Anybody try it out on these modulars? With my old 4.9l you could get a reasonable increase with other mods done (eg. FIPK, exhaust, Blaster coil, fuel pressure regulator) I did do some mods to my 5.4l which yielded little gains except for the chip, but would larger injectors help get some more giddy-up-and-go. I'm asking this because I know where to get some parts from a Mustang Cobra with a 4.6L and I pretty sure i could get the injectors pretty cheap compared to new but I need to know how many lbs/hr my 5.4l has compared to the Cobras which I'm pretty will be better.

 

The reality is that assuming all else stays the same, larger flow injectors will add nothing and possibly make things worse.
Lets assume that you start with a stock setup, and only swap injectors and the fuel pump/regulator from a larger engine designed to use them.

Now you have a stock PCM trying to regulate the engine with fuel components that it is not programmed to use. At best, it has enough slack in the fuel tables to correct the flow, but at worse, the fuel flow exceeds the engine capicity to burn it properly. The result would be a decrease in performance, fuel economy, and higher pollutants discharged.
Real power is as more science than art. The simple stuff is the airflow in and out of the engine, alterations to the spark advance values ,etc. Anything you can do to make that process smoother adds small gains by allowing the engine to work less hard to produce the maximum power it is capable of. After the simple stuff power increases gets more complicated and expensive. Displacement increases (or turbo/blowers), compression ratio, more radical timing advances/ specialty cams, alternate fuels.
But in the end, no matter what you do to the engine, you must still get the air/fuel ratios in line.

Dialtone

 

Only if you force inducted the engine would going with bigger injectors help. Stock 5.4 injectors should be 19lb/hr. The 300 was a different animal, as Ford tuned it for emissions, so they went with a design that would pass using an engine that was designed in the carb days. The 5.4 is pretty well maxed in stock form. Remember Ford had to change the intake and improve the heads to get 30 hp. Adding things like an FIPK, headers, chip/programmer will help, nothing drastic though. Adding injectors isn't going to really help, the intake is holding any improvements up, as it will only flow as much air as the heads allow.

As Dialtone pointed out, add them, then you need to get the F/A back in line. If you plan on going with other mods, then do it all at once including injectors and have it all tuned at once.

-Kerry

 

Great feedback fellas, good to hear professional advise. You confirmed my curiousity about the bigger injectors, and like I stated earlier, the mods other than the chip didn't do squat and this motor and is pretty much maxed out. A supercharger was on my list for a power increase but that's a major investment, but it doesn't hurt to ask about the small stuff.