The Stovebolt Site Forums The Shop Area Engine Shop Oxygen Sensors and Stovebolts

Thanks to Mar-Ktech and Hot Rod Lincoln for giving us the idea of adding an O2 sensor in the exhaust stream. This sensor is really valuable in that it will tell you right away if you are running too lean or too rich.

I added mine just below the manifold using a weld-on bung that I got at Summit Racing. The O2 Sensor is a Standard Motor Products SG5 for $20. It takes awhile (10 minutes at idle) for it to warm up enough to start sending valuable data. There are O2 sensors with warmers that give the result right away, but I am not in a hurry.

Its a simple install. Drill a 7/8" hole in a place that doesnt interfere with anything with the sensor sticking out about 6 inches near the manifold. Weld in the bung and then screw in the sensor. Dont forget to put the flange ahead of the bung before welding.

To read it is even simpler. Using a voltmeter that reads in millivolts, plug the + lead of the voltmeter into the sensor wire, the - lead to engine ground. The center of the sensors universe is .5 volts. .5 volts represents a perfect oxygen to fuel ratio of 14.7:1. Less than .5 volts represents too lean and more than .5 represents too rich. It produces as much as 1 volt.

Through some initial testing, I am finding on a stovebolt engine that was designed long before O2 sensors were even a thought, the proper way to fix a WAY TOO LEAN or WAY TOO RICH condition would be changing the Carb Jet. If you are getting around .25 to .65 I wouldn't worry about it.

Another way to adjust for optimum is the fuel mixture screw on the carb, however, that goes hand in hand with your timing and engine performance, so that may not be the best choice. If your plugs are gray, you are good to go without an O2 sensor, but I found it quite interesting to actually see the soot on the spark plugs without even taking them out! It is an indicator, nothing more, but an interesting one.

Anyone have other experiences with this? I am learning as I go.

Deve, just go buy the electronic fuel injection/engine management system and do it. You have already pretty much halfway re-invented the wheel. It isn't all as magical as it seems at first. Get a couple of good books on the subject, (there are a whole bunch of them out there) Like I said you can use the junkyard parts,(cheap) or buy a dedicated aftermarket system (not as cheap) I just don't have the time right now. Even just playing with TBI would give you reams of information you can use towards SFI, even if it doesn't produce any noticeable gains in power.

Doing sophisticated electronic stuff to a stovebolt engine is an exercise in futility, sort of like putting lipstick on a pig. Trying to measure exhaust O2 concentration with a multimeter- - - - -that's downright ludicrous since one of the diagnostic procedures scan tools monitor is how many times PER SECOND the sensor flip-flops across the median voltage, and if it slows down much, the sensor is deemed "lazy" and needs to be replaced. I hope the meter-reader has extraordinarily fast reading comprehension as the digital meter toggles through a bunch of gibberish numbers. Early automotive computer systems operated on a clock frequency (rate of information sampling) of 10 HZ. Newer ones upped the rate to 90 HZ. Good luck getting any useful info with a meter! LOL!

Jerry

Its funny at this point. We need to start calling you "Drive By". Every time someone says something, you drive by and yell something derogatory out the window! It's like talking to a Cat!

The O2 sensor has no circuitry in it that would create clock cycles. It creates its own voltage through a chemical reaction. The voltage is nice and stable from .1 volts to .8 volts. I can even change it, at will by simply turning the mixture screw. Its very responsive once its reached its temperature. And wherever you turn the mixture screw, the spark plugs color will coincide with that, EVERY SINGLE TIME!

The information is not only useful, but very telling during all RPM speeds of engine operation. I was able to use it for my testing. No gibberish unless you count what you say.

