Jeep Cherokee Performance - "How do I get the most performance from my Jeep Cherokee?"October 16, 2009 by Mike Strawbridge
First, we have to define performance. Since the Jeep Cherokee is such a versatile vehicle, people use them for many different purposes and therefore have different performance expectations.
I have different performance expectations from each of my Jeep Cherokees. So each of them is prepared differently.
My off road farm truck has big tires, a welded differential and no sway bars. It has an old 2.8L V6 as I don’t need much power where I go. Traction and articulation are more important to me off road than speed.
My Rally Racing Jeep Cherokee has a 4.7L stroker motor with a high lift cam built by Titan Engines especially for high speed gravel road racing. The stock intake is used but the exhaust is open with no muffler only the required catalytic converter as a restriction. The suspension is stock with small sway bars and rubber bushings. The tires are small with stiff sidewalls and an aggressive rally racing tread. The emphasis on this vehicle is on speed, stability and durability.
My daily driver Jeep Cherokee is more of a compromise. Since it spends most of its life on pavement, I have used the middle sized sway front sway bar and poly bushings. The front control arms are also fitted with poly bushings. The stock rear sway bar is used in the stock rubber mounts. The tires are 30" BFG All Terrains. The engine is stock for now but has a K&N air filter and a Dynomax exhaust. The rear differential is fitted with a lock rite automatic locker. For off road adventures the rear sway bar is removed and the front sway bar is fitted with quick disconnects.
So, you are still asking’ "How do I get the most performance from my Jeep Cherokee?"
Begin with simple things in the engine. Whether you are running a hot stroker or a stock 4.0 I recommend regapping the spark plugs. The stock coil will fire up to about a .055 gap. A hotter coil, like a Jacobs or MSD, will fire a .065 gap. In either case, you must use high quality plug wires. The larger spark gap seems to give more complete combustion as I have seen increases in both torque and fuel economy by increasing the spark gap. I use the RC9YC Champion Plugs or the Autolite 3923.
Opening up the intake and exhaust will also help in the upper RPM range. I have mixed feelings about the K&N filter on my 1991 Jeep Cherokee. It makes a cool sound and reduces the chances of taking in water on creek crossings, but its location allows it to suck in hot air. I think this reduces torque and fuel economy. I have reinstalled the stock air box in the Rally Jeep as it seems to work better at rally speeds. I have opened up the exhaust on both the 1991 Jeep and the Rally Jeep. I have not tried a header on either one but I plan to in the future. The Rally Jeep uses as straight a pipe as possible from the cat back. No muffler is used and the sound level is still below the required 96 db. On my daily driver I use the Dynomax 2.5 inch muffler and tail pipe. It makes a nice mellow tone.
I just made a huge improvement in the handling of my 1991 Jeep Cherokee Laredo that I use as my daily driver. I replaced the front Gabriel Shocks with Bilstein shocks. The bushing were worn on the Gabriel's letting them rattle. I could have just replaced the bushings as the shocks are fine but I wanted to see what improvement better shocks would make. I chose the Bilsteins because they had the largest piston diameter (46mm) I could find in a shock with the stock cross bar and stem mounting system. They we also a lot less expensive than true off road racing shocks. I have to say I am absolutely amazed by the difference in handling! The truck now tends to oversteer in corners rather than understeer like it always has. I may have to get a matching set for the rear axle to even things back out.
For more information on my RallyJeep see www.rallyjeep.com
For more information on installing Poly control arm bushings, see this page.
For more low cost suspension tricks see my Cheap Jeep page.
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Mike Strawbridge October 16, 2009
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