Just thought I'd chime in on a discussion from Dec.4th. Brad, you mentioned that you have noticed fuel pump inadequacies when fuel pressure was increased to levels commanded by an RRFPR. My custom adjustable FPR I have adjusted anywhere from 2.5 to 3.5 bar, basically in an attempt to downsize my injectors to 24lb/hr from 30. Like you, I have noticed significant transient improvements related to drivability when using the 24's, especially in the 3,000 to 4,000 RPM range. I do understand the fueling issues you mention at high RPM (say above 5,000) My previous assumptions suggested that a Walbro Pump would be capable of operating safely and reliably up to perhaps the 4 bar range, but since I am running about 20 PSI (or shy of 1.5 bar of boost, I am expecting the pump to be able to handle 3.5 bar + 1.5 bar = 5 bar at worst case. Perhaps this is too much as you suggest? I never tried to take a time history of fuel pressure as a function of load and RPM. Seems even more difficult to measure with an RRFPR as you really dont know fuel pressure over time unless you use a pressure transducer with a time trace.

Do you know what the limits of the Bosch and Walbro fuel pumps are? I am getting a much clearer understanding of why 30's are preferred for high outputs. Sounds like the pump is the limiting factor. 30's give you the same lb/hr with no taxing of the pump, even though idle and moderate loads see negative effects.

JT

posted by 68.79.81...

• Brad, your comments on max pump press. intrigue me, JT, Wed, 10 Dec 2003 17:40:13 <-- Viewing This Message
  • here's a few pump graphs, davenew, Fri, 12 Dec 2003 05:48:03
    • Re: here's a few pump graphs, Brad, Fri, 12 Dec 2003 07:13:36
      • Re: here's a few pump graphs, JT, Fri, 12 Dec 2003 15:51:31
  • Re: Brad, your comments on max pump press. intrigue me, Brad, Wed, 10 Dec 2003 19:30:13
    • Try checking the voltage at the pump..., SteveW, Fri, 12 Dec 2003 11:02:21
    • Re: Brad, your comments on max pump press. intrigue me, JT, Thu, 11 Dec 2003 16:06:40
      • Re: Brad, your comments on max pump press. intrigue me, Brad, Thu, 11 Dec 2003 19:26:38
      • Re: Brad, your comments on max pump press. intrigue me, lms, Thu, 11 Dec 2003 17:10:44
        • Re: Brad, your comments on max pump press. intrigue me, JT, Thu, 11 Dec 2003 18:17:26
          • Re: actually new style double adjustable RRFPR, steveC, Thu, 11 Dec 2003 23:42:20
            • that's the one I'm talking about.., lms, Fri, 12 Dec 2003 09:13:46
              • Re: that's the one I'm talking about.., stevec, Fri, 12 Dec 2003 23:04:48
              • Re: that's the one I'm talking about.., JT, Fri, 12 Dec 2003 15:40:19
    • Numbers, Brad, Thu, 11 Dec 2003 13:45:35
      • Re: analysis?, damien, Thu, 11 Dec 2003 17:41:43
        • Re: analysis?, JT, Thu, 11 Dec 2003 17:58:34
          • Re: analysis?, Brad, Thu, 11 Dec 2003 19:30:36
  • Re: Brad, your comments on max pump press. intrigue me, gorper, Wed, 10 Dec 2003 18:14:31

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