Ghettodyne Narrow Band A/F Ratio

[SixSick6]

As said previously on measuring voltage with narrowband O2 sensors:
http://www.mx6.com/forums/showpost.p...5&postcount=11 (Running Lean Need Advice)
http://www.mx6.com/forums/showthread.php?t=153896 (A/F Question....)
http://www.mx6.com/forums/showpost.p...&postcount=103 (Vaf Hack Thread?????)

Granted it's nothing compared to an actual wideband sensor with module but should give you an idea much better than a standard Autometer 4375 type:



Which is nothing more than a lightshow if you don't equate each light with a theoretical A/F reading.

Most if not all narrowband sensor read as follows:

14.7:1- 0.50v
14.6:1- 0.60v
14.5:1- 0.70v
14.2:1- 0.80v
13.5:1- 0.85v
13.2:1- 0.90v
13.0:1- 0.92v
12.5:1- 0.94v
12.0:1- 0.95v

It looks like this:




In closed loop mode the ECU will monitor the O2 sensor and the voltage should be between 0.3v~0.7v. But under acceleration (open loop) the ECU will ignore the O2 sensor and switch to default maps at which point you should see voltage between 0.70v~0.96v.

You can measure this with any digital multimeter:



Then correlate the voltage readings to your fancy light show:









^ The above numbers and lights are not accurate with a narrowband and should not be considered accurate with anything but an actual wideband sensor. It's just for demonstration purposes. If you wanted to confirm accuracy you'd need a wideband and a narrowband to confirm which light correlates to which voltage. The lights on the above .gif are with an actual wideband sensor.

Keep in mind that the transition between lean and rich with a narrowband O2 sensor is very steep and there can be quite a difference between on voltage reading while cruising and the same or close to the same voltage WOT.

Originally Posted by Zeitronix

In a closed loop mode the ECU monitors the oxygen sensor output to adjust the amount of fuel required to maintain a perfect mixture, which will lead to the the best fuel economy and minimal smog pollution. The perfect mixture for gasoline engines is 14.7:1 and the equivalent oxygen sensor output is 0.5 V. The transfer function between rich and lean mixture is really steep. This is why the air/fuel meter readings will fluctuate from 0.3V to 0.7V in a closed loop operation.

This is not meant to be hooked up and called a day. There is a BIG difference between a narrow band O2 sensor and an actual wideband. This is just to help gain some idea of what is going on, when, where, and why.

Here is the Autometer pdf file for the fancy lightshow:
http://static.summitracing.com/globa...s/atm-4375.pdf

According to their info, the gauge lights one LED for every 50mV. This means that theoretically you should be looking for at least 3 green LEDS lit for 0.85v (somewhere in the 13.5-14.0 vicinity), 4 lit for 0.90v (13.0-13.5), and 5 lit for 0.95v putting you in the 12.5~13.0:1 vicinity. Again, this is not fact and not true in all circumstance.

Originally Posted by Zeitronix

At a high load (acceleration), the ECU ignores oxygen sensor output and will switch to the open loop mode using default maps to determine the amount of fuel needed for a certain amount of air. The engine will run rich at a high load and the oxygen sensor output will be in a range of 0.85V to 0.96V. The higher the voltage, the richer the mixture. The oxygen senor output monitored on the air fuel meter will indicate if the engine is running lean under the load, which is very important to keep the pistons and the rod bearings happy. The open loop maps are usually poorly optimized for performance driving since the car manufacturer must take into account all manufacturing tolerances. Adding any performance modification to your car will affect the mixture so it needs to be monitored. The Air Fuel Meter is must for any true tuner.

Basically, even though the ECU ignores the O2 sensor under load/heavy load does not mean the O2 sensor stops working. The values may change due to the stock fuel maps and the amount of fuel being injected, EGT, etc, etc etc, but the O2 sensor itself is still goign to give you a voltage reading based on heat generated.

Again, these numbers are a guesstimate and by no means factual or a subsitute for a wideband.

Originally Posted by Zeitronix

Happy turbocharged engine likes to be above 0.92 under the load. Naturally aspirated cars can get away with a little leaner mixture. Stock narrow band O2 sensor is temperature dependent. If you are running closer to the edge and looking for fast responding and temperature compensated air/fuel ratio measurements you may want to look into a wideband meter.