Of course Mr Drive By is the one who also said that stovebolt engines do not react to gap changes in spark plugs when using HEI. LOL! RIGHT BACK AT YA! Maybe if you did some research about O2 sensors and how they work in retrofitted older engines? Naw, you wouldn't believe it anyway. It's getting embarrassing Jerry. I could read the clock cycles on the Oscope, but no, there is no clock cycles built into that thar O2 sensor. So, in review, WRONG on PCV testing, WRONG on O2 Sensors, and WRONG AGAIN on Gaps/HEI. Maybe you could stick to something you are good at?

Without sounding caddy, honestly, some of us are sincerely trying to learn here. We ask stupid questions in the learning process and since that yields halffast results, we GOOGLE stuff. I come here to get information and the reason I do is because MOST people are caring, willing to help, and understand they do not know everything. It's a great community for the most part. I give back every chance I get. The very thorough and complete testing I refer to starts in about the middle of this document. I couldn't have done it without the members HERE!

http://devestechnet.com/Home/HEIgnition so don't get me wrong folks. But I am NOT in the habit of CAT HERDING!

I'm very interested in installing a setup in my ride to see whats going on. Mine would have to have 2 separate bungs as its a dual fenton setup and would be cool to see how each of the dual carbs is feeding each side of the engine.

its too bad they don't fit in the heat port bungs on the headers already.

I think the reason the idea isn't more popular is because there isn't very much you can do with the results on our engines. The only tweak you can really do without affecting other things adversely (arguably) is maybe change the carbs jet up or down.

While it's fun to pull the choke and watch the sensor go very high, or turn the mixture screw, you can get similar results by just looking at your plugs. It IS pretty cool though!

I have run my truck with an actual air fuel meter in the exhaust. It's a very accurate tuning tool. Using dual W-1 Carters, its easy to adjust for rich or lean by raising or lowering the metering rods. It only take .020" to see a difference. I tuned for highway speeds in which I drive the most. I then set the idle mixture screws. With two of them, and a very accurate gauge, I can get them dead on even. Just the slightest twist will change the fuel ratio more then you think it does.

Joe

Joe do you have a brand and model number for your preferred meter? It comes with a sensor but does it fit in an 18mm bung like the standard O2 sensors? I can see that being useful for dual carb setups.

Mine is pretty old and was sold by NAPA years ago. It has a magnetic sensor head with a hose on the end you shove up the tail pipe. I have been watching e-bay for meters so I could mount a 02 sensor in the head pipe, but just haven't found one I like yet. Mine works like this one, http://www.ebay.com/itm/Vintage-Sea...9395d8&item=301697570264&vxp=mtr .

I will prob opt for the Auto Meter one and pick up a second o2 sensor. When i need to i will just hook the gauge to the appropriate lead to see whats going on in each down pipe.

One thing that is missing from this thread is a separation between NARROW band and WIDE band O2 sensors.

Deves first comments seemed to describe a NARROW band sensor. If that is correct I would have to agree with HotRod Lincoln. The narrow band sensor is designed to flip up and down around the stoic point of 14.7:1 air/fuel ratio. This flipping is nearly impossible to work with unless you have a computer as HotRod describes. Narrow band is '70s technology.

WIDE Band is a completely different animal and gives a nearly linear output curve over the whole range of air/fuel ratios 5.0-20.0. It will teach you a lot about what is "actually" happening in your engine.

I always recommend welding in an O2 bung on ANY engine so you'll have it if you want to test and tune. Wide band sensors and systems are relatively cheap these days at about $200.

Paul

Agree or disagree I know what I am seeing and can repeat it all day. This is the sensor we are talking about, not the associated circuitry. There is NO FLIPPING! So, maybe they redesigned it or something. In any case, I can tweak my mixture screw and get a perfect change on the voltmeter all the way up and all the way down.

I would like to go to a heated model though. It takes a good 10 minutes to start getting readings at idle.

If the wide band is even more accurate somehow, I would like to go to that one as well. I guess it's nice I don't have alot of experience with these things, I don't have preconceived ideas on them beforehand. In this case, I don't know how much more perfect a reading I can get.

