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Thread: ESE's works engine tuner

  1. #14581
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    Ski-doo fuel injection animation. Looks to be quite a simple system.

    http://www.ski-doo.com/technologies/...gies/2-strokes

    I like the voice coil style injector, and it looks like there is no air injected with the fuel and the fuel itself is delivered to the fuel injector body at quite low pressure. The injection pressure is developed by a plunger piston driven by the voice coil and as we all know from speakers the movement of a voice coil can be very accurately controlled.

    Click image for larger version. 

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    Orbitals air assisted fuel injection system.

    With these clean technologies and the inherent power and simplicity of a two stroke its hard to imagine that strokers won't make a serious comeback sometime.

    But I am not sure if trying to adapt 4T EFI car technology to a high revving 2T like I am trying to do is going to work.

    Car technology EFI seems to work ok on a big single that tops out at 8 - 9K rpm and I can pretty easily get my engine to rev to 8 or 9K rpm OK too but much past that and the fuel injection time exceeds the transfer port window open time.

    When the injection time exceeds the transfer port open time a portion of the fuel required is left floating in the transfer duct and I think the problem with that is that on the next cycle this slug of fuel is blown right around the scavenge loop and out the exhaust port leaving the trapped mixture that follows behind it on the lean side.

    And no matter how much more fuel (longer) you try to inject into the transfers the trapped mixture in the cylinder is still lean. This could easily explain why I keep getting deto at high rpm no matter how much I increase the fuel injection map numbers.

    Click image for larger version. 

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    So with my transfer duct injection setup. Calling for more fuel is self defeating and I think the answer (if there is one) is in fast opening injectors, the balance between injector sizing and in timing the end point with width of the injection squirt so as to coincide as much as possible with the airflow in the transfer duct that is finally trapped in the cylinder and not the first slug of purging air that loops out the exhaust port and is lost, not much point in having that wasted air super fuel rich and the following trapped charge lean.

    Click image for larger version. 

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    For my bike, at 12k ish the delivery ratio is about 120% of the cylinder volume and the amount of air (charging ratio) in the cylinder at BDC is only about 80% of the delivered air and less than that actually gets trapped (trapping efficiency) at exhaust port closing, so you can see that a fair swag of air is lost out the exhaust port.

    And my guess is that the bulk of the air that is lost is the first air entering the cylinder as the transfers start to open and if there was extra fuel already in the transfers that would be lost with it.

    So unlike a 4T where you can get a head start by storing fuel behind the inlet valve ready for it to open you cant do the equivalent thing with a 2T's transfer port window without loosing it down the exhaust pipe.

    It is looking like the moral of the story is to keep the transfer port injection time shorter than the real time that the transfer ports are open and at 12.5k that is about 1.5ms.

    Transfer port injection has the potential to clean up the 2T's emissions as the first lot of purging air can be sent through with little fuel in it but if I can't get it to work on my bike above 8-9k rpm I will have to go to inlet injection and aim to get a more homogeneous fuel mixture in the crankcase just like a carburetor does.

  2. #14582
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    Quote Originally Posted by TZ350 View Post

    But I am not sure if trying to adapt 4T EFI car technology to a high revving 2T like I am trying to do is going to work.

    Car technology EFI seems to work ok on a big single that tops out at 8 - 9K rpm and I can pretty easily get my engine to rev to 8 or 9K rpm OK too but much past that and the fuel injection time exceeds the transfer port window open time.

    When the injection time exceeds the transfer port open time a portion of the fuel required is left floating in the transfer duct and I think the problem with that is that on the next cycle this slug of fuel is blown right around the scavenge loop and out the exhaust port leaving the trapped mixture that follows behind it on the lean side.

    And no matter how much more fuel (longer) you try to inject into the transfers the trapped mixture in the cylinder is still lean. This could easily explain why I keep getting deto at high rpm no matter how much I increase the fuel injection map numbers.

    So with my transfer duct injection setup. Calling for more fuel is self defeating and I think the answer (if there is one) is in fast opening injectors, the balance between injector sizing and in timing the end point with width of the injection squirt so as to coincide as much as possible with the airflow in the transfer duct that is finally trapped in the cylinder and not the first slug of purging air that loops out the exhaust port and is lost, not much point in having that wasted air super fuel rich and the following trapped charge lean.



    For my bike, at 12k ish the delivery ratio is about 120% of the cylinder volume and the amount of air (charging ratio) in the cylinder at BDC is only about 80% of the delivered air and less than that actually gets trapped (trapping efficiency) at exhaust port closing, so you can see that a fair swag of air is lost out the exhaust port.

    And my guess is that the bulk of the air that is lost is the first air entering the cylinder as the transfers start to open and if there was extra fuel already in the transfers that would be lost with it.

    So unlike a 4T where you can get a head start by storing fuel behind the inlet valve ready for it to open you cant do the equivalent thing with a 2T's transfer port window without loosing it down the exhaust pipe.

    It is looking like the moral of the story is to keep the transfer port injection time shorter than the real time that the transfer ports are open and at 12.5k that is about 1.5ms.

    Transfer port injection has the potential to clean up the 2T's emissions as the first lot of purging air can be sent through with little fuel in it but if I can't get it to work on my bike above 8-9k rpm I will have to go to inlet injection and aim to get a more homogeneous fuel mixture in the crankcase just like a carburetor does.
    Fuel in equals Pressure and duration can your pressure not be bumped up? before you give up on transfer injection.
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  3. #14583
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    Quote Originally Posted by husaberg View Post
    Fuel in equals Pressure and duration.
    You wish. Raising the pressure may raise the fuel amount but the relationship is far from linear and above a certain pressure quotient it's simply not true at all.

