Part 1: Powerjection III-Hard To Believe It's So Easy
If you're reading this magazine, then we surely don't need to sing the praises of fuel injection. On-road benefits are easier start-up, more consistent performance over elevation changes, and usually better mileage. But hit the dirt, and the difference between a carburetor and injection is like night and day. With injection there's no stumbling, flooding, or missing when your vehicle is operated over rough terrain or at extreme angles. As long as you've got the oil pressure to keep the rotating parts happy, injection will let your rig run upside down or on its side all day long.
We've used lots of aftermarket fuel-injection systems, ranging from fully-exotic MPI setups that require their own intake manifold, electronic ignition, sensors, harness, and computer, to dirt-simple TBI conversions. The exotic systems usually offer the ability to fine-tune for power and drivability, but you need a degree from MIT to understand and manipulate the tuning software. On the other hand, the simple TBI setups require a bit less tuning, but seem to leave a lot of performance and drivability on the table.
We recently acquired a Performance Products Powerjection III fuel-injection system, and believe us when we tell you that this latest iteration is a dream for the average off-road enthusiast. Once the system is bolted to your engine, all you need to do is plug in your laptop and answer a few questions like how many cylinders and the peak torque your engine makes. Then just drive it. That's it. No tuning via laptop or staring at tiny little air/fuel ratio cells until you're blind and half-crazy. The system learns on its own as you drive the vehicle.
Since the engine from our project truck was still on the dyno at Westech Performance, we decided to first see how the Powerjection III stacked up against the carburetor we were using for our testing (see "Jp350, Part II" in this issue). Bolted to an unmoving engine with perfect atmospheric conditions, the Holley 750cfm mechanical secondary double-pumper is a tough act to follow on the dyno, but it would be an absolute nightmare off-road. Heck, it wouldn't even be that pleasant on the street. However, the Powerjection III will deliver nearly the same performance out in the real world as on the dyno. In the dunes, over whoops and dips, or on the street, consistent injected performance will be ours. Check the sidebar in this article Top Twelve Tricks for our favorite aspects of this system. Next month, we'll highlight the installation of the unit in our '68 M-715 and share our on- and off-road driving impressions.