Narrow and Broad band O2 sensors and open vs close Options

[lmcchesney]

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

[airsix]

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.