o2 sensor heaters

[CrUZida]

I'm about to install a heated o2 sensor, mainly so I can tune cold start and cruise. (o2 sensor is about 1m from motor)

Is there anything wrong with leaving the heater on all the time?
I don't plan to, I'm more curious.
Once I'm happy with the tune I'll be removing the o2 sensor as its not needed, and only replace it when I want to check AFR's.

2ndly, is it straight 12v? does it chew much current?

Lastly, how long does the heater need to be on for before the sensor will read correctly?
I know they'll read leaner than actual when they are cool.

Ta

[MWP]

Leaving the heater on all the time should be fine.
I havnt seen/heard of any ECUs that turn them off...
AFAIK they are always just wiried to ignition.

As for heating time, maybe 1min?
I guess it would depend on air temp, if the engine is idling from start, or being driven, etc.
Factory ECUs know when they are hot by variation around stoic.

[oldcorollas]

should be ok on all the time.... only time you would want to turn it off is under substantial load anyway (ie when closed loop is not used) during cruise idle, you want it on.

yes, 12V. i wired it to fuel pump (so that when ECU turns off fuel pump, it also turns off O2 sensor...) better than just ign, as sometimes you sit in car and play with stuff with ign on.. or that is possibility anyway.

Bosch use 4 or 5 amps when cold, but once hot, the resistance of the heater increases, and they only use about 1amp running current at temp. i believe others are pretty similar.. 3-5amps cold, 1-2 amps hot.

when they are cool they may not be generating voltage at all!

for my bosch one, it was about 30 seconds heating time, but yeah, anything up to a minute..

at idle you will be running rich anyway, so it will not hit stoich during warmup..

for tuning warmup, you do want it rich, but you can do by ear pretty much.. you just want it to not stumble.... as it warms up, quickly scale each point up and down (as temp reaches it) and you will quickly get a feel for what is too lean/rich....

cruise... can you adjust the rate of change of the correction?
on the MS, i gave it +-20% leeway, 16 or 20 ignition events per step, and either 1 or 2% change per step.....(2% for inital setting of maps, 1% for normal running)..

Cya, Stewart

[CrUZida]

Thanks.

The Microtech doesn't use the o2 sensor as an input, just displays its value.
So there is no correction map, I'll just be tuning it on rpm vs load I think (haven't really looked into it).

I realise cold start you don't aim for stoich, its just something I want to play with.
Car used to behave wierd for a couple of the temp ranges, I want to iron that out.

5 amps hey? I'm running it off the DOME fuse atm, I might increase it to 15A, (not sure if its 10A or 7.5A). I'll be sure to check the manual that comes with the sensor.

[oldcorollas]

actually, if you measure the resistance of the heater when cold.. that will tell you what the cold current will be...

[CrUZida]

Ah, indeed it will, heres hoping its 4 or more ohms.

[CrUZida]

6.5 ohms - so draws 2 amps. I presume as it gets warmer it draws less?

I presume the 2 white ones that are continuous are the heater, and the black one is the signal wire?

[MWP]

6.5 ohms - so draws 2 amps. I presume as it gets warmer it draws less?
I presume the 2 white ones that are continuous are the heater, and the black one is the signal wire?

Yup * 2.

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