Air/Fuel Ratio (AFR) Gauge Online ...

[cfg83]

Hello -

(This Jaycar outfit originates from Australia)

Last year I bought this :

Digital Fuel Mixture Display Kit for Cars
http://www.jaycarelectronics.com/pro...Max=&SUBCATID=


I finally have it online :

Attachment 842

I used a trading card box as the case for the "IMac" C-Thru look.

I got it because I want to be able to monitor the effect of the EFIE I bought :

Electronic Fuel Injection Enhancer (EFIE) Device
http://www.eagle-research.com/store/...products_id=16

Using the gauge already taught me something about my ECU/PCM that I didn't know :

Oxygen Sensor Information
http://www.mr2.com/TEXT/O2_Sensor.html

How does an O2 sensor work?
... The mid point is about 0.45 volts. This is neither rich nor lean. A fully warm O2 sensor *will not spend any time at 0.45 volts*. In many cars, the computer sends out a bias voltage of 0.45 through the O2 sensor wire. If the sensor is not warm, or if the circuit is not complete, the computer picks up a steady 0.45 volts. Since the computer knows this is an "illegal" value, it judges the sensor to not be ready. ...[/B]

This is *exactly* what I am seeing on the digital display when my Saturn starts up. It stays at 14.7 for maybe a minute, and then it starts fluctuating.

This also implies (to me) that I need to keep the EFIE off until the 02 sensor is warmed up, because the bias voltage from the EFIE causes the ECU/PCM to throw codes because it thinks the 0.45 volts + EFIE voltage is "bad" (i.e. the 02 sensor must be bad). This shouldn't be a problem, because when the EFIE is turned off, it just passes the voltage through.

Soldering it wasn't hard, except for one mistake I made. The unit is made of two breadboards. The wire connectors between the breadboards are supposed to be "not flush" to the breadboard. I pushed them all the way in and tried to solder them on the wrong the side . It was agony fixing it with a de-soldering vacuum tool.

The part I wasn't looking forward to was calibrating it. I finally got it done, but it was a Multimeter PITA.

CarloSW2

[skewbe]

Can you clarify something, does your AF display require a wideband sensor? ($200ish) or is it looking at the "duty cycle"?

P.S. here is a thought, if you put your LED stack in bar mode (add r1), you can use one of the upper LEDs to trigger a buzzer for an audio "hey your running rich, lighten up on the pedal" indicator to aid in efficient accelerating.

[mrmad]

I think with a narrowband O2, you would see alot of fluctuating as the ECU is adjusting the mixture to stay at the target AFR. Since the narrow band will only read accurately at 14.7, the output from the sensor would be bouncing all over. The real AFR (if you had a wideband used as a monitor) would probably be closer to 14.7

[cfg83]

skewbe -

Originally Posted by skewbe

Can you clarify something, does your AF display require a wideband sensor? ($200ish) or is it looking at the "duty cycle"?

It's for narrowband (I e-mailed the manufacturer to verify this). I don't know about duty cycle. I'll go back and read the instructions/explanation.

P.S. here is a thought, if you put your LED stack in bar mode (add r1), you can use one of the upper LEDs to trigger a buzzer for an audio "hey your running rich, lighten up on the pedal" indicator to aid in efficient accelerating.

Ha ha, that's true.

CarloSW2

[cfg83]

mrmad -

Originally Posted by mrmad

I think with a narrowband O2, you would see alot of fluctuating as the ECU is adjusting the mixture to stay at the target AFR. Since the narrow band will only read accurately at 14.7, the output from the sensor would be bouncing all over. The real AFR (if you had a wideband used as a monitor) would probably be closer to 14.7

Yes, wideband is always better than narrowband. If I were starting from scratch, I would used a wideband + a fuel controller (megasquirt or an Apex SAFC fuel controller as in DRWs laser http://www.gassavers.org/garage/view/207), but I didn't know then what I do know now.

I got this AFR gauge because it was $40 before shipping and handling, and I wanted the digital display so that I wouldn't be guessing on the bargraph lights I am seeing.

The other reason I got it was because I wanted to know what the EFIE is doing (next step). The EFIE has a teeny tiny screw pot to change it's voltage bias, so I don't really know what it is doing to the 02 sensor signal . With the AFR gauge, I have a lot more control.

It does jump around a lot, but not in an extreme way, and it "cheats toward the lean", which is telling me that my car is running as I want it to.

CarloSW2