fuel presure
05-17-2009, 08:15 AM
#6
All fuel pressure on all nissan fuel rails with regulators at stock idle is 34.5 PSIG at idle.
This means when you test the pressure it should be at 33.8 ~ 34.5 PSIG any lower and any higher you have a bad regulator. Now using stock 270cc injectors the fuel pressure should rise to almost 47~49? PSIG at the fuel rail during WOT and an rpm of about 5800RPM. This number drops if you use larger cc injectors such as sr20det 370cc injectors, that's why it's important to swap out to a larger pump that can handle that injector pulse width.
When you install a q45 fuel pump on a 240sx fuel tank without the Q45 relay, or a 350z pump, and you use the stock fuel rail and regulator static PSIG becomes 46.3 PSIG at idle.
I believe the same thing happens when you use a walbro pump, but I havent checked that myself to make sure its valid.
The higher fuel pressure at 46.3 PSIG is better if you use E85 on your engine, or if you are turbo charged with gasoline.
I believe Jecs injectors are only meant to handle 50 PSI, but people have been know to run them notoriously higher like in the high 85PSI range.
This means when you test the pressure it should be at 33.8 ~ 34.5 PSIG any lower and any higher you have a bad regulator. Now using stock 270cc injectors the fuel pressure should rise to almost 47~49? PSIG at the fuel rail during WOT and an rpm of about 5800RPM. This number drops if you use larger cc injectors such as sr20det 370cc injectors, that's why it's important to swap out to a larger pump that can handle that injector pulse width.
When you install a q45 fuel pump on a 240sx fuel tank without the Q45 relay, or a 350z pump, and you use the stock fuel rail and regulator static PSIG becomes 46.3 PSIG at idle.
I believe the same thing happens when you use a walbro pump, but I havent checked that myself to make sure its valid.
The higher fuel pressure at 46.3 PSIG is better if you use E85 on your engine, or if you are turbo charged with gasoline.
I believe Jecs injectors are only meant to handle 50 PSI, but people have been know to run them notoriously higher like in the high 85PSI range.
Last edited by BigVinnie; 05-17-2009 at 08:41 AM.
05-17-2009, 04:49 PM
#8
I mean in most circumstances if some one was to upgrade to a larger turbowith a a/r higher than .65, i would defenitely upgrade the fuel pump, since the injectors would demand more fuel at less PSI.
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