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Air Fuel Ratio Gauge
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Author:  kxracer728 [ Mon Oct 07, 2013 10:37 am ]
Post subject:  Air Fuel Ratio Gauge
I bought this narrow band o2 sensor off ebay for $10.56

http://www.ebay.com/itm/370604133022?ss ... 1497.l2649

Which was a really good deal since autozone wants $45.99 for it...

I was going to use it to setup a AFR gauge. Just wondering how many people are using them and which ones are good. I've read in some of the reviews on the Sunpro CP7011 that those are more of a light show that moves so quickly that it's hard to get a good indication of how the AFR is changing as you drive

I'll probably go with one that has a needle indicator instead of an LED display. I assume you connect the gauge signal wire to the o2 sensor wire? Since we don't have computer modules...

Since the HEI conversion my plugs have been running a lot leaner...they are pretty "WHITE" now :o i'm going to start riching the circuit
Author:  Reed [ Mon Oct 07, 2013 10:52 am ]
Post subject: 
Narrow band O2 sensors only read a very narrow mixture range on either side of stoichiometric (hence the name "narrow band"). Narrow band sensors are really only useful for very fine tuning once you get pretty close to stoich. A narrow band sensor can tell you if you are grossly lean or grossly rich, but only because the gauge will be "pegged" in one direction or the other.

In fuel injected vehicles that use narrow band sensors, the computer samples the exhaust several times per second and constantly adjusts the mixture. If you hook a gauge to a narrow band O2 sensor on a fuel injected engine you will see that it is constantly ping-ponging back and forth between rich and lean. This is because that is how the computer determines the fuel mixture. The computer changes the mixture so fast that the average mixture ends up being correct.

For tuning purposes, especially with a carb, a wide band O2 sensor and gauge are a better choice. They also cost about ten times more.

As far as gauges go, if you are using a air/fuel ratio gauge with an O2 sensor, I say go for a digital readout. That way you know EXACTLY what the fuel mixture is. When you start tuning you really want know as accurate of information as possible about your motor. Since you are putting the effort in to tune your motor this accurately, why not go all the way and get the best tuning aids possible?
Author:  wjajr [ Mon Oct 07, 2013 3:53 pm ]
Post subject: 
kxracer728,
I used a three wire o2 sensor that fit a '93 v6 small Chevy van that was on clearance at Rock Auto a few years ago, and the same gage you are looking at with the LEDs. It works just fine for carb tuning because carbs are a close enough kind of device. As soon as throttle plate moves the mixture goes lean, rich, any which way because of accelerator pump, and too much air at low vacuum momentarily... if that makes any sense. For stable run condition such as idle mixture adjustment, dialing in main jets, and seeing when power valve or high speed enrichment comes on line this set up works nicely.

The reason for the three wire is it has a heater (+12v & ground, and signal) in it to keep probe functioning at low rpm (cool exhaust) and after cold starts before all the rigg’in is warmed up as opposed to a single wire sensor. My car has headers, and o2 bung is just aft of 3â€￾ collector (a long ways from head).

Single wire sensor will work if it is close enough to head, and can be kept at the proper temperature to generate a voltage to trigger gage; say just aft of where head pipe connects to exhaust manifold.

If you don’t want to try to decipher the light show on gage while adjusting idle mixture, or if you really need to have a number to gawk at, just attach a pigtail to signal lead & ground at gage, and connect to your volt meter. I used a three wire connector under the hood to connect homemade sensor harness to gage harness and just stick the red probe in to signal wire connection, and back probe to negative battery terminal, and it reads voltage .9 to .66v = rich; .65 to .45v = ideal; .42 to .1 = lean.

This [url=http://www.bob2000.com/carb.htm]site[/url] will outline the process, as well as the gage directions.

