TRex

iTrader: (3)

Found this while surfing the other day, from this site:

http://www.dynotunenitrous.com/store...p?idproduct=15

Thought it was an interesting chart of how to use a NB for a WB

NB Voltage READING FULL THROTTLE AIR/FUEL RATIO
.000 17.0:1
.100 17.0:1
.200 16.0:1
.300 15.5:1
.400 15.0:1
.500 14.7.0:1
.600 Dangerously Lean 14.6:1
.700 Getting lean 14.5:1
.800 Max power(Lean) normally aspirated 14.2:1
.875 Max Power normally aspirated 13.5:1
.900 Max Power (Rich) (NOS,blower,Turbo) 13.2:1
1.000 Very Rich 12.5:1

Enjoy !


Mod Edit for those that don't want to read the entire post... It is strongly adviced you do not follow the above readings ... Everyone's O2s read differently depending on how lazy they are and manufacturer...

As mentioned by Brains below:

Bombguy99z28

That doesn't really seem right, in my experience 930-940 usually shows up as 12.1-12.4 on a wideband, 880-890 around 12.7-12.9. What I saw from logging dyno runs with wideband in my cutout (no cats). But hey, I hear narrowbands suck for a reason..

TRex

iTrader: (3)

Yeah, I can't vouch for the quality of the data, just sharing. I'm going to try and plot a curve for my NB's using my LM1 in the next few days. I will probably share for educational purposes.

Bombguy99z28

Cool. I would be interested in how the curve turns out. I know narrowbands are 'innacurate', but I'm wondering about accuracy versus precision...

If each narrowband is innacurrate (will read different from other narrowbands) but precise (will give you the same number over and over at the same AF/R noted on the wideband), then once you know what your specific narrowband reads then you can actually use that data with some level of confidence, still with a grain of salt, of course.

YellowToy/A

iTrader: (1)

Do not use NB for anything other 14.7. May work may not. Bad if not

Bink

Dangerous internet myth - which has been proven repeatedly.
Do some searching.

Bombguy99z28

Ya think? We're just debating the accuracy and precision. I think everyone knows that narrowbands suck.

TAQuickness

iTrader: (28)

i'd have to agree - if the NB output is consitant to the WB reading, you should be able to use them.

Still have to have a WB to do this though

Brains

iTrader: (7)

If you tune by that chart, be prepared to buy a new motor.

Put as simply as possible, it is IMPOSSIBLE to tune by your narrow band sensors for an air fuel ratio other than stoichiometric. Attempting to do so is like trying to shoot an apple off your wife's head with a flamethrower -- you might eventually get the apple, but you're gonna wreck things you care about in the process.

Take a look at the following images. One depicts the voltage to AFR chart posted at the top of this thread. The other posts the TRUE AFR to voltage curve of a typical narrow band O2 sensor at various exhaust gas temperatures. You'll note the two don't match, and you'll also note that NBO2 sensors don't give you a good indication of AFR anywhere other than stoich (hence their name, NARROW band).

TAQuickness

iTrader: (28)

very well put. you gotta knack with words

TRex

iTrader: (3)

Interesting chart, although it brings up an interesting question.

I am familiar with EGT measurement in turbodiesels, and would assume that EGT varies similarly in a turbo gas engine, but does EGT vary that much in a NA engine ?

Also, I notice that the offset of the voltage based on EGT seems linear. If one were to do a correlation test between WB output and NB output, for a particular engine, wouldn't you expect the correlation to be fairly accurate ? If not, why not ?

Finally, can you please provide sources for the charts ?

Brains

iTrader: (7)

The first chart is what you posted in the first post of this thread -- I simply entered the numbers into Excel and graphed it to show how inaccurate it is, when compared to a real curve from a NB o2 sensor. The other chart I posted was found via a Google search. Feel free to do your own research if you feel you're on to something, but this has been hashed out MANY times in the past several years

If you're going to go through the headache of either building or buying a thermocouple compensator and measuring device, why not just do it right in the first place and get a wideband kit? I shake my head every time this topic comes up, because people come up with all these hair brained ideas on how to get around not having to buy a wideband -- but many of the "solutions" put the cost right up there with the cost of a wideband Take your idea of trying to compensate a NB in the very narrow voltage range outside of stoich. First off, you'd need to accurately measure sensor temperature. Second, you'd need to be able to accurately measure voltage. Third you have the problem of sensor age, because over time those brand new sensor specs WILL change. Fourth, you have no basis for comparison to begin with to even know if what you're doing is anywhere close to accurate. Ultimately you've spent days, an untold amount of money, and you STILL have no idea if you're reading your true AFR.

