Fuel pressure question

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livingez_123

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08 Denali with fresh engine, new everything. I've started tuning the new build and noticed that my fuel pressure starts out at 58-60 on a cold start and when the engine temp hits 100° it drops down to 42-45psi. I replaced the pump module with a new Bosch unit and the pressure is the same. Do these use a PWM pump? If so that explains why it drops. I've looked everywhere and I can't find a definitive answer.
The Denali runs great so I'm inclined to just move on with the tune.
 

B-train

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Yes, they are a PWM controlled pump. Eliminated the need for a return fuel line and pressure regulator.
 

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