[img]http://i294.photobucket.com/albums/mm87/wjajr/Dart%20electrical/003_zpsc5738338.jpg[/img]
Author:  kxracer728 [ Mon Oct 07, 2013 8:13 pm ]
Post subject: 
Quote:
In fuel injected vehicles that use narrow band sensors, the computer samples the exhaust several times per second and constantly adjusts the mixture. If you hook a gauge to a narrow band O2 sensor on a fuel injected engine you will see that it is constantly ping-ponging back and forth between rich and lean.
It sounds like with a carbureted vehicle i won't have as much of a problem with the gauge jumping around then? It's amazing that a computer controlled AFR can dial it in so accurately the way it works
Quote:
For tuning purposes, especially with a carb, a wide band O2 sensor and gauge are a better choice. They also cost about ten times more.
With my engine setup i'm just trying to get in the ballpark for now and in time maybe upgrade to better tuning aids. This truck is a long term project...i did get my speedo cable reconnected, so i can finally put a number to what kind of gas mileage i'm getting

wjajr,
Quote:
I used a three wire o2 sensor that fit a '93 v6 small Chevy van that was on clearance at Rock Auto a few years ago, and the same gage you are looking at with the LEDs.
It looks like you can get the

Universal BORG WARNER OS702 3 wire for $13.50 on ebay

http://www.ebay.com/itm/NEW-BORG-WARNER ... 17&vxp=mtr

Or the BOSCH 13077 3 wire for $20.53

http://www.ebay.com/itm/NEW-BOSCH-OXYGE ... 37&vxp=mtr

I got my single wire in the mail today...i should have posted this topic before i ordered one :roll: i'll try the single wire 1st and if i don't think it's giving me good results at idle, i'll goto the 3 wire sensor
Quote:
Single wire sensor will work if it is close enough to head, and can be kept at the proper temperature to generate a voltage to trigger gage; say just aft of where head pipe connects to exhaust manifold.
My o2 bung is pretty close to the exhaust manifold...i'll take a pic tomorrow so you can see. Thanks for the pic of yours! Looking pretty nice and clean under the hood :)
Author:  emsvitil [ Mon Oct 07, 2013 10:34 pm ]
Post subject: 
http://www.slantsix.org/forum/viewtopic ... 42bc329258
Author:  wjajr [ Tue Oct 08, 2013 5:33 am ]
Post subject: 
[quote]It sounds like with a carbureted vehicle i won't have as much of a problem with the gauge jumping around then? It's amazing that a computer controlled AFR can dial it in so accurately the way it works[/quote]


Gage jumps all over under certain throttle conditions once carburetor is dialed in. It is fairly steady when throttle is not moving quickly, or at WOT. Reason it jumps all over once mixture is dialed in is it is reading the steep portion of mixture graph found in gage literature and combustion pulses disrupt exhaust mixture particularly if cam has a lot of overlap. In other words gage sees the gamut between some unburned fuel and lean combustion and reacts instantly with a voltage change. Fuel injection loves this impute, but with a carburetor makes it makes no difference carb delivers what it delivers, it is an analog device controlled by vacuum signal and throttle opening. One cannot maintain 100% perfect A/F mixture 100% of the time using a carburetor, but one can come close if engine is in good repair, and cam is not too big.

After all that hot air above, you will grow accustom to how your gage reads while going down the road, and will be able to see how A/F mixture affects drivability, exhaust pipe color and odor.


[quote]My o2 bung is pretty close to the exhaust manifold...[/quote]


Good; reading all six close is better than my setup reading front three 30â€￾ downstream from head.


emsvitil's post will make more sense as you get used to the gage. Good explanation by the way.
Author:  kxracer728 [ Tue Oct 08, 2013 8:43 am ]
Post subject: 
Here's a pic of my exhaust bung...Do you think the single wire sensor may work out alright? I know it's only theory until tested :lol:

Image

Quote:
After all that hot air above, you will grow accustom to how your gage reads while going down the road, and will be able to see how A/F mixture affects drivability, exhaust pipe color and odor.
I noticed after the hei conversion that the chrome tailpipe has browned a little bit. Which i think would indicate a rich condition but the plugs are white (lean). I'm running this without a cat so the exhaust coming out isn't as clean i guess...

I may have lost a little on MPG too which doesn't make since to me with a hotter ignition. I read some of the http://www.bob2000.com/carb.htm article and it says
Quote:
You always want to go a bit rich, as excessively lean mixtures will cause damage to your engine, create pollution, and give you bad gas mileage and performance.


