Power Grid controller vs. Digital-7

Discussion in 'PSI Superchargers Tech Questions' started by Critical Mass, Nov 18, 2015.

  1. Critical Mass

    Critical Mass Member

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    What are the advantages of a Power Grid controller (7730) over my Digital-7 (7531) for my 44 Mag and 8147 Box setup? It appears that they have the same capability?
    Thanks for any info, Joe
     
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  2. BEDNAR1320

    BEDNAR1320 Member

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    Subscribing
     
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  3. Mike Canter

    Mike Canter Top Dragster
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    Had to think about that. One thing is that the Digital 7 does not have the ability to record the ignition during the warm up or run. I have used this numerous times to successfully troubleshoot a problem. Also the Grid has the expansion capability so you can add traction control or future capabilities. The Grid also allows you to record its data on the Racepak. Future Grids will have Bluetooth capability so you can make quick changes in the staging lanes. The base software in both the Digital 7 and the Grid is very similar.
     
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  4. Critical Mass

    Critical Mass Member

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    I use a Digital-7 with a crank trigger to control the launch and to limit the max rpm of my 44 Mag. The reason I'm asking about the Grid is that I am having trouble with my motor dropping cylinders during the run. I thought it could be the connection between the Dig.-7 and the 8147 box; so I disconnected the Dig-7 rev limit connection from the 8197 box and started the motor, and it is still dropping cylinders after ~1.5 sec into the run, even with the max rpm limit set at 8000 rpm in the Dig-7.

    Does anyone have any ideas what is causing this to happen?

    Thanks, Joe
     
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  5. Mike Canter

    Mike Canter Top Dragster
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    Most common reasons are bad plug wires or coil wire or if you are using a crossover switch on the crank trigger then the switch contacts are bouncing due to vibration from the motor. Usually caused by the switch being hard mounted. Have you tried running it directly off the mag? If it still continues then see if you can borrow a known good Points Box and coil. In this case the internal recording of the ignition data in the Grid would show you right away if the crank trigger was causing the problem but it cannot show if it is the Points Box or Plug wires causing the problem because they are all after the Grid
     
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    Last edited: Nov 19, 2015
  6. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    You are probably looking at a points box going away if your wires are not real old. Also how old is your coil wire. You will probably need a new cap and rotor. Whether or not it was the chicken or the egg, misfires usually carbon the cap and rotor up pretty good.
     
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  7. Critical Mass

    Critical Mass Member

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    Well it looks like a bad points box or coil. The plug wires were all about 40 ohms/ft. I changed the cap and ran the motor directly off the mag. It sounded like it was on the rev limiter; it started dropped cylinders proportionally to the increase in rpm. I wished I had an extra box and coil to try.
    Thanks for all the help, Joe
     
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  8. Mike Canter

    Mike Canter Top Dragster
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    Well the fact that all the plugs wires read good resistance does NOT mean they are good. The biggest problem with plug wires is that the insulation breaks down over time and the spark starts jumping to ground or from one wire to another. If you have used those wires for the whole season then they should be changed. If you run a full season using a Promag then you should have changed the wires two to three times and the coil wire about every two races. If you can safely run the motor in the dark then try it and see how much high voltage spark you can see jumping from the wires.
     
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  9. Critical Mass

    Critical Mass Member

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    Thanks Mike for your reply. I just thought you only had to ohm out the plug wires. The fact is that I've run these plug wires for two seasons!

    I'm going to purchase new plug wires in near future. What do most racers run? I was thinking about shielded Phillips plug wires instead of the MSD wires?

    Thanks, Joe
     
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  10. Mike Canter

    Mike Canter Top Dragster
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    We have never had a problem with the MSD wires. Figure you got two seasons on them. That's pretty good
     
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  11. Critical Mass

    Critical Mass Member

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    Update on my misfire problems:

    I had the 44 mag, point box, and coil checked out by MSD and all of them came back with a clean bill of health. It looks like it's coming down to the crossover switch. It is activated by the starter switch and I only used to start the motor. I plan to remove it and replace it with a three position DPDT hand operated switch so I can look at the other ignition signals and have the option to run the motor on mag only.

    I was curious if anyone has found a good quality DPDT switch or a digitally/transistor switch to replaced the current over-the-counter switches.
    Thanks, Joe
     
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  12. Mike Canter

    Mike Canter Top Dragster
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    A standard DPDT can't take the high frequency vibration and the contacts will bounce. Try the switch offered by Fuel Injection Enterprises. If you have a Grid you can use the recorded data within the Grid to tell you if the misfire is coming from the switch. Look at Ignition In and if there are spaces then for sure it is coming from the switch or crank trigger. No guessing
     
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  13. Critical Mass

    Critical Mass Member

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    Thanks Mike,
    I'll take your advice and try the FIE switch, but what makes their switch vibration proof?
    Joe
     
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  14. Mike Canter

    Mike Canter Top Dragster
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    Call Spud at FIE and talk to him about and what he has done with it.
     
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