Click for Coverage
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

Fool-Proof Fuel

Posted in How To: Engine on March 1, 2010
Share this

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.

The Powerjection III is offered in four versions. The PN 70020 and PN 70021 versions (cast and polished finish, respectively) come with software, wiring, and sensors, but do not include the fuel components. You'll need to supply your own fuel pump, filter, and regulator. The PN 70026 and PN 70027 versions (cast and polished finish, respectively) include the fuel components, but you still need to supply the fuel feed and return lines from the tank. Professional Product offers its fuel line kit, PN 70107, which we'll show you next time.

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.

powerjection Power Fuel Injection System fuel Rail Photo 32131725 The Powerjection III installs just like a regular square-bore four-barrel carburetor. Check out the nice fuel rail that comes pre-installed on the PN 70026 and PN 70027 systems. The included fuel-pressure gauge is a nice feature, as is that little nipple on the fuel-pressure regulator, which can be hooked up to offer boost-referenced fuel metering for turbo or supercharged applications. The system can also be programmed to step up the fuel for nitrous, run E85 blended fuels, and countless other options.
Engine Test 1 Test 2
(rpm) Hp Tq Hp Tq
3000 208 367 212 359
3200 220 361 219 360
3400 242 374 241 372
3600 262 383 264 385
3800 281 389 283 391
4000 301 395 303 398
4200 319 398 318 399
4400 332 397 330 394
4600 346 395 340 388
4800 359 393 353 386
5000 371 389 369 387
5200 381 384 378 382
5400 385 374 383 373
5600 386 362 385 361
5800 383 345 384 348
6000 383 336 387 339
6200 381 323 388 334
6400 375 308 380 311

Test 1: Chevy 350 engine: Lunati Voodoo 227/233 @ 0.050, .489/.504 camshaft, Professional Products Hurricane intake, 1/2-inch phenolic carb spacer, Holley 4779 Double-Pumper carb, 37 degrees ignition timing, 13/4-inch long-tube headers

We initially installed the PN 70026 Powerjection III on a Wieand dual-plenum Air Strike manifold, but experienced some fuel distribution problems we suspect stemmed from the intake charge stacking up at higher rpms with our stock cylinder heads and high-lift camshaft, so we swapped on this Professional Products single-plenum Hurricane manifold. Although the Hurricane shaved off a little torque, the upper rpm horsepower went up and the increased plenum volume helped mitigate our fuel puddling issues.

Test 2: Same as above with carburetor substituted for Powerjection III fuel injection Peak values are in bold

Top Twelve Tricks
The advantages are many, but here are our favorite points about the Powerjection III.

Although you can crack into the Powerjection III's software to manually tune the system, we didn't. Instead, we chose to let the system self-learn for a few minutes as the engine ran on the dyno to see how it stacked up against the dyno carburetor. However, if the need ever arises, we'll be able to compensate fuel delivery to adjust overall air/fuel ratio for a poorly-operating cylinder, run in open- or closed-loop mode, adjust fuel delivery in any given rpm range, compensate for different camshafts, intakes, or any tuning scenario you can imagine.

•There's no need to change out your ignition system. A tach signal from the ignition coil or ignition box is all that's required.

•There's no need to swap your intake manifold. The unit uses a standard four-barrel mounting flange, so you can use an affordable one- or two-barrel-to-four-barrel adapter if your intake manifold doesn't already have a square-bore, four-barrel flange.

•The throttle body works with standard carburetor throttle linkage and any off-the-shelf air cleaner with a 55/8-inch carb neck.

•There's no bulky computer to mount, since the computer is located in the throttle body itself.

•The wiring harness consists of only six wires, and technically you only need three of those to make the engine run.

•Comes with the fuel rail, adjustable pressure regulator, and fuel gauge already installed on the throttle body, as well as the correct fuel pump and filter supplied with the PN 70026 or PN 70027 systems. The regulator is pre-set at the required 45psi.

•If the engine stops running, the computer shuts off the fuel pump when the tach signal is lost, which can be beneficial if there's a rollover or crash.

•Four 62lb/hr injectors in the 930cfm throttle body supply enough fuel to feed 550hp, but can also work on small V-8 or V-6 engines. Injectors can be swapped out for smaller units to work with small four-cylinder engines or ordered with four 75lb/hr injectors for up to 600hp.

•It's designed to be installed by the home-hobbyist, so installation and setup are simple and almost everything is included (fuel lines and fittings aren't included, but can be ordered under PN 70107 from Professional Products). There's also no welding required to install the supplied O2 sensor in the exhaust.

•Parts are of high-quality and not Chinese-built junk.

•At roughly $1,500, it's one of the less-expensive systems available.

•There's no tuning necessary! Plug in your laptop , answer a couple of questions such as number of engine cylinders and peak torque, then just drive it. The system self-learns by itself.


Westech Performance Group
Mira Loma, CA
Professional Products
Hawthorne, CA 90250

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results