Originally posted by 4g62bt2c30a:
HUH? since when? Do you have an example?
Um, I always have been under the impression that fuel pressure is measured relative to manifold pressure (where it counts), not atmospheric pressure. For example, if you are running fuel at 43 psi with a N/A engine at WOT then manifold pressure is approximately atmospheric pressure and fuel delivery inside the manifold is at ~43psi. But when you add, let say 5psi of boost then the manifold is 5psi greater than atmospheric pressure (which I think is around 14psi compared to a perfect vacuum—but that doesn’t matter) and the fuel pressure inside the manifold is now only 38psi so it needs to be increased to maintain the proper pressure differential. I believe this is conventional wisdom within the auto industry and scientifically sound.
Keep in mind here, that I could be completely wrong, but I live in the Detroit area so when we discuss things like this, there’s usually an engineer around to help us out and this is the conventional wisdom I’ve picked up on. On the same note, tomorrow I’ll be hanging out with a guy who has been designing engines for about 30 years and will try to pick his brains about some of the issues we’ve discussed on this thread.
I have a couple of basic questions regarding our fuel system:
To come close to calculating the min/max duty cycle of our injectors can I assume that our injector firing sequence is sequential? Are they high or low impedance injectors?
Can someone point me in to some information that shows that our stock injectors are in fact 240cc when measured at ~43psi.
Can we assume that our max stock rail pressure is 50psi, which is what I believe the service manual says is the regulator’s max setting.
Thanks,
DanO