fuel pressure question

[aaron_mc_03]

do i always want my fuel pressure to be at 37psi reguardless of what size injectors i have installed. i have 860cc injectors.

 

[absolute_DSM]

Typically yes. (speaking 1g)

What are you using to tune? If you want to get a little more out of those 860ccs to handle more airflow, you can bump your FP up a bit. But dont forget to retune it after that

 

[aaron_mc_03]

I have DSMlink. What would you recommend?

 

[Splitpi]

I believe most injectors are rated at 80% duty cycle and at 43.5 psi. So if you lower pressure to the 1G stock of 37 psi you must do a little math to figure out a ball park flow amount.

New Flow percentage = sqrt(37/43.5) * 100 = ~92.2%

Or more appropriately

New flow Percentage = sqrt(New pressure/Old Pressure)*100

Duty Cycle can be neglected as they would be rated the same for either pressure. What this means is that if you run 860cc injectors at 37 psi ... they would actually flow 860*0.922 = ~792.92 cc at 80% duty cycle. This is ofcourse assuming the initial assumption that the 860cc injectors were rated using 43.5 psi.

Does that make sense?

 

[aaron_mc_03]

Yea it does. How do i know what psi my injectors were rated at?

 

[Talesin]

1G stock pressure is 37psi without vacuum. The injector timing should take care of the flow difference, allowing the same percentage gain over stock when moving to larger injectors, making the fuel map alterations happy.

You can bump pressure, just make sure your connections are solid. Since 1Gs are OEM lower pressure than 2Gs, they can develop fuel seeps/leaks when you bump up... ran into that problem on the feed side rail fitting when I added a bit to compensate for having a hacked MAS.
The plus side being better atomization and overall flow, so if your fuel system is up to it, doing so will produce some gains on those lines, at the expense of potential additional wear on your fuel fittings.

Personally, I'd keep it at stock pressure. If you have the flow to handle 860s at peak demand, there's no real reason to bump fuel pressure. You can get a much better atomization effect by adding an ounce or three (but no more than four per ten gallons) of acetone to each tank of gas, anyway, and it won't put undue and unneccessary stress on your fuel components.

 

[aaron_mc_03]

exact response i was looking for. thank you