In the last Steal-J installment we upgraded the interior and made it much more livable for longer drives. Now we'll turn our attention to what needs doing under the hood.
For the most part, we were happy with the power of the stock 4.0L. While a header and exhaust are popular upgrades -- unless your manifold is already cracked and you're looking for a more aggressive sound -- the stock exhaust system isn't all that restrictive and delivers a nice, quiet ride.
We had been eyeballing Edge Product's Trail Jammer performance kit for the 4.0L Jeep engine since it was introduced. We liked the fact that it uncorks the restrictive stock air intake and throttle body and includes a completely plug-in electronic control module that increases fuel delivery to better support the increased air supply.
The Trail Jammer is modular, in that you can do just the intake, intake and throttle body, or the whole deal with the electronics. We installed the whole package, including the cold-air intake, 62mm throttle body, and electronic module. While we didn't have a chance to dyno the system, based on our seat-of-the-pants estimates we have no reason to doubt Edge's power gain claims of 20 hp and 26 lb-ft.
Our mileage also went from 15.5 mpg stock to 16.8 mpg with the full Edgepackage. Disconnecting the electronic module resulted in an average of 17.4 mpg, but we did notice a slight drop in power, so we run with the electronics hooked up.