Bolt-On EFI Buyer's Guide - Bolt-On Configuration

MSD Atomic EFI

MSD, known the world over as the "go to" ignition component company for street and racing products, has added another tab to their business portfolio with the much celebrated Atomic EFI system. Who better to put together an EFI system than an ignition products company, right? For combustion you need spark, fuel, and air; and while MSD doesn't provide the air (last time we checked that's still one of the free things in life), now you can configure your ignition and fuel needs from the same company with the knowledge that the parts will work hand in hand with each other. MSD's Atomic EFI mounts to the standard 4150 carb flange like the other bolt-on units in this roundup, but that's pretty much where the similarities end. The MSD engineers designed their EFI as a pulse width modulated system. PWM means the fuel pump's voltage is controlled by the ECU, which in turn controls the pump's pressure/volume characteristics. This is the basis of many OE "returnless" fuel systems. However, if you already have a full fuel system with pressure and return lines rated for EFI, the Atomic unit can easily run at a fixed fuel pressure as well via the hand-held controller and the addition of a fuel pressure regulator. Furthermore, the actual design of the Atomic throttle body is very "carb like" for a retro look and includes the ECU built into the side of the throttle body. You'll even notice what looks like annular boosters; however, these are actually very carefully designed injector nozzles that help spread out the fuel, helping to make more consistent high rpm horsepower.

System Specs:

• 1,000-cfm cast throttle body with four 80-lb/hr fuel injectors and integral ECU
• Wideband O2 sensor with weld-in threaded fitting
• PWM returnless fuel system stan- dard in Master Kit, including fuel pump, fuel line, and filter handles up to 525 horsepower (at the crank)
• External power module connects via CAN-Bus technology and fea- tures two electric fan outputs, A/C idle "kick up", and more
• High Horsepower Fuel Kit increases horsepower capability to 620
• Retail Price $1,990 -$2,290

Professional Products Powerjection III

Of all the 4150-flange bolt-on EFI units we've discussed here, probably the most carburetor-like unit (visually speaking) is the Powerjection III unit. The four fuel injectors are covered by simulated fuel bowls and the unit uses a dual-feed inlet line assembly, plus all electronics are built into the unit so there are no external modules, ECUs, etc. needed that stand out and yell "EFI" to those checking out your engine bay. Like other systems here, the Powerjection III utilizes a wideband O2 sensor to allow on-the-fly fuel system adjustments while driving. The Powerjection III doesn't technically require a laptop, as it is a self-tuning design, but the unit does supply a software CD and a single wire USB adapter for laptop tuning use. The software allows for fuel mapping, idle control, and other functions at the stroke of a keyboard if you so desire to deviate from the self-tuning feature. While the original Powerjection III required a return line (it was stealthily routed from the bottom of the pressure regulator and owners usually ran the line down the rear of the engine), Professional Products now offers their FuelOnDemand fuel pump controller, which works with carbureted (using an electric pump, of course), return-style, and returnless-style fuel systems. Professional Products offers the FuelOnDemand as a separate product for just about any fuel system or in a Powerjection III offering as a complete returnless EFI solution.

System Specs:

• 750-cfm cast throttle body with 62- lb/hr fuel injectors and integral ECU
• Wideband O2 sensor with clamp- on "no weld" bung
• Does not control ignition but will work with everything from points to CD ignition boxes
• Complete Kit includes fuel pump, fuel filter, dual-feed fuel inlet, fuel pressure regulator, fuel pressure gauge and fittings; however you must supply your own -6 AN hose
• Basic Kit is for cars that already have pressure and return lines, fuel pressure regulator, and fuel pump installed
• Optional hose and fitting kit available to connect Complete Kit components
• Supports up to 550 horsepower
• FuelOnDemand fuel pump controler available separately or as part of Powerjection III returnless kits
• Price $1,682.95-$2,104.95