# Fuel system talk.

**URL:** <https://forums.speedlife.net/t/fuel-system-talk/256583>\
**Category:** Shift518 Automotive\
**Created:** [January 24, 2011, 10:36am UTC](https://forums.speedlife.net/t/fuel-system-talk/256583 "2011-01-24T10:36:08Z")\
**Posts on this page:** 1\
**Showing post:** 26

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**Author:** ![imported\_hybrdthry91](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/imported_hybrdthry91/32/6315_2.png) [@imported\_hybrdthry91](https://forums.speedlife.net/u/imported_hybrdthry91)\
**Post date:** [January 26, 2011, 10:05am UTC](https://forums.speedlife.net/t/fuel-system-talk/256583/26 "2011-01-26T10:05:15Z")

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> [@A plump scotch girl](https://forums.speedlife.net/t/a-plump-scotch-girl/39129/2):
>
> so do i.
> 
> ok so base pressure will be say 50psi @ 0 vac, under idle it will be down around 32 or so psi, under boost the fpr will bump it up to about 70 psi at the rail (with 20 psi boost ref).
> 
> So I have to put 830 cc injector at 70 psi into a calculator (please link me to the one your using if you can save me a google search to find a good one)to find the lb/hr right?
> 
> Then I need to make sure the lb/hr is something the pump can pump. But if there is two pumps, the load will be halved, so what would the flow rating be I would expect?

the injectors dont flow any more when the fuel pressure increases because of boost. this only happens to create an equilibrium between the intake manifold and rail to again achieve your base pressure injectors capacity.

50base base +20psi of boost needs an additional 20psi of rail pressure to push against the 20psi of boost in the intake manifold or else you would get less fuel from the injectors.

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