When upgrading your mustang and adding more power, one good thumb of rule is to upgrade the injectors for that application, especially when your car hits a certain horsepower range after modifications. When it comes to injectors, the bigger the injector might not always be the best for your modifications. Fuel injectors have a variety of different flow rates and styles ranging from 19 lb/hr to 80 lb/hr and more. Upgrading the injectors to too large of size might cause your motor to run very rich and could cause catastrophic failure or lose the power that you are attempting to gain. If your Mustang is bone stock or has minor bolt-ons the original factory size fuel injectors are perfect for this kind of application. If you’re running a forced induction setup or your engine is making more power than your stock numbers, you will need to use the formula listed below to find the correct size fuel injectors needed for your application.
The Mustang EV1 fuel injectors are often referred to as the “fat” style fuel injectors seen on the early model fuel injected Mustangs. The EV6 fuel injectors replaced them in the next line of fuel injector evolution. The EV6 injector is nearly identical in height but the body of the fuel injector is narrower or “skinnier” when compared to the EV1 injector. The third style is the EV14 fuel injector. The EV14 injector is shorter than the EV1 and EV6 injectors and features a slim style body.
The 1999-2004 4.6L 4V Mustangs (SVT Cobra & Mach 1) and 2005+ Mustangs all use the USCAR style connector. All other 1986-2004 Mustangs use the Jetronic/Minitimer style injectors. Rule of thumb is if the connector is slim rectangular shape it is Jetronic/Minitimer and if it is a square shape then the connector style is USCAR. See the picture below to see the differences between the two connector styles.
You can now tell the difference between the three types of fuel injectors used on Ford Mustangs but what if you have a set of EV6 Mustang high flow fuel injectors with USCAR connectors and you want to use them on your Mustang that has EV1 injectors with Jetronic style connector – can you use USCAR style injectors on your Mustang if it has Jetronic wiring harness? The answer is YES! Thanks to Ford Racing, they made plug-and-play style fuel injector adapter kits to make this an easy task. The Ford Racing M-14464-A8 Fuel Injector Adapter Kit will adapt USCAR style injectors to a Jetronic/Minitimer style harness. The Ford Racing M-14464-U2J Fuel Injector Adapter Kit will adapt Jetronic/Minitimer injectors to fit the USCAR style harness.
The formula for calculating the correct size fuel injector for your Mustang is calculated by:
Injector Flow Rate (lb/hr) = (Engine HP) x (BSFC) / (Number of Injectors) x (Injector Duty Cycle)
If you are trying to compare injector flow rates and you have flow data at one delta pressure, you can easily calculate the flow rate at a different delta pressure as follows:
Flow rate at new delta pressure = (flow rate at old pressure) x v(new pressure/old pressure)
Engines require a certain fuel flow rate that is generally measured in lb/hr (pounds per hour) and can be calculated via knowledge of its Brake Specific Fuel Consumption (BSFC). BSFC represents how much fuel (in lb) is required per hour per each brake horsepower the engine produces. More clearly stated, this means that if you have a gasoline engine that makes 300 brake horsepower, its total maximum fuel requirement in lb/hr can be calculated as follows:
Fuel flow requirement = (brake horsepower) x (BSFC)
This calculation can also be reversed to give the maximum safe hp a set of injectors can support, which gives:
Max safe hp = [ (injector size) x (total # of injectors) x (max duty cycle) ]/BSFC
Example: The following guide is a general rule of thumb for sizing fuel injectors on an 8-cylinder engine using a BSFC of 0.50. Forced-induction engines typically range from a BSFC of 0.55 to 0.65, with the latter value arising from the fuel enrichment necessary to keep exhaust temperatures below 1650 deg F and catalyst temperatures below 1750 deg F.
|Inj. Flow Rate (@ 40 psid)||Naturally Aspirated HP (@ 0.50)||Forced-Induction HP (@ 0.65)|
|19 lb/hr||258 hp @ 85% Duty Cycle||199 hp @ 85% Duty Cycle|
|24 lb/hr||326 hp @ 85% Duty Cycle||251 hp @ 85% Duty Cycle|
|30 lb/hr||408 hp @ 85% Duty Cycle||314 hp @ 85% Duty Cycle|
|32 lb/hr||435 hp @ 85% Duty Cycle||335 hp @ 85% Duty Cycle|
|34 lb/hr||462 hp @ 85% Duty Cycle||356 hp @ 85% Duty Cycle|
|36 lb/hr||490 hp @ 85% Duty Cycle||377 hp @ 85% Duty Cycle|
|38 lb/hr||516 hp @ 85% Duty Cycle||398 hp @ 85% Duty Cycle|
|39 lb/hr||530 hp @ 85% Duty Cycle||408 hp @ 85% Duty Cycle|
|42 lb/hr||571 hp @ 85% Duty Cycle||439 hp @ 85% Duty Cycle|
|44 lb/hr||598 hp @ 85% Duty Cycle||460 hp @ 85% Duty Cycle|
|47 lb/hr||639 hp @ 85% Duty Cycle||492 hp @ 85% Duty Cycle|
|60 lb/hr||816 hp @ 85% Duty Cycle||628 hp @ 85% Duty Cycle|
|72 lb/hr||979 hp @ 85% Duty Cycle||753 hp @ 85% Duty Cycle|
|80 lb/hr||1088 hp @ 85% Duty Cycle||837 hp @ 85% Duty Cycle|
|98 lb/hr||1333 hp @ 85% Duty Cycle||1025 hp @ 85% Duty Cycle|
Remember, the above calculations assume a fuel pressure of 39.15 psid. If you can raise fuel pressure and still be sure that your fuel pump can supply the desired flow rate, then these maximum horsepower numbers will increase.