fuel pressure confusing me !!

[red gt500]

hello

i did a dyno run yestrday but the fuel pressure is driving me crazy
with the sct live link data log it shows a solid 40 psi throw all the rpm range
but i did install a exturnal fuel pressure gauge and it shows 60 psi at wot

and the a/f ratio at 5500 rpm 10.5 !
i dont know whats right and whats wrong ..is the motco fuel pressure adapter has something to do with it ? :shrug:

 

[69b302]

The PCM is usually looking at the pressure drop across the injectors, and not absolute fuel pressure. The drop across the injector takes into account the intake manifold vacuum or pressure(boost). The vacuum line from the front of the intake manifold to the fuel rail pressure sensor is how the fuel pressure sensor links in the manifold pressure. A solid 40 from the PCM sounds ok, and an external guage would read 60 psi, if you had 20 psi of boost. 10.5 A/F ratio seems fat, but depends on how aggressive your setup is.

 

[fullboogie]

There are about 4 different PID's to log fuel pressure - one of them will give you absolute pressure.

 

[red gt500]

The PCM is usually looking at the pressure drop across the injectors, and not absolute fuel pressure. The drop across the injector takes into account the intake manifold vacuum or pressure(boost). The vacuum line from the front of the intake manifold to the fuel rail pressure sensor is how the fuel pressure sensor links in the manifold pressure. A solid 40 from the PCM sounds ok, and an external guage would read 60 psi, if you had 20 psi of boost. 10.5 A/F ratio seems fat, but depends on how aggressive your setup is.

yes I have 3.6 kb 20 psi .. from what I understand 1 psi (boost)= 1psi (fuel)
so I think its fine
but what made me confused is the fuel pressure reading in the livelink datalog
thanks for clearing that up

 

[red gt500]

There are about 4 different PID's to log fuel pressure - one of them will give you absolute pressure.

I will check it out thanks