recommendation for wideband meter for carbs

[user-23911]

Fifty inches is along way from the heat source, unless the senor is heated.

But they're ALL heated.

They don't work when cold.


The downside of the NB is that when it gets too hot it reads lean. So long as you know that then it's not a problem.
When the WB sensor gets too hot it won't work right either.
They can easily be heated but it's a lot harder to cool them under full load.

[Tuner]

Fifty inches is along way from the heat source, unless the senor is heated.

But they're ALL heated.

They don't work when cold.


The downside of the NB is that when it gets too hot it reads lean. So long as you know that then it's not a problem.
When the WB sensor gets too hot it won't work right either.
They can easily be heated but it's a lot harder to cool them under full load.

Joe, I hesitate to say this, but you are mixed up again, in fact you got it exactly backwards. When they are hotter NB sensors output higher voltage. In other words, they read richer the hotter they are. Within the more or less normal range of EGT, the same actual A/F can have sufficiently different voltage output to be interpreted anywhere between 10/1 and 14/1, depending on sensor temperature.

Click this link and scroll down https://www.innovatemotorsports.com/resources/news3.php to read How Wideband Sensors Work (and why Narrowband meters don't work for measuring AFR)

[F-BIRD'88]

Look at that graph again. The hotter the NB sensor is the lower the output voltage is when in the richer than stoic zone.
You got it backwards... The NB sensor will not tell you the AFR at WOT. But it will tell you if/when the AFR is just too &^%^ lean at WOT. It is great for cruise part throttle tuning.
And a useful warning indicator for WOT tuning.
if at WOT it shows LESS than say .8 volts Like .75 V it may be too lean...look at the your plugs. ALL of them.
if when you dyno/track tune jets and you start plenty rich at WOT and progress towards leaner jetting while noting engine power output it will warn you when its just too lean..it does not tell you the AFR.

Assuming you don't have excessive exhaust temp it will show about .8 to .85V at WOT when the WOT jetting is about right
and ex temps are "normal range".. If you have one and use it you will know what is "normal" and will clearly see if things have CHANGED. Tune with a Wide band, once tuned, monitor with a (lower cost more reliable) NB.

[Tuner]

Look at that graph again. The hotter the NB sensor is the lower the output voltage is when in the richer than stoic zone.
You got it backwards...

You're right, I got so wrapped up in telling Joe he was backassward about temp vs. A/F that I went that way myself trying to make the point that with NB senors varying temperature introduces an unacceptable error. The embarrassing thing is I think I made this same 180 degree error (pun intended) in one of these WBO2 threads a few years ago.

The point is, the difference between NB and WB O2 sensors is like that of a windsock and an anemometer.

The green line in the graph is at about 880 mV. Because the offset of the curve changes with EGT, at 900C the 880mV output would mean about 10.3 AFR. At 500C the same voltage means 14.1 AFR. So without knowing precisely the sensor head temperature, there is no way of relating the output voltage to a specific AFR. An output voltage above 450 mV just means richer than 14.7, below means leaner. The numbers on a NBO2 meter are just paint. The only correct one is 14.7.

[user-23911]

Joe, I hesitate to say this, but you are mixed up again, in fact you got it exactly backwards.

I think you need to do more tuning and use a few more instruments at the same time.

So you can compare them side to side.


BTW a good working Bosch 4 wire NB sensor will output about 930 mV at max rich with just the heater making it hot.
Typically a cheap universal equivalent will only output about 860 mV. Don't waste your money on one.
As they get older and worn out / contaminated the max voltage (full rich) decreases to the point where they're no longer usable.

Now convert that to the workings of a WB and think on it for a while.


The above chart from innovative is good but it doesn't name the brand of sensor nor mention the above.........well they won't even know. All they're concerned about is selling more widgets.

[F-BIRD'88]

Typically a cheap universal equivalent will only output about 860 mV. This is pretty much true. I find mine does not give more than a .86 .88 v reading at WOT no matter how much I increase the carb jetting.
BUT... It clearly shows a voltage reduction as you do drop the jetting progressively from rich towards leaner and indicates very clearly if when you are getting carried away with leaner jets in search of performance. You don;t know the AFR but you do know to look at your plugs, then.
Its a good (you're gettin too friggin lean) warning device.

