Thoughts on Hi spd leanout vs leaning main pill

Discussion in 'PSI Superchargers Tech Questions' started by Crew, Jun 4, 2007.

  1. Crew

    Crew Volunteer

    Joined:
    Jul 31, 2005
    Messages:
    126
    Likes Received:
    0
    Curious what the benefits are in running a high speed lean out versus leaning it with the main pill? PSI FC deal.
     
    #1
  2. MotorPsycho

    MotorPsycho Member

    Joined:
    Sep 1, 2006
    Messages:
    156
    Likes Received:
    0
    basically, at high revs the motor (and blower) cannot ingest enough air for the amount of fuel being thrown in because of the high RPMs so the mixture goes rich and the car can nose over a bit towards 1000ft, also an alcohol motor requires different air fuel ratios for max power and max torque, 5:1 and about 5.5:1 (I think) so you have it at 5.5:1 roughly until a given RPM for max torque then high speed lean out takes the air fuel ratio down to produce max power at the top end of 2nd and 3rd gear
    thats what I understand of it anyway, but I'm by no means an expert
     
    #2
    Last edited: Jun 4, 2007
  3. dragcars

    dragcars New Member

    Joined:
    Dec 9, 2005
    Messages:
    58
    Likes Received:
    0
    changing the main pill would change the entire fuel curve whereas the high speed is preset to open at a target rpm to subtract fuel at max airflow.
     
    #3
  4. Dale H.

    Dale H. Member

    Joined:
    Dec 7, 2005
    Messages:
    302
    Likes Received:
    5
    I don't know many guys who use a highspeed any more, but alot of people use pump loops ( from the outlet top of the fuel shutoff back to the intake line). One advantage using a pump loop over than using just a mainjet is that,some times the main has to be very large to handle all the returning fuel when it is used alone, and is harder to adjust than when it is split up with a pump loop jet.
    I think most guys use shift air operated leanouts to take or add fuel on the run.(easier to control )
     
    #4
  5. nitro4100

    nitro4100 New Member

    Joined:
    Sep 26, 2006
    Messages:
    44
    Likes Received:
    0
    Dale, So are the guys that run TAFC just running air lines to a management system that when they hit the buttons it starts pulling the fuel away? I Know Nitro cars use the button under the throttle that starts everything, Never really seen a Alky cars up close. Thanks
     
    #5
  6. Crew

    Crew Volunteer

    Joined:
    Jul 31, 2005
    Messages:
    126
    Likes Received:
    0
    I saw a few hard running cars have them over the weekend at Topeka. Just curious if your taking fuel away at low gear and taking it away at high gear, why not just take it away at the main?
     
    #6
  7. nitrohawk

    nitrohawk New Member

    Joined:
    Dec 28, 2003
    Messages:
    1,016
    Likes Received:
    0
    Most pumps when jetted with the main jet for max low end and midrange will increase the fuel flow faster than the engine demands at increased rpm. That is the reason for a hi speed. If the pump had a perfect flow curve for the engine demand you wouldn't need to use a hi speed jet. It really is all in the cc's of fuel flow per turn.
     
    #7
  8. Will Hanna

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

    Joined:
    May 6, 2003
    Messages:
    6,706
    Likes Received:
    132
    hi speed on a psi

    the typical 'high speed' leanout, high gear leanout, etc., is very rare on a psi motor. the cooler intake charge the psi produces vs the warm, inefficient air charge of a roots doesn't make it necessary to lean the motor out down track.

    the psi manual describes a low gear leanout system that most cars run. you can open a jet through low gear then close it when you go into second, putting the fuel back in the motor. some people call this an 'enrichment valve'. essentially it is, but most refer to it as a leanout. it leans the motor out in low gear. you can start with a 40-50 pill and go up if neccessary, the motor allows it and track conditions allow.

    i wouldn't stray too far away from a main jet, pump loop and leanout starting out.

    i would definitely not recommend a high speed leanout that doesn't get closed before high gear.
     
    #8
  9. Eric David Bru

    Joined:
    Sep 4, 2005
    Messages:
    417
    Likes Received:
    1
    Where can I get a copy of this manual?

    EDB
     
    #9
  10. OSI Tafc

    OSI Tafc New Member

    Joined:
    Nov 25, 2006
    Messages:
    70
    Likes Received:
    0
    #10

Share This Page