DIY fuel ratio gauge

[gkmaia]

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[TOOLS1]

 This one for Sarge.
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[gkmaia]

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[TOOLS1]

Sarg is the engineer around here, and if anyone would understand what you are wanting to do, it would be him.
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[shinyribs]

Quote stole from this wiki page: http://en.wikipedia.org/wiki/AFR_sensor

RE: you question about the heater:

"Operating temperature

Another major difference between the wide-band AFR sensor and a Zirconium O2 sensor is that it has an operating temperature above 1200°F (649°C). On these units the temperature is very critical and for this reason a special pulse-width controlled heater circuit is employed to control the heater temperature precisely. The ECM controls the heater circuit."


I don't know if that sensor you linked to will interface with that gauge unit or not. It very well might. There are several different types of O2 sensors. Since the one you linked to is listed as an upstream sensor I'm assuming it's designed to install upstream of the catalytic converter. I don't know,just an assumption. If that's the case it may need to operate in conjunction with a second,downstream sensor. But i really don't know that either. Just what came to mind when I saw the term upstream.


 Jegs and Summit sell several a/f ratio gauge kits that you know will interface with each other, but they start at about $150 and go up from there. Your approach is definitely much more affordable. Good luck!

[sgtslag]

The parts you reference are components of a fuel injection system.  The air-to-fuel ratio has an ideal mixture of something like 14.7:1.  A fuel injection system is a closed loop system which monitors various things, to alter the air-to-fuel ratio, to achieve optimum combustion, and power.  To build a fuel-injection system is quite complex, multiple inputs/sensors feed all of the variables into a computer (air temperature coming in; oxygen level in; oxygen level of the exhaust gases; air flow rates/pressure; ad nauseum), which consults a map, to find the optimum mixture for the current conditions.  The computer is known as the Electronic Control Unit (ECU).  This is also why they don't use a choke -- it is all done auto-magically, by the ECU, continuously adjusting on the fly, for the changing conditions.

Carburetors use different jets to crudely achieve almost the same results (14.7:1, air-to-fuel, throughout the RPM range) as an injection system.  Carbs are an amazing thing -- MPG on injected engines is not dramatically better than carbs can achieve (disappointing, really, considering all that electronic, computerized, closed loop feedback jazz...).

Are you interested in building your own injection system, or something else?  

[gkmaia]

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[gkmaia]

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[sgtslag]

Essentially, you want to build a poor man's "engine analyzer", to tweak the air-fuel ratio.  OK.  Now I understand what you are trying to do, and why.

I am not familiar with the set-up you reference, but if you have done your homework, it should be good, as illustrated.  Not sure about the Red wire to the ignition switch, on top of the White Headlamp connection -- seems redundant, as both will have their power switched off by the key.  There is very little difference between the Red and White wires' connections, so I wonder if they couldn't both be connected to the switched side of the ignition?   Research the reason why, before taking my word for it!  The headlight loses power when the ignition switch is pressed, while the keyed wire remains hot, but this still doesn't make a lot of sense for a simple O2 monitor.

Your bike is carbureted, so you are interested in fine-tuning it?  Just remember that with carb's, you can only get "close", as in horseshoes, hand-grenades, and thermo-nuclear devices 'close'...  When the weather changes, so will your O2 output, due to humidity, temperature, etc.  If you use the system to fine-tune only, knowing that it will get you "closer" to optimum performance, as opposed to running down the road, fretting about your dynamic tuning under varying conditions, you will be fine.  To get 'near-perfect' performance, at all times, requires a closed-loop feedback, fuel injection system.

What about the O2 Sensor?  I believe that needs to be located within the hot exhaust gases, inside of the muffler, shielded from the atmosphere, to avoid false readings.  Do you connect a shroud to the exhaust, with the O2 Sensor inside of that, to take readings?  Sorry, just curious how it is done (permanently altering the exhaust to take an infrequent tune-up reading seems out of line, but that is just me).  Cheers!

[sgtslag]

Forgot one detail:

If you use a shroud over the exhaust pipe, be sure to connect a black, Grounding Wire, between the Sensor's outer threads (Ground connection -- a soldered & crimped ring connector on both ends of the Ground Wire should suffice), and the chassis of the bike.  The O2 Sensor needs to be electrically Grounded, and a slip-on shroud won't give it a solid Ground connection.  Without proper Grounding, the Sensor won't function, or it will give faulty, flaky readings.  Cheers!

[gkmaia]

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[sgtslag]

Oops!!!  [Hangs head in shame...]  The O2 Sensor is a battery, not a variable resistor, like many of the sensors used in automobiles and bikes.  It generates voltage, rather than sinking it.  Your set-up should work with the gauge, just as you listed prior.  The Sunpro gauge measures the voltage coming off of the Sensor, and reacts accordingly.  Here is a web page that is very informative:  link.

If you cut into the pipes, and use a threaded bolt to seal it after adjustments are made, be sure to use anti-seize on the threads, or they will never come out...

Sorry.  Cheers!

[gkmaia]

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