o2 sensor spacers ?
 

considering o2 sensor spacers to lean afr some. wondering if i should do both or just the up stream o2. not looking for much but every bit helps.

never heard of O2 spacers... it seems to me that moving the O2 sensor out of the main flow of exhaust gases will not change the reading of oxygen content in the system.

but even if it did, i would think that shielding the O2 sensor would trick the sensor into reading a lean condition, which in turn would tell the ECU to richen the mixture.

O2 spacers that I am aware of are designed for early EFI systems to lean the mixture slightly by shrouding the sensor from the exhaust stream, which causes it to see less oxygen in ppm of exhaust, thereby leaning the mixture to compensate. If it were to detect more oxygen in the system, that would indicate an already lean condition, causing fuel enrichment to compensate.

On newer EFI systems, they would likely have no effects, since the feedback system doesn't rely solely on oxygen sensor input.

so by shrouding both,they would both see less oxygen then adjust fuel to get back to proper ratio but readings shrouded (leaner).
i currently have a computerchip on the iat sensor (warmer reading)
50% blocked iac port (to lower high idle)
still want to put in hotter thermostat

Assuming this is your LSI we're referring to, you'd be better suited to work on things proven to do what you're trying to achieve, such as driving tactics.

Is your car auto? That would explain the dismal mileage figures you show thus far...

yeah it's an automatic. temporary car while waiting for the scion iq and chevy spark to come out

If it has a lockup clutch, spend some time exploring those threads where some of us have tried forcing early full lockup on our similarly equipped vehicles. Limiting the time that your engine is moving in less than a one to one relationship with the transmission will net better gains than probably anything you've done so far. Learning to drive wouldn't hurt, either. :wink:

Ahh... got it backwards. DOH.
Damn you left hand!

the scond O2 sensor is there only to determine if the cat is functioning properly, so I'd do the front sensor and then see if the car throw a code. If it does, you can then add the second shroud, or look for a cat MIL eliminator to wire inline with the O2 element.

I have been thinking about ways to acheive a leaner mixture, can't see any way apart from changing the sensor for a wider range one and adding some electronics as the sense basically switches at the mixture it is aiming at. What would happen if I connect the first sensor to the 2nd? may need some more electrical mods, but the CAT would remove some oxygen and the car would adjust the fuel down to keep the same level as I had before the CAT?