starting wideband O2 sensor

[Yves]

I read some conflicting info on using a wideband sensor in startup procedures of the engine. I use bosch LSU 4.9 and recently had one sensor fail.

On the one hand I read that you should only start your sensor when the engine already runs to prevent thermal shock on the other hand I read that the sensor shouldn't be exposed to engine exhaust without being heated and in operation.

So what is it now. FWIW, my sensors start up immediatly as this also gives info on startup behavior.

Thanks

[benckj]

Sensor should not be in exhaust if not heated and being used. Also needs to be around the 9 or 3 o'clock position and between 18-24" away from engine exhaust manifold. Life does depend on fuel used as well as items like silicone couplers on intake.

Jimb

[CRSTune]

If the sensor is left unheated in the exhaust, it may remain too cold, allowing carbon to build up and eventually clog the sensor. The sensor must remain above a minimum temperature to self clean.

[racingmini_mtl]

You don't want to start the heater before starting the engine because there might be some condensation that will create a thermal shock if it hits the heated sensor. That's is instantaneous. The question of not leaving an unheated sensor in the exhaust is a longer term effect and having the sensor initially cool is not an issue.

Just connect the heater to the fuel pump relay; that's also what is shown in the wiring diagram from the manuals.

Jean

[Yves]

Controller is 14point7. Don't think it lets you contol the heater seperately. I could wire in a relay that prevents actuation when the engine is not running. Kind of a hassle since I run individual wb's

[racingmini_mtl]

Then power all the controllers from the fuel pump relay or a separate relay controlled from the fuel pump relay. You must already have all the controllers connected to some switched 12V so you should only need to change that part of the wiring.

[Yves]

Might be wrong, but if the goal is to have a firing and some running engine to remove the condensate, what is it going to help connecting that relay to the fuel pump relay ? In fact it will start running as soon as the engine turns and not specifically when the engine is firing.

I also have another problem with that approach : I use open loop fuel pump control. This puts the fuel pump relay out of use, althought there will be other ways to get around that.

[racingmini_mtl]

It takes around 30 seconds for the sensor to heat up to operating temperature. The fuel pump will run at most 2 seconds before the engine starts. That should be sufficient to get rid of any thermal shock issues.

I assume you mean PWM fuel pump control (open or closed loop) and that is an issue that hasn't been acknowledged yet by the MS3 firmware developers (as far as I know). The very least that would need to be done on that subject would be to propose a new wiring diagram when that is used because the current one would definitely fail. But it would also be good to have an alternative output to have both a 'starting/running engine' output and a PWM fuel pump output.

Jean

[Six_Shooter]

ALL of my WBO2 controllers have been connected to 12V ignition. NEVER had an issue with sensors or controllers failing. If I know I'm going to have the ignition on for an extended period of time without the engine running, I pull the fuse or disconnect the WB,

What I've done on a friend's car since I can't control how he uses the ignition on his car is set up a general I/O to trigger a relay at above 50 RPM (some set low RPM anyway). Currently my spare WBO2 is just simply connected to 12V ignition, but will be changed to the I/O controlling the power when he gets his WBO2 controller.

[Rick Finsta]

It takes around 30 seconds for the sensor to heat up to operating temperature. The fuel pump will run at most 2 seconds before the engine starts. That should be sufficient to get rid of any thermal shock issues.

I assume you mean PWM fuel pump control (open or closed loop) and that is an issue that hasn't been acknowledged yet by the MS3 firmware developers (as far as I know). The very least that would need to be done on that subject would be to propose a new wiring diagram when that is used because the current one would definitely fail. But it would also be good to have an alternative output to have both a 'starting/running engine' output and a PWM fuel pump output.

Jean

Jean, I just switched to MS3 and I use FIdle for a PWM control signal to my pump but it looked like the FP light was on my stim as well? I have everything engine-related powered off the fuel pump on relay signal so if I need to go back to my MS2 control scheme where I using a boost control output I can do that until the firmware comes around. I haven't gotten back out to the car to attempt to fire it up since the swap.

[racingmini_mtl]

Jean, I just switched to MS3 and I use FIdle for a PWM control signal to my pump but it looked like the FP light was on my stim as well?

I'm not currently in a position to test that on a bench because I don't have an MS3 setup available. If you tell me that the FP light goes on then goes off after 2 seconds when you turn on the unit then there is no issue. If the FP light is either always on or always off, that's not the desired behaviour.

Jean

[Yves]

When you switch to pwm fuel pump control (either open or closed loop), the regular FP pin won't work anymore. I already tested. However I used an older firmware (1.4 something) because of can related issues. Not sure how it goes in the newer firmware.

Must say this is a first time I've had this issue. However, this is also on one of the exhaust tubes were placing a wb was most difficult. In 2 places the O2 was not completly horizontal in the tube, but almost and that due to space constraints. The one that failed was in one of those tubes.

[Rick Finsta]

I will get it back on the stim after the holiday weekend and report back. should I move to another thread? MS3 development?

[jsdevel]

You don't want to start the heater before starting the engine because there might be some condensation that will create a thermal shock if it hits the heated sensor. That's is instantaneous. The question of not leaving an unheated sensor in the exhaust is a longer term effect and having the sensor initially cool is not an issue.

Just connect the heater to the fuel pump relay; that's also what is shown in the wiring diagram from the manuals.

Jean

Seems to me like the hardware manuals should be updated with either a big caution sign, or a different schematic for WB power:

wb.png

That diagram shows power being applied with ignition (not with the fuel pump which should signify a running engine).

I'm in the process of troubleshooting the famed E8 error code with my LC-2 WB controller and came across this article. One of the key quotes therein from Bosch is as follows:

Never switch on sensor heating or the control unit before engine start.”

[whittlebeast]

I always wire my on the fuel pump wire so that the wide band is operating any time the fuel pump is running and the motor is spinning.

Andy

[jsdevel]

I always wire my on the fuel pump wire so that the wide band is operating any time the fuel pump is running and the motor is spinning.

Andy

That's what I'm going to start doing! Learned that $60 lesson the hard way