So i'm going to richen the circuit and drive it a little today...right now after richening it a 1/4 turn i will be about 1 1/2 turns out.

Before the conversion i felt like i had it pretty close, the plugs were a light tanish brown color. It looks like all of the cylinders are burning pretty evenly, they all seem to have a similar plug color...

emsvitil

I'll read thru that post...thanks
Author:  DusterIdiot [ Tue Oct 08, 2013 9:11 am ]
Post subject:  Sensor position
The position in the pipe is OK but should be closer to the flange (I install mine about 2-3" down for clearance). Being that far away from the immediate vicinity of the outlet can allow the sensor to cool down and not give a positive reading (the meter will fall of as "lean" because it is not getting any signal).

FYI.

After reading this, I run mine with the LED meter and the one wire sensor (and wait until it's up to operating temp to make sure I am getting a good reading). If your vehicle runs and drives the carburation is "close", carbs rarely run at stoich since they rely on the delayed vacuum signal from the engine via the manifold to change it's state. Typically carbs are set a little rich so that way it's ready to anticipate the up and coming load and can rely less upon a large acc. pump shot to fill the hole (and wash down the cylinders by dumping a bucket of gas in the manifold), and/or being in the power valve/circuit all the time due to load (you got a truck so this is important as well). I don't use the wide band sensor as 1) it's expensive, and 2) if it tanks on our crappy pump gas we get locally I'm out a lot of money for not much feed back.

It is also important to note that the O2 sensor is not 100% reliable when tuning this way, you will do a fair amount of physical plug reading to determine if 1 notch rich is really rich or if your engine says "that's just right", or if "stoich" is correct or if your plugs are burning too clean/actually lean...


FYI.

-D.Idiot
Author:  wjajr [ Tue Oct 08, 2013 1:42 pm ]
Post subject: 
You can smell "too rich" it stinks, it makes your clothes stink, garage stink, and stuff in trunk stink, and also deposits dusty black soot coating in exhaust pipe, and sometimes on rear bumper. When too rich soot will deposit around base of plugs where threads end in combustion chamber, and turn porcelain dark brown to black.

Too lean will deposit small flakes of melted metal on bright white porcelain of plugs and melt electrode. Proper mixture will take a lot of miles to tan up plugs.

Lean idle at no load will not hurt engine, running lean pulling trailer or loaded, or at high rpm will destroy engine.

Idle circuit is different than running off main jets and power valve enrichment if a Holley.


Plug reading made simple.
Author:  pishta [ Thu Oct 10, 2013 11:57 am ]
Post subject: 
Widebands have come down to 29 bucks but you need a controller to run them. The controller is over 100 bucks, but there are plans available to diy it if your handy with a soldering iron and a breadboard. They are very good at telling you exactly what is going on. THey usually have 5 to 7 leads.
Author:  SlantSteve [ Thu Oct 10, 2013 6:25 pm ]
Post subject: 
Here is a company that does DIY kits.....I have never dealt with them but I believe they have a good reputation. Not exactly low buck but lots of features
http://wbo2.com/2y/default.htm
Cheers guys
Author:  kxracer728 [ Fri Oct 11, 2013 8:47 am ]
Post subject: 
Here's a wideband kit on ebay for $109.99 looks like it has everything you need to set it up!

http://www.ebay.com/itm/BPSX-D1-Digital ... 88&vxp=mtr

I'm sure i'll start out with the narrowband for now and consider a wideband later on...according too wjajr, DusterIdiot, narrowband isn't a bad bang for the buck and will give you a general idea of AFR after you calibrate it to actual plug color

But it sounds like if you can setup a descent wideband for under $120 it's a good deal!
Author:  pishta [ Fri Oct 11, 2013 1:07 pm ]
Post subject: 
Dang, thats almost cheaper than you can source the parts for. And includes the LSU4.2??? Go for it! Notice the warranty doesnt cover the sensor, kits like this-you run the sensor until you dial it in, then you unplug the sensor to save it. Pig rich damages it as well as silicon gasket makers and leaded fuel.but thats still a smokin deal.
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