a supercharger can cram more air into the cylinders, more fuel will need to be delivered as well. Larger injectors and a fuel pump to feed said injectors are mandatory; however some of the kits mentioned above include a fuel pump.