Cheap Air/Fuel Ratio Tuning

Discussion in 'General Ranchero Help' started by Vasili Brown, Apr 20, 2016.

  1. Vasili Brown

    Vasili Brown In Third Gear

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    So I was looking at wideband kits today so that I can tune my carburetor easier. I came across this site and I feel like this would be a great alternative to just get it running good. All you need is a 1 wire O2 sensor and a voltmeter. Way cheaper than the $300 for an actual wideband kit. The voltages given off by the O2 sensor can be converted into air/fuel ratios. On the site it says that .7V is optimal. Let me know what you guys think. I think it might be worth the $10ish for the sensor

    http://www.bob2000.com/carb.htm
    [​IMG]
     
  2. Vasili Brown

    Vasili Brown In Third Gear

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  3. aquartlow

    aquartlow In Maximum Overdrive

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  4. burninbush

    burninbush In Maximum Overdrive

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    Those graphs are for 'narrow-band' sensors -- which are really only good for making over/under decisions.

    The way the EFI computer uses that property of the oxysensor is to repeatedly =force= the sensor to switch states by alternately leaning/enriching the mixture to force it to switch, thus the computer concludes it was =close= to being at a stoich mixture before the last forcing. This is what is meant by 'closed-loop' operation. Fine mixture trims are done by comparing dwell times high vs low.

    The sensors switch quite fast, in my Chrysler cars I can see it flipping at like 16 hz. It's hard to see how a simple indicator dial is going to be of much use -- once the carb is close to being correctly tuned. It will always be reading either lean or rich, and will appear to switch instantly between states.

    I have been hoping to hear reports from Ranchero users. BTW, if you poke around on the net you can find cheap kits to build your own LED readout -- it's just a very simple voltmeter.
     
  5. burninbush

    burninbush In Maximum Overdrive

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    That seems like a much closer to ideal solution. But what's your experience of using it? Did it solve problems, etc? Does the readout react quickly/slowly during normal driving? What does it show during acceleration?
     
  6. Vasili Brown

    Vasili Brown In Third Gear

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    Thanks for the link quart. Well worth $170. Thanks for your info as well BB. Are you saying after I have the right mixture I won't get the same reading, whenever you say " It's hard to see how a simple indicator dial is going to be of much use -- once the carb is close to being correctly tuned. It will always be reading either lean or rich, and will appear to switch instantly between states. "
     
  7. burninbush

    burninbush In Maximum Overdrive

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    Well, the only two things a narrow-band sensor can report with certainty are "too rich now" and "oops, too lean now". It is folly to try to turn it into a wide-band sensor by narrowly parsing that vertical switching interval. Not to say that rich/lean isn't valuable to know, but only when you are far away from ideal. I wrote 'switch instantly' above, it actually takes a few milliseconds to pass through that .7v region.

    And in general, you want a carb to run a little rich, in order to be certain it isn't lean, and what good is the readout in that situation? My opinion, you can get as close as you need to be from reading plugs and listening for pings. If you want to do something about mpg, then a vacuum gauge would be a better investment.
     
  8. aquartlow

    aquartlow In Maximum Overdrive

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    It is a wideband and it reads/notices changes very quickly.
    BB,
    It definitely helped with tuning my 770 and 870 SA carbs. It "supposedly" reads accurately(have no way of testing it against another meter/sensor) and it reacts quickly to throttle and/or carb adjustments. Really helped with my IFR (idle feed restrictor) tuning on both carbs as well as IAB, MAB, main/sec jets and PVCR sizing for WOT operation. With both carbs being VS the meter shows a quick "flick" to lean when mashing the GO pedal to WOT, then the PV's open(870 uses 10.5" pri and 8.5" sec) and WOT AFR's start to settle around 12.5-12.8. It isn't the best unit out there, but it has treated me well and it seems very accurate/consistent . I would buy another AEM unit without hesitation
     
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  9. Basstrix

    Basstrix In Maximum Overdrive BRONZE MEMBER

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    One of these wide band O2 sensors would go really well with a tach signal and one of these data loggers you can connect to your phone/ipad/laptop. Have any of you set up anything like this?
     
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  10. Vasili Brown

    Vasili Brown In Third Gear

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    After I can actually drive the car I'm going to try the voltmeter thing and then get a wideband. Or maybe go straight to wideband. I've tuned with a vacuum gauge before BB. Hard to tell what jets you need with a vacuum gauge though haha. But yeah I definitely wouldn't go for a narrowband
     

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