Starting an A/Fuel car?

Discussion in 'PSI Superchargers Tech Questions' started by William Payne, Sep 4, 2008.

  1. William Payne

    William Payne New Member

    Joined:
    Jul 19, 2008
    Messages:
    87
    Likes Received:
    0
    I was watching some drag racing dvds earlier and when they start the big blown nitro cars they use the primer bottle in the injector hat , yet a/fuel guys seem to use a methanol tank why is that ? .

    I have read some horror stories about the blown nitro cars and the injected nitro cars that when you start them if there is nitro residue in the cylinders you end up having a desastor and hydraulic the motor . What do you guys do to prevent that ?
     
    #1
    William Payne, Sep 4, 2008
  2. GregM784

    GregM784 Member

    Joined:
    Aug 24, 2008
    Messages:
    915
    Likes Received:
    14
    It's mostly their setups. We use alky and a squirt bottle to start the car when it's warm, but on the first fire up to get heat, it runs on a alcohol system for 30 seconds or so. It burns better than nitro in a cold motor.

    nitro motors should ALWAYS be backed off right before you start them. You roll the motor backwards a few times to get the fuel out of the cylinders, and out of the lines so they don't drip.
     
    #2
    GregM784, Sep 5, 2008
  3. fuelslut

    fuelslut New Member

    Joined:
    Sep 13, 2007
    Messages:
    107
    Likes Received:
    0
    i heard dyno dave had a good time trying to get a car started last weekend.
     
    #3
    fuelslut, Sep 5, 2008
  4. William Payne

    William Payne New Member

    Joined:
    Jul 19, 2008
    Messages:
    87
    Likes Received:
    0
    Why do you run a removable alcy tank (weight im guessing) , why not run a full size nitro tank but with a smaller alcohol tank aswell and have 2 fuel lines (one for each tank ) that join into a y-block valve kind of thing which then goes to the pump . Then you could have a hand lever that switches tanks using the valve in the y-block thingy after you have enough heat in the motor to burn the nitro . I am no expert im just a fan , the idea just popped into my head so thought I would ask if it would work .
     
    #4
    William Payne, Sep 6, 2008
  5. nitrohawk

    nitrohawk New Member

    Joined:
    Dec 28, 2003
    Messages:
    1,016
    Likes Received:
    0
    Backing an a-fuel motor down a couple of times is not nearly enough information to stay out of trouble and keep the heads attached to the block.
    There is a blow down procedure that has to be preformed anytime the engine has been run on nitro. Starting one of these cars safely is very important. Do not attempt it without doing some research and asking some of the a-fuel racers.
    The reason for starting engines on alcohol is because it makes it easier to crank, and you can get some temp in engine without burning 30 to 40 dollar nitro.
     
    #5
    nitrohawk, Sep 6, 2008
  6. GregM784

    GregM784 Member

    Joined:
    Aug 24, 2008
    Messages:
    915
    Likes Received:
    14
    Agreed, I didn't mean for that to be a complete starting procedure, just trying to help & answer questions. :)

    A/F is one of the most dangerous classes in the pits I hear.
     
    #6
    GregM784, Sep 7, 2008
  7. Dale Finch

    Dale Finch Member

    Joined:
    Dec 29, 2004
    Messages:
    271
    Likes Received:
    2
    Nitrohawk is right! Kids, do not start at home without explicit directions. Prepping an A-Fuel motor to start is very precise and dangerous if you have not been taught how.
     
    #7
    Dale Finch, Sep 7, 2008
  8. Oldsmoduck

    Oldsmoduck New Member

    Joined:
    Mar 27, 2007
    Messages:
    2
    Likes Received:
    0
    How does one start an A/fuel motor anyhow?

    What make it so dangerous? Can someone explain the procedure?
     
    #8
    Oldsmoduck, Sep 9, 2008
  9. Will Hanna

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

    Joined:
    May 6, 2003
    Messages:
    6,706
    Likes Received:
    133
    starting A/FD

    The reason why it is so treacherous to start an injected nitro motor vs. blown nitro typically comes down to compression. Most Top Fuel motors have very low compression ratios, so it's not necessary to start them on alcohol and get heat in the motor first. A typical injected nitro A/F motor has 12.5 or more compression, so it has enough static cranking compression to ignite nitromethane, which is very combustible and volatile under pressure.

    Let's say you try to start a cold A/F motor on nitro. If one cylinder isn't firing, it will get enough nitro in that cylinder to cause a catastrophic hydraulic situation, with enough energy to blow the head completely off the car among other things.

    It's not only that, ANY amount of unfired nitro can cause a big explosion. That's why the blow-down procedure is so important.

    First thing is to remove all 16 spark plugs and double triple check that both sides have 16 plugs out.

    Our particular blow down procedure was to disconnect and cap the main fuel line from the barrel valve to the distribution block. Disconnect the lines going to the down nozzle rail, then blow through the main inlet to the dist. block to purge the nitro from the intake nozzles and down nozzle hoses. Once this is done thouroughly, cap the down nozzle hoses, then move to the down nozzle rail. Uncap the front of the down nozzle rail and blow through the rail from both directions, using a hand to open and close the other side to insure maximum purging of the down nozzle circuit.

    After all lines to the motor are purged, the motor needs to be 'windmilled.' Reconnect the starter, once again insure all plugs are out of the motor, then spin the motor over with the plugs out to get all of the nitro out of the cylinders. Once the majority of the nitro has been pumped out of the plug holes, cover the plug holes individually to try to blow some more out of the headers. Usually you do one more quick cycle to make sure all nitro is gone.

    Then recap the front fuel rail lines, and cap/plug the main line going to the dist. block, the dist. block and the 2 down nozzle hoses. We usually just warmed the car on alky in the pit, so we didn't connect those lines until just before we were going to run in the staging lanes.

    This is a very important procedure because an injected nitro motor can kill or seriously injure someone if nitro is left in the cylinder.
     
    #9
    Will Hanna, Sep 9, 2008
  10. It's Fixable...

    It's Fixable... New Member

    Joined:
    Jun 20, 2005
    Messages:
    12
    Likes Received:
    0
    Had a nasty incident here at Santa Pod Raceway in the UK some years back when an AFD hydrauliced the motor in the pits :eek:

    IIRC a faulty nozzle was the cause.

    The driver and crew guy who were working on the motor took some shrapnel, and the rear part of the left cylinder head went into low orbit and grounded some hundred yards away in the bike pits.

    I was standing watching those guys from the other side of the motor on spectator side and always counted myself mighty lucky not to be hurt, just had my ears ringing...

    BBFA Pilot who posts on here might have some pictures as I believe the car that blew belonged to his father.
     
    #10
    It's Fixable..., Sep 10, 2008

Share This Page





XenPorta 2 PRO © Jason Axelrod from 8WAYRUN.COM