Fuel injection swap
Fuel injection engineered for the masses
Nic Conley - December 08, 2011 10:00 AM
For your information:
1 Our donor for this project is a clean 1961 Corvette that has already been resto-modded. It features a GM ZZ3 crate engine, 700R4 trans, and a Jim Meyer front crossmember and suspension system. The owner was looking for a bit more performance and driveability.
2 The ’Vette was equipped with an old Quadrajet and was not performing as it should. So, it got its walking papers.
3 After accessing the fuel tank behind the seat, the fuel supply line was disconnected and fitted with a female -6 AN fitting. The fuel lines must be able to withstand up to 60 psi. This system will run at a constant 45 psi.
4 The high-pressure fuel pump was mounted on the right-hand frame rail with the supplied insulators. Make sure the pump isn’t too close to the exhaust. Heat will kill these things.
5 Next, a hose was made to connect the fuel pump and the supplied EFI fuel filter.
6 The Fuel-on-Demand module is the brain behind the return-less system. This unit wires in line with the fuel pump and modulates the voltage being applied to keep the fuel pressure constant and continuous. Suddenly, there’s no reason to plumb in a fuel return line back to the tank! We mounted this one under the dash to the firewall.
7 The main throttle body contains the injectors, map sensor and fuel pressure transducer. It simply bolts down exactly where the Quadrajet once resided. Even the throttle linkage hooked up with very little modifications. We did have to obtain a new return spring bracket, but that’s it.
8 The fittings are only finger-tight, so we went around everything with a wrench to ensure we wouldn’t have a fuel sprinkler when we turned the key.
9 The main harness seems very small, but since the system only controls fuel and not spark, the wire count is dramatically reduced. This harness will run to the sensors and to the Fuel-on-Demand module.
10 We also installed the engine coolant temp sensor (ECT) in the intake manifold. This will tell the ECU when the engine is cold or at operating temperature.
11 The main harness was routed through the firewall to the FOD module. The only other wires are a main battery power line, which was taken from the hot starter lead; a chassis ground; and the oxygen sensor harness.
12 The switched power wire was tapped from the coil’s positive terminal directly behind the throttle body.
13 Professional Products includes this nifty oxygen sensor bung. Instead of welding it on, simply drill a hole in the exhaust pipe close to the exhaust manifold. Install their high-temp gasket and clamp-on bung. Then screw in the sensor and plug the harness into it, and don’t forget to put some anti-seize on the threads.
14 There are two wires from the FOD that are run to the fuel pump, and that finishes up the wiring.
15 And there you have it. Looks like a carburetor sitting up there, and with the air cleaner on it doesn’t look any different than it did when it rolled in the shop.
16 With a twist of the key, the car fired right up and went into its fuel enrichment mode (choke) and idled at 1,500 rpm for about one minute, then settled down to 850 rpm. The dashboard software lets you see in real time exactly what’s going on. The only change we made was to drop the idle to 750, which takes nothing more than a few keystrokes on the laptop.
Remember when electronic fuel injection was first introduced from the OEM? As car guys, it scared us. Then, it made us angry. How could the manufacturers take away the best part of being a gearhead?
Tinkering with cars and engines is as American as apple pie. With all these sensor do-dads, pounds and pounds of wiring, and, gulp, a computer, how can we possibly have any control over our cars? But within just a couple of years, the aftermarket was cracking the codes on the ECMs and figuring and reconfiguring the tables to make things easier. But EFI still had limitations. Nowadays, aftermarket EFI systems are fairly plentiful and work well, with one drawback. A good EFI system that enables plenty of end-user adjustments and tuning will empty your wallet faster than a teenage daughter.
Professional Products has designed a system that not only looks like a carburetor and blends right in with the retro look, but it’s less than HALF the cost of some of its brethren. The Powerjection III system employs a throttle body with four injectors hidden under faux “float bowls” built into the unit. The injectors are above the throttle blades, which they claim exhibits better all-around idle quality and control. The system comes complete with a high-pressure fuel pump and filter, throttle body assembly with dual-feed fuel lines and fuel pressure gauge already attached, and a wide-band O2 sensor.
The ECU or “computer” is tiny and mounted directly to the side of the throttle body. Talk about compact! They even have a return-less system that eliminates the need for a fuel return line, which is a big plus for the older cars.
We wanted to find out first of all, if it’s as simple to install as they claim, and second, is it really better and easier to tune than a good ol’ Holley carburetor? Performance Solutions in Boise, Idaho, specializes in racing engines, street engines, and chassis EFI systems, and happened to have a 1961 Corvette owned by Don Copple, who was interested in making the GM ZZ3 crate engine run a little better. The ’Vette is equipped with a Quadra-jet and suffers from cold-start choke issues, and flat throttle response. Sounds like a perfect candidate for EFI to us!
When we finished, the car started easier, idled smoother, and exhibited incredible throttle response. The fuel enrichment circuit worked perfectly, and as the coolant temperature moved from dead cold to operating temperature, you could literally watch the air/fuel ratio lean from 12:1 to 14.5:1. Once warmed up, it settled in at a crisp and clean 14.7:1 air/fuel ratio — all that without any adjustments!
If tinkering is your thing, or if you have a combination that they don’t supply a base tune file for, the software is extremely simple to follow. Custom tailoring is what’s so great about this system. This is truly a high quality EFI system for the masses that doesn’t come with a high quality price.