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O2 sensor output for carb tuning.....

Quaddawg

Quaddawg

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Hey guys, I was searching for a decent article on fine tuning my Edelbrock, and came across this, on a guys Volvo site (302 Ford in a Volvo..:o )

The first page is pretty standard stuff, but go to page two, very interesting testing procedures using a standard O2 sensor in the header, and a volt meter for fine tuning..

This may be old news for you guys, but I had never thought of using an O2 sensor output to fine tune fuel mixture on an older non-ecu N/A small block (or anything else)

Anyway, I thought it was a good article, and has applications other than Edelbrock of course...

Here is the link:

Sorry if this is old news

http://www.telusplanet.net/public/gilesij/Volvord/section_2.htm
 
Yeah, that's true, I had never seen them... but look at the price!!!


LOL, $500 bucks? you could make one for less than 50 bucks... might not be quite as pretty though... or do everything those do... but the data would be there..
 
You can use a typical O2 sensor for tuning, but they are not wide-band sensors. There is a Bosch senosr that is an OE VW part that is the wide band sensor commonly used by those meters. I don't know the app or the p/n, but pm me if you need it as I may be able to find it.

I'm told some (all?) of the trailing sensors in a OBD II system are wide band, but I don't know about their calibration. Ford reportedly tweaks the sensor calibration depending on application and regional destination, so stay away from them.

You can read a std O2 sensor with a DVOM. Stoch is .75 volt, 12:1 is about .69 volt.
 
FWIW, a normal O2 sensor doesn't give much info, mostly just rich or lean with no in-between. I think it'd be real hard to use it for carb tuning. A wideband sensor will tell you your actual air/fuel ratio, but you need a controller box in addition to the sensor itself. I recently bought a ZT-2 from Zeitronix which will give your exact AFR and log it to a PC if you want. Much more useful.
 
Did you guys read the article??

Give it a read. An O2 sensor and DVM can be used quite easily to tell you your fuel mixture..


not flaming, but it seems noone even read the tables and such.....

a normal o2 sensor will give varying voltage outputs reflecting the amount of oxygen in the exhaust..... a simple table is all you need to translate that into A/F ratios.... if the darned HTML wasn't turned off, I would post the table for you... gimme a minute and I will turn the table into a jpeg or gif and post it for the clicking and reading impaired....
 
In theory, you could use a narrowband, but the slope is very steep in the area of interest and then saturates - which is why I say it's mostly just a rich/lean indicator. You'd also probably have to calibrate your specific NB sensor, and it might change vs. temp.


O2transfer.gif
 
OK, I guess I wasn't being CLEAR with my first post.


You DO NOT need a wide band O2 sensor to do this, you don't need a $500 A/F meter with bells and whistles..

This is NOT for injected vehicles, this is NOT for computer controlled vehicles.

This is a way to fine tune a CARBURETOR. period..

OK, now that this is cleared up....

you need an O2 sensor installed in your header or front exhaust pipe, and a Digital Voltmeter.

Look at the tables below, if you can't make sense of this, then skip it, and go on to another post.... OR, you could always read the article that I posted.

Noone is talking controllers, or computers or anything, I am talking about fine tuning the various power circuits on a carburetor, FINE TUNING!!! EXTRA FINE TUNINING... LOL.... (I hate it when people don't read a post before replying...)

Here are the tables... maybe someone can use this idea, I certainly will try it out for fun.....

o2sensorvoltages.jpg

o2mixture.jpg
 
Mastiff, I am not slamming you man, but, remember, we are talking carburetion here, not injection... a rich/lean indicator is enough to tune the circuits just fine.... most of the time, they don't get tuned at all, so this is a good idea to try out.


Did you read the article I posted the link to?????
 
This is all very good info. I may have to try something similar this summer. My only question is why is it not effective to take a reading at idle?
 
RustBuket said:
This is all very good info. I may have to try something similar this summer. My only question is why is it not effective to take a reading at idle?
Click to expand...
I am pretty sure that the exhaust temp is not hot enough, and consistant enough for the O2 sensor to produce reliable voltages, when the engine is running at ldle. It would be simple to test, just play with the idle mixture screws and watch the readings...
 
K5MONSTERCHEV said:
I think it would be easier to just use a smog machine, that is the best way.
Click to expand...
As far as using a smog machine to tune your carb, and that being easy? Maybe I don't know what a smog machine is, or where I can use one at my discretion for a day or two, and take a bunch or readings at the parameters I want?

I am afraid you didn't read the article did you?

