CAT Converter: risks due to running on open-loop / without O2 Sensor

[GeeEss]

Car is an 86kW 4AGE fitted with Jap aftermarket AE111 Headers+CAT-back exhaust running a 4-Wire O2 Sensor just ahead of CAT (OEM unit is 1-Wire running to upper Ex. Manifold.

Got Exhaust done about 50k ago and have been running it on Open Loop / minus O2 sensor as I'm waiting on 2nd-hand Adaptronic so I can hook up 20V ITBs.

Took off AE111 sensor that came with Jap Headers today and bench tested it - got up to about 0.7V initially but then it Died ITA, barely pulled 0.1V even under 1-2min heating; worried I might have fkd unit so afraid to use car in case I stuff up CAT too.

I'm not quite sure how to (or even if you can) wire up a 4W Sensor to 86kW ECU.

My question is, how long can you run a CAT on open loop (i.e.w/out functioning O2 Sensor before you risk damaging it? 50/100/500/1000km???

[Radar]

How about if your sensor is in the exhaust and you've had no power to it, its useless and will need replacing. 02 sensors have a heater coil in them so they dont burn while exhaust gasses rush past them. Why rush a build when its just gonna cost you more in the long run, im sure EVERYONE here will agree with that statement.

[CrUZida]

Several hundred thousand km's...

Unless you are running REALLY rich (ie you have masses of unburnt fuel in the exhaust and are getting like 3km/L), then the CAT will survive fine.

[oldcorollas]

How about if your sensor is in the exhaust and you've had no power to it, its useless and will need replacing. 02 sensors have a heater coil in them so they dont burn while exhaust gasses rush past them. Why rush a build when its just gonna cost you more in the long run, im sure EVERYONE here will agree with that statement.

wot?
the majority of O2 sensors do NOT have a heater in them.
those that do reduce the amount of heating as the sensor gets to temperature, ie only really needed for startup and idle.
the sensors die from the zirconia cracking, from poisoning, or from getting completely caked up with carbon/ash/crud (esp oil eating motors)

as Cruz said, unless really rich to the point of masses of carbon depositing and either blocking it, or then burning in the cat core, resulting in melting of the substrate, it should be fine-ish.

I'm not quite sure how to (or even if you can) wire up a 4W Sensor to 86kW ECU.

has been posted many times.
run power to the heater from a relay switched by the fuel pump (imo, or, to ign switched relay if you want to preheat sensor for some reason)
run ground from the heater to any good solid ground.
run signal wire from the sensor to the original ECU wire
run sensor ground to the ECU ground.

too easy

[Radar]

Heh thanks man, I was well under the impression they needed that heater going to survive, do the same rules apply for boost? learn something new everyday. Sorry to hi-jack the thread there but can an o2 sensor be run without a controller to an aftermarket ECU?

[oldcorollas]

please google about oxygen sensors.... you are well confused.

O2 sensors run in a temp range. check the Bosch spec pdfs. how you achieve that range is either distance and/or heater

controller? only widebands use a controller.... google...

[Radar]

So it seems, cheers mate.

[GeeEss]

On reflection I doubt I did any damage to it; the Sensor came off a 90K AE111 front cut and was probably already stuffed before they took the axe to the car. The engine, while not exactly a sewing machine (@ BZR) actually runs pretty well considering its been ported for the Quads & not the TVIS I put back on.

Having said that I still need a new O2 Sensor; universal Denso 4wires online in USA from USD $60-$100!! so will go with that & hope OK for JDM spec BigPort as even ex Japan prices ($500+) give me a Heart-attack.

[oldcorollas]

hmm, two 4 wire bosch sensors for under $30?
BOSCH Oxygen Sensors x 2 Part # 0 986 258 007/004 NOS | eBay

from bosch cat (section A)
pat number wires check interval
0 986 258 004 4 80,000
0 986 258 007 4 80,000

or an NTK sensor for commode (single wire) ($37)
http://www.ebay.com.au/itm/COMMODORE...item3a68f78907

or bosch 4 wire for commode for $53
http://www.ebay.com.au/itm/Holden-Ox...item415bbc9241

[GeeEss]

I would just like to confirm I have the wiring for the Heater+12V IG correct.

Referring to the marked up Haynes diagram (colours don't match JDM cars) and Junction box Photo;

1. I will take power for heater by splicing into either one of the B-O wires @ bottom ctr of LHS connector. (picture)
2. I will run this wire via a 5A inline fuse to the switch terminal of a 4PIN 30A Horn Relay or similar
3. I will run a wire from the other switch terminal to the O2 heater
4. I will then run a power wire from one of the Coil terminals to fuel pump side of the circuit opening relay; i.e. Terminal 1 (this relay is piggy-backed on ECU which makes this a hassle as it means I have to run wire through firewall) so. . .
4b. Can I instead run power wire to EFI relay side of circuit opening relay (i.e. to terminal 2 of EFI main relay? this would be much easier as its also at bottom of same Junction box . .
5. I will finish by running a wire from other coil terminal to an earth on chassis.

[mattysshop]

any benifit running a 4 wire sensor vs the normal single wire??

Never mind.. i just googled it..

but of background info on the differences, how effective they are etc etc...

Bosch 4-Wire O2 Sensor

[GeeEss]

Hmm, you seem a pretty clue-y guy Matty, if you're asking the question?
< i.e. I'm surprised; I thought the general consensus from what I've read here & elsewhere was that this was a worthwhile upgrade that would bring tangible benefits in starting up / fuel economy (especially when running a stock ECU, as I will be intially; for at least 1-2 months) >

To be honest, I'm trying to sus this out myself because my usual Auto-Electrician* refused to wire up the 4wire Sensor and both other local guys are booked out for another week or so.
* His reasons were;
1. He said he didn't believe it would really make a difference
2. Probably really the above again (he was pretty set in his opinion). He said he wasn't prepared to undertake non-standard wiring that involved the ECU because if he fried it, I could legally come back at him. .

[mattysshop]

i've just never really worried that much about O2 sensors on 4age/gze conversions that i've done..

i honestly wouldn't think there would be 'that' much difference.. as the 4a's ecu's arn't really all that dependant on them from my own experiences (usually not running one at all).. they pretty good at just sorting themselvs out even with a host of buggered sensors, and a open thermostat (constantly running cold) doesn't really seem to significantly hurt economy...

i know a host of other cars that will just run in failsafe mode, if anything at all without an o2 sensor... but on 4A 16 valves it doesn't really make a huge difference as there pretty old school tech..

just my 2 cents George

[oldcorollas]

wiring sounds ok. just make sure you get power when you want and not when you don't

if an O2 sensor works, it works, and the benefit is fuel efficiency being.. not maximised, but maximised within the ECU's programming.

Heated sensor means it warms up faster and can go into closed loop sooner, and also the sensor should never get too cold.
in aftermarket, it allows you to move the sensor further away from the engine, and still give good readings..

Re: that page, O2 sensor is not used outside of cruise or idle (for older cars anyway), so it should make absolutely zero difference to "power". might make a difference to the cruise to power transition perhaps?

[GeeEss]

OK; all done and no warning lights ; now idles 200rpm higher (1100rpm). Will adjust that tomorrow and then hopefully get stuck into fitting the Quads. . .