  4. #14584
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    Quote Originally Posted by Frits Overmars View Post
    You wish. Raising the pressure may raise the fuel amount but the relationship is far from linear and above a certain pressure quotient it's simply not true at all.
    I do wish everything was simple.... Frits but from memory Rob is only at 40 psi so would be pretty near the bottom of the curve.
    I actually used to design the odd water reticulation systems so I know pressure isn't a get out of jail free card.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  5. #14585
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    The ETEC system is insanely clever technology and would easily keep up with the fuelling requirements of a racing 2T.
    Its voice coil driven pump/injector enables stratified charge completely controlled as to timing and volume, but the issue is that its locked into a very
    robust patent,and the owners want a fortune for the rights to use it.
    Running on the big Rotax engines the mechanical/electrical system is hardly stressed at all, its dead reliable and enables those powerplants to completely kick any 4T
    off the planet as far as light weight,fuel efficiency and emissions compliance are concerned.
    It really is the silver bullet for 2T domination, but this simply wont happen while the technology is locked up.
    The air over fuel systems are another step forward for direct injection, and that is also patented, but cant compete with ETEC for simplicity and pin point fuel control.
    Evinrudes big 2T outboards are now considered the benchmark in every measurable category you can think of, so the swing has already begun,but whilst the technology
    is strongly protected from general ( read cheap ) everyday use, we simply wont see 2Ts overunning the streets of Bejing any time soon.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  6. #14586
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    Quote Originally Posted by Frits Overmars View Post
    You wish. Raising the pressure may raise the fuel amount but the relationship is far from linear and above a certain pressure quotient it's simply not true at all.
    And Husa's example has reminded me that the relationship between flow and orifice size isn't linear either, double the size and you get roughly 4 times the flow at the same pressure.

    More injectors.
    Go soothingly on the grease mud, as there lurks the skid demon

  7. #14587
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    hi guys on my piston underside its turning black. is this normal on a good tune or does it suggest a problem like stinger diam too small causing overheating of the piston ?

  8. #14588
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    "You can raise an engines compression ratio until the varnish ... underside of the piston crown turns as black as a race officials heart and if you've done everything else right you down have to worry until the varnish begins to char. That's the danger point" - Gordon Jennings
    http://homepage3.nifty.com/penta2/bi...reparation.pdf
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

  9. #14589
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    http://publications.lib.chalmers.se/...ext/149154.pdf

    A Masters Thesis on 2T direct injection. Evenrude Outboard.

  10. #14590
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    Quote Originally Posted by pete376403 View Post
    "You can raise an engines compression ratio until the varnish ... underside of the piston crown turns as black as a race officials heart and if you've done everything else right you down have to worry until the varnish begins to char. That's the danger point" - Gordon Jennings
    http://homepage3.nifty.com/penta2/bi...reparation.pdf
    compression ratio is moderate. noticed black on pistons with 2 different cylinders and heads using the same pipe. so if there is a problem im thinking it may be stinger diam holding in too much heat. im not even sure theres a problem though. do any of you guys get black undersides ?

  11. #14591
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    Heck yeah
    .
    Don't you look at my accountant.
    He's the only one I've got.

  12. #14592
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    I like my pistons well done also.

  13. #14593
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  14. #14594
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    My experience is that the higher the state of tune ie bmep, and the better the actual tuning is ie optimum advance and no more, the less the crown
    darkens on the underside.
    Running low bmep setup like say a TZ350, needs plenty of advance, as the dynamic com, even with very high static com, is low due to the compromised transfer and inlet ducts.
    Thus running plenty of advance heats the piston during the expansion phase, and the crown gets hot enough to burn on the oil.
    When you have a very high state of tune, with plenty of dynamic com being developed and have advances such as head inserts with plenty of water around the plug threads,
    the piston crown doesnt see enough temp for long enough, as alot more of the fuel energy converted to heat release, is used to raise the gas pressure early in the cycle.
    Then you have the case of KZ2 kart engines with straight line ignitions, and these put plenty of heat into the crown due to the excessive advance at high rpm.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  15. #14595
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    Quote Originally Posted by wobbly View Post
    The ETEC system is insanely clever technology and would easily keep up with the fuelling requirements of a racing 2T.
    Its voice coil driven pump/injector enables stratified charge completely controlled as to timing and volume, but the issue is that its locked into a very
    robust patent,and the owners want a fortune for the rights to use it.
    Running on the big Rotax engines the mechanical/electrical system is hardly stressed at all, its dead reliable and enables those powerplants to completely kick any 4T
    off the planet as far as light weight,fuel efficiency and emissions compliance are concerned.
    It really is the silver bullet for 2T domination, but this simply wont happen while the technology is locked up.
    The air over fuel systems are another step forward for direct injection, and that is also patented, but cant compete with ETEC for simplicity and pin point fuel control.
    Evinrudes big 2T outboards are now considered the benchmark in every measurable category you can think of, so the swing has already begun,but whilst the technology
    is strongly protected from general ( read cheap ) everyday use, we simply wont see 2Ts overunning the streets of Bejing any time soon.
    i feel your patent pain

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