Tuning with very erratic O2 signal

ihenter · Post by **ihenter** » Sun Jun 04, 2006 8:01 pm

I am running megasquirt (fuel only) on my 1990 RX-7 with a narrowband O2 sensor. I have gotten it tuned so that its drivable but am unsure about using auto-tune or mega tweak because I can't get a steady O2 signal below 25% throttle (75 MAP). I have headers and the O2 bung is pretty far away from the exhaust port so i feel that the problem is with the O2 sensor staying hot enough. My datalogs generate tons of crossover points because the O2 voltage is constantly jumping from 0 to .75 V or so (see attached) but is this really usable to fine tune my car? Any ideas on what to do aside from getting a wideband.

-ian

willys59cj5 · Post by **willys59cj5** » Mon Jun 05, 2006 2:21 pm

You could try using a heated O2 sensor. I found that tuning the VE table with a narrowband heated sensor was doable, but with a wideband much easier. Hope this helps. Remeber that your NB sensor must be at a high enough temp to work correctly.

fscott · Post by **fscott** » Mon Jun 05, 2006 9:27 pm

I have to ditto that. Tuning with a one wire sensor is an exercise in misery and frustration. Been there, done that.

The problem is that when the sensor is cold, it will give bad data. And you have no way of knowing if the sensor is cold or not.

Buy, beg, borrow or steal a wideband. You won't regret it.

Fred