Fuel Injector Flow Rate versus Fuel Pressure

Fuel pressure plays a big part in the actual fuel flow of a fuel injector. Stock fuel pressure for a 2.3L Ford engine is 40 psi (lb per square inch). The fuel injectors have a flow rating based on a fuel pressure of 40 psi. When you increase the fuel pressure, you increase the fuel injector's flow rating. The Accel data sheet has the formula listed for determining the new flow rating of an injector when the pressure is increased. To make it easier, here's an online Fuel Injector Flow Calculator for doing just that.

Unfortunately, the practical safe limit for increasing the fuel pressure is only about 45 psi for a stock 2.3L fuel system. That increases the flow rating of the stock fuel infector by 0.8 lb/hr to 14.8 lb/hr. Not significant considering you would have to replace the stock fuel pressure regulator with an aftermarket adjustable regulator for about $100.

1998 - 2001 Ford 2.5L Fuel Pressure

Now it gets interesting. In 1998, Ford stroked the 2.3L to make the 2.5L engine (8% increase in displacement). They used the same 14 lb/hr fuel injector as the 2.3L engine except they increased the fuel pressure to 60 psi. This makes the 14 lb/hr fuel injector perform like a 19 lb/hr injector! The hp increased from 1992's 100 hp to 2001's 119 hp. The increase to the 2.5L displacement would account for 8 hp and it looks like the remaining 11 hp could be due to the fuel injectors.

Here's a video on how to change the fuel pressure regulator. It's not for a 2.3L but it gives you a good idea of what's involved.

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Copyright February 2011 Eugene Blanchard