Peter

The emissions were absolutely spot on!

Yes I am sure you are right about the downstream O2 sensor flat lining. However, I suppose there must be a limit to what the catalyst is capable of dealing with (volume wise).

This is the first capture of this nature that I have taken so I can’t offer a confident generalisation. It would be interesting to perform the same test on a 60,000 mile catalyst that is still functioning efficiently (comparatively I mean) to compare the level of switch & at what engine speed.

I think that what we are seeing in the first frames of the animation is the result of the catalyst working at the limit of its Oxygen storage capacity. It looks like the catalyst is saturated with oxygen at this engine speed & the excess O2 is what is driving the lean state on the downstream sensor. In the middle section of the animation, when the RPM is reduced to 2,500 RPM & the downstream sensor volts rise, it shows that there is no Oxygen present. This switch from low volts to high volts is not a switch in the same sense as we see it in closed loop fueling; it is more a display of how the catalyst is coping with the volume of gasses thrown at it.

Please don’t take my comments as Gospel, as I am only saying what I believe is happening in the captures. My opinion is always open to question!

There is a very interesting post from William Mclarren on the subject of Catalyst efficiency.

Tom

Thanks for the comments mate. I don’t have allot to offer diagnostically, but I enjoy discovering things with the Pico & I hope others are learning as much as I am from the images.

Cheers all

Dave (Hill)