Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

secondaries on q-jet

Discussion in 'The Garage' started by K5Redneck33, May 1, 2003.

  1. K5Redneck33

    K5Redneck33 Registered Member

    Joined:
    Aug 31, 2002
    Posts:
    47
    Likes Received:
    0
    Location:
    INDIANA
    how do the secondaries on a factory quadrajet work? does the top plate just open up from a vaccumm? i mean i know that the secondaries kick in from the trottle bein open at a certain position but i wasnt sure how the top plate opened, i'd appreciate a reply thanks.. /forums/images/graemlins/k5.gif
     
  2. mosesburb

    mosesburb For Rent Premium Member GMOTM Winner

    Joined:
    Apr 20, 2003
    Posts:
    2,175
    Likes Received:
    132
    Location:
    Phoenix AZ
    You is right! When the lower secondary throttle plates open it creates a negative pressure (vacuum) under the secondary air valve (upper spring loaded plates) which causes them to open, thus activating the secondary metering rod cam, lifting the secondary rod hanger/rods letting fuel flow into the secondary main well, to get sucked into the two steel tubes pointing into the secondary venturies just under the secondary air valve, to be burned by the engine and eventually be donated back to nature /forums/images/graemlins/grin.gif. They are spring loaded to reduce the bog when you mash the gas. They are tunable as well, it is kind of a beeatch if you haven't done it before, but it is not thermonuclear science either. Hope this answers your question. Have Fun! Nick
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    Actually, it's air demand of the engine that creates the force necessary to open the secondaries. Most Q-jets have vacuum cannisters that holds the secondary air valve *shut*. The spring is there to make sure it closes once the demand ceases.

    The shape of the air valve is such that airflow over it will keep it open.
     
  4. mosesburb

    mosesburb For Rent Premium Member GMOTM Winner

    Joined:
    Apr 20, 2003
    Posts:
    2,175
    Likes Received:
    132
    Location:
    Phoenix AZ
    We are basically saying the same thing about how the secondaries open. I spoke of negative pressure/vacuum and you spoke of demand. negative-pressure/vacuum=demand="force". As for the secondary vacuum pulloff you refer to, it is there for "fine tuning" the rate of the air valve opening. All Q-jets have the micro spring on the passenger side of the air horn but only some of the Q-Jets have that secondary vacuum pulloff. If a person so desired, for max tuning, the secondary vacuum pulloff could be removed and all secondary air valve functions would be controlled by that little spring. There is a different adjustment procedure with and without the secondary vac pulloff. I guess I didn't mention that some of the Q-jets have a secondary vac pulloff and its functions relative to secondary air valve opening in my original post. Thanks for the catch /forums/images/graemlins/thumb.gif
     

Share This Page