Here's a good pages giving more info:
http://www.aa1car.com/library/o2sensor.htm
http://www.aa1car.com/library/wraf.htm
http://www.aa1car.com/library/2004/us10438.htm
http://en.wikipedia.org/wiki/Oxygen_sensor
http://en.wikipedia.org/wiki/Air-fuel_ratio_meter
http://www.freewebs.com/air-fuel-met...n-sensors.html
http://www.forparts.com/BoswidebandO2.htm

[SXE MX6]

hey, my autometer A/F gauge and its light show works 100%
(it doesn't bounce around any more though)

















yea, ok, its also hooked up to my LM-1

[turboed2.2]

this might be a good thing to use for this ..

http://cgi.ebay.com/ebaymotors/STING...09340733QQrdZ1

can mount it and itll look good and show low voltage unlike analog meters...

good infor sick..

one question about my a/f guage as it doesnt work it just lights all the lights or some [shizzle].. would a bad o2 sensor cause this?? ive tried several gauges.///

what happends when ur runnig like a a/f of 11s? at .95-1v its only 12..can the o2 not read that rich ?

also what about taking a wideband from a honda/volkswagen since some of them had them and then installing it and running just a gauge off that would that work...how would u wire it...

thanks

[SixSick6]

Yup you could use that too, BUT, the point is that they're not all that accurate.

The voltage itself is based on temperature which is different than how a wideband operates:

http://en.wikipedia.org/wiki/Oxygen_sensor

http://www.wmsracing.com/o2/tech.htm

http://www.gmtcny.com/WBO2S.htm

http://www.plxdevices.com/AppNotes/P...Technology.pdf

Be sure to check out the MegaSquirt Manual for great info on Oxygen Sensors etc

http://www.aa1car.com/library/wraf.htm

[Dyoel182]

Originally Posted by SXE MX6

yea, ok, its also hooked up to my LM-1

I've always wondered about that. It just hooks up to one of the analog outputs?

[SixSick6]

Most wideband controllers have an option for simulated narrowband. That way you can get a true/accurate wideband reading from the O2 sensor and your ECU still gets the signal it expects from the narrowband sensor. This eliminates the need to multiple O2 bungs.

[turboed2.2]

thanks

[Dyoel182]

Originally Posted by SixSick6

Most wideband controllers have an option for simulated narrowband. That way you can get a true/accurate wideband reading from the O2 sensor and your ECU still gets the signal it expects from the narrowband sensor. This eliminates the need to multiple O2 bungs.

Yes I knew that, but thats not what I asked. I mean which output from the wideband hooks up to the narrow gauge and is it anymore accurate than using the narrow band sensor to begin with?

[SixSick6]

#1 does. You hook it directly to the O2 wiring going to your ECU. The ECU is already preprogrammed from the factory to expect the signal from a narrowband sensor and will still work the same way regardless if there is a wideband sensor attached. Of course the sensor will be more accurate but it doesn't matter. It's only more accurate to the control unit, not the ECU. The ECU could care less and the signal is merely a simulated 0.5~1v signal.

[Dyoel182]

I'm not asking about faking out the stock ecu with a fake signal. I just want to verify that you can hook up the autometer gauge to the lm1/lc1 and actually get a usable signal, not just a disco light show.

[SixSick6]

Yes Joel. But the bigger question is why you're questioning things things that you've already gotten the answer to in a different thread?
http://www.mx6.com/forums/showthread.php?t=156004 (autometer a/f gauge to: wideband??)

Or maybe my hard drive is just bigger and stores more useless info?

Look here too:
http://www.mx6.com/forums/showpost.p...0&postcount=10 (Magik 8, question... [just bought an innovative motorsports xd-1 and lc-1...])

[Dyoel182]

I'm not questioning that it hooks up, I'm questioning that the autometer can really act as an accurate wideband gauge off of the output.

[SixSick6]

YESSSSSSSSS. Why is that so hard to understand?- two links. 6.5 is what you want to read.

[Dyoel182]

No ever came out and said that, they just kept repeating that it hooked up and worked. I didnt care that it hooked up and worked because what would be the point if the signal was a narrowband imatation that wasnt accurate in the first place?

[SixSick6]

That's what programming it is for. The LED's light up with every .50mV. You program the command unit and let the sensor do the rest.