Dual O2 sensors

[JustCallMeOrlando]

I'm considering dual exhausts for when the JZA80 receives its 1UZFE next year. It'll be running an Adaptronic, so I'd like a wideband plumbed in all the time to really let the ECU do its thing.

Is there a need for dual O2 sensors? The anal-retentive side of me says yes, the side holding my wallet says no. Please discuss.

Cheers,
Nathan

[YLD-16L]

I'm not that familiar with Adaptronic but can it process the information from two sensors when performing its autotune feature and make adjustments accordingly i.e. to each bank of injectors?

[thechuckster]

put a heated wideband at a cross-over pipe?

no need for dual WB sensors unless you can trim per cylinder or per bank anyway.

[CrUZida]

For the purpose of this discussion, assume the ecu can adjust each bank individually

[thechuckster]

would the ECU have 2 x onboard wideband controllers ? otherwise you have two controller boxes to deal with (fitment and wiring wise).

[YLD-16L]

In that case I'd spend the extra few hundred $$ on a system that controls the two o2 sensors and feeds that info into the ECU e.g the techedge dual channel unit.

If the ECU couldn't utilise that info though or you couldnt control and adjust banks/cylinder trim then I'd go with chucks suggestion of mounting it in the crossover pipe.

It'd be great to have the info from each bank but if you can't do anything with that info it's of little use other than tuning to your limiting factor.

[CrUZida]

Can you give me a situation where it would be beneficial to have it?

[YLD-16L]

The only situations that spring to mind are at the initial tuning stage you would have the confidence of knowing what is happening in each bank (possibly more valuable info than that taken at the crossover), especially if some custom work on the intake has been carried out and the possibility of uneven balance between the cylinder banks is introduced (unlikely though??).

From there though it would be more so a diagnostic/information tool and the benefit of that would be entirely up to Nathan.

Depends on how far you want to go though really and how much control you have with the ECU to utilise the info being collected.

Tuning air:fuel based on the reading at the crossover pipe - good, tuning by bank - better (??), tuning by cylinder - best. But is it necessary? Depends on the application and what the owner wants I guess.

[brett_celicacoupe]

id borrow 2 widebands and compare the 2 banks. one will probably have a slightly higher VE due to intake manifold design and throttle body placement - it will run leaner. the headers will also alter this.

figure out which one is running leaner and tune based on that bank. the other bank with a lower VE and will run richer so it will be safe.

so this in an extreme case would answer your question cruzida.

it also depends how knife-edge you want to tune it. if your getting close to stoich then youll want to compare banks. but then you may also argue that individual cylinders on each bank may differ slightly also. if you wanted to be really tricky you could put a thermocouple in each header and check temperature consistency.

[JustCallMeOrlando]

I too see little benefit in running two. ECU-wise, if I went two O2 sensors, it'll have to be using the new Super ECU that Andy from Adaptronic is making. If I go one, I'd probably get away with an e420c, and although it wouldn't have all the same bells and whistles, chances are I'd not notice the difference

The only thing that's bugging me is, why would the factory run twin O2 sensors if the benefits aren't really there?

[brett_celicacoupe]

they probably run 2 because the sensor has to be X distance from the cylinder for temperature reasons.

[jezza323]

i would have 2 bungs, 1 wideband, just tune on 1 bank, then occasionally swap to the other bank to make sure its all running sweet

[-GT-]

The only thing that's bugging me is, why would the factory run twin O2 sensors if the benefits aren't really there?

As Brett said, it's because of distance. O2 sensors need to be pretty hot to work properly and send meaningful info to the ecu. The quicker they get up to temp the sooner the ecu can utilise them for efficient closed loop running too, so you should put them as early in the exhaust as possible, so that all cylinders are sampled. It's also why some O2 sensors have heaters in them too, if they're too far down the exhaust they don't heat up quickly enough, or maybe don't stay hot enough all the time for the readings to be accurate.

As an example, 4age 16v, it's in the bottom of the manifold, but 20v, it's back down just in front of the cat because the 20v has a 4-2-1 system that's as long as possible, from the factory. Hence, it's a 4-wire heated type, whereas the 16v is just a single wire one.

Edit: And the point of all that was, the 1uz will run twins from factory because two can be mounted much earlier in the exhaust, as opposed to one after the final merge, so that all cylinders are sampled.

[CrUZida]

Edit: And the point of all that was, the 1uz will run twins from factory because two can be mounted much earlier in the exhaust, as opposed to one after the final merge, so that all cylinders are sampled.

His question was related to why do they run one on each side, as opposide to just one on one side (in the same position), and nothing on the other.

Not why don't they run one at the final collector.

[YLD-16L]

If it's a heated sensor then the manufacturer will only recommend a minimum distance from the head or turbo (due to overheating and damaging the sensor) and a minimum distance from the tail pipe outlet (so as to not get false readings from free-air) and it's recommended to be reading pre-cat converter. Anywhere within those boundaries though is fine for a heated sensor.