SilvercamZ28

Please for give the stupidness of this answer.. but can someone please tell me the stock size (lb) of the fuel injectors on a 96' Z28. I would like to upgrade my injectors to get a little more fuel to the motor.. but I don't know what size to get sice I don't know what the stock size is. Thanks for the help!

madwolf

Stock injector size is 24 lb/hr. (close to 25 set in the PCM programming)
Most bolt ons will not require any more fuel than that, so I'd recommend staying with stock injectors. Or if you really need to replace your stockers, I'd recommend some 24# Ford SVO injectors which actually flow a little more than 25 lb/hr on LT1's fuel pressure.

Either way, don't get any LS1 26.4 or 28.8 lb/hr injectors. They run at a higher pressure and will actually flow less than stock on LT1 pressure. (43.5 PSI)

SilvercamZ28

Wow thanks for the quick reply. There are two reasons I was thinking of changing my injector size. First I was told by running the mods I have (some include bigger TB, CAI, Ported Intake, headders, deleted 1 cat.. other is Random High Flow, and SLP Loudmouth exhaust) my car could be running lean in the higher RPM range. Also I was told that my new Aeromotive Fuel Press Regulator won't actually change my fuel press unless I go to a bigger injector or change my my injector pulse..

madwolf

The adjustable fuel pressure regulator will set the pressure to whatever you set it. That's what it was meant for, right?
So yes, it will work just fine with the stock injectors.

Also, it doesn't have anything to do with the pulse.

If you bump the fuel pressure some, the injectors will flow more, but for your mods, stock fuel pressure and flow is enough.

Some people actually lower the fuel pressure with the regulator to lean out the fuel flow. (since it's a bit rich from the factory) Some say it helps, but I would recommend doing this through programming instead.

Injuneer

If those are the only mods, and there is no heads or cam work, it is unlikely that you are "running lean at the higher RPM range". The stock 24's will take you up to 400flywheelHP with no problems (as will your stock fuel pump and regulator). Several people here are running 450HP in stock injectors.

Unless you are over 400HP, increasing the size of your injectors will not give you any performance gain. You are not running lean. In general, the stock programming on the LT1 for WOT is way too rich from the factory.

I'm not sure what you mean by:

If you increase the fuel pressure with an AFPR, it will increase the flow capacity of the injectors. And the pressure will remain where you set it. Increasing your fuel pressure from the stock (no vacuum) 43.5psi to 58psi will turn you 24's into 28's. But just increasing (or decreasing) the fuel pressure isn't going to have a real impact. Add pressure without programming and its going to force the long term fuel corrections to reduce the injector pulse widths to keep the tune at part throttle/closed loop conditions. Go WOT, and since the PCM was cutting fuel, it will revert to 0% correction, and you will run richer, which is probably the last thing you want. It's already using a target A/F ratio of 11.7:1 at WOT, and that's too rich for peak power or torque.

All this is really irrelevant... the size injectors you need is determined by the peak HP and torque brake specific fuel consumption (BSFC), and unless you have mods you aren't telling us about, you probably don't have the HP.

Easy way to find out is a dyno pull, with a wide-band analyzer to see if its running lean or not... otherwise you are just making random guesses.