Fuel Injection Conversions 101 - Fuel Injections

Note that in the case of the turbocharged engine, the fuel supply pressure would have to be increased by at least the same psi as the amount of boost being used.

To avoid much of this complexity and planning, install a kit designed for the engine in your Mustang. We'll have a look at this kit in an upcoming issue, so join us then.

In 1984, EEC IV was released and included the first level of standardized onboard diagnostics (OBD-I). A decade later, EEC V arrived, incorporating updated diagnostic and reporting capability, known as OBD-II. Most recently, EEC VI arrived with added capability to handle more electronic sensors and control functions. EEC VI is fully based on what is called flash memory, a kind of permanent but reprogrammable memory.

For V-8 Mustangs, CFI arrived in the mid-'80s and persisted through the '85 model year on AOD trans Mustangs only. In 1986, the 5.0L Mustang engine was converted to sequential electronic fuel injection (SEFI), which provided one fuel injector for each cylinder. With this design, fuel is sprayed directly into the intake valve port. Because of this, there is no chance of fuel "puddling" in the intake runners, so much tighter control on the amount of fuel dispensed is possible.

Beginning with California-bound Mustangs in 1988, Ford began the migration from a speed-density-based control system to a mass airflow (MAF) sensor system. MAF systems have proven to be more adaptable and "mod-friendly" than their predecessors. If you're considering a conversion to electronic fuel injection using parts from a donor car, you should make sure that it's at least an '88 California, or an '89-or-later Mustang. The compromises and performance issues associated with earlier systems are simply not worth the aggravation.

Design Your Own
If it hasn't become plainly evident by now, engineering your own EFI system is a notably complex task. Still, you might be in the situation of having started with OE Ford parts and needing to update certain aspects because of your engine. One of the least understood issues in this scenario is that of finding the appropriate size or capacity of parts to handle an engine of increased power.

If the 302 engine in your classic Mustang has about the same output level as a '90 5.0 Mustang donor car, then all should go fairly smoothly during the conversion. However, if you have increased the output with intake or compression changes, you'll need to get more fuel to the engine to fully realize that increased power.

Dealing with Ford Racing replacement parts, one of the first things you need to know is that the flow rate of fuel injectors assumes a particular pressure difference between the fuel rail and the cylinder, which should be about 39 psi. When you look at the flow rate of any particular injector, it's based on this pressure difference. If your soon-to-be fuel-injected mill is also supercharged, then you're going to have to increase the fuel rail pressure by the same amount as the boost that you're putting into the engine if you want to rely on the published injector flow rates.