Another Grid Question

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Critical Mass, Jul 5, 2018.

  1. Critical Mass

    Critical Mass Member

    Joined:
    Aug 5, 2010
    Messages:
    152
    Likes Received:
    3
    Hi Guys,

    I am using a 44 mag with a 8147 box, the one with the rpm module slot, and a 7730 Grid. In the Grid settings I have set Burnout, Launch and Max rpm limits.

    My question is: Which rpm module will limit the max rpm of the motor, the one in the box or the one entered into the Grid? Or will it be the lowest rpm module?

    Thanks in advance, Joe
     
    #1
  2. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
    Staff Member

    Joined:
    May 6, 2003
    Messages:
    6,365
    Likes Received:
    61
    When you select Ignition Type - Pro Mag, it will use the plug in chip to the 8147 to limit the rpm. When Network ignition is selected (non mag systems) then the Grid limits the rpm.
     
    #2
  3. drew556

    drew556 Member

    Joined:
    Jan 21, 2016
    Messages:
    30
    Likes Received:
    0
    The grid plugs into the 8147 box where the chip would normally go that’s how it controls rpm limit.
     
    #3
  4. Critical Mass

    Critical Mass Member

    Joined:
    Aug 5, 2010
    Messages:
    152
    Likes Received:
    3
    I'm using a rpm chip plugged into the 8147 box right now, because the two yellow rpm wires were too short to reach the Grid. I had MSD make me a longer one but it didn't work.

    The motor is in a 6 second index jet drag boat. I have plenty of power for the 6 sec; I just wanted to get my 660 times under 4.0 sec. So I wanted to try 2-stepping the motor at launch so I connected a 3-Step to the box to limit the launch rpm but didn't try it. I was told you don't want to just mat the throttle on a blower motor, you have to control the launch rpm using the butters and a chip, so I unplugged the 3-Step and put a max rpm chip back in the box.

    I found with my new jet nozzle I was able to rev the motor to around 6000 rpm and still stay on the line without the boat moving. On this pass I did 4.1 sec in the 660. With a little more tuning I think I get under 4 sec. That all said, I guess I don't need the 2-step after all. Thanks for all the input. Joe
     
    #4
  5. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
    Staff Member

    Joined:
    May 6, 2003
    Messages:
    6,365
    Likes Received:
    61
    For what it's worth there's nothing special about the MSD extension. I'm not a fan of butt connectors but if you needed to, you could make your own extension with wire and butt connectors. I prefer to use the .093 Molex connectors that come with the MSD kit. Deutsch is a better option still.

    There's plenty of blown motors that go WOT on the two step. The thing you have to compensate for is the barrel valve going wide open and putting all the fuel to it. Most roots applications will open a bleed jet while on the two step. You also have to remember you will be making ALOT more boost on the two step than you would at part throttle.
     
    #5
  6. Critical Mass

    Critical Mass Member

    Joined:
    Aug 5, 2010
    Messages:
    152
    Likes Received:
    3
    Will and drew556,

    Getting back to my basic question, I check the ignition setting in the Grid and it is set at: 6AL/7AL/MSD8/PRO MAG

    If I understand both of your replies, the Grid at the above setting, should be able to control the rpm limits of the motor with the right cable?

    Note: Mike Canter also warned me about the length of the rpm cable in the past. I even ran it inside a SS tube to protect it from extraneous RF noise.

    Thanks, Joe
     
    #6
  7. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
    Staff Member

    Joined:
    May 6, 2003
    Messages:
    6,365
    Likes Received:
    61
    That is correct. That is the only proper setting to run the Grid with the Mag. The network ignition setting will work and limit rpm, but it will run like crap because the mag puts out a different wave than a distributor.
     
    #7

Share This Page