Upgrading fuel system Q's

On a built LS, at what point do you need an FPR, Fuel rail, and upgraded injectors? Can’t the stock Fuel pressure and rail feed the stock injectors to their maximum capability? I’m wondering what is necessary to build an engine that is not going to be starved. I’m guessing that starting off with an A/F guage and adjustable FPR will help me at least set everything to about 13.5:1 which to my understanding is where you want to be. I’d like to learn more about fuel management on honda motors, be it non-vtec or vtec, coming from people with first hand experience or a lot of internet knowledge! Thanks

Basically here’s how fuel injection works:

The ECU sends a signal to the injectors telling them how much fuel to spit out, called duty cycle. This is a percentage of the injector’s flow rate. The stronger the signal from the ECU, the longer the injector stays open and the more fuel gets into the engine. The higher the flow rate of an injector, the more fuel it will spit into the engine given the same signal from the ECU. The stock injectors flow 240cc/min and I believe the stock fuel pressure is 48 psi, I think.

The only reason people run high-flow fuel rails and super-high fuel pressure is because they’re trying to squeeze the most fuel possible out of the same duty cycle on undersized injectors. Just for comparison, the H22A uses 310cc injectors and puts about 170 hp to the wheels. On any n/a built-up B-series motor I’d reccomend that size. Other tuning tools are a B&M Command-Flo fuel pressure regulator/guage, an A’PEXi S-AFC (or V-AFC if you have VTEC) and an air/fuel ratio guage. Basically it boils down to slapping the car onto a dyno, and playing with the fuel pressure (which I would keep at stock or close to it) and V-AFC until you have an indication of “stoich” on the a/f guage all the time. Generally this will net you a bit more power throughout the rev band as well.

Do Prelude injectors from OBD-I cars fit and plug in?

I’m not sure on the Prelude injectors fitting or not. All I’ve heard of is people running RC Engineering units, although I don’t know if those are universal fit or what. Regardless, remanufactured lude injectors are about the same price as ones that have been exactly spec’d by RC, so I would go with RC.

Reason is I know of a guy who put in prelude injectors on his 93 civ hatchback that had an LS & JRSC and apparantly it helped him out a lot.