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Edge Trail Jammer - Jeep 4.0L

Story By Gary Wescott
Photos By Gary Wescott, Michael Cohn

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The Jeep 4.0L six cylinder has been a popular engine for years, and a reliable power plant for Wranglers, Cherokees and Grand Cherokees, but it would be nice if the naturally-aspirated 4.0 had a little more zip. Now there’s a way to gain a 15% increase in horsepower with the Edge Trail Jammer.

Well-known for their diesel-performance products, Edge Products in Ogden, Utah, has applied their air/fuel and electronics expertise to Jeeps. The company offers the new Trail Jammer system for 1997 to 2004 Wranglers and Cherokees that have the fuel-injected 4.0L straight-six engine. A kit to fit the 2005 and 2006 models is on the way.

Edge Trail Jammer
The new Trail Jammer system comes complete with all necessary parts for the simple installation.
Edge Trail Jammer
The Trail Jammer’s (top) high performance filter flows 97% better than stock, (195 cfm compared to the OEM 99 cfm).

We recently had the opportunity to test the Trail Jammer on three vehicles. The first was a 2000 TJ Wrangler Sport with a 5-speed manual transmission. The Jeep was bone stock except for a set of BFGoodrich 31 x 10.50R15 Trail T/As, which are slightly larger than the original 30 x 9.50 rubber. Running the Wrangler on the dyno showed a baseline rear-wheel output of 156HP and 202 ft-lbs of torque.

Edge Trail JammerIn addition to highway performance, we were interested in how the Edge kit would affect the idle and throttle response in low range rockcrawling. For this purpose we borrowed Jason Antonucci and his 2003 Wrangler Rubicon, which also was equipped with a manual tranny. Jason is an experienced four-wheeler with a passion for difficult trails like The Hammers in Johnson Valley and the Rubicon, or you might find him playing around Cougar Buttes. He also has a custom rock buggy built by Rock Equipment that sports Unimog axles with an Atlas transfercase, and an ’89 Wrangler with an Atlas box and coil-over suspension. While the 2003 Rubicon we used for our test sees its share of wheeling, it’s also a daily driver. It was running 35 x 12.50 R16 Goodyear MT/R tires and a Rubicon Express Long Arm 5 1/2” lift kit.

The third installation was on a '97 TJ Sahara with 31 x 10.50 R15 BFGoodrich Mud Terrains. This Jeep was not used in dyno testing but was used for photography and seat-of-pants response evaluation.

Shawn Maxey at Browns Valley RV Performance Center in Browns Valley, California, walked us through the simple installation. The Trail Jammer kit includes three main components: a throttle body, an electronic module and a cold-air intake system. Edge’s high-flow throttle body with a 62mm bore accommodates increased airflow and improves overall driveability. The Edge Trail Jammer Electronic Module optimizes fueling between the Jeep’s PCM and the 4.0L engine on-the-fly. This black box uses a factory-style harness to plug into engine sensors under the hood. Air enters through the Trail Jammer’s cold-air intake (built by AFE), which flows 97% better than stock, (195 cfm compared to the OEM 99 cfm). The system’s oil-impregnated, cotton-mesh filter traps dirt and debris, and is washable & reusable.

Like most Edge Products, the Trail Jammer performance kit has been designed so that even the non-experienced owner can install it in about an hour, with very minimal tools. After disconnecting the throttle body and removing the four bolts, Shawn lifted it off the intake manifold. Then it was simply a matter of moving the throttle position sensor, the idle control valve, and the MAP (manifold absolute pressure) sensor, all attached with a couple of screws, to the new Edge throttle body, which was then reinstalled on the intake manifold using the original gasket. The two sensors, throttle cable, and return spring were reattached.

Edge Trail Jammer
Edge’s high-flow throttle body (right) with a 62mm bore accommodates increased airflow and improves overall derivability compared to the stock (left) 60mm.
Edge Trail Jammer
The MAP (Manifold Absolute Pressure) sensor was moved over to the new throttle body.
Edge Trail Jammer
The idle controller was moved over using a small Torx bit driver.
Edge Trail Jammer
Completed Edge throttle body assembly.

(Editor’s Note: swapping the idle control box requires a Torx screwdriver. In addition, early model TJ’s have a secure Torx bolt, which will require a special bit. Craftsman Tools offers a secure bit set which includes a range of bits including the one needed for this task)



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