Sean in CT wrote:
Thanks Alex -
The collector for the 2 rear cylinders is about 14" from the head, which was my original Idea for the location.
Are you saying that the ECU has to be programmed differently if reading off of 1 or 2 cylinders, rather than all 4?
No, I'm not talking about a calibration for the number of cylinders being measured, I mean that there's a calibration in most aftermarket ECU's for delay from combustion event to O2 sensor reading. It depends on how long it takes the gas to get from the chamber to the O2 sensor (and, I assume, the characteristics of the sensor itself?). In a factory system or a tuned factory controller I imagine you want it to be somewhat close to the factory distance. It's a tiny number, 200ms or something, but I worry that pushing the sensor 30+" from the head will probably come into play. I didn't want to have to worry about it which was part of my decision to keep it close.
In your case I personally would put it in/just after one of the first 4-2 collectors 14" from the head. You get info from 2cyl and you keep under the AEM recommended 18" number. I'm no expert, though, just sharing what I decided based on advice from one source!
Alex