WHAT I FOUND

A narrow band o2 sensor is an oxygen sensor that is only calibrated to know three things. Rich, stoic, and lean. What I mean by this is that it only has a narrow window that it see’s the air fuel mixture through. The sensor can tell the computer when it’s stoic. If it’s not stoic, it can tell the ECU that it’s either Rich, or Lean, but that’s it. It doesn’t really output any particular value other than that. How rich the car is the sensor has NO IDEA about. Same with how lean the car is. All it does know is that it’s not stoic. The ecu with a narrowband o2 sensor, when in closed loop mode, will then lean on the fuel map if it is receiving a rich signal from the o2 sensor till its stoic. The opposite would be true if the sensor was telling the ECU that it was currently running lean, it would richen the fuel map till the o2 sensor was reading stoic.

A wideband o2 sensor is much more sophisticated than a narrowband sensor, and can be relied upon to be used as a tuning tool. Wideband sensors not only are a lot faster acting in the reading, but can tell you the exact a/f ratio that the motor is currently at. So instead of just telling the ECU that the motor is running rich, it will read a voltage that correlates to an actual value, like 11.2. One thing to remember with a wideband sensor is that it has a heating element that needs to be heated up before the sensor will be accurate in its readings. This usually only takes a few seconds, but just remember that for those first few seconds the gauge is not useful. Wideband sensors give the ECU the ability to tune exact A/F value’s to a tenth of a decimal instead of just richening and leaning the mixture till a stoic value is seen.

Wolf, those are good choices from what I know about it. My el-cheapo $20 sensor would not be accurate enough for twin carbs. I can see the numbers being off because of its slowness to catch up with real time and the carb being so inaccurate in the first place. You don need to wrestle with two things that are slightly out of whack!

Wolf, that is true about the narrow band if you are using the customary electronics, but if you are looking at a voltmeter, you can see just how lean or how rich it is. I am glad I didn't know anything beforehand. That is such a beautiful thing discovering things that others pass by because of things they read. I too read about these sensors and agree with your findings. But if you research further, you will find that the sensor is a manufacturer of voltage. It makes its own and reports depending on how rich or how lean the fuel mixture is. A max of 1 volt, a min of 0, and any number in between. It is not smart enough to skip over certain voltages, or flip flop or anything. Its just a sensor. Sensor connected direct to the voltmeter. I want a wide band now since I am using it for testing!

Does anyone have any information as to the need for the gauge? Can I just purchase the wideband sensor and hook it up to my voltmeter like the one I have? Then the cost is only $80.

http://www.summitracing.com/parts/avm-30-2001/overview/

Wolf, read the review on the FAST model.. I don't think I want to risk that one.

The advantage of the meter, or gauge, would be in getting an actual A/F reading, instead of interpreting voltage signals. More accurate and easier to use, now and in the future.

cm

From what I am reading, the wide band sensor requires feedback from the ECM and the optimal voltage varies between manufacturers. So no way to use a multimeter anyway. Also, to Pauls point, here is what I found at Innovative Motorsports: ECU's with NBO2 (Narrow Band) sensors use the sensor only during cruise and idle. They operate by checking if the voltage is below 0.45V, richen up until it is above 0.45V, then lean out, then richen up again and so on. Therefore the mixture oscillates around 14.7AFR. This AFR is optimum for minimum emissions. The oscillations are caused by the operation of the ECU, not by the sensor as many people believe. This is what I am talking about.. take the electronics out of the equation and consider JUST the sensor. I get a very nice and very responsive voltage change when I adjust the mixture screw with the narrow band sensor and it is repeatable all day long.

Back in the 60's and 70's we had engine analyzers that used a "sniffer" in the tail pipe to assist in air/fuel settings. Very old ones used a Heyer Scope IIRC and ours was an Allen. I think Sun was the most popular. No idea how they worked.

