Jeep Turbo City 258 Engine Kit - 4Wheel & Off-Road Magazine

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 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.
This Jeep isn't used for extreme off-roading, but the stock carburetor had been rebuilt on
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 Turbo City fuel-injection system for Jeep 258 engines comes with a new intake manifold
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.
The wiring is usually one of the more intimidating parts of retrofitting fuel injection, b

The first hour or two of the install is spent removing the carb, the old intake, and the exhaust manifold along with everything attached to them. This Jeep had an AIR pump, which complicates things a little but can be made to work with the new system. It's helpful to clean the engine at a coin-op car wash before beginning the swap, and to soak the manifold and exhaust bolts with WD-40 or another penetrating oil. The intake and exhaust manifolds are bolted together and are easiest to take out as a unit.
The first hour or two of the install is spent removing the carb, the old intake, and the e
On the other side of the engine, the distributor must be removed. Mark the location of the rotor so you can install the new distributor in roughly the same position. If you're having to update to a later distributor, your original plug wires will still fit.
On the other side of the engine, the distributor must be removed. Mark the location of the
When your engine looks like this, you're nearly ready to start adding new components. Inspect the freeze plugs in the block. If they're hashed, you can easily change them now that the manifolds are removed. This is also a good time to consider changing radiator and heater hoses.
When your engine looks like this, you're nearly ready to start adding new components. Insp

This Jeep is a 1977, a model that used a Prestolite ignition. The Turbo City computer will now control the timing curve, so a magnetic-pickup distributor (right) from an 1981-or-later 258 is needed. You'll need to gut the distributor of its mechanical and vacuum advance mechanism.
This Jeep is a 1977, a model that used a Prestolite ignition. The Turbo City computer will
To disable the mechanical advance, you must remove the distributor shaft and weld the weights in place. The shaft can be slid out of the housing after the roll pin retaining the timing gear is removed. If you're not comfortable doing this, most automotive repair shops can do it.
To disable the mechanical advance, you must remove the distributor shaft and weld the weig
The Turbo City kit is one of the few TBI retrofit systems that can legitimately claim a power gain in addition to the benefits of fuel injection. The gain comes from the Offenhauser intake manifold included in the kit. The plenum is much larger, as are the runners. Even on our well-worn engine we noticed a big difference in power, especially at part-throttle.
The Turbo City kit is one of the few TBI retrofit systems that can legitimately claim a po

If you use the stock exhaust manifold, it must be bolted to the bottom of the new intake manifold. You may use a header with this system
If you use the stock exhaust manifold, it must be bolted to the bottom of the new intake m
This is the hardest part: swinging the intake and exhaust manifolds over the fender, lining them up with the dowel pins, and getting all the bolts in. The AIR line made this even more challenging on this Jeep.
This is the hardest part: swinging the intake and exhaust manifolds over the fender, linin
The throttle body is a two-injector GM unit that Turbo City reconditioned. Which accelerator cable bracket you need depends on the year of your Jeep. In this case, the original cable connected with an S-10 bracket, leaving a loop in the cable.
The throttle body is a two-injector GM unit that Turbo City reconditioned. Which accelerat

Fuel injection requires steady fuel pressure in order to function properly. The Turbo City system uses relatively low pressure (about 9-13 psi), and an electric, inline fuel pump gets the job done. The pump is spliced into the stock 5/16-inch fuel line and must be mounted lower than the fuel tank to make priming the pump easier.
Fuel injection requires steady fuel pressure in order to function properly. The Turbo City
A block-off plate is installed where the factory mechanical pump was. The plate has a threaded hole in the center to accept the knock sensor for the ECM. This detects engine knock and automatically retards the ignition timing.
A block-off plate is installed where the factory mechanical pump was. The plate has a thre
Other sensors used on this system include the MAP sensor, which along with the O sensor determines how much fuel to add relative to the throttle opening. The opening is measured by the throttle-position sensor. The system also includes its own fuse-block and fuel-pump relay.
Other sensors used on this system include the MAP sensor, which along with the O sensor de

The throttle-body has a return outlet that needs to be connected to the stock 1/4-inch fuel-return line to the fuel tank. The AIR pump was retained on this Jeep and was in the way several times.
The throttle-body has a return outlet that needs to be connected to the stock 1/4-inch fue
The ECM should be mounted under the dash, where it'll be relatively protected from the elements. Because it's based on the GM TBI system, there is a diagnostic port and a check-engine light. Custom chips can be burned to create the perfect fuel and spark curves for your modified Jeep. We snapped the check-engine light into a hole in the dash.
The ECM should be mounted under the dash, where it'll be relatively protected from the ele
You should perform a couple of prestart checks, such as making sure the fuel pump runs for 2-6 seconds when the key is turned on and that the engine light comes on for a second to verify that power is reaching the ECM. Also, check for fuel leaks. Then you're ready to start the engine. Our initial testdrive indicated that the exhaust was completely clogged, so Turbo City installed a Car Sound catalytic converter and a DynoMax performance muffler. Turbo City offers complete high-flow exhaust systems for YJs and TJs and the parts you'll need to piece together a similar system for CJs.
You should perform a couple of prestart checks, such as making sure the fuel pump runs for

The completed installation makes the Jeep look like it came this way from the factory. Driving tests with the fuel injection proved it worthwhile. On hills the engine would keep running even when the hill was steeper than the Jeep could climb. Also, the idle-air control motor bumped up the idle speed a little under load to reduce stalling, but not so high as to make rockcrawling difficult.