Here's something I've been thinking about:

If I replaced my stock 460cc injectors with 550cc primaries, threw on two 550cc secondaries, got a new fuel pump, fuel rail, and fuel pressure regulator along with a Haltech F5 (to control the extra injectors), would I be able to alter my air/fuel mixture so that I would have MORE fuel and more air flowing into the engine? If so, how much power would this make. I currently have an AFC-II, so I was thinking that I could use that to alter the A/F ratio.

My concerns are that the stock ports would not be able to throw all this fuel and air into the engine effectively. Does anyone know if this could work and pick up some power?

 

the only reason for upgrading the injectors and/or adding more, is if you have increased your air intake. As in porting your manifold and motor. Use the search tool to find this and many other ways to improve volumetric efficiency.

 

Are you making more than 220-240 HP that you need bigger injectors?

Putting bigger injectors on won't really help anything until you get to that power level or are going with Nitrous as non-turbos run way way rich on the 2ndaries anyway

 

That brings up an interesting question: do the guys running nitrous on their NA's get the fuel they need leaving the 460's in there?

 

Icemark made a very important point here. Highly modified N/A's pick up more power from a AFC by decreasing the fuel at high rpms. They already run pig rich under stock ECU control. Get your car dyno tuned and you could pick up as much as 15 wheel HP on the top end. Add bigger injectors and you are just creating problems.

 

if not what size do they go up to?

 

Alright, I get it. I wouldn't be able to flow enough air to get an optimum air/fuel mixture, so it wouldn't be able to provide me with any real power. I'd have to seriously get more air flowing into the engine before adding more fuel, and stock porting and a stock intake manifold can't provide that, right? Thanks for the info.

 

yep, got it exactly right

 

Around the end of the year I'm thinking of going forced induction. Do you think that 550cc secondaries and a Nippondenso performance pump would be able to provide enough fuel for as much as 250whp?

 

I don't know about a forced induction N/A, but the previous owner of my TII dynoed the car at 215RWHP with the stock injectors, fuel pump, etc, and he was running VERY rich still. So I think you could do it with 550CC secondaries.

 

The pump alone would probably be fine... but dyno it and find out.