Injection question

Discussion in 'PSI Superchargers Tech Questions' started by PROMOD63, Aug 26, 2011.

  1. PROMOD63

    PROMOD63 Member

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    This will be a little hard to explain so here goes...... I have a big and ugly with a new k valve it was all set uup by a guy who knows his stuff the question i have is it seems like with the engine running the fuel pressure is holding the barrell valve closed it is set correctly and we adajust it for air but when you try to lenghten the rod it has pressure against the rod for it is hard to turn also when we had the motor on the dyno the guys air throttle wouldnt pull the valve open which he said had never happened before we had to throttle im manualy and now it is in the car and it looks on the graph like the throttle which is air operated is not coming open like it should it seems to have a small amount of delay in it which is effecting the launch the fuel pressure is not overly high at that point either and the car runs good after it gets past this point any ideas? I have thought of turning the arm around and using the hole that is out further to gat more leverage on the valve is this a doable thing ?
     
    #1
    PROMOD63, Aug 26, 2011
  2. SoDak

    SoDak Active Member

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    Sounds to me like a geometry issue from the butterfly shaft arm to the linkage device (be it air cylinder or cable). When the throttle is halfway to wide open I make sure the cable/cylinder is 90° to the shaft arm. This is what I do, I have played with goofy geometry also.
     
    #2
    SoDak, Aug 26, 2011
  3. Mike Canter

    Mike Canter Top Dragster
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    I doubt that it is fuel pressure holding the K valve closed. I would guess that it is vacuum against the blades that is holding them closed which is common. What do you have the closed blade airgap set at? .012" or .016" or what? Is this a convertor car or a clutch car and what is the RPM idle speed.
     
    #3
    Mike Canter, Aug 26, 2011
  4. PROMOD63

    PROMOD63 Member

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    mike it is idling about 2100 i do not know what the blade spacing is how do i correct this ? it is a converter promod with a whipple
     
    #4
    PROMOD63, Aug 26, 2011
  5. PROMOD63

    PROMOD63 Member

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    mike this dosent happen at idle it is when i let off the transbrake and the blades are open slightly and rpm is at 4400
     
    #5
    PROMOD63, Aug 26, 2011
  6. overkill69

    overkill69 Member

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    throttle

    We fought an air throttle for 2 races that wouldn't open properly on a screw. It worked fine on a roots at 40 psi of CO2 but it took 120 psi to make it happy with the screw blower. Same deal launching at 4100rpm.

    The only way we caught it was pictures of the car 80 ft out and the blades were still shut. I couldn't see anything crazy on the data.
     
    #6
    overkill69, Aug 26, 2011
  7. Mike Canter

    Mike Canter Top Dragster
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    Do you really want it idling that high? Have you tried lowering it to 1800? I would have thought that being that high the suction on the blades would be too much. Check the air gap at the bottom of the throttle butterflies with a feel gauge and see where they are at. Open the throttle a little and lay the feeler gauge in there and let the throttle close. Keep trying different thickness until you get one that has tension on it when you pull it out then check the other openings and see if they are close. .010"-.012" gap is good. I have found that any smaller creates too much vacuum on the butterflies. Any wider can raise the rpm up too much and create a vacuum. 1800 rpm has always been a good idle rpm but never messed with a Whipple. If you can't get enough RPM with a .010"-.012" gap then use a open plug on one of the not used hat injector holes. I am talking about a plastic tube type fitting that you can put a plug in. My mind is blank to the correct naem so can somebody chime in.
     
    #7
    Mike Canter, Aug 26, 2011
  8. Charles Stewart

    Charles Stewart Member

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    The name is an "air plug bleeder".
    And like Mike said, it will really help with your situation.
    Take care,
    Charles Stewart
     
    #8
    Charles Stewart, Aug 28, 2011
  9. blown375

    blown375 New Member

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    Do you have 2 throttle springs attached to the throttle ?..... If you do you could try putting 1 down at the peddle and one at the injector so there is less spring tension that the air throttle has to overcome.
    How does it operate when the car isn't running ?
    I know my air throttle has a adjustable opening rate bleeder screw that can really slow the opening rate way down , is yours set to open slowly ?
     
    #9
    Last edited: Aug 28, 2011
    blown375, Aug 28, 2011
  10. john348

    john348 Top Alcohol

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    why would moving the spring have any effect on it since it still is attached by a cable
     
    #10
    john348, Aug 28, 2011
  11. blown375

    blown375 New Member

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    No Jonh348 one spring gets attached to pull the peddle shut so if your foot came off the peddle it would push the cable shut. that way you overcome one spring with your foot, then your air throttle is only having to pull against one spring to open the injector not both of them :cool:
    Thats the way it is set up on my roots blown dragster and it works great !
     
    #11
    blown375, Aug 28, 2011

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