TRex

iTrader: (3)

Wow, for all the smilies I sense a little hostility.

BTW, I have a LM1 wideband. I was just sharing some information, like that is a bad thing

It is well known and generally accepted that NB are not as accurate as WB's, can't do compensation, yada yada.

However, some of us are old enough to remember how we used to do it before we had all this computer crap. Plug cuts and et slips. You started rich and went leaner until it slowed down.

Widebands allow you to do it faster and more accurately, yes. And with the LC1 as low as $169 from some sponsors, I personally see no reason for someone not to have one.

However, I understand that some people may not have one, and with some decent information they may still be able to use their NB to improve their fueling. Certainly isn't something that should be considered if you building an expensive blown motor, but on a relatively stock motor a person might be able to use this information to get a little closer to optimum.

Also, I enjoy participating in this forum, sharing information (and referencing the source), and understanding the technical details behind our tools and toys.

I would thoroughly enjoy reading a more detailed analysis of NB inaccuracies, correlation studies, etc. I am sure there are many SAE papers on this subject, however I don't work in the industry, don't really have time to google everything and read all the references it returns, and thought posting it here might provoke some interesting discussion and comment by people with better hard data confirming or disproving the information.

Now, back to the technical discussion of "hair brained" ideas, Mr. 80 IQ score

jimmyblue

iTrader: (11)

I've gone through the exercise of correlating NB to WB
and even same-car, same-session, there is a fair bit
of data fog. Car to car, different exhaust plumbing,
fuggedaboudit.

Here's one logging session's worth of NB:WB correlation.
Notice the futility of trying to pin a particular WOT AFR
on an arbitrary voltage at richer mixtures:

TRex

iTrader: (3)

NICE ! Now that is what I am talking about ! Good job Jimmyblue, this is the kind of stuff I like to see !

Can you post the excel data file as a zip ? I would be interested in the data analysis in the 12.0-14.0 range - would like to understand just how inaccurate the NB's are, if for no other reason than to actually explain to people with facts just how inaccurate they are.

BTW, I will do my own study next week and post results - just for educational purposes

jimmyblue

iTrader: (11)

One thing I don't like about that data is, the poor
correlation-in-time between NB and WB data. I
think the LM-1 smoothing function is probably a
good part of this, it's well slower than the NB
sensor because of it. Not an issue at WOT so
much but the closed loop just does not match
all that well to the real-time bouncing-around.

The Excel file zipped runs to about 250KB and
can't be uploaded. You can PM me an email
address if you want me to send it.

Brains

iTrader: (7)

Do a few searches on this very forum, and you'll find where it was discussed several times in the past. Each time its bit more frustrating the issue is still pressed and attempted to be "proven" you somehow can use a NBO2 sensor outside of its designed response range. What's worse is if a post is made and someone follows some incorrect info, and causes damage to their vehicle.

But hey, you might just uncover something, you never know

Ragtop 99

iTrader: (7)

I'm not going to tune WOT with NB's, but can we use the NB to help us tweak the A/F during warm up? I had to cut the OFLA to get the car not to be so rich on start up and I'm wondering if the NB can be used to help tweak the OFLA table? Once winter gets here, it takes a bit to hit 33*c and go into closed loop.

Steve Bryant

iTrader: (1)

The only thing that you can tell from a NBO2 sensor is where 14.7:1 AFR occurs as you go through it from lean to rich or vica-versa. I do see how you could tune to get the VE table about right for times when you do not need any fuel enrichment with a lot of trial and error. However, I see no suitable way of tuning for conditions where you need to be running in an enriched condition (say 12.7 to 13.0 AFR) using a NBO2. If you are going to be using tuning software/hardware, bite the bullet and buy a wideband. At today's gas prices, you'll go through more money in fuel trying to get things right (which you can't without a WBO2) than you would spend on a basic wideband.

Steve

Bink

Everyone here should heed Brains' warning.

I don't understand why anyone would argue the science and facts of the matter- after repeated warnings.
There are some of us who can remember members taking the advice of "others" and blowing their motors - while carefully monitoring their NB output.

The NB sensor is basically a switch. Here's some good, non-biased. generic info -> http://www.autoshop101.com/

Go to tech article -> #37 Sensors#6 - Oxygen / Air Fuel Sensors w/ques.pdf file size 328KB