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Old 05-29-07, 03:57 AM   #8 (permalink)
Mal
malb
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Australia
 
Join Date: Apr 2007
Location: Melbourne Aus
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Re: Economical 2 stage EFI fuel system for the DIY Guy

Quote:
This in turn raised a question in my mind - if the swirl is at say +3psi pressure and the retun from the rail to swirl is full, will that mean that the preset pressure regulator will be runnig at 3psi higher than it was set for? Professionals on the engine I am using said not and I accepted it. (Still could not figure out why not) - It does not appear to have any adverse effect.
Ian,

The fuel pressure regulator will reference directly to atmostphere, not to the return pipe. Thus if set for x psi pressure, it will allow sufficient (within design limitations) fuel to bleed into the return line to drop the injector feed pressure to x psi above atmospheric pressure.

Provided that the return line can physically carry that volume without developing undue backpressure, the regulator system will function correctly.

In order to assure this, the return line should be as short as practical, and appropriately sized.
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