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Exhaust gas analyzer for tuning mixture

Discussion in 'XJ Technical Chat' started by dkavanagh, Aug 25, 2019.

  1. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    With the little ports at the bottom of the exhaust down-tubes, I'm sure that's how the factory did the initial mixture setting. (My FZR1000's plugs are hard to get at, so it's impractical to keep removing those to check color). I'm curious if anybody has used such a method to set mixture? It seems like a "1 and done" method in that once you get it right, it should be good for quite a while.
    I'm curious to see what a "good enough" one would cost. Is O2 enough, or CO better?
     
  2. StahlMaster

    StahlMaster Active Member

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  3. Polock

    Polock Well-Known Member

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    O2 sensors make a voltage that you can read with a DVM, if you can get the exhaust to flow over the sensor and the sensor is the right temperature, you've got it.
    heated sensors take care of temp, now just figure out how to get pure exhaust to flow over it.
    i tried to make one awhile ago and got wild readings on the bike but the car was perfect...?
    it's easy to shove it up the tail pipe of a car but not so easy on the bike
     
  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    They are for gas analyzer probes. In the old machines the sensor is onboard the anaylzer and a small pipe is used to send gas into the unit.
    Many used sensors that were wired to the analyzer, but only had a short probe tube and kept the sensor outside of the exhaust pipe.
    You can fine used ones pretty easily, but for some reason they cost quite a bit now. I used to see full-service Sun machines for less than $50.
    [​IMG]
     
    Last edited: Aug 25, 2019
  5. squidx85

    squidx85 Member

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    The best way in my opinion is a wideband 02 in the collector. With a modern system, connect an rpm reference, you can datalog across the rpm band with it too.
     
  6. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Far more resolution and data than a carbureted engine needs. It would be a good tool to use when developing a starting map for an EFI conversion though. Get the fueling data for the carbs before switching the hardware to get a rough idea of what the engine really likes.
     
  7. Polock

    Polock Well-Known Member

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    if it goes in the collector you get all four, mixed. that's what i tried, it don't work
     
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  8. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    I was toying with making something that fits into the fairly small openings in each down-tube. I figure with a little back pressure, a tube attached there would get some exhaust flow and I could have an O2 sensor fitting mounted very close. Then, just use one of these (or something slightly cheaper) https://www.summitracing.com/parts/...R-6Jng7ruvab--rGKUrqNuHkin0ApclwaArBuEALw_wcB

    Of course, if I could fashion a tube with a 90" bend in a properly sized arc, I could have it function like a pitot tube on a plane and get the velocity of the exhaust to push more gas into the tube.
     
  9. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    I'm convinced I have a clog on #4's pilot passages since pipe temp at low RPMs is much lower than the other 3. I was about to tear down the bike to get the carbs and plugs out, so I thought I'd check the main jet functioning. I ran the bike and then held it at 5000 RPM for 10-20 seconds, then shut it down. The mains start taking over between 3 and 4000 RPM, so I got a reading of main jet mixture by doing this.
    It told me #2 is lean and #4 is rich, so that's something I can work with! Setting up a way to use an O2 sensor would be better to get them dialed in properly though!
     
  10. Polock

    Polock Well-Known Member

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    i'm not on board with that. to be in the main jet circuit the slide needs to be all the way up or at least close . until then the needle jet and main are in play, but, the vacuum operated slide is controlled by load/vacuum. without a load i doubt the slide moves very much at all.
    take a cable operated carb and turn the idle screw to get 5k and the slide only moves a little bit, like 1/8 inch
     
  11. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    hmm interesting. So, being really rich, I could have a colder pipe from all the unburnt fuel. That would also explain the popping in the exhaust as that fuel combusts.
     
  12. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Does the popping happen when throttling up, or when throttling down?
     
  13. dkavanagh

    dkavanagh Well-Known Member Premium Member

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    When the RPMs are holding steady, I want to say. I plan to throw the plugs back in and run it on the stand after tweaking the mixture before I pull the carbs out. I'll know more after I do that.
     
  14. dkavanagh

    dkavanagh Well-Known Member Premium Member

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  15. Ryengoth

    Ryengoth Active Member

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    You will need quite a bit of exhaust flow to affect a wide-band element properly. Those are designed to be sampling in-stream, not in a stagnant pool of gas. Make sure you calibrate any sensor you use to open-air before you reference it for AFR.
     
  16. mlew

    mlew Well-Known Member

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    I have been working on building one also. No way was I going to spend 130$ on a air/fuel ratio meter. I found an A/F meter on Wish.com for 15$ and a 4 wire O2 sensor for 20$. Still have to assemble it and make and adaptor for my exhaust pipe. Hope it works like I think it will
     
  17. Ryengoth

    Ryengoth Active Member

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    I have some parts left over from the turbo genesis project including an Innovate SGC-1 and wide-band. I think there are some 45° O2 adapters around. I have the exhaust off my 550, are the ports the same thread pitch and size?
     
  18. mlew

    mlew Well-Known Member

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    Im going to install an adaptor in my 4 to 1 headers when Im ready, I already got one.
    I believe all Yamaha exhaust test ports are the same size. At least they are between my XJ11,Xs11 and Venture. I assume they are the same on other XJs.
     
  19. XJ550H

    XJ550H Well-Known Member Premium Member

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  20. squidx85

    squidx85 Member

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    Well, it depends on what you're trying to do, if you're trying to diagnose a problem with one carb, it won't. But if everything is running correctly cylinder to cylinder, it will allow you to determine what exactly your jetting is doing across the powerband. Every fuel injected motor, car, pickup, etc since about 1985 has used closed loop o2 feedback, usually 1 sensor per bank of cylinders. I would be very curious to datalog the fueling on my maxim x, the way it feels doggy at around 5 or 6k, then comes alive at 7k-10+. I'm not saying I want to go buy a wideband just for that, but I still am curious. I know I'll never use another one on another gas car, for me it's all diesels from here on out until electric cars become affordable.
     

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