[user-23911]

You need to get rid of it, go find a Bosch 4 wire out of an old BMW, use that instead.
They're far better. So long as they work which is easy to confirm with a bench test.

[F-BIRD'88]

Again your misunderstand the practical use VS the theories.
There is nothing wrong with the sensor and Bosh will not tell you what you really need to know when using a NB as a tuning aid and better than mine.
What you need to know is if/when you are getting too lean
as you tune progressively from plenty rich towards leaner.
When at part throttle and idle it can be forced to a higher volt output .9+ by adjusting the carb richer.

the exhaust is cooler. When you under stand what it actually does it becomes a useful tool for tuning. It does not tell you the AFR.

[F-BIRD'88]

In its real OEM use it does not tell the EFI computer what the afr is either. It just tells the Computer the voltage is now more or now less than the crossover switch point Usually .450 v.
Richer than and leaner than. The efi computer trims the fuel +/- on the fly, quickly based on this to maintain a stoic afr. at cruise. 14.7: ish.

[Circlotron]

If you have a WB installed it might be useful to put a NB in right beside it. Have the NB wired to a simple red/green LED indicator so you know when you are (momentarily at least) at 14.7:1, the NB's only accurate point. The WB should read the same at that point. Whether there is some way to calibrate the WB to read 14.7 at an actual 14.7 I don't know.

[F-BIRD'88]

Thats why I like the NGK Powerdex afr gauge. It has a simple free air calibration. easy to do. Less likely to bs you.
Yes the nb is a good backupand for monitoring.
It will tell you if when things have changed and save your wb from ex deposit degrading etc over time.

[David Redszus]

The only output from any Nernst Cell, which is the actual working part of the Lambda sensor, is milivolts .
The milivolt output increases with temperature and will range from about 10mV (lean) to 1000mV (rich).

The output mV output slope in the rich range has a more pronounced curvature than the lean range, particularly near the stoich point. At the switching point from rich to lean, the mV output falls dramatically.

The stoich value of 14.7 is a myth and is completely arbitrary and dependent on the fuel type and engine. Lambda sensors are tuned using a synthetic exhaust gas in a test engine.

While every lambda Nernst cell will produce nearly identical values, that mV output is modified by the controller to
other engineering units using a look-up table.

A wide band sensor uses a pumping cell that pumps air into the Nernst cell to keep it at a selected value. It then computes the current necessary and outputs that as a mixture value. The output being in the range of about 1 to 5v is much more compatible with computers than is a low voltage output of 750mV.

[user-23911]

The only output from any Nernst Cell, which is the actual working part of the Lambda sensor, is milivolts .
The milivolt output increases with temperature and will range from about 10mV (lean) to 1000mV (rich).

The output mV output slope in the rich range has a more pronounced curvature than the lean range, particularly near the stoich point. At the switching point from rich to lean, the mV output falls dramatically.

The stoich value of 14.7 is a myth and is completely arbitrary and dependent on the fuel type and engine. Lambda sensors are tuned using a synthetic exhaust gas in a test engine.

While every lambda Nernst cell will produce nearly identical values, that mV output is modified by the controller to
other engineering units using a look-up table.

A wide band sensor uses a pumping cell that pumps air into the Nernst cell to keep it at a selected value. It then computes the current necessary and outputs that as a mixture value. The output being in the range of about 1 to 5v is much more compatible with computers than is a low voltage output of 750mV.

You're a bit mixed up there too.

A "Nearnst cell" when it's working as a nearnst cell only outputs a max of about 300mV, that's when it's at the lean side of lambda 1....that's by definition.
https://en.wikipedia.org/wiki/Nernst_equation

It's the half cell reaction in electrochemistry.

When it's at the rich side of lambda 1 (explained in the link from "Innovative")the excess fuel turns it into a fuel cell (full cell reaction).
That's why there's a sudden jump in voltage. You're either going to have a zero to 300 mV lean or a 700 to 830 mV rich with no in between.