O2 sensor

[itsallgood]

guys,

Found out last week whilst on dyno run that my oxygen sensor had sh*t itself and now need a new one. What can i expect frm the car when i replace it this weekend? Better performance? Fuel efficiency?

[BigDatto]

Short answer: all of the above. O2 sensor provides data to the ECU which then makes corrections to theair/fuel ratio based on that data - essential to keep the vehicle in tune. You should be pleasantly surprised !

[poyz]

As far as I've had it explained to me the factory ecu works as follows from the engine speed input and the air flow meter input the ECU calculates a pulse width that should give a stochiometric air:fuel ratio ie 14.7:1. The with that speed and air flow information it looks up a table which contains a number. That number is a multiplier for the pulse width. I do not know for certain, but I don't think that the multiplier can be less than one, ie acts to shorted the pulse width with should give an leaner mixture then 14.7:1.

If you are running in closed loop mode, the ECU can run leaner, but anything over about 30% load/throttle and the ECU will not enter closed loop mode, ie the 02 sensor isn't even looked at most of the time.

[predator]

Adding to the above, the oxygen sensor (I'm assuming you are talking about the one off the exhaust?) is not the only one that the ECU makes it decision, and its a balance of that, AFM sensor, the intake air temp (before the intake manifold), and THR position (butterfly open/close %). Then of course it has to work out how much fuel is going in, boost levels, etc.

Its a complex equation thats for sure!

[poyz]

Oh, and to answer your question...

Fuel economy would be marginally improved. During closed loop, the O2 Sensor is used. Anything else, ie WOT, it's ignored by the ECU.

As for Performance, as above.

[mrskyline777]

are we able to use an aftermarket sensor on a std ecu and can we get brand o2 sensors

[Guest MRE]

When I put mine on the dyno I had the same problem.

They replaced it with a VL one. All sweet now.

[blind_elk]

The only time you should have noticed the O2 sensor was faulty would be on 'cruise' (constatnt throttle, constant speed). On a WOT ie accelerating, which most dyno runs are, the O2 sensor would be out of the equation. Nissan programs the ECU to run rich-as on WOT.

So its possible the dyno operator was having a lend of you.

I have replaced mine - for a different reason - and it cost about $150 from Nissan (its a NGK unit, so you might try contacting NGK).

[Guest MRE]

Idle mix was not to bad but at normal highway speed she was running rich.

And it was stuffed, 1. All the little slits were blocked and 2. It was my own doing from runing octane boost, evil stuff imo.

[darkhalf]

im in the middle of building an Air/Fuel meter from one of those jaycar kits. it says the chip in the kit is matched to a particular bosch o2 sensor (making it not perfectly accurate with other o2 sensors). this is because of the skew of the lamda values outside stichiometric ratio (14.7) can be different between various sensors.

anyway to use this accurately on my r31 im going to have to reprogram the PIC chip mappings

hence i think you need an o2 sensor which reports similar lamda values to the original one (for the factory ecu)

mine is rattling (ie stuffed - the sensor inside is broken in half) and i'm planning to go the NGK ones for my RB30 which was $130 repco