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Power Brake Vacuum pumps and EFI MAP sensor

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  • Power Brake Vacuum pumps and EFI MAP sensor

    As you can read in the regular tech section I now have, thanks to James (SeeRed), a Master Power electric vacuum pump designed for power brake systems paired with engines that produce low vacuum at idle. Mine was around 9 inches at an idle speed of 1000-1100 and I anticpate it will be even lower when I start up the new combination in a week or so as the new cam has a narrower LSA, 109 vs. 112, so I'm expecting 7-8 inches of vacuum.

    It appears that the Master Power unit is intended to be tee'd into the vacuum booster line between the manifold and the power brake booster, It is setup with a switch that turns the unit on when the vacuum signal falls below 12 inches, meaning it will run always at idle and at large throttle openings.

    Currently I pull signal for the MAP sensor off a junction block that gets vacuum from the manifold via .375" vacuum hose that goes to block and out again on the other side. Two small ports feed the MAP sensor build into the EMS-Pro unit and the cowl mounted mechanical vacuum gauge.

    Vacuum generated by the pump would play havoc with these I suspect as it would pull from those lines as it is currently configured. My thoughts are run a separate vacuum line for the gauge and MAP off of the plenum, or use some kind of check valve to isolate the vacuum pump form the junction block when it is running. I'm not sure how it would get a turn off signal unless manifold vacuum actually pulled the check ballback against the pumps own vacuum.

    I obviously haven't got that idea completely sorted out yet in my feeble brain.

    Ideas...suggestions... better yet, proven solutions?
    Drag Week 2006 & 2012 - Winner Street Race Big Block Naturally Aspirated - R/U 2007 Broke DW '05 and Drag Weekend '15 Coincidence?

  • #2
    Re: Power Brake Vacuum pumps and EFI MAP sensor

    I'd try using a check valve and put the MAP sensor on a separate port of the plenum from the pump.


    • #3
      Re: Power Brake Vacuum pumps and EFI MAP sensor

      The check valve helps, but we can "tune" the VE table to feed the same fuel at idle with or without the pump running.

      Even better, we can use a spare output on the EMS to run the pump based on vacuum, or throttle position, or RPM, or any other parameters.

      We can use the shift light output, or there are a few others that can be converted too. e-fans, etc.

      -Scott - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!


      • #4
        Re: Power Brake Vacuum pumps and EFI MAP sensor

        My vacuum at idle is just low enough that my power brake booster could use some electric pump assistance. If I add one, I'll definitely put an additional check valve in the hose from the intake (before the "tee" for the electric). That way, I should have good booster vacuum any time the ignition is on, even with the engine off.
        The entire line after the added check valve would hold vacuum (and keep the electric pump off) until the brake pedal is depressed.
        If the check valve and lines held vacuum well enough, the electric pump could actually be on any time the battery disconnect is on.
        I've already been surprised by a total lack of brakes when I've "gravity" rolled my truck out of the garage... Both feet on the pedal or it keeps goin'...
        D R A G - W E E K - '05 - '06 - '07 - '08 - '09 - '10 - '11 - '12 - '13 - '14 - '15 - '16 - '17