Promag and Capacitor

Discussion in 'PSI Superchargers Tech Questions' started by Flyboy68, Jul 28, 2011.

  1. Flyboy68

    Flyboy68 Member

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    When using a capacitor w/ a Promag 44 and a 8973...is it normal for the the power to slowing turn off once the ignition switch is turned off? We run a "kill" solenoid to ground the coil wires, and once the ign switch is turned off...it takes about 3 sec for the solenoid to "snap", so it'd take 3 seconds to kill the motor? Is this normal?

    Josh
     
    #1
    Flyboy68, Jul 28, 2011
  2. Mike Canter

    Mike Canter Top Dragster
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    Josh, there are several reasons why MSD recommends using the capacitor on there systems. One reason is to filter the 12 volt input power and the other is to have it work as a battery for a few seconds if you either intermittently loose power or totally loose power. This is so the car will not shut down and will save the run. What you are experiencing is normal. One option is to use the capacitor only on the main input power and have the switch power between the capitor and the 8973. This way when you shut the switch off it will shut the motor down immediately.
     
    #2
    Mike Canter, Jul 28, 2011
  3. Joad Donnelly

    Joad Donnelly Member

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    Josh,

    I noticed the same thing as when I wired in the capacitor this year. The 'Vette came with the big Promag kill solenoid so I wired up the ground side of that solenoid through the mushroom style emergency kill switch & that is what I use to shut the car off with. So even though it takes a few seconds for everything to power down, the solenoid is activated as soon as the switch is pushed so there is no delay in killing the engine. As soon as I hit the kill switch the ignition is dead.

    You going out to KID this weekend?


    Joad
     
    #3
    Joad Donnelly, Jul 28, 2011
  4. Flyboy68

    Flyboy68 Member

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    Thanks for the replies guys. That helps clear things up.

    Yeah Joad we'll be there. Got wider tires this time too :D Do you know if there is assigned parking? See you there.

    Josh
     
    #4
    Flyboy68, Jul 29, 2011
  5. jody stroud

    jody stroud ZOMBIE Top Dragster

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    My car does the same thing, but first I kill the fuel then hit the switch and by the time the motor quits it has burned off most of the fuel in the motor...rpms start to go up like when you are running mag only and kill it by shutting off the fuel.
     
    #5
    jody stroud, Jul 29, 2011
  6. Mike Canter

    Mike Canter Top Dragster
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    Put the power switch between the capacitor and the 8973 instead of before the capacitor then you it will shut down immediately
     
    #6
    Mike Canter, Jul 30, 2011
  7. jody stroud

    jody stroud ZOMBIE Top Dragster

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    yep. Mikes right.
     
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    jody stroud, Jul 30, 2011

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