How important are the o2 sensors?

[Spinnetti]

So this is in my race car... I know on my old EFI (Bosch based Toyota setups), the o2 didn't do anything at higher rpms.. what's the impact of having them out or not working in a race setting?

 

[Zukijames]

I'm wondering the same thing

 

[4U2QUIK]

Most o2 sensors work only in closed loop mode, and have very little to do with rpm.
you could be cruising at 8000rpm (yeah i know its not realistic) and if you stayed there it would go into closed loop mode.

 

[LO LYF]

I don't run any o2 sensors on my conversion, stock motor factory ecu.

As far as i can tell it runs fine, I think it would be fine in a race application.

 

[gloverman]

I wire o2 sensors onto pretty much everything I wire. Even aftermarket ECU in race situations. They arent always turned on in these situations but help with basic monitoring of the engine.

On the 1uz stock ECU 10 series/131crown/sc400/soarer single wire they only have small amounts of trim. They will run fine without them but everytime I have connected them the customers have noticed the engine is smoother and slightly more economical. Most of the time wont even throw a code without them.

10 series and like ecus with the 4 wire sensor but still with grouped injection they make a little bit more difference but still not a whole lot. Will throw codes without them. Not sure about check light on this one.

20 series - sequential injection. They start making more difference. Codes and check light without them or the heater circuits. Some people link primary and secondard together to remove secondard codes. This stuffs up the primary circuits operation. Generally done to overcome other issues caused by incorrect wiring.

Anyone seeing a trend here?

20 series VVti - They make a massive difference. They have 25% adjustment factor. If there is a fault in the primary system the ECU runs out to 20% adjustment then resets to no fuel adjustment for a time and starts again. It will cycle through this over and over again causing drivablity issues.

30 series 3uz VVti - testing these at the moment but I suspect they are similar to 20 series/151 crown 1uz VVti . Also looking at the 170 series crown which is most likely similar.

Correct wiring is also correct for the ECU to hold the long term fuel trim figures. I see incorrectly wired engines all the time that dont even throw codes when they should. Single wire can be pretty much any universal unit. After that having the correct sensor is important. Toyota/lexus chose to fit a sensor with a different wattage for the heater element to other manufactures. Getting the correct unit is important. A generic universal sensor can also cause issues.

Every single vehicle manufacturer fits oxygen sensors to their vehicles and as we get into later model vehicles they are placing more relience on these sensors , many now have AFR sensors as original equipment.

 

[lux project]

Got a question on the best way of setting up the sub o2 sensors.

I have the ole 'lets connect the subs into the primary's', and I think this is whats giving me fault codes on the primary's. This is fitted to the vvt-i motor.

I have done a bit of searching on this forum, but can't see sure way around the problem as yet. Seen resistors plumed in to simulate the rear o2's? The way I see it, someone must have found a reliable way to get around this problem, without going to the expense of buying another set of o2 sensors.

 

[gloverman]

What is the problem you are having? I have done a few VVti 1uz and 3uz now (nearly 50). Is the check light coming on? poor running? Cheers

 

[lux project]

The engine seems to run fine. this is during short local test runs, as I haven't got the ute legal yet, hopefully in about 2 weeks.

So, if I reset the fault codes, nothing pops up initial. After a short drive, the cel comes on. I have a scanner so can pull the codes, and I get both primary O2's as well as the traction control code being the main issues. Got a few other codes as expected in my case, such as VSS and transmission codes (running a manual gearbox). I even did a reset while driving which worked for a wee bit, then primary O2's came on again, amongst others. I have tested the heater circuit, and I get battery voltage at the sensor.

The engine is a 4 liter VVT-I out of the celsior, running the factory ECU. Going off what you said above, it might be an issue with the sub O2 wiring being linked to the primary's. This is what was done by the bloke who wired it.

 

[gloverman]

The VVti can be wired so there is no CEL. The trans codes wont cause the check light to come on.

 

[gloverman]

If you have paid someone to wire it then I think you should take it back for him to fix it. Anyone good at their Job should stand behind their work.