Question on my first LS based vehicle. I am trying to track down a bog off of hard acceleration on my LQ4 6.0.
It does have an aftermarket fuel filter, and fuel pump, but it still has the stock vacuum controlled regulator with return.
Fuel pressure at idle and running/revved with everything hooked up on it is about 47 psi. Remove the vacuum hose and I am back at 58 psi which is approximately what it is with just the ignition turned on.
Does this sound right?
Thanks

 

You really need 58-60 PSI all the time. With both of my LS engines, I got rid of the vacuum referenced fuel rails and went returnless.

Rick

 

Reading online, they say to take the vacuum hose off to get a baseline reading. Then reinstall the vacuum hose and it will be a lower reading.
Just seems like 11 pounds lower is a big difference.
May try changing out the regulator and see if that does anything. Who knows, maybe I have something in the screen.
Opinions?

 

Thats normal pressures .. you dont need 58-60 all the time unless your computer is tuned for it. The pressure differential from the fuel rail to the intake manifold affects injectors flow rate. Thats why fuel injector flow rate is tuned different in a vacuum referenced system vs non referenced

is it goin lean when its bogging on hard acceleration?

Just because your fuel pump can make good pressure at idle doesnt mean it can keep up the volume under high demand.

If it is goin lean you will need to log/monitor fuel pressure under said conditions to know if that is really even your issue

 

Thank you sir, good info. Especially about it seemingly being the correct fuel pressure. Keeps me from tracking down certain things.