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Thread: 2-stroke excel for ports, heads and pipes

  1. #1
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    2-stroke excel for ports, heads and pipes

    My 2-stroke spreadsheet is ready (for now at least), so I'm throwing it on the net so everybody can use it.
    It contains pages for ports, the head and FOS pipe
    On the seperate ports pages (exhaust and transfer), it calculates the STA numbers (Specific Time.Area) of your ports and you can matcch them to the target's, determinned by the BMEP
    On the Head page, you can design your head and it calculates the MSV (Mean Squish Velocity) 100% accurtly with Blair
    On the FOS-pipe page, it calculates a Frits Overmars FOS pipe, and you can ad a Wobbly-duct , and you can add extra header/diffusor/baffle sections to the pipe.

    you are free to do with it what you want, as long as it is not for commercial use. If somebody has idea's to improve or add extra features, please share so we can all benefit.
    In the manual I've tried to explain how it works, please read it first before you ask questions.
    If somebody has any idea of how to print a portmap to correct size, please let me know, as I don't have a clue right now.


    excel : http://users.telenet.be/jannemie/Jan...oke%201.0.xlsm
    manual : http://users.telenet.be/jannemie/Jan...oke%201.0.docx

  2. #2
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    Quote Originally Posted by JanBros View Post
    My 2-stroke spreadsheet is ready (for now at least), so I'm throwing it on the net so everybody can use it....you are free to do with it what you want, as long as it is not for commercial use.
    excel : http://users.telenet.be/jannemie/JanBros%202-stroke%201.0.xlsm
    manual : http://users.telenet.be/jannemie/Jan...oke%201.0.docx
    Bravo Jan ! I know that it has been a tremendous amount of work.
    I noticed that you refer to my 'Leaning Tower of Pisa' story. If you wish, you can download the complete Pisa-story from https://drive.google.com/drive/folde...rNTk89_KgwgWof , from the folder 'FOS Tips & Concepts', and bundle it with your masterpiece.
    In fact, you can use everything you find there and use it, provided credits are respected.
    You might also take a look at the disclaimer accompanying the 'FOS Exhaust Concept'; it is a bit more extensive than the older version that you quoted.

  3. #3
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    Thank You Very Much

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    Great stuff

  5. #5
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    apparently I seem to make the same mistake over and over : I keep forgetting the variable for the FOS pipe is speed of sound and not exhaust gas temperature. It had no effect on the workings of it all, but I've corrected it now in the manual and the spreadsheet and uploaded corrected versions ;-)

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    what an effort! thanks for making it available for everyone!

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    Thank You Very Much

  8. #8
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    Have played around with your excel along side EngMod the last days and I can say its a great complement.

    You mentioned above that you uploaded a updated version of the program with corrected units (C° and m/s that I always get mixed up )...

    ...but cant find or see any new or different file compared to the initial one.

    Just want to know so I haven't missed anything and that the version I have work as intended. So far, my hand calculations say its all ok but you never know.

    Thanks again for great work!

    Edit: If its not to much to ask...but the option for a straight header in the pipe section would be great. *wink wink*
    I can add it my self, but your layout skills beats mine by far so...

  9. #9
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    aparently there was an error in a BMEP-link in my 2-stroke excel, fixed it now.

    and now there is a way of printing the portmap to actual size, so you can print it, cut out the ports and place it in your cylinder to see where you have to grind the ports some more.


    anyone used it already ? any comments ?

    I can'y edit my openings-post ? would be better to have the latest download links in there.

    new download links to version 1.1 :
    excel : http://users.telenet.be/jannemie/Jan...oke%201.1.xlsm
    manual : http://users.telenet.be/jannemie/JanBros%20%202-stroke%201.1.docx




  10. #10
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    Arrow

    Not tested the "Print"-function yet, but I like the idea.

    Can see that you updated the C° vs m/s as well. Good.

    Have thought about the straight header of the FOS pipe combined with a Wobbly duct and realized that this might be something that ain't considered wise at all? Have to ask Frits what he thinks and the most logic approach to a set up like that. Hmm...

    Thanks again for your time putting this program together. Its a great help.

    When adding all zeros to i.e. the aux port data, I have an error (########) in "Data" for both the total exhaust as well as the BD total. In both tables.
    If adding a small value, like 0.1, to one off the port width cells, it seems to work. At least no errors than.
    If that was a bit hard to understand, ask and I will try to explain better when not in a hurry.

  11. #11
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    Sorry, I seem to have mist/forgotten your request for straight headers.
    but you can easily do it within the program as it is now : use the 2 (or 3-) stage diffuser, in which you can adjust all dimensions with the sliders.
    all the way to the belly, the diameters can never be lower than the previous one, so just slide all the D-headerS to the minimum and they will have the same diameter as the spigot. only thing that is missing is that you have to add both length's together to get the length of a single header/diffuser/baffle. But you can easily make 3 cell's for that.
    than if you don't want a staged diffusor SHOWN THE GRAPH, just change the the diameter of Diffuser-1 so that the cone-angles of diffuser-1 and -2 are the same and you have one big diffuser . And you can do the same with the baffle.

    I haven't touched any of the port-pages, only repaired BMEP on the exhaust old page as that wasn't working.
    for your zero's, you'll have to give me an example, as it's not quite clear to me where you are entering the zero's.

  12. #12
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    Hi Jan, for the moment I am loading my engine data. I can't quite understand what it is or how to measure the horizontal flow directión. I interpret what would be the line that would link from the center of the port to the center of the cylinder, is this so?
    I appreciate your work and your time

  13. #13
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    they are the flow direction in the horizontal plane of the mixture/exhaust gases going through the port.

    for the transfers and auxiliaries, they are the dotted lines you can switch on and off the in the circular graph on the transfer pages.

    they depend largely on the directional angles (the full lines on the same grap) of the ports, and the curve the transfer tunnels make (A port to the front in the RSA, whch means the leading is more important, B port to the back, making the trailing more important).
    You'll have to make an educated guess of the angle.

  14. #14
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    another small error has come up : on the Data page , in cell Q14 both "exhaust new" should be "exhaust old" , so change it yourself or download it again in my previous post

  15. #15
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    Great JanBros!
    That took care of one of the issues I encountered.

    My problem still persist in the 'Data' - 'Port Areas effective flow'-table if adding only “0” to the 'Exhaust Old' - 'Port Map Data Aux'-table. (To simulate a single port exhaust.)
    This gives empty cells in “Y20” and “Y23” thus an error in the Total Exh (“Y21”) and Total Bd (“Y24”) calculations. My workaround so far has been to add a small value to any of the “Aux Port Data”-cells resulting in “0” instead of empty spaces in i.e. “Y20”.
    The same thing for 'Exhaust New' obviously.

    Edit: Think I found it! Since the Total Tr sum is correct regardless of the number of ports used, I looked in to that formula. For the Total Tr a “SUM(xx:yy)” is used. For the exhaust ports above a addition (+) of the cells is used. Changing this to “SUM...” as per the transfers gets rid of this error and no need for the workaround mentioned above anymore.

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