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Old 01-04-2018, 09:06 AM   #2
01yellerCobra
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Join Date: Jan 2013
Location: San Diego, CA
Posts: 1,104
How are you measuring fuel pressure? Is the car running bad? Returnless set ups will change more than a return style.

The FRPS maintains a 39-40psi drop across the injectors. Meaning the pressure in the rail is about 40psi higher than what would be at the outlet of the injectors. Easiest way to think about it is if you have 10psi of boost going into the engine, then fuel pressure would need to be 50psi at the fuel rail to maintain the 40psi difference. When the engine is in vacuum it doesn't need as much pressure. So the 21.5" can be thought of as negative. 21.5+19=40.5. Of course I'm using absolute values. But going by that math your pressure is correct.

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