1983 euro model AFR across warm up

[SkiVT]

I am wondering if the following AFR readings are "normal" across the warm up cycle. My Innovate gauge provides the following readings at idle (so at stop signs, etc):

- Cold startup is 10.5 to 11.0
- Begins to lean after 30 seconds or so into the 12's, then 13's, then 14's over a couple minutes
- Idle drops as the AAR closes and ends up at 950rpm but AFR climbs to 15.3

- After another 2 or 3 minutes the AFR drops ending up at 13.8 fully warmed up.

I think I am questioning if the air provided by the AAR ends up leaning the mixture, until it closes, more than the WUR would just by it's pressure climbing to WCP. I had always thought there would be a steady climb in AFR that matches the climb in pressure from the WUR. However, mine sends AFR a bit high before settling back to the desired range (13.8 to 14 in my mind). I am assuming/guessing this is occurring in the last bit of time before the AAR fully closes. Once AAR fully closed, the AFR matches the mixture controlled by WCP of the WUR.

My car runs great so no complaints but this is just something sparking my curiosity.

Thanks

[bluelectron]

My AFR from a cold start

Time (min) AFR
0 10
1 11
2 12.7
3 13.5
4 13.5
5 13.5
6 14.5
7 14.5
8 14.5
9 14.5
10 14.5

The RPMs drop around the 5 min mark. The car smokes until this 5 min mark.

[SkiVT]

Thanks fro posting. Your numbers show the consistently climbing AFR I would expect. I think you have a US spec 82 based on your other recent post, which has Lambda that I think mostly controls the mixture and uses an 090 wur? I have much less knowledge of that system so I could be wrong but I think it's more proficient at balancing AFR as things warm up and the AAR etc close off excess air. If Lambda is working correctly, I am not sure it's capable of going lean (above 15 say) at idle across the warm up cycle. The euro models operate similarly to the 78/79 models which do not have a Lambda "brain" helping to adjust/balance the mixture. It relies on the various components heat up timing to keep AFR in an acceptable range. The more I think about it, the more I lean toward my data simply showing the "acceptable error rate" of not having the Lambda brain involved......

[bluelectron]

Originally Posted by SkiVT

Thanks fro posting. Your numbers show the consistently climbing AFR I would expect. I think you have a US spec 82 based on your other recent post, which has Lambda that I think mostly controls the mixture and uses an 090 wur? I have much less knowledge of that system so I could be wrong but I think it's more proficient at balancing AFR as things warm up and the AAR etc close off excess air. If Lambda is working correctly, I am not sure it's capable of going lean (above 15 say) at idle across the warm up cycle. The euro models operate similarly to the 78/79 models which do not have a Lambda "brain" helping to adjust/balance the mixture. It relies on the various components heat up timing to keep AFR in an acceptable range. The more I think about it, the more I lean toward my data simply showing the "acceptable error rate" of not having the Lambda brain involved......

You are correct, my car is a US spec 82 with lambda. But I conducted the test with the O2 sensor disconnected. If I am not wrong the Bentley manual says, disconnect the O2 sensor and measure CO before the cat. Adjust CO when the car is warm.

[SkiVT]

Got it. Thanks

[Reiver]

My AFR (AEM) also an 83 Euro with SSI's and the lambda in the driver side SSI in the collector pipe prior to the muffler.....indicates about the same when the red (working) light goes out 10's on cold start gently rising as it warms to a 14+ then when full warm settles at 3.5 where it seems to like to run the best.
I run it a little fat as I live at 2400 foot and live in a hotter area.

[SkiVT]

Thanks Reiver. So it would seem if the AAR closes off faster than the wur warms, afr would not surpass fully warm afr and subsequently drop back. If the AAR stays slightly open until after the wur fully warms, afr will climb to the lean side and then drop back after the AAR fully closes. The cause (my guess) would be the resistance of the wur and AAR not matching sufficiently to reach warm at similar times and/or the bimetalic strips not bending at the same rate as when new.

[Reiver]

Perhaps.....my WUR is newly rebuilt by Flowtech and works as it should....nice thing about the AEM is I can watch the AFR drop into the 10's/11's when I get on it....my AAR is not so fresh.