Does anyone know what the ideal volt reading from the O2 sensor lead should be.

I heard .700 is the best ratio

I am looking to hook up a multimeter to the 02 sensor lead to my A/F guage and try to fine tune the optimal reading across the board with my VAFC

Any help is greatly appericated

 

As for the O2 sensor...

I can't remember if the sensor is a 3 or 4 wire setup but it should be as follows ( I don't know colors off hand either but you could go by voltages.

wire one.... battery voltage
wire two.... signal to ECU
wire three.. ground (chassis ground and signal ground on 3 wire)
wire four.... (if applicable) ground

To verify which color wire is which. use a voltmeter and turn igntion to on BUT DO NOT START THE CAR. Get under car and disconnect O2 sensor plug (wire harness). Place negative lead on chassis (ground). Place the positive lead on each wire individually.

12 Volts is the battery voltage supplying power to the Sensor

.1V-.9V would be the signal to the ECU (this is where you tap a/f meter in.)

0 Volts is ground.

if 4 wire then you will have another wire with 0 Volts. This is also ground.


I understand what you are trying to do and this will work fine for tuning at normal (cruising) driving.

As soon as you go heavy load on the motor or WOT, the O2 sensor pretty much means nothing to the computer as far as controlling a/f mixture.

If you are going to be tuning with an AFC or any fuel controller, you would want to use an Exhaust Gas Temperature Gauge for more accurate tuning.

If you were to use a voltmeter like you were wanting to do, you would get a basic idea of a/f mixure, but it would give you less accurate readings under hard accelleration. This could result in an extremely lean condition which is very hazardous to the motor.

An Exhaust Gas Temp gauge would be used with and A/F meter. The EGT meter will constantly be telling you how rich or lean the mixture is strictly by temp readings. The temp readings are going to be as accurate as the meter being used to actually measure the temp. The leaner the mixture is the hotter the exhaust temp. The richer the mixture, the cooler the exhaust temp is. With the fuel controller, if the temp is too high, you could add fuel to richen the mixture, thus reducing exhaust temps to normal levels. And if too rich, you could lean the mixture out to a normal temperature level.

Then the a/f meter would be used as a reference rather than your only way of monitoring what is actually going on. Temp pretty much doesn't lie in terms a properly running engine.

oh yeah and by the way i believe .7V to .8V is correct on proper tuning voltage for the best power.

and just in case you get the EGT, I believe between 800 and 1100 degrees F is the limits for EGT. But don't quote me on that one.

Hope I was able to help out. Probably more information than you needed.

Good luck


[Modified by Shft@9GSR, 8:28 PM 3/19/2002]

 

make sure you have some form of high impedence buffer on the lead(s)...


.8-.91 is ideal.

Yack -who ain't gona pay for a wideband on Dyno unless it's turboed!!

 

i'm interested as well , sorry for the dumb question but i dont know what or where to get a high impedence buffer ---- is it a radio shack item ?

also anyone know of step by step directions for this set-up as far as a basic aid to tune a little -

thanks , Jamie - who is now very stoked on a response to this

 

i'm interested as well , sorry for the dumb question but i dont know what or where to get a high impedence buffer ---- is it a radio shack item ?

also anyone know of step by step directions for this set-up as far as a basic aid to tune a little -

thanks , Jamie - who is now very stoked on a response to this

 

back to the a/f meter for a second... I would say just to go buy an a/f meter. They are pretty cheap for a simple meter. If you were going to look to put a voltmeter in there to just read measurements, that could get to be more expensive than an a/f meter itself. I got my cyberdyne for like $25 and i think the autometers go for like $50. Which is still cheaper than an accurate voltmeter. And it will fit into a normal gauge pod.

 

NO

The resolution of most off the shelf A/F meters is a joke....(I.E. a 1 or 2 point ratio delta in AF will go unseen.

 

actually, the halmeter af30
and this one: http://www.techedge.com.au/vehicle/wbo2/default.htm.
are pretty accurate compared to wideband.

Greg

 

I tried going the route you are taking, Trying to tune with a voltmeter, I eveb tried to build a small voltmeter so I can put in on my dash and keep and eye on it, but from what I have read it is not as useful or precise. I bought a voltmeter setup where all you have to do is tap in to the O2 sensor input to the ECU, power and the ground. The voltmeter reading jumps around too much even in idle to determine what the right number is, only when you are driving is when it stays idle (the numbers on the voltmeter I mean) but then you better keep your eye on the road. That is why I began to look into Hondata for datalogging, but yes it is too much money when all you really want to do is tune the A/F. The next best thing is the Aussie product, but it will take a while to get it, they are pretty backed up. I would really suggest spending $100 USD for an hour on a Dyno and tunning, it will save you time spent trying to tune with a voltmeter. I will try to post pictures of the voltmeter unit I bought. You can also find it at, I think it is www.jumptronix.com (they advertise it for and Eclipse but it works just as well on any other car)if you are really interested in buying it I can sell you mine. I am going to order the Aussie Oz wideband and invest in Hondata.

By the way you should invest on the factory electrical guide, I use it all the time, it gives you all the electrical drawings.

As always this is my opinion and experience, I hope this helps you.

 

I tried going the route you are taking, Trying to tune with a voltmeter, I eveb tried to build a small voltmeter so I can put in on my dash and keep and eye on it, but from what I have read it is not as useful or precise. I bought a voltmeter setup where all you have to do is tap in to the O2 sensor input to the ECU, power and the ground. The voltmeter reading jumps around too much even in idle to determine what the right number is, only when you are driving is when it stays idle (the numbers on the voltmeter I mean) but then you better keep your eye on the road. That is why I began to look into Hondata for datalogging, but yes it is too much money when all you really want to do is tune the A/F. The next best thing is the Aussie product, but it will take a while to get it, they are pretty backed up. I would really suggest spending $100 USD for an hour on a Dyno and tunning, it will save you time spent trying to tune with a voltmeter. I will try to post pictures of the voltmeter unit I bought. You can also find it at, I think it is www.jumptronix.com (they advertise it for and Eclipse but it works just as well on any other car)if you are really interested in buying it I can sell you mine. I am going to order the Aussie Oz wideband and invest in Hondata.

By the way you should invest on the factory electrical guide, I use it all the time, it gives you all the electrical drawings.

As always this is my opinion and experience, I hope this helps you.

 

In a nutshell,

.45V = stoich , although stock o2 sensors are not accurate (at all) in that range and you will never see a steady .45V value

Less than .45V = excess fuel (rich) = no excess oxygen

More than .45V = lean = excess oxygen

As for a high impedence buffer, any digital voltmeter has an inherent high impedence, as will any voltage monitoring device (LM3914 ect.)

keep in mind tho that stock sensors are really only designed to monitor rich/ lean conditions. anywhere near stoich it will have no accuracy (or resolution)