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Old 01-15-2013, 08:46 PM   #36
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Originally Posted by fast4d View Post
most newer EFI systems run 'returnless'. there's no circulation of fuel

I would think the returnless pumps are cycled and don't run constantly on the same intensity therefore eliminating overheat conditions.
Returnless simply means that the regulator is at or in the pump assembly. These systems will run a set pressure and modulate the IDC to account for changes in manifold pressure. I've never seen a pump that cycles (although many autos use voltage modulation to the pump to keep it quiet at low load and prevent regulator overrun at low IDC)

edit to add: There are also semi-returnless designs (such as BMW auto) where the fixed pressure regulator is contained in the external fuel filter with output to the engine and return from filter to tank.
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