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Thread: EngMod2T Q&A

  1. #61
    Join Date
    4th December 2011 - 22:52
    Bike
    Yamaha XJ750 1982
    Location
    South Africa
    Posts
    138
    The "proposed" power possible or the "suggested" STA values are based on BMEP values. So even though power is shown the calculation is based on the BMEP value.

    It assumes very good scavenging and very good delivery ratios and very good trapping efficiency. It is what is possible if everything works as expected.

  2. #62
    Join Date
    20th June 2020 - 07:10
    Bike
    ETEC 800
    Location
    Minnesota, USA
    Posts
    67
    As always, thank you for the great support

  3. #63
    Join Date
    12th October 2016 - 01:24
    Bike
    1964 Vespa GS
    Location
    San Francisco
    Posts
    68
    I'm trying to model a single exhaust port where the side walls are not parallel (as pictured). my approach was to use a bridged exhaust with a bridge width of zero as this allows for a "side wall angle". The side wall angle is 22.6, but after saving and reopening this always gets lowered to 19.798. Also, the area in the STA screen shows NAN, so clearly it's not liking the numbers.

    Is this the best approach or is there a better way to go?

    Click image for larger version. 

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    Patrick Owens
    www.OopsClunkThud.com

  4. #64
    Join Date
    4th December 2011 - 22:52
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    Yamaha XJ750 1982
    Location
    South Africa
    Posts
    138
    There is a built-in limit to side wall angle. It is very conservative, I will update it to a less conservative value in the next day or two.

  5. #65
    Join Date
    12th October 2016 - 01:24
    Bike
    1964 Vespa GS
    Location
    San Francisco
    Posts
    68
    Quote Originally Posted by Vannik View Post
    There is a built-in limit to side wall angle. It is very conservative, I will update it to a less conservative value in the next day or two.
    Thank you!

    spent some time today mapping out the cord width across the port, and it seems like that would drive the natural limit. the angle I had (22.6) was in excess of that limit (21.3) but that value is still larger than engmod lets you set.

    I could use the profiled type if need be, that would likely get around the issue, but not as clean.
    Patrick Owens
    www.OopsClunkThud.com

  6. #66
    Join Date
    8th December 2014 - 14:39
    Bike
    1980 Suzuki Gs1100E
    Location
    SWPA
    Posts
    116

    A new project!

    Hello Neels
    I've had your program for a couple of months but just now have time to play with it. I'm trying to model an old school engine ( single exhaust port, straight transfers, piston port) and I ran into a problem with the exhaust system. I started with the TZ 250g model and just changed the engine, some of the transfer info) I kept the TZ250g info when I didn't know the answer to some inputs because the engine I'm trying to model is very much like the TZ. In fact it is very much like the Yamaha 350 engine except for the reed intake. It's a Polaris 340 snowmobile race engine. Bore= 62mm, Stroke= 55.6mm, Rod center dist= 112mm but it has no boost port. When I put in the dimensions for the exhaust pipe then I try to run the sim it gives me a error code that says that this pipe will not work. I have checked my numbers a couple of time and cannot find the problem. I know the pipe works because I've used it racing. I do not have the file completed yet so I can not pack it, I don't think. Is there anything I can do?
    Thank you, Jeff Neilan

  7. #67
    Join Date
    4th December 2011 - 22:52
    Bike
    Yamaha XJ750 1982
    Location
    South Africa
    Posts
    138
    Hello Jeff,

    Two possibilities assuming you get the message from Dat2T and not EngMod2T:

    1. Try to pack it and if it does pack, email me the pack file.
    2. If it does not pack, open it with Dat2T, open the exhaust and save it, then save the project. Then, before opening Dat2T again, send me the following file: "C:\2Stroke\Dat2TErrorLog.dat"

    I will then see if I can find the issue.
    Kind regards
    Neels

  8. #68
    Join Date
    8th December 2014 - 14:39
    Bike
    1980 Suzuki Gs1100E
    Location
    SWPA
    Posts
    116
    Thank you Neels I will try and see what happens. I let you know.

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