Upstream lambda even needed?

[Wiggman2030]

Hi all, I was just wondering if the upstream lambda is needed when running an aftermarket ECU and mapping?

Thanks

 

[Jake_rorx7]

I'm not massively familar with the 7's lambda system in particular, but most cars generally have 2 (or more) lambda sensors in order to read conditions across the catalyst, in order to determine the state of the catalyst and if it needs replacement. The upstream sensor is between the exhaust port and the cat, and the downstream sensor is after the cat. The first lambda sensor that is closest to the exhaust port is almost always the sensor that is used for closed loop fuelling control in the ECU. I've not seen a second lambda sensor after the catalyst on my early JDM 7, but I've never looked for one...

If you have an aftermarket ECU, I'm going to assume it doesnt have catalyst monitoring support, and would only read from one lambda sensor. Also regarding aftermarket ECUs, check if your ECU supports aftermarket wideband sensor inputs, as it would be greatly beneficial to swap over to a wideband system that can read all oxygen ratios, not just ratios close to stoich (narrowband). This would enable the ECU to perform closed loop fuel control in all conditions.

TL;DR: you only really need one sensor before the catalyst.


Edit: Hm I think I interpreted your question wrong. I thought you meant do you need 1 sensor instead of 2, not 1 instead of 0. I'd run at least 1, it wouldnt hurt..