Im sure the Auto Meter one was fully stand alone and would not require any other connections other than dash light, power, ground and a heater power lead. Data log system optional.

http://www.autometer.com/media/manual/2650-1469-00.pdf

There was an OTC 4 gas analyzer identical to the one I used in my shop for several years on Ebay recently, and not too expensive. That one can be used with a moderately-sized inverter for road testing. It measures O2, CO2, CO, and unburned hydrocarbons. That approach makes sense- - - -trying to make an O2 sensor work without the associated ECM support and a feedback loop system is ridiculous. Whine about it all you want- - - -there's a reason it took approximately 6 years for manufacturers like GM, Chrysler and Ford to come up with a workable closed loop fuel system once the Clean Air Act of 1968 mandated it.
Jerry

Jerry, a whole lot has changed since those days, in 1968, a computer that would do what we do with a smart phone would take up an entire room. Modern engine management isn't all as complicated as many would like us to believe. All Deve is doing is playing, no need to get all serious. I've told him once, to just go ahead and get the set up (probably from a junkyard) read the hundreds of pages of posts on the subject on this forum, as well as several others, and to get a couple of books on the subject and just do it. He is halfway there already.

I've learned a bunch from reading through this topic and appreciate the mind stretching it created. So, keep on Deve! I wish I knew enough to at least add a smidgen of useful help.

What am i missing? why does the o2 sensor need a ecm as indicated by jerry? I can see that if you were making it a closed loop system that would self adjust but to just use the sensor and gauge as a means of getting data this should work should it not?

The narrow band O2 sensor doesn't need an ECM and the kit you are getting from Summit [I ASSUME would have what it needs to communicate with the wideband sensor on its own??] Maybe not? Better check.

It's like I said before, the 'professionals' have always used the narrow band sensor with an ECM so wrongly think that the erratic behaviour of them is due to the sensor when all along it was the ECM. You don't get any better than Innovative Motorsports for a reference.

Even though the narrow band sensor is doing the job they designed it for, the problem with using it with a Stovebolt engine is the Carb. These 1 barrel carbs tend to surge. Even if you don't notice it happening in your truck, it's happening all the same just not noticeable. In a 74 degree shop where I can run these engines all day (exhaust vented outside) you can tell in a few different ways. One is the RPM fluctuates plus or minus 20 RPM and depending on the Carb sometimes alot more than that. But you can't really hear the difference in 20 rpm. So the very exacting narrow band sensor.. what do you think it does in this surge environment? The numbers move about the very same up and down. You can't test below .175 volts or so because that is too lean for the engine and it will stall. You also can't test above .800 because it's too rich and will stall.

To verify run the engine at or below about .300 and then pull the plugs. They should be clean. Then do it again with the setting above .600 as significantly as you can, and pull the plugs. Soot will cover the electrode on the plug.

Thanks Brokenhead.. that is exactly what I am doing! This is an old truck forum where people from all walks of life meet to share information. It is not a high tech engine forum where all of the gurus meet to discuss their craft. Driveby didn't last in those forums so he is here treating everyone else like he was treated there. But character flaws, being wrong a lot, doesn't matter here. That's the beauty of what John and Peggy have created. We should all celebrate this! KOOMBAYAAAAAAAAA!

There is nothing so positive as ignorance, and stubborn ignorance is an order of magnitude worse. The self-diagnostic loop of an ECM system slows down the response of all the circuits it monitors (not just the O2 sensor) to make the gibberish somewhat understandable. The diagnostics filter out at least 90% of the raw data so there can be some hope of understanding the remaining information. Trying to monitor the raw data stream with a meter without the filtering capability of the diagnostic loop is a fool's mission.