You take readings at various engine speeds, change metering rods etc, retest, change , retest, maybe take 20 or 30 readings... just wondering how you could do this with a "smog machine" if you didn't have one? I mean almost everyone has a DVM, and can get a generic O2 sensor for a few bucks.....

This was just a neat article and idea I ran across for garage tuning an Edelbrock Performer carb... to a degree that 99% of them NEVER get tuned to...


Please, I welcome all criticism, and comments, but if you are going to comment, I think it would be a great idea to read the article I am refering to, don't you? (just a thought.....lol)
 
good post

Good post Quaddawg. I guess sometimes you have to spell it out for the young:D that this is a cheap & easy way to check your A/F ratio if you have an O2 sensor and a voltmeter. I would like to see a part# for the wide band sensor though. I would think it would be more accurate.
Since we are on the subject of adjusting the carb, check out this link
http://bbs.off-road.com/ubbthreads/showflat.php?Cat=&Board=offroadjeepjeepster&Number=970779&Forum=offroadjeepjeepster&Words=propane%20trick&Match=Entire%20Phrase&Searchpage=1&Limit=25&Old=allposts&Main=970779&Search=true#Post970779
It's another low budget way to check out your carb if you dont have an O2 sensor and cant use the first method.
bob:saweet:
 
Thanks Bob, ah......... the young...... :D what WOULD we do without them..

Yessir, I agree, a wide band sensor could only be better and more accurate...


Ah, the old Propane trick... I remember that one......

that particular article was written very well, and with some humor too!
I like this part the best:

To make sure you have correctly removed the orfice, hold the
bottle with the valve down and open the valve - you should
get lots of propane, some liquid, mostly gas.
DO NOT DO THIS NEAR A FLAME - or you'll be surprised
Click to expand...
THANKS!!
 
Well from what I have read using a narrow band sensor and volt gauge is fine for fine tuning. Problem is getting your mixture down to the area that a narrow band sensor can pick up a[font=&quot]ccurately and keeping it their. Here is a link to the bosch website that tells about the wideband sensor...
http://www.forparts.com/BoswidebandO2.htm
This link goes int othe science of it and also includes part numbers for the sensors......
http://www.megasquirt2.com/PWC/
And last but not least, this kid put a whole system in his car that he got from down under and paid about $400 total including the sensor....
http://www.negative-camber.org/crispyrx7/wideband.htm


[/font]
 
scuba_steve said:
Well from what I have read using a narrow band sensor and volt gauge is fine for fine tuning. Problem is getting your mixture down to the area that a narrow band sensor can pick up a[font=&quot]ccurately and keeping it their. Here is a link to the bosch website that tells about the wideband sensor...
http://www.forparts.com/BoswidebandO2.htm
This link goes int othe science of it and also includes part numbers for the sensors......
http://www.megasquirt2.com/PWC/
And last but not least, this kid put a whole system in his car that he got from down under and paid about $400 total including the sensor....
http://www.negative-camber.org/crispyrx7/wideband.htm


[/font]
Click to expand...
Thanks for the links Steve..

(once again though, the kid has an ECU, and we are talking manually adjusting the carb, not injection, or ECU parameters.. but thanks still)
 
If you do this, I'd like to know the results.

As was alluded to, the voltage changes extremely fast, (we're talking milliseconds here to change .1 volt+ which is the difference between rich and lean) and in a carbed application, I don't see the reading ever being consistent enough to tell you anything other than it's around 14.7 based on it jumping rich/lean, except if the engine vacuum was rock steady.

Even the more advanced ECM's in injected applications using the O2 sensor just bounce between rich lean. I wish I could find a datalog showing O2 mV output on an idling engine, but I can't. It is NEVER steady, although it will hang in a range of values if nothing is changing elsewhere in the system.

Perhaps under WOT the fuel delivery in a carbed application could be held steady enough under long pulls to determine rich/lean. I read the article, I would just like to see how effective it actually is. Since you are looking at optimum fuel under WOT typically around 12-13:1 AF, looking at the sensor graph shown, .8-.9 volts is going to be pretty tough to tell accurately I would *think*. The difference between voltage and AFR is extreme at that point.

Again, I think this is an interesting topic to follow up on. There are plenty of people that have no inclination to switch to fuel injection, and spending a bit of time with a meter to try to dial in the carb better can't hurt if the system works. Just one word of advice from what everyone else says. Stay away from the Bosch O2's, Delco's seem to be good. That said, I'm running a Bosch and am not complaining thus far.
 
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