Creeping AFR indication - What's the cause?

[dos531]

So just to be clear, you've used 2 different wb02 controllers, and 2 different o2 sensors with the same results, but you're still dead set on it being a sensing error and not an actual creeping afr?

[flightlead404]

Originally Posted by dos531

So just to be clear, you've used 2 different wb02 controllers, and 2 different o2 sensors with the same results, but you're still dead set on it being a sensing error and not an actual creeping afr?

lol Its a good point you make.

Yes, 2 controllers, 2 sensors, same behavior. Checked all the grounds, verified the MS configuration.

What I have NOT done is actually verify the voltages coming from the controller to make sure they are indeed creeping and its not some weird Microsquirt thing. But I think the likelihood of that is very low.

The only reason I feel it *might* be a sensing error is that the car idles just fine even though the indications reach up into the 16:1 range and nothing changes in the sound, speed, or smoothness of the idle. I would have not expected the car to idle the same at 13.5:1 as 16:1, or even idle at all at 16:1

Am I making a bad assumption?

Other than a sensing error, another poster hypothesised a vacuum leak. But I'm unsure the mechanics of a vacuum leak causing CREEPING AFR, rather than just a lean AFR.

My other hypothesis was that it was due to either CHT or MAT increases while idling, but the logs don't bear that out.

Here is a log file showing a cold start though about 16:1 AFR.

[dos531]

I'm going to vote that your afr is actually moving. CIS does these kinds of weird things and it frustrates those of us that want good control over the engine. If it idles fine, and your afrs are in spec during driving i'd probably just drive it. You will never achieve perfect results with CIS, the best you can really hope for is "good enough".

Originally Posted by flightlead404

lol Its a good point you make.

Yes, 2 controllers, 2 sensors, same behavior. Checked all the grounds, verified the MS configuration.

What I have NOT done is actually verify the voltages coming from the controller to make sure they are indeed creeping and its not some weird Microsquirt thing. But I think the likelihood of that is very low.

The only reason I feel it *might* be a sensing error is that the car idles just fine even though the indications reach up into the 16:1 range and nothing changes in the sound, speed, or smoothness of the idle. I would have not expected the car to idle the same at 13.5:1 as 16:1, or even idle at all at 16:1

Am I making a bad assumption?

Other than a sensing error, another poster hypothesised a vacuum leak. But I'm unsure the mechanics of a vacuum leak causing CREEPING AFR, rather than just a lean AFR.

My other hypothesis was that it was due to either CHT or MAT increases while idling, but the logs don't bear that out.

Here is a log file showing a cold start though about 16:1 AFR.

[flightlead404]

Originally Posted by dos531

If it idles fine, and your afrs are in spec during driving i'd probably just drive it.

Well therein is the crux of the matter. If I don't know whether its actually accurate or not, how do I know whether they are in spec while driving?

If it actually is creeping for some reason, meaning the AFR indication is correct, then that's fine although weird.

The problem I'm struggling with now is can I trust the AFR indication while driving?

[dos531]

Well you've replaced all the wideband components with the same results, so in my book that would rule it out as the culprit.

[bleucamaro]

I've had similar issues with Innovate's LC-1. I also have their LM-1 and don't have this issue. Since you've repeated the anomaly with multiple sensors and controllers, could it be the temperature? Since you're located very close to the turbo, have you considered putting a heat sink in between the sensor and the mounting flange?

see linked article for ideas: https://www.torquenews.com/2696/wide-band-o2-sensor-heat-problems

[flightlead404]

Originally Posted by bleucamaro

I've had similar issues with Innovate's LC-1. I also have their LM-1 and don't have this issue. Since you've repeated the anomaly with multiple sensors and controllers, could it be the temperature? Since you're located very close to the turbo, have you considered putting a heat sink in between the sensor and the mounting flange?

see linked article for ideas: https://www.torquenews.com/2696/wide-band-o2-sensor-heat-problems

Interesting. I'm a bit limited on room with the bumper there, but I could do some tests at least.

The thing is, it worked fine before the mods. So, maybe something I've done has increased the head to the sensor? The two possible things that could do that are:

1) Ignition timing changed. However, I went from a stock dizzy so probably around TDC or maybe even 5 ATDC to 10-11 BTDC. I would expect that to make the exhaust COOLER rather than hotter. Am I wrong there?

2) My mixture could be way off, since I can't get a good reading to adjust it maybe that's the issue. Looking at the log I linked though, I think its probably more or less correct.

I'll try and whip up a heat sink and maybe do some tests with the bumper off and some cooling air or something.

[dap930]

This is probably not your issue, but I saw a car program on Motor Trend channel where an O2 bung was being installed and that weld must be good with no cracks or pin holes or it will affect the O2 readings.