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.
Power Delivery
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.
We ordered a complete Edge...
We ordered a complete Edge Products Trail Jammer system for our '97 Wrangler's 4.0L. The system had everything we needed for the install, including the correct anti-tamper Torx bit for swapping the TPS and MAP sensors and IAC housing from the factory throttle body to the Edge throttle body.
Note the difference in bore...
Note the difference in bore between the factory 58mm throttle body (left) and the 62mm Edge throttle body (right). We do notice a slight whistle from the IAC window at certain rpm, due to the Edge unit's untapered bore, but the increase in power is well worth it.
Sharp eyes will note the AFE...
Sharp eyes will note the AFE cold-air intake. Advanced Flow Engineering is the company that makes the intakes for Edge, which was back-ordered at press time. The only difference between our intake and the production Edge piece is cosmetic. The intake fits very well and doesn't flop around at all.