I thought about this this morning ...

The rear O2 checks the functionality of the cat. Essentially it looks for a lower voltage in relation to the front O2 , right?

So, since I'm using my LC-1 instead of the front 02 to lean out the idle/cruise mix, wouldn't that just fix the rear O2 CEL by itself? The LC-1 will report ~.5v and the rear O2 will automatically read leaner because the mix is already leaner.

I'm currently using the anti-fouler fix on the rear O2. I'm considering taking them off to test this.

 

I think it looks for a difference between front and rear 02 voltage. Even if the mix is leaner the difference between the two sensors is not enough.

I don't know if this is how it works, but it's what I have heard.

 

So a full point leaner wouldn't be enough to make it think the cat is there? With the dramatic fall off of a 1v sensor I'd think 1 full point would be a large voltage shift.

Anyone know specifics? I don't ...

 

I suppose that should be suffecient to stop the CEL. try it and let us know.

 

Dudical, I'm not sure you are picking up what he is saying... he is talking about using a different lambda for his front sensor. IE, switchover point of 15.5 which is about 6% leaner than than a 14.7 base. Touring... I think you are thinking of it backwards though. Your front O2 is going to be leaner in this instance, not the rear ......I think

 

.5v will be ~15.6 on the front O2 signal. This means that the rear will correctly read leaner because it doesn't share the modified voltage offset. The actual rear sensor reading will be valid.

Front sensor reports .5v @ 15.6:1
Rear sensor reports (?).2v @ 15.6:1

We're thinking on the same lines ... just saying it differently.

 

I think it will set CEL. If the rear o2 is measuring oxygen content after the cat then it should cycle between no oxygen in the gas and oxygen in the gas (if you're at 14.7 AFR). I was reading on this yesterday coincidentally. During closed-loop the ecu tries to fluctuate a little above and below 14.7 purposely because the cat will have 2 different reactions depending on which side of 14.7 the gas is.

Being constantly at 15.5 the cat will use up more oxygen in the exhaust to convert the CO and hydrocarbons resulting in no oxygen after the cat (rear o2 reading no oxygen). I think when the rear o2 voltage doesn't fluctuate then the CEL will be thrown.

But I think you don't run any cat at all, right TouringBubble? You'll still have the same effect though probably, just the opposite - rear o2 always reading o2.

 

Short answer is it won't work. mrfred and I had a discussion about the rear o2 sensor readings in the 'eliminate your rear O2 sensor' thread and when he wrote his patch for the rear O2 sim and I applied it to the 05 ROM.

To use mrfred's words, the ECU is basically looking for an attenuated signal from the rear O2 sensor as compared to the front. The FSM states the following:



It states that the ratio of the frequency from the rear/front has to be .15 or greater. Since the cat is attenuating or smoothing the signal, the rear O2 will never dip too low to drop that ratio below .15, or at least that's my understanding. If you remove the cat, the rear O2 now cycles in a much wider range, similar to the front, and since it will be slightly lagged behind, it now can be at it's low point in the swing while the front reading may be at the high point and the ratio may be below that .15 criteria.

There are also many other conditions it has to satisfy that mrfred talked about, but to answer your question, I don't think using the LC-1 as the front O2 input will eliminate the cat efficiency cel.


Eric

 

Also the de-fouler is so simple and works well, why bother changing it.

 

Mainly because I had to use 2 anti-foulers and it makes the sensor stick out a ways and I'm worried something will catch the sensor/wire and damage it.

So, for the math ... if O2 2 / O2 1 = more than 0.15 (averaged over 10 sec.) the CEL trips?

So, O2 2 would have to average .07v if O2 1 averaged .5v ... I need to log both and do a comparison. I see why it wouldn't work though.