Installing second O2 sensor (wideband)

[Solamar]

I just ordered an Innovate LM-2 handheld air/fuel data logger



I am not running a cat so planned to use the tail pipe 02 adapter. But, after further research the tailpipe adapter isn't the most accurate, especially at idle. The recommendation is to install the wideband O2 in the cat bypass -



Plenty of room for it, but I have two questions -

1) Does location matter?

2) It will be for rare/occasional use. Will the wideband O2 sensor get damaged riding in the exhaust stream unused (un-powered)?

Appreciate any insight!

[brighton911]

From the Innovate web page: it should be located at least 24" from the exhaust ports, ideally in an upright position and on a one inch bung to keep the wideband sensor out of the direct exhaust stream. A worthwhile addition for sure.

Important Tips to Get the Maximum Life Out of your O2 Sensor - Innovate Blog

[Techno Duck]

Take the test pipe off and have another bung welded on. If your only using it for diagnostic / tuning, i would remove the sensor and put a plug in.



BTW, did you happen to see a group of old cars up around i think Del Mar or Carlsbad a few weeks ago? I think we may have rode along side for a few miles.

[Koizumi]

Hey what engine? I’m about to go down this path with a motronic 3.2 and cat bypass

[AndrewCologne]

1) Does location matter?

The wideband sensor comes with an internal heater, so its not that important like in case of a non heatet narrowband sensor. Just weld the bung as Techno Duck suggested and showed in the pic above..

[911obgyn]

I use that wide and sensor to adjust CO values on my over2k motor and adjust idle air CO. I removed and disconnected O2 sensor,installed innovate,adjusted O2 and now it is more driveable.

[AndrewCologne]

How do you know what AFR corresponds to a specific CO?

If you refer to those charts in the www where an AFR of 14.7:1 or Lambda 1.00 matches 0.0% CO then ... your on the wrong path.

[Solamar]

Originally Posted by Techno Duck

Take the test pipe off and have another bung welded on. If your only using it for diagnostic / tuning, i would remove the sensor and put a plug in.

Perfect, thats what I'll do.

I downloaded the LM-2 instructions and on the first page -

"When installed in the exhaust, the oxygen sensor MUST be connected
and operating with the LM-2 whenever the car is running. An unpowered oxygen sensor will be quickly damaged when exposed to hot exhaust gases. "

That answers my second question.

Originally Posted by Techno Duck

BTW, did you happen to see a group of old cars up around i think Del Mar or Carlsbad a few weeks ago? I think we may have rode along side for a few miles.

That was probably me My wife and I both grew up in Del Mar and still enjoy cruising up the coast (just as we did back in the 80's in my VW Bug ).

Planning to stop by RSF in the morning for some 'Socially Distant' C&C

[Solamar]

Originally Posted by Koizumi

Hey what engine? I’m about to go down this path with a motronic 3.2 and cat bypass

Same. 3.2 Motronic w/bypass.

I know the PO messed with the spring tension on my AFM and suspect I am running exceptionally lean. Need to get it figured out...

[Solamar]

Originally Posted by AndrewCologne

How do you know what AFR corresponds to a specific CO?

If you refer to those charts in the www where an AFR of 14.7:1 or Lambda 1.00 matches 0.0% CO then ... your on the wrong path.

I'm learning as fast as possible about the subject, but my understanding is Lambda, AFR and CO% are simply different metrics used to evaluate level of complete combustion. I think Lambda is the most intuitive as it's the same across all fuels. Tuners seem to prefer discussing AFR.

My plan is to pick one (AFR) and stick with it for tuning.

Per reputable sources I'm shooting for -
13.8-14.1 Idle (find smoothest idle in that range)
14.7 Cruise
12.6-13.2 WOT 3k to 6k rpm

I've read differing opinions about disconnecting the Motronic O2 sensor for each of the above settings. Idle AFR will definitely be set with the O2 disconnected.

Am I misunderstanding the importance of tuning for CO?

[Techno Duck]

I had the same issue with the AFM... one of the PO's set it to run lean; my guess is because it wouldn't pass smog. The collateral damage from that was a rebuild.

Be very careful adjusting the AFM and retesting...this is a quick way to kill your engine.

I recommend disconnecting the O2 sensor, then adjusting your CO and idle speed. The AFM CO adjustment really only affects idle. I did exactly as you plan, adjusted idle AFR to slightly richer than 14.7. Once you plug the O2 back in, it will revert back to a target AFR of 14.7.

At cruise, the motronic is relying on the O2 sensor and AFM adjustment for the target 14.7 AFR. There is very little adjustment you can do short of adjusting spring tension of the barn door on the AFM. You may get lucky and find scribe marks on the wheel inside the AFM with where it appears was the factory setting. If you do this, disconnect the narrowband O2 sensor. At cruise, the Motronic is using the narrowband to try and achieve 14.7 AFR; so it throw off your results.

