Are we all clear on the advantages of fuel injection? Better fuel economy and lower emissions are why the OEMs abandoned carburetors in favor of electronic fuel injection, but there are more important reasons for off-roaders.
At the top of the list is the ability to keep your 4x4's engine running whether the vehicle is bouncing, coming to an abrupt halt, or tilting to near-rollover extremes (or rolled over, for that matter). Another bonus is that most fuel-injection systems will monitor and correct the air/fuel mixture for changes in air density (altitude). That means less loading up, stumbling, and stalling when you take your trail rig 4,000 feet higher than its accustomed stomping ground. All of these traits make fuel injection a bonus no matter what type of off-roading you do.
To get fuel injection, you either have to buy a newer 4x4 that already has it or retrofit it onto your favorite old vehicle with the aid of various kits. There are systems to convert nearly any carbureted engine to fuel injection, and we've detailed the installation of a few in past issues. For this article we looked into Turbo City's kit for the 258 Jeep engine.
The Turbo City system is pretty much a complete bolt-on. It doesn't require major reworking of the Jeep, such as adding an in-tank fuel pump, so two experienced backyard mechanics can bolt it on in one very full day, or you can do it by yourself over a weekend. The Turbo City kit includes a new Offenhauser manifold, which also adds power along with the advantages of fuel injection. With a good running engine and a decent exhaust system, gains of up to 40 hp may be realized. Perhaps the biggest shortcoming of this system is that it is not emissions-legal because it has not been certified. The company may pursue this if they get enough requests.
We performed some before-testing, including on- and off-road driving and recording the fuel economy of a CJ-7. Then Tom Miller at Turbo City installed a throttle-body fuel-injection system on the Jeep. The improvement in off-road performance was exactly what we had hoped for. With the carburetor, the Jeep had feared all hills and didn't fare well on bouncy stretches of trail. But now the driver could beat himself silly over rough stretches without stalling the engine, and there was no hill too steep for the engine (traction is another story).
On road, the Jeep was just a hair better than with the carburetor, mostly because the carb was tuned well for driving on pavement. The fuel economy increased from 12.5 mpg to almost 16 for the daily commute, which is about half freeway. Itll be a long time before the coins saved at the gas pump pay for the fuel injection, but the advantages off road are priceless.
This Jeep isn't used for extreme...
This Jeep isn't used for extreme off-roading, but the stock carburetor had been rebuilt on a regular basis and the engine would still cough and sputter if the front tires were 2 feet higher than the rear. It was time to give fuel injection a try.
The Turbo City fuel-injection...
The Turbo City fuel-injection system for Jeep 258 engines comes with a new intake manifold, a two-injector throttle-body, an ECM, an inline fuel pump, a fuel filter, a wiring harness, and the necessary sensors. Almost all of the components are made by GM. If your Jeep is an early one (pre 1981), you'll need to purchase a used or rebuilt magnetic-pickup distributor for an 1981-1985 258.
The wiring is usually one...
The wiring is usually one of the more intimidating parts of retrofitting fuel injection, but this kit makes it easy. The harness uses all GM connectors and sensors. The weathertight connections can only snap together where they're supposed to, and all the ends are marked with tags.