Other than that, go right ahead and try to understand raw data off the sensors.
Jerry

Guys, notice how Driveby didn't try to help wolfcub with his very urgent question on if the kit can read the wideband on its own or if it is expecting to be plugged into the ECM, thus saving wolf the trouble of hours on the phone. This is what he does.. criticizes, attempts to make others look stupid, but absolutely ZERO help. Yet really listen to all the schooling and experience he says he has. Its like we are dealing with a cat or someone who doesnt possess the cognitive skills to understand this is a help site.

wow! what else is there to say? I am right here in the shop watching the output of the narrow band sensor off the multimeter and getting precise results as I turn the mixture screw! Just like Innovative Motorsports points out. Keep up the drive-bys is all I can say. People will understand more clearly who you really are. Lots of us know already, but keep embarrassing yourself. Then I won't get as much flack for calling it like it really is.

Not that I advocate using a narrow band sensor on our vintage engines because of the surges mentioned above. I am sure a wide band would be better, but we are not adding an ECM to the mix yet. ECMs can be expensive, and confusing. Best to learn how each system works before putting down that kind of money.

bravo

What grade are you pulling, and at what manifold vacuum is the power valve opening? Where does the mixture transition from economy to power, and is there any hesitation at the transition point? I have done all these road tests, and more, with many hours' worth of dyno testing to back up my research. Where are your practical test results, corrected for atmospheric pressure, temperature, and humidity? Can you get any useful information from an engine on a test stand, running without any load on it?

Educate me about what, exactly, you're trying to prove.
Jerry

Sounds like you should have a lot of great positive support data to share on the subject.

So if the mV signal from the narrow band sensor can't be properly read on a DMM, I wonder what it would look like on an analog meter or a scope.

I have made repeated attempts to share information, and always end up getting called names. My info is never good enough, or accepted in the spirit it's offered. The nice thing about beating one's head against a stone wall is that it feels so good when you finally figure out it's a pointless effort and stop. If our resident whiner would ever actually get his truck on the road, I'd be more than happy to assist with some real-life information. That's about as likely as finding a streetwalking hooker singing lead solos for the Mormon Tabernacle Choir.
Jerry

Seeing that the narrow band sensor is a three state device one should be able to use a variety of methods to see the changes occur as long as your sampling of its state change transistion occurs at a reasonable rate (no flutter) to read the transition and tie it to what external influence that caused the change.
Each device DMM, Analog meter, or scope has its issue related to reading fluctuating transition but all can easily show a shift in transition state if that state stays changed.
It would be far simpler to monitor with a analog to digital state reader on a laptop (again with high enough sampling).
Or simply use an Arduino or Raspberry PI and a three state LED indicator.

http://www.enginebasics.com/EFI%20Tuning/Images/AF%20Basics%203.gif

Spirit? Try to understand that the narrow band sensor is always thought of together with an ECM. Its the ECM that gives it is erratic behavior. NOT the sensor. Jeeze. Spend the $20 and see for yourself. No flutter, no wierdness, just smooth voltages up and down the spectrum. Its still not good enough to do dual carbs but great for single carb systems if you just want to ensure your carb is adjusted correctly.

There are always people who insist they are right in the face of other people with actual tools in their hands and testing in progress.

The big question right now driveby, is wolfcubs question. Once again, deflecting on others to keep you from having to actually show that you not only have fancy words, but you have actual real information. I just want everyone else to see what I do.. nothing but excuses and deflection.

There is a shortlist of people on these forums who like to talk and deflect the conversation to other things so they don't have to show their true character. Show everyone I am wrong! Chances of that are slim to none. I have several trucks on the road BTW. They sure didn't get there because of you.

Case in point- - - -anyone want to have a conversation that's not based on a third graders' playground one-upsmanship mindset? Drop me a PM.
Jerry

Deflection. Its all Driveby is about. Since you didnt know the answer to wolfcubs question in public, why would anyone care about what you have to say in private?

Now that the trash has been appropriately taken out, Wolfcub, did you get an answer from anywhere that would help? All of us are interested. I will find out if you don't get anywhere.

I read this as well, and it seems to me it is a standalone kit with no ECM necessary. This would mean the ECM circuitry that is talked about on some of the websites must be in the gauge itself. Sounds to me like a worthwhile kit.