For wide open throttle, first make sure the switch is working and is adjusted correctly. (press pedal to floor and make sure switch activates... do this with the car off using a multimeter). Leave the narrowband O2 connected when you start testing WOT. The narrowband O2 is ignored at WOT so you are relying entirely on the chips tune and AFM.

I am usually at RSF with a car in my sig; but obviously not for a month or two now. Maybe ill take a ride up tomorrow.

[911pcars]

Originally Posted by Solamar

I'm learning as fast as possible about the subject, but my understanding is Lambda, AFR and CO% are simply different metrics used to evaluate level of complete combustion. I think Lambda is the most intuitive as it's the same across all fuels. Tuners seem to prefer discussing AFR.

My plan is to pick one (AFR) and stick with it for tuning.

Per reputable sources I'm shooting for -
13.8-14.1 Idle (find smoothest idle in that range)
14.7 Cruise
12.6-13.2 WOT 3k to 6k rpm

I've read differing opinions about disconnecting the Motronic O2 sensor for each of the above settings. Idle AFR will definitely be set with the O2 disconnected.

Am I misunderstanding the importance of tuning for CO?

There are several charts on the internet with corresponding values. Those metrics depend on the type of gauge used to measure fuel mixture, CO or A/F.

Sherwood

[AndrewCologne]

Originally Posted by Solamar

I'm learning as fast as possible about the subject, but my understanding is Lambda, AFR and CO% are simply different metrics used to evaluate level of complete combustion. I think Lambda is the most intuitive as it's the same across all fuels. Tuners seem to prefer discussing AFR.

Lambda is THE reference, ... AFR and CO just du stay in relation with Lambda.

1. The resulting AFR from Lambda depends on the used fuel, so stoich AFR at Lambda 1 for 5% ethanol gas actually is 14.4:1 and not 14.7:1 ... these are peanuts, but just for the understanding

2. CO results also could do vary significantly on different engines, all with lambda 1 read by the an O2 sensor. On a lambda CIS based 911 SC with removed catalysator and SSIs and O2-Sensor installed, a perfect lambda 1 reading by the O2sensor actually can result in 2% CO!
I checked that with the setup mentioned above, with sensor connected and lambda control running, which pulls the mixture to stoich, means a resulting lambda 1.
When using a calibrated BOSCH 4-gas emission tester, the result was 1.8-2 % Vol. CO. At a german TÜV/DEKRA service station the emissions here also do result in 1.8-2% Vol. CO ---> with Lamda regulation running at Lambda 1 and SSIs instead of cat.

With an engine build still kept in factory state where a cat is present, then at lambda 1 the resulting CO Vo.% -still measured before cat- could result in 1.2% Vol. CO.
Here the exhaust flow back pressure, cams, mixture unit (CIS or DME) and a lot of other things of an engine will affect the resulting CO % Vol. at Lambda 1 before cat.

So again, those charts in the www saying that in general AFR 14.7:1 or even Lambda 1 equals to 0,0% CO are ... sorry to say ... pure waste if you want to set up CO using a Lambda sensor. Even when mesured after cat, these charts do not take into account the state of the cat and its effectivenes when converting the emissions.

My plan is to pick one (AFR) and stick with it for tuning.

Per reputable sources I'm shooting for -
13.8-14.1 Idle (find smoothest idle in that range)
14.7 Cruise
12.6-13.2 WOT 3k to 6k rpm

On engines with CIS or DME/Motronic where ECUs are reading narrowband sensors you want Lambda 1 at every rpm as its also best for combustion and ... engine life. Idle at Lambda 1 results verrrry smooth if the whole injection system runs flawlessly.
The moment where the ECU must change from Lambda 1 to approx. 0.85 is at WOT or acceleration – independant from the present rpm. Here the optimum would be a direct presence of Lambda of 0.85 at combustion when stepping on the gas which can be recognised by the ECI by reading a throttle position sensor or vacuum loss in a WUR.

On EFI system based engine builds the story is different.

[AndrewCologne]

Originally Posted by Techno Duck

I had the same issue with the AFM... one of the PO's set it to run lean; my guess is because it wouldn't pass smog. The collateral damage from that was a rebuild.

Be very careful adjusting the AFM and retesting...this is a quick way to kill your engine.

I recommend disconnecting the O2 sensor, then adjusting your CO and idle speed. The AFM CO adjustment really only affects idle. I did exactly as you plan, adjusted idle AFR to slightly richer than 14.7. Once you plug the O2 back in, it will revert back to a target AFR of 14.7.

Yes, thats exactly what many people do not take into account. Often the initial CO setup is set to the common factory default of 0.4-0.8 %Vol. CO which - in case of a SC for instance – will result far too lean IF the sensor won't be reconnected again – as its needed that the control pulls the mixture back to stoich, which -beside other advantages- prevents overheating/damage to the engine.