calling all knowledgeable 2smokers, brace your self .. 3d ignition questions!

Discussion in '2 smokers' started by Reino, May 24, 2012.

  1. Reino

    Reino Been here awhile

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    In the next 3 years i would probably have gathered enough money to start my project (don't ask its a secret till its done).In the meantime i am doing research especially on 3d ignition maps, but so far i have not yet found a collection of 3d maps or good explanations on what happens under load in 3d maps.I am replacing the cdi on my 250sx with a system that can do anything so it would be a shame not to use a 3d map.

    my questions:

    1-is a 3d map worth it

    2-what happens under load

    3-how would a 3d map look like (i am well informed about 2d maps):deal

    I live in Namibia (just above South Africa) so because of my time zone i would probably take a while to respond.
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  2. Reino

    Reino Been here awhile

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    so no replies, well thanks anyway :cry . :pep

    Can someone just answer one of my 3 questions?
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  3. Ever Onward

    Ever Onward Older,Wiser, Smarter

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    Best to ask these questions over on a Honda RS board or a Yamaha TZ website.

    Its a very complex tech question. Far beyond a simple ignition advancer. Way beyond my grey market 2 stroker knowledge, sorry.
    #3
  4. Reino

    Reino Been here awhile

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    thanks for the reply, around 2 o'clock this morning i found a guy by sheer luck on the interwed that may be able to answer my question.
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  5. Shocktower

    Shocktower Long timer

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    Dam n00bs :rofl, good luck with that, I had no idea WTF he was talking about, if it does not have points whats the points :D
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  6. Reino

    Reino Been here awhile

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    good points :lol3 .
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  7. hrcs90

    hrcs90 Adventurer

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    I think load is going to be pretty hard to determine on a 2 stroke. I would maybe look at tying into a knock sensor.
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  8. Reino

    Reino Been here awhile

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    The load i am referring to is throttle opening which is measured by a tps in % or vacuum by the map sensor in pascal.

    ignition curves for cr500 below

    http://i870.photobucket.com/albums/ab265/rsss396/graph9.jpg

    A 2stroke ignition sees most advance in the early parts of the rpm range (30 degrees) to get the exhaust temp high to maximize scavenging and drops after max torque to something like 9 degrees btdc to maximize over-rev, this is for a 2d map of coarse but you get the point.

    I thought about this topic for a while and realized an expansion chamber's scavenging effect is optimized for a certain temp, so with less load you can effectively increase advance to increase exhaust temp for throttle response. under load you would retard to decrease temp to decrease chance of melting the piston:kboom.

    this is why i love 2strokes, deceptively complex bastards:rofl.:raabia
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  9. Ever Onward

    Ever Onward Older,Wiser, Smarter

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    Not sure how this will tie into your design theorys, but, sometimes builders use thermal retention pipe wrap on expansion chambers to increase the working temperature of the pipe itself.

    You see this on two stroke snowmobile race engines sometimes. No idea the adverse effects if run in a application where it would make the pipe run too hot.

    Most also run EGT sensors a specific distance from the piston skirts in the headpipe of the expansion chamber to keep a close eye on how hot things are running, and to help judge if their air / fuel mixture ratio is right at different throttle positions.
    #9
  10. Reino

    Reino Been here awhile

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    Thanks for your input low budget, i am probably going to use a EGT to measure my temp so that i am just under melting a piston at every rpm and load situation under max torque.

    I Know the yz250, rs250, tz250 and tzr250 used 3d maps.

    But i am still not certain if it is worth while to use a 3d map, at the moment that's my biggest problem.
    #10
  11. Ever Onward

    Ever Onward Older,Wiser, Smarter

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    Yes, a good quality EGT gauge thats located in the right spot will let you know when things are getting to hot early enough to shut it down before damage.

    It reacts very fast, and is a better indicator than a typical engine temp gauge as to whats going on at that moment in the combustion chamber.

    Once you have a engine setup all dialed in, and note the EGT running temp at a given situation, you can then use that number as your benchmark for doing further tuning. Like rejetting for altitude differences or temperatures and humidity changes.

    You may very well be OK with a 2d ignition and other things than be overly complicated trying to combine the extra variables of the 3d .

    Its all rocket science at that point ! :lol3
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  12. Reino

    Reino Been here awhile

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    i think i should drop 3d map and stick with a 2d one. I have a big test on the 7th next month on centriods and moment of inertia:norton. My time is better spent studding. Afterwords i am going to have a lot of these :1drink and do a lot of this :snore and this :ricky.:D
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  13. Reino

    Reino Been here awhile

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    I know this thread is old but, I have my answer.

    My assumption was correct. The less load the more advance there is below peak torque the difference becomes less the more you rev the engine.

    Finally some closure! :freaky
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  14. Twin-shocker

    Twin-shocker Long timer

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    The dynamics of a 2T motor are entirely different to those of a 4T, and unless you have access to a dyno, and have an ignition system which can be programmed, you are going to be wasting time and money with this.
    #14
  15. Reino

    Reino Been here awhile

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    I am well aware of the differences regarding 2t and 4t. As i have explained in my first post, I am scrapping my cdi with a programmable unit.

    I am not going to stop at the ignition side. Also having access to a dyno is not a problem for me.

    This is going to be a long term project (3 or 4 years).
    #15
  16. hrcs90

    hrcs90 Adventurer

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    Cool, keep us posted on your findings. :jjen
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  17. Reino

    Reino Been here awhile

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    will do. It's going to be slow progress for a while, but i will update my tread with new info when i have it.
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  18. Twin-shocker

    Twin-shocker Long timer

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    If you are serious then I would suggest you look for an ignition system with sensor inputs for both heat and pressure, and remember that about 95% of manufacturer claims about programmable CDI units are BS.

    For full 3D map you will need a 12v DC control unit, and in most cases some sort of toothed wheel ignition trigger wheel, so the control unit knows the exact engine position at any given time.

    In regard to 2T applications its worth remembering that any system without pressure/heat sensor inputs, will mean that a map which makes very good power on one day, may well burn a piston the next.

    This is the main reason OE 2T ignitions have pretty conservative settings, and why someone who doesnt know what they are doing can very easily destroy motors with systems that can actually be mapped.
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  19. Reino

    Reino Been here awhile

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    Thanks for the info Twin-shocker.

    The sensors i am going to use for the ignition side is as follows: intake air temp, engine temp, map, throttle position sensor and my project calls for a toothed wheel( 36-1 ).

    This hole system is going to run off a battery or a capacitor-battery substitute. My bike already has the 2k-3 stator (110Watt's of power). I am also going to make the system in such a way that i can go to original setup if need be.
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  20. Twin-shocker

    Twin-shocker Long timer

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    That sounds fine and should work well, after you establish what works on the dyno, and make careful notes regarding conditions when you are making the runs.

    When you are doing the dyno runs, use a thermocouple under the spark plug washer, as well as EGT, and load as many maps as you can into memory, and use them in accord with atmo conditions on the day.

    If its a road or drag race bike use a li-po battery to power the system, if its an off roader you should be able to run off rectified ac generator, using a capacitor to help with starting.
    #20