69cc Torque Pipe plans

Discussion in 'Performance Mods' started by jaguar, Jun 12, 2013.

  1. jaguar

    jaguar Well-Known Member

    Below is plans specifically for a 69cc Grubee engine with its exhaust port raised 1.2mm (to 28.1mm from cylinder top) for an exhaust duration of 150 degrees. (Standard is 141 degrees). The transfers should be left mostly as-is other than matching the left and right side so that they open at the same piston position.

    Theory of torque pipe: The straight extension in the converging cone (the baffle) spreads out the return baffle wave for a broader range of rpm in which it has the same effect of preventing fuel loss out the exhaust port as the piston ascends (to increase delivery ratio which boosts power). And the return diffuser wave is maximized which gives the effect of the engine being more torquey. And the waves return timing is scientifically calculated for maximum power due to complete harmonization between pipe and engine. That timing is determined by the cones distances from the engine (measuring along the pipes interior).

    ps- in case it isnt obvious, the header distance is 430mm. Divide millimeters by 25.4 to get inches. The ideal stinger length is 8.5" inside the pipe, and 9.5" sticking out of it. But that isnt critical.
    Fabian likes this.

  2. Fabian

    Fabian Well-Known Member

    Jaguar, can you please provide templates to lay over flat sheet steel so as to cut out the metal sections prior to bending them into a cone.

    Ideally the best method would be something that you can just print off at a 1:1 ratio and lay directly on sheet steel.
  3. HeadSmess

    HeadSmess Well-Known Member

    use "cone layout" download. free. easy. unfortunately the dxf files it produces are hard for anyone without CAD to open... unnecessary when using it, just hit print, its all done for you ;) the "dxf" is more for getting profiles machine cut...

    add 2mm for 1mm steel :) work on ID.


    i worked out how to do this for you...no idea what scale it is though!!!! thats tommorrows lesson :)

    out of interest. i designed with various software, several sets of pipes, all of the same RPM, all the same header pipe, all the same port times...

    see how they compare graphically :)


    btw, 22mm ID pipe is much closer to the size of the port ;)
    Fabian likes this.
  4. Fabian

    Fabian Well-Known Member

    Thanks for that layout information.

    When will you be manufacturing a 69cc lower rpm torque pipe that exits on the left hand side of the bike?
  5. HeadSmess

    HeadSmess Well-Known Member

    cough cough ahem....

    i could, posssibly maybe...

    PICT0380 (Small).JPG

    meh, its not perrrrrrrrrrrrrrrrfect enough for me yet! i like the shape but :) its now my standard layout :) it does scream and really compliments a high-compression head :) ie its not as peaky as others im making for stock motors.

    otherwise i wouldnt do this...

    and heh heh heh, this ones for a 48 :jester:

    here goes, this maynt make any sense...

    1 H (0) 24 (18) 51
    join 36
    cone I
    2 I (18) 24:25 (18) 29
    join 36 (72)
    3 I (18) 25:27 (0) 58

    join 0

    4 I (0)27:29(18) 58
    join 36 (36)
    5 I (18) 29:30 (18) 29
    join 36 (72)
    6 I (18) 30:31 (18) 29
    join 36 (108)
    7 I (18) 31:32 (18) 29
    join 36 (144)
    8 I (18) 32:35 (18) 87
    join 36 (180)

    cone II
    9 II (18) 35:56 (0) 109

    join 0

    10 B (0) 56 (20) 30
    join 40 (40)
    11 B (20) 56 (20) 30
    join 40 (80)
    12 B (20) 56 (0) 26
    13 R (0) 56:13 (0) 187

    open cone, uncheck "automatically minimize", set to zero. means the seams line up.

    the angles, make the top positive, bottom negative if you want the seams on the inside of bends.
    theres three sections. the 0 degree joins are for tweaking to the frame. weld last!

    you gotta work out the header flange and trim the thickness off the first section. thats the only parallel section other than belly and stinger.

    when i have my design perfect and i stop overlooking small things i shall sell the profiles, prints, etc :)
    Fabian likes this.
  6. HeadSmess

    HeadSmess Well-Known Member

    is that for moi? im laying out a 66 at the moment but its on the right too....why the left?

    i lay it on the right to get the profile down.

    contemplating a belly one with a gooseneck on it... cant go straight down cus the pedals get too tight around the rear wheel.

    also, when is a matter of "how much?!?!"

    hard when it cost more than the motor :(
  7. jaguar

    jaguar Well-Known Member

    this post is about the torque pipe, my design, and I am here to answer any questions about it.
    Where the cones are , distance from piston, is a scientific question answered only by physics, which is what my Excel file relies on. The fact that the free programs can design pipes of all different dimensions for the same engine proves my point that except for my file and others of high cost, the world of pipe design is still in caveman days of superstition and heresay about how they work and what changes make what effects. The laws of physics demolishes all that old trash. This is the 21st century, damnnit!
  8. jaguar

    jaguar Well-Known Member

    These bikes are made for low rpm power and so really need anything else that can compliment that goal. This pipe is perfect in that regard and if people would just try it they would see what I'm saying is true. Just ask lazylightning if he thinks it was worth the effort to make his own torque pipe.
    Last edited: Jun 17, 2013
  9. Fabian

    Fabian Well-Known Member

    Jaguar, as i am always a person who respects other peoples opinions, i have requested the moderators assistance to remove all of the posts relating to a "canister style expansion chamber" from your "69cc Torque Pipe plans" thread and have them transferred into a dedicated new thread.

    The posts that were included in this thread (but now deleted) have been moved here:

    Last edited: Jun 17, 2013