Wideband question

[Daniel196]

I have been reading a ton of information on here and need to buy a wideband. I am not sure what wideband would be best for my setup or application. I have an mpvi2 pro with link. Most all engines I run are DBC with minimal electronics due to my application. Also, I will not run a wideband permanently so it will be for tuning purposes only. I have heard horrible and good things about all but would like to stick with something lower end like the aem X series since I do not need anything fancy.

Also, I saw not so great reviews on the aem like dead o2's and bad things out of the box. Just want some experienced opinions that will work good with what I have and what I run/need. Thank you!

[dr.mike]

Almost all of the deal sensor issues; not just for the AEMs, but, almost all widebands; are caused by thermal shock. This happens when the sensor is heated up before starting the engine. The internal element of the sensors are made of ceramic. They are heated to about 650C/1200F which is glowing orange hot. When hit with a rush of relatively cold ( and, often, wet ) air, at startup, they form fractures. Eventually, one of these fractures hits something vital. Or, it just causes leakage, which ruins the accuracy of the sensor.

Never "pre-heat" a sensor, before starting an engine. Unless, you are analyzing start-up behavior. In which case, be prepared to go through a few sensors. And, test them before and after each start-up.

Ideally, the wideband should not be started until the engine has been running for a few seconds; and, the EGT has stabilized a bit. Usually, if the wideband is wired directly to run-power, and the engine is started immediately upon turning the key, the wideband's heater cycle will still be initializing during the cold/wet portion of the start-up. But, if you turn the key to run, and let the wideband get up to full temp, before starting the engine. It is better to turn the key off for a few seconds, before starting the engine.

Somebody out there should make a wideband power control relay that delays the wideband power until the EGT is stable. Or, just that the engine has been running for 15 seconds, or so

[Daniel196]

Being in a cold climate wouldn't I just want to leave the sensor in the exhaust and quickly start it so it can warm up with the motor?

[dr.mike]

If you just avoid letting the wideband turn on before cranking the engine, you should be OK. It's the sudden change in temperature that kills the sensors. Kinda like throwing a bucket of ice-water on a very hot windshield.

This is 90% of why these wideband sensors can live out normal lives in OEM applications. The ECU knows when the engine is running. And, it doesn't start the wideband heater until after is is safe.

