I was wondering what my fuel pressure should be set at. I know that I have #24 injectors and that was my mistake in buying them in the first place. When I set my fuel pressure I should have the regulator hose off and plugged right? If someone could let me know what it should be, that would be great. BTW I will have a chip made to compensate for it in the future.

 

On a 305 with almost no mods you should have it 'around' the mid-high 30s

 

With an AFPR I have mine set to 45. Anywhere between 40-48 should be a good setting but you need to take it to the dyno to tune it correctly.

 

He has 24# injectors though on a 305

 

and also is that with the vacuum line disconnected and the fpr plugged?

 

Yes

 

On a 305 With 24 PSI injectors on the stock program you should have no more than 40 psi. What injectors are you using. SVO or GM? If you have a chip for your #24 injectors then the setting should be around 46 PSI. You will still have to fine tune on a dyno.
BTW.... That is with the vacume tube disconnected from the fuel pressure regulator.

 

I have accell injectors. I had another question though. If I get a chip programmed for the #24 injectors will I still run rich, lose hp, and gas mileage if I even have the correct setting? I am a little unclear on this. I was told I am better off getting #19 injectors and making the fuel pressure a little higher then stock. That was my last resort cause I don't want to pay another $240 for injectors and tear down the top half of my engine again. I would like to know if the chip would fix everything

 

With the chip you will still need to turn down your FP quite a bit. I would even say low-mid 30s because a near stock 305 does not need nearly that much fuel.

 

Will it hurt quarter mile times, gas mileage?

 

OK, here's the quick rundown on fuel pressure, injector size, and pulse width. Your original PROM chip was calibrated for a #19 injector. That means the injector would flow 19lb/hr of fuel at stock fuel pressure, which was probably 43.5psi or very close to that. Your computer reads the mass of air coming into the engine from the mass airflow sensor, and determines how long to open the injector for during each engine revolution. This is called the pulse width. The more air the engine pulls in, the longer the injector stays open and the more fuel is fed to the engine. When you reach 85% of the rated pulse width of the injector, that is when you will have to use larger injectors. Here is where your problems began.

When you upgrade to larger injectors, you MUST recalibrate your PROM chip so that it knows there are injectors that flow more for a given pulse width.
Here is an example:
You have 20lb/hr injectors and switch to 40lb/hr injectors without reprogramming the PROM chip. The computer opens the injectors for the programmed amount of time that it always has but now you are dumping in twice as much fuel as you need.

In your case, you upgraded to 24lb/hr injectors, and the computer thinks it still has 19lb/hr injectors. The pulse width is still the same, but the flow rate of the injector has changed. So, to compensate for too much fuel, now you reduce the fuel pressure and you are back to the same flow rate as the 19lb/hr injectors and you spent a bunch of money for nothing.

The bottom line is, you have to reprogram your PROM chip for the new injectors running at the stock fuel pressure. I would set the fuel pressure for 46psi becuase the spray pattern of the injector is better with higher pressure. You should be able to get Hypertech to do it for you.

 

I know that this is kind of an old topic, but some has changed since then. I did get the chip tuned for the 24# injectors. It shaved .3 off my quarter mile. Since I posted this I have put an Accel coil, ported plenum and slp runners. I have a computer kind of like a diagnostic tool that can tell you if the car is running rich or lean. It kind of just goes back and forth. What should I run my fuel pressure at now? Also do I cap off the AFPR and plug the vacuum line when I do this? I just want to make sure I am doing this right.
Thanks again.

 

Anybody know what it should be at this point?

 

If you have a FP gauge and access to a track then I would try raising and lowering the FP in 2psi increments to see which psi you run the best at. What is it set at now?