Sorry guys, but I've been doing some reading again. Dave, you and I have had some of this discussion before and I would respect your continued thoughts on this setup. The crux of the matter requires understanding of the circuit utilized to turn the lamba analog data into useful information. Well, here goes.
O2 sensors in a distal position provides indirect input for the estimation of the A/F ratio seen by the engine. This information is useful in defining a lean or rich mixture seen by the sensor for the most recent peroid of time. Broad band O2 sensors are capable of producing a wide range of output voltages which can be inturpeted for measuring the ratio. In fact, the output from broad band sensors can be feed into the Electronic Control Unit several times a second. This allows for real time adjustment of the A/F mixture. Thus output from the O2 sensor is recieved as input by the ECU which inturn alters injector time/volume to preprogramed mixture. This feedback/adjustment defines a closed loop system.
Narrow band O2 sensors also read A/F ratios. However, A/F mixtures ranging from 13.7:1 to 14.4:1 results in a change in voltage output from lowest to highest (0.1v to 1.0v).
If you use a analog voltmeter or equalivernt A/F gague, the response rates are such that your readings bounce requiring seat of the pants estimate as to where the mean is.
However, with the use of circuitry involving a IC unit, the voltage output can be lengthed to a series of LED's.
My question, can not a narrow band O2 sensor be utilized to monitor A/F ratios throughout the power band. Noting the results, provide information for enrichment/leaning in the adjustable ranges of D-jet. ie, idle, partial throttle and WOT.
Cannot in dash monitoring with such an A/F circuit be helpful to identify serious alterations in the engine and prevent damage from excessively lean running?
Cannot the useful information from such an A/F monitor be inproved by silmiltaneous monitoring of CHT/oil temp?
I still do not understand the advantages of a broad band O2 sensor when used in a open loop system.
I cannot also see the significant advantage of a heated O2 sensor for monitoring the A/F ratios during that first 3 minutes.
Thanks,
L. McChesney

First off, heated sensors aren't just useful during the first few minutes of operation. In order to be able to "read" all of the cylinders on most engines, the sensor has to be far enough away from the exhaust ports that it typically won't get hot enough (or stay hot enough) to read properly. Exhaust gas temp also changes pretty significantly based on load. One thing your included graph doesn't show is the response curve v. temperature. It changes quite a bit as the sensor temp changes. A heated sensor will maintain something close to the correct temp all the time. One of the aspects of the more complicated circuitry used to drive the wide-band sensor is temperature control, which has to be kept correct to a much higher degree of accuracy for the results to be at all meaningful. The narrowband sensor is less touchy, since it's response curve so non-linear.

13.7:1 and 14.4:1 probably isn't correct. Stoich is 14.7:1, and the sensors are biased around that figure. It's probably more like 14:1 to 15:1. Engines reliably operate over a range of about 11:1 to 17:1. For best power, you usually want a mixture in the 12:1 range. For best economy, you want it to be close to 16:1. Some specially designed "lean-burn" engines are designed to run at mixtures of 17:1-20:1, so they require a wide-band sensor capable of operating that lean. A narrowband sensor obviously won't operate out there, so the engine is restricted to running in a tight mixture range around stoich, which is the best compromise for emissions. It's quite common for ECUs (at least for pre-LEV cars) to go "open-loop" at or near full-throttle, to provide best power with a rich mixture that's beyond the range of the sensor. Running at 14:7:1 at full throttle is likely to cause lean engine failure over a long enough time, esp. for an aircooled engine.

You can certainly use a narrowband sensor to tell you when something has gone wrong and your mixture has gone very lean or very rich. It's just not useful as a tuning aid if you're deliberately trying to make the car run at 12:1 or 17:1.

L

Several things to consider: 1)What is your target A/F ratio? 2) What is the value of an 02 sensor? 3) How can you use the information? 2) Which type of sensor provides the information you need?

1) The A/F ratio changes with load and RPM. Mine is targeted between 12.5 and 13.7 because that is the range that provides proer cooling and reasonable performance. It is a fact of life with aircooled engines that they must run rich or they burn up.

2)The value of an O2 sensor is that it is a tuning device whether you manually adjust the fueling or the ECU does it. Along with temperature (especially exhaust gas temperature) it gives you insight into how efficiently the engine is running.

3) You can use the voltage from the O2 sensor to adjust the airfuel mix: 1) by viewing the data and manually changing the injector opening times (hard to do on the street as load changes plus you gotta drive) 2) by datalogging and changing the points that are outside of the target later 3) by letting the ECU do it closed loop (fueling table must already be close)

4) Wide band is the only option because the target A/F are not anywhere near the range a narrowband covers. Sorry about that but it is afact of life for aircooled engines. You tune blind with a narrow band.

Dave

Ok, I'm going to make my comments quick because I'm going to go drive my 914 (seriously). I am running atermarket programable engine management (fuel/ignition). I got a cool little LCD with a built-in 0-1v analog volt-meter that I mounted in the dash (It's only about 1.5"x.75"). I hooked this up the the highest quality narrow-band Bosch lambda sensor I could get. The sensor was rummored to hit .8-1 volt at a mixture of close to 12.0:1. In theory I should have been able to tune the EFI for 13.5:1 at part-load by getting the needle on the guage about 3/4 of the way across. Tuning WOT so the needle was just tickling the far edge should have gotten me a nice 12.5-12.0:1 mixture.

