1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Shift Points?

Discussion in 'Racing and Driving Techniques' started by dohcvtec_accord, Jun 10, 2003.

  1. dohcvtec_accord

    dohcvtec_accord WRX Sellout

    Messages:
    8,433
    Likes Received:
    1
    Joined:
    Sep 29, 2002
    Location:
    The left lane
    Maybe I haven't spent enough time looking at dyno graphs and trying to understand them, but can someone help me out here? I'm in a debate on another board, and I'm not wording my argument correctly.

    Let's say you've got your engine pretty well tuned (hypothetically). When looking at your dyno graph and trying to determine shift points, wouldn't you want to shift at the point where the slope of the tangent of the "horsepower" line goes from positive to negative? To try to maximize area under the curve? Or is it for a different reason?

    Can anyone help a brotha out? Thanks y0.
     
  2. K2e2vin

    K2e2vin Senior Member

    Messages:
    8,446
    Likes Received:
    92
    Joined:
    Jan 2, 2003
    Location:
    Raleigh, NC
    ive read in some other forums(exvitermini to be exact) you shift at your peak torque for best results.
     
  3. SixtySecondAssassin

    SixtySecondAssassin Senior Member

    Messages:
    1,071
    Likes Received:
    0
    Joined:
    Sep 30, 2002
    Location:
    Austin, TX
    i dont think it works like that. to determine your shift points you need to do dyno pulls in 2nd, 3rd and so on. where those graphs cross is your shift point:

    [​IMG]
     
  4. dohcvtec_accord

    dohcvtec_accord WRX Sellout

    Messages:
    8,433
    Likes Received:
    1
    Joined:
    Sep 29, 2002
    Location:
    The left lane
    It's ghetto, but it works. That makes some sense now.
     
  5. asmallsol

    asmallsol Super Moderator

    Messages:
    8,074
    Likes Received:
    3
    Joined:
    Sep 28, 2002
    Location:
    Houghton/Livonia Michigan
    what I would say (dont know how true this is) even if the HP is going on a downwards slope, if you shift higher, you can keep the lower RPMS on the next gear up (get what i am saying). You would need dyno sheets and a speed/gear ratio calculator to find out the best shift points.


    Lets say that at 5000 rpm you spike up to 150hp you peak at 190hp @ 8000 and drop to 155 hp at 9500 rpm (just making up numbers) when you go to the next year, you want to make it so that you have about 155 hp at the begging of the next gear so maybe you want to shift at 9300 rpm in second and end up at 5400 rpm in third (again just pulling #'s out of my ass). It is all about keeping the most area under the curve and having the begging and end up as much as possible.

    If your car had 1000 hp but only between 7000 and 7100 rpm, then drops back down to 100 hp, your still only going to run with a 5th gen civic si (again dramtizing)
     
  6. SixtySecondAssassin

    SixtySecondAssassin Senior Member

    Messages:
    1,071
    Likes Received:
    0
    Joined:
    Sep 30, 2002
    Location:
    Austin, TX
    yea, the paint shop skills are a little haggard.
     
  7. dohcvtec_accord

    dohcvtec_accord WRX Sellout

    Messages:
    8,433
    Likes Received:
    1
    Joined:
    Sep 29, 2002
    Location:
    The left lane

    I think what you just said, put SSA's graph into words. :D
     
  8. asmallsol

    asmallsol Super Moderator

    Messages:
    8,074
    Likes Received:
    3
    Joined:
    Sep 28, 2002
    Location:
    Houghton/Livonia Michigan
    yea, your paint skills explained it alot better then my mumbo jumbo talking crap.


    BTW, when i clicked on the thread, there was only the orginal post, when i was done talking, there was 6. I took to long to write.
     
  9. dohcvtec_accord

    dohcvtec_accord WRX Sellout

    Messages:
    8,433
    Likes Received:
    1
    Joined:
    Sep 29, 2002
    Location:
    The left lane
  10. SixtySecondAssassin

    SixtySecondAssassin Senior Member

    Messages:
    1,071
    Likes Received:
    0
    Joined:
    Sep 30, 2002
    Location:
    Austin, TX
    you almost had it. but if you go all the way to redline, your hp will be lower than where the graphs cross.

    :edit: nevermind that, i see what your saying now :D
     
  11. asmallsol

    asmallsol Super Moderator

    Messages:
    8,074
    Likes Received:
    3
    Joined:
    Sep 28, 2002
    Location:
    Houghton/Livonia Michigan
    But i was just pulling #'s out of my ass, redline could be at 465465132132465465654654 rpm, I never said where it was :p
     
  12. pissedoffsol

    pissedoffsol RETIRED

    Messages:
    49,693
    Likes Received:
    53
    Joined:
    Sep 28, 2002
    Location:
    Retirement Home
    the FASTEST way to go is to shift at your peak horsepower, to fall on to your peak torque.
    gearing plays a major roll in this
     
Verification:
Draft saved Draft deleted

Share This Page