Do you want v-8 performance from your XJ without the cost and complexity of a V-8 swap? Are you tired of driving a slug on the highway, even though it's a great trail rig? The answer may be in the thin air you breathe, by simply packing that thin air into your engine with a supercharger designed to increase the ponies, the driveability, and the fun factor. If you stayed awake during auto shop and chemistry classes, you know there is an ideal ratio of air to fuel that makes an engine very happy. Too little fuel and you run the risk of expensive engine damage. Too much fuel is a waste of a valuable resource. To achieve the proper balance, since we are forcing more air into the engine with a blower, supercharger guru Rick Rimmer developed this kit using an auxiliary fuel system. Since the fuel-pressure increase only comes when the regulator sees boost, stock mileage is retained as additional fuel is only supplied as needed.
The candidate for this swap is a '98 XJ Cherokee with 120,000 on the clock, which is basically stock except for the 4-inch TeraFlex lift and 32-inch tires. Our goal was to be able to pull a small tent trailer up and down the hills of Utah and Colorado without being passed by every 18-wheeler on the road, while maintaining decent fuel economy and good daily driveability. The kit we installed is a Rick Rimmer-developed 4.0L non-intercooled supercharger kit. It fits under the hood of the XJ without a hole in the hood and with no modifications to the vehicle sheetmetal at all. So this kit is invisible from the outside, making it a true sleeper.
We were successful in our goals of more power, driveability, and fun. The mileage rose to 17 mpg, up from 14. It now pulls the tent trailer up a 6 percent grade at 60 mph, and even stays in lockup overdrive all the time at freeway speeds. On top of that, we can embarrass the black-cloud diesel pickups from 0 to 60 and still have fun getting to drive it every day. Follow along as we install a supercharger on a high-mileage XJ Cherokee.
The new supercharger kit includes an Eaton supercharger, a new intake manifold that has been modified to accept the adapter plate, and a box of brackets, hoses, and fittings. The intake manifold is a dual-plane design from an '06 Wrangler, so it does require you to have the latest style power-steering pump. Look at the photos here to see if you have the latest mounting design pump, and if not, visit your local parts store or Pick-n-Pull before taking your vehicle out of service. The Eaton supercharger has an internal oil system that is independent of the engine so there is no need to plumb in an oil-pressure or return line.
Installation requires basic...
Installation requires basic handtools and about 8 hours of your quality time. A special tool to disconnect the high-pressure fuel line at the injector rail can be purchased at most auto parts stores if you don't have one already. The fuel system will be opened up so release the fuel pressure before starting the installation. Remove the fuel-pump relay, remove the gas cap, and start the engine, then let it idle till it runs out of gas. Then lay a rag over the test port on the fuel rail and push in the Schrader valve to relieve any residual fuel pressure. Put the gas cap back on but leave the fuel pump relay out until the end of the installation just in case someone decides to listen to the stereo while you are working under the hood.
Remove the stock intake manifold....
Remove the stock intake manifold. If you are careful you can pull the exhaust manifold back from the engine far enough to clean off and install a new gasket without disconnecting the exhaust under the vehicle. The intake and exhaust share a common gasket so they both have to be unbolted from the engine. Using a new intake-manifold gasket, install the supplied intake manifold and reinstall the exhaust manifold.
Bolt the throttle body onto...
Bolt the throttle body onto the new supercharger using two new gaskets to sandwich the bracket that will be used to hold the throttle linkage. We used a throttle-body spacer on this installation to provide clearance for the idle air control (IAC). Set the supercharger in place just to check clearances. Once everything lines up the way you want it to, take the supercharger off, put a thin film of RTV silicone on the mounting plate, and install the supercharger assembly. You will need a short 10mm wrench to tighten the bolts that come up through the bottom of the manifold plate into the supercharger.
The intake-air temperature...
The intake-air temperature sensor is taken out of the original intake manifold and installed in the air-intake elbow. Just drill a hole in the elbow and push the sensor in and put some silicone on the outside to seal it up against air leaks. The elbow fits onto the throttle body but it is tight against the firewall. A new air-intake hose is supplied with the kit that locates the air filter on the outside of the brake booster alongside the master cylinder. There is a vacuum tee supplied near the base of the throttle body where the vacuum line from the brake booster connects. Make sure to use the check valve when hooking up the heater controls so your heater and defroster will work when driving up a long hill under boost.
The fuel line from the stock...
The fuel line from the stock in-tank fuel pump is routed to a high-pressure pump mounted on a new bracket on the side of the new intake manifold. Next to the pump is a rising-rate fuel-pressure regulator that actually increases fuel pressure in the fuel rail when the engine sees boost. Higher fuel pressure in the fuel rail means more fuel enters the cylinder for a given fuel-injection cycle.
The last part of the installation...
The last part of the installation is the power-steering pump. The nose drive of the supercharger is in the way of the factory steering-pump reservoir, so the plastic reservoir is removed and a new tank is added in a remote location. A fitting is provided to press into the body of the pump so the hoses can be routed to the new reservoir. A new longer serpentine belt is used to drive the supercharger and all the factory engine accessories.