Well, I tuned the EFI accordingly and the car never seemed to run like I felt it should. So I bit the bullet. This week I got my LM-1 wideband O2 kit in the mail. The expense was a hard pill to swallow - it cost almost as much as the PEFI conversion ($400) but it payed for it's self the moment I plugged it in and turned it on. At part load I was running between 14-15:1 (way too lean) and at WOT I was running between 9-10:1 (way too rich).

I've run the two sensors together (narrow and wide), and the narrow really is useless. It is unresponsive compared to the wideband, and inconsistent depending on temp. The wideband is instantanious and the readings are repeatable. It seems to be quite resistant to temp-influenced reading errors.

I'm so dissapointed with the narrow-band sensor and dash display that I probably disconnect it.

-Ben M.

ps - after only 1/2 hour of driving around with the laptop and the LM-1 the car was litterally transformed. No LM-1 buyers remorse here.

One way to recognize the limitations of the narrow band is to look at the graph....

The graph shows that the narrow band is basically designed to read one a/f setting... hence the very step curve at 14.7

narrow band is a yes/no type system

wide band tells the degree of richness of leanness....not "its rich, or its lean"

Some modern vehicles use a combination of wb and nb sensors....

wb before the cat, nb after the cat as a check.

My Mountaineer had 4 02 sensors.. a wb before each cat, and a narrow band after each cat...

Some, not all of the aftermarket WB gauges have a simulated narrow band output, so that the wb output is conditioned to be used as a narrow band sensor... in order to control the ECU...

I have an FJO wide band sensor... it uses NTK LH1 sensor... the sensor costs about $180... and lasts about 20000 miles in leaded fuel

I just finished a build and calibrated a Tech Edge wide band to replace the beat to crap FJO... and Im quite happy with the results...the Tech Edge uses a 7057 Bosch sensor (about $30) and the accuracy is equal to that of the FJO unit..

The megasquirt people are working on a "wide band controller" which is even more accurate than a wide band a/f gauge...

So Ben you bought one of these??

Yep. That's the one. I just got the rpm-converter working tonight (first one was bad - they Fedexed me a new one). Here is a partial shot of the log viewer. Don't judge my tuning yet - I just got this thing hooked up. It's great. You can see that I'm a little lean below 3,500rpm, a little rich from 4,400-4,700, and just a hair lean from 5k and up (It was WAY rich the first go-around and I overcorected a hair). I'll fix that in the morning. You can also see that I'm going rich on over-run between shifts and need a little more acceleration enrichment (notice the little spikes where the rpm's are at the lowest - that's where I mashed the throttle after a shift. Those spikes were huge 10 minutes earlier). This graph shows a first and second gear run (going up a hill). You don't get to see the rest of the graph because someone would do the math and give me a lecture.

I highly recommend the aux-in cable for logging rpm (throttle possition would be nice too - I might try to hook that up). Trying to drive and make mental notes of mixture at give rpm just wasn't very effective. And things like acceleration enrichment happen so quickly you can't see it all happening in real-time. Dump it to the computer though, and it's all right there for your chin-rubbing pleasure. I love this thing!

-Ben M.

Here's another shot with the Y-axis set to AFR instead of RPM. (X-axis is time in seconds. Stop laughing. I was climbing a grade. It's easier to tune going up a hill because things happen more slowly)

-Ben M.

I was thinking of getting one of those. So you think its a good enough tool, huh. Pretty cheap at $300

Thanks all,
Dave H., you are exactly right. I appreciate your experience with use on the megasquirt.
My purpose is in a open loop system, or the output of the sensor does not feed directly into the ECU.
I want to fine tune the MPS/CHT of the D-jet to prevent lean burn of the engine and to optimize the effiency.
lapuwali, if our desired range is 12.1 to 15.3 then the NBO2 sensor Bosch 11027 with circuit will cover that range.
LED Voltage Range Lambda Air/Fuel Ratio Output Torque Observations

>945mV <0.80 <12 <98% Too rich, power loss
900-945 mV ~0.85 ~12.5 100% Maximum power
855-900 mV ~0.90 ~13.2 99% Good operation
810-855 mV ~0.93 13.8 98% Good operation
540-810 mV ~0.97 14.3 98% Good operation
225-540 mV ~0.98 14.4 97% Good operation
180-225 mV ~1.0 14.7 97% Good operation
135-180 mV ~1.02 ~15 96% Good operation
90-135 mV ~1.04 ~15.3 95% Maximum economy
45-90 mV 1.05-1.25 15.4-18 74-94% Pretty lean
All out <45 mV >1.25 >18 ? Too lean, misfires

Temp variation can be stabilized with a heated NBO2 sensor, correct?
I believe WBO2 sensors have been used in several late model cars, NK etc., so they must be in the salvage yards with their bungs as well. Is there not a circuit we can make which will provide our needs with a WBO2 sensor for in dash monitoring?
Tim T, I looked at the Tech Edge.com site and it will take longer to review all of the products, and circuit. However, with purchase of the o2 sensor in US the cost for monitor, readout and sensor in a DIY kit is $235 plus shipping and building time.
If you do go with a WBO2 sensor, which has a some what linear mv:A/F ratio, how hard would it be to design/build a readout? I have a A/F meter made by Sunpro from my _LAPS ( complient with new forum standard of deciency) but cannot find the web site to understand its compoents and capabilities.
Does anyone know what model cars would have a useable WBO2 sensor that we can salvage from a yard to make a circuit? I believe that there is enough intrest in our group and knoweldge that it could make a reasonable project and PP tech article.
I also remember a PP tech article on building a A/F monitor with LED display, but for the life of me, cannot find it again.
Thanks,
L. McChesney

Heating the NBO2 won't get the temperature stable enough to make the readings useable. You will have to bite the bullet and pick up one of the setups pictured earlier.

See my response on the Bird board for more of my opinion on the subject.

--DD

the Daves are right. This was my experience. The NBO2 I talked about above was a heated one. Reputed by others (auto-groups like this) to be the best NBO2. Bosch, sorry - don't have the Bosch #, but it's a Napa part # OS204 for 86 Ford Escort.

Anyway, my finding is that the NBO2 are too influenced by temp, and too slow to react for useful tuning. In 20 minutes with the wideband I was able to do more for my car than I did in a YEAR with the NBO2.

-Ben M.

ps - This morning I made some tweaks based on the data I logged last night. WOT mixture now stays between 12.2-12.5:1 and the car is running great (autocrossed today). I'm going to fire off an email to the guys at Inovate Motorsports to thank them for making a reasonably priced WBO2 that works so well.

All I want to know is the computer interface user friendly? has lots of options?
decent data memory ?

Geoff

The computer interface is a piece of cake. You plug in the LM-1 to the pc serial port, start the LM-1 manager, select the log screen (from among 4 or 5 tabs), select "Load", select "from LM-1" (or you can open a previous log you've saved). Then click "view" or "save". "View" gives you a nice graph with time in seconds on the X-axis, and mixture or rpm on the Y-axis. You can slide a marker along the graph to read the exact values at any point on the graph. You can save the data to disk as a "Microsoft Excel Data Interchange Format" 'DIF' file. The file opens just fine in Excel with a nice easy to read table.

As far as logging goes, you can log multiple sessions on the LM-1. You just hit the "Record" button to start and hit it again to stop. Each time you turn on the LM-1 it displays the percentage of log memory currently in use so you always have a rough idea of how much more data you can collect before it's time to head back to the pc. You use the LM-1 Manager software on the pc to clear the memory. When you upload the data to the pc the LM-1 sends all the sessions in memory. From the LM-1 Manager you can then choose which session to view from a pull-down menu. It's pretty nice.

The only trouble I had was with the RPM-converter/Aux-in cable. It will accept an inductive input from an ingnition cable (like you use on a timing light) or a tach-input signal from an ECU. My ECU has a tach signal input so I tried that first - no joy. Next I tried the inductive input using the inductive pickup from my timing light - no joy. I emailed Inovate Motorsports tech support and detailed all the tests I'd run to try to get it working (I tried everything I could think of). They asked a couple of questions and then almost imediately FedEx-ed me a new RPM-converter/Aux-in cable. The new cable works great. $100 for the rpm converter seems kind of steep, but it is REALLY helpful and I'm glad I bought it. Without it the log graph would just be a mixture log with no reference. If there was a trouble spot on the graph, without the RPM log you'd have no idea what was going on when it happened. The Aux-in cable will take four inputs in addition to RPM, so I plan to set it up to record throttle possition in addition to RPM and mixture.

-Ben M.

Same thing im using.

Amazing tool.

LM-1 rocks


Andrew

Appreciate it all.

David Hunt, do you use a WBO2sensor with the MegaSquirt system? I could not find one identified at the Bowling/Grippo site. What do you think would be a requirment? Since my 96x78 D-jet combo may require conversion to an after market, it would be best to use an WBO2 system compatable with the MegaSquirt.
Dave, how much temp flucuation occurs if the O2 sensor is placed distally where it can monitor all cylinders and proper mixing. I was thinking of placing the bung following the 4 to 1 in my sebring system. I can see temp changes at the header level, but what about the just before the muffler site?
What other WBO2 sensors would be usable? Really, the WBO2 produces a wider range of mV for a wider range of A/F values. Since I am not looking to produce a closed loop system, I'm not married to a specific FI system. If you go the salvage route, cannot you take the system working the WBO2 as well?
Thanks,
L. McChesney

I've been running it but it has been a pain. I used the DIY-WB and the board has been difficult. It was an absolute necessity for tuning but is just WOW now that everthing is tuned. I'm trying to hold out for the wideband portion of the Ultramegasquirt project. It seems this will be a very good product but, it may be a while before it is out.

Dave