o2 sensors and fuel trims

[3000gttom]

hi, i was wandering which of the 4 o2 sensors have what tasks

i have an n/a dohc and i put headers in and i have a fuel trim code for bank 2, or does any one have the evoscan ID locations for all 4 sensors?

i have the front o2's with their respective banks but the bank 2 rear o2 is not with its bank because there just wasnt the room on the headers for it

[mb3000]

IIRC Bank 1 is the front, bank 2 is the rear. Sensor "1" is the primary, closest to the engine.

I.E. "Bank 2 Sensor 1" would be the rear primary sensor.

[3000gttom]

do the primaries have full control over the trims or do the secondaries also play a part in that?

[Hans@GZP]

secondary O2's are just there to make sure your precats are working. They do no effect fuel trims. You may have to space out your downstream O2's so you don't throw a CEL.

[3000gttom]

ok good thats what i thought, i just did some logging and my o2's are working just fine, my low trims are around +5 for the front and +11 for the back and mids are +11 front and +12 back

i reset the trims and immediately they started adding lots of fuel...

right now i dont think there are any problems with my car other than the headers give more than 12.5% VE more than the stock DP and the ECU is throwing a CEL because of that...i guess i need to learn how to tune the ecu to expect more VE now

[99 vr4]

Just a quick note, using Mitsubishi notation, Bank 1 is actually the LEFT side of the engine, other wise referred to as the "rear" or the side closest to the firewall. It is commonly though that Bank 1 is the front or right side of the engine, but that is a common mistake. The stock EVOScan locations that EVOScan provides are incorrect.

[3000gttom]

got my fuel trims to +/- 5% but i still threw a CEL, i guess i'll read it later and see if its the same one or something new

[3000gttom]

fuel trim is no longer a problem, the codes now are from not having precats... guess i need to find a fix for this now...

[NOMIEZVR4]

Kinda on topic, but how much a variance in fuel trims is allowable between the 2 banks of cylinders? I'm talking about the lo and mid trims...

[3000gttom]

i dont think the difference between the banks matters... my bank 1 trims are about 5-8% less than my bank 2 trims... i would believe this is due to the rear manifold definitely being more restrictive than the front

i just tuned it so they split across 0 and the bank 1 are -2.4 to -4 and bank 2 are 2.5 to 4... they can go either direction to +/- 12.5 i believe before it throws a CEL