LSEGHATCH

I don't understand fully how this works with a turbo setup. Do you need to turn up the psi to correspond w/ how much boost you are running? I know it can decrease and increase the psi but of what, the fuel lines, the fuel rail? And when you do increase/decrease, what do you do it for.

The Weather Man

the point of a fuel pressure regulator is to send excess fuel back to the fuel tank.

A fuel pressure regulator just helps tune the fuel. If you have 450cc injectors, and your setup calls for 550cc - up the psi of the fuel pressure regulator and you'll be able to maintain with the 450s.

It increases the psi in the fuel rail.

At a certain psi, the fuel pressure regulator opens to release fuel.

If you set the fuel pressure regulator to open at 40 psi, it will open enough to maintain that pressure in the rail.

BlueShadow

One other thing with running boosted setups, is the amount of fuel pressure in the system is raised by the amount of boost you are running. For example a NA setup witha base fuel pressure of 45 psi will not go higher then 45 psi at WOT. However if you are running a turbo at 10 psi, then the amount of fuel pressure is added to the amount of boost pressure you are running. So if you are WOT at 10 psi then you fuel pressure at WOT would be 45 + 10 or 55 psi. Another example is if you are running a turbo at 20 psi and your base fuel pressure is 40 psi. At WOT and 20 psi your fuel pressure will be 40 + 20 or 60 psi of fuel pressure.

The reason you need to know all that is because when you raise the fuel pressure in the system you lower the amount of fuel your fuel pump puts out. Below is a pic of what the corrected Walbro 255lph and 255lph fuel pump flow would be for different fuel pressures. So say if you were to raise your idle fuel pressure to 55 psi and you were running 20 psi of boost. Your pressure at the rail would be 75 psi at WOT/20 psi of boost. At 75 psi of fuel pressure the regular Walbro 255lph pump is only actually flowing 75lph, while the Walbro 255LPH "high pressure" pump is actually flowing 170lph.

SwedBoy2999

Great Info

LSEGHATCH

i get it but i don't. What is safe to run and what is dangerous. What do you have to look out for when raising the pressure? I will be running aeromotive a1000 external pump with 1000 precision injectors.

BlueShadow

For larger injectors/high boost you'll want to run your base fuel pressure lower. You probably dont have to worry about exceding the fuel pump capacity on the A1000, but for 1000ccc injectors it helps themidle better if you lower the fuel pressure. You can try going to 30-40 psi of fuel pressure for the 1000cc's.

LSEGHATCH

Thanks guys, is there a certain psi where it can get dangerous when boosting? Like is 70-75psi something you don't want?

BlueShadow

The same concept applies to the Aeromotive fuel pump. If you look on their site they have a chart for the A1000 similar to the one I posted above. The only thing is it's in pounds of fuel per hour. I'm not sure what the conversion is to convert xx lb of fuel per hour to liters per hour. So I just went on http://www.onlineconversion.com and converted lb/h to ounces/hour then converted ounces/hour to liters/hour. I had to do all that cause onlineconversion wont convert lb/hour directly to liters/hour.

So say you have your base pressure to 35 psi and you are running 20 psi of boost. 35 + 20 gives you a total fuel pressure of 55 psi. At 12 volts your fuel pump is putting out about 420 lb/hour or 198 liters/hour. The reason I mention voltage is because more voltage going to your fuel pump will raise fuel pump output, but if you are losing voltage at the pump your fuel pump output drops. This is why it's important to make sure your fuel pump is getting the maximum amount of voltage at the pump, and that it is not being lost through bad wiring, or wiring that is too small.

LSEGHATCH

Awsome, what gauge wire would you reccomend running? I take it you can wire it straight to your battery terminals and have a relay or could you just tap into the oem fuel pump wiring that has the realy built into the ignition?

BlueShadow

Well I cant really help you with the wiring, but do a search in the forced induction archives for fuel pump wiring. There are some hits on that topic. Check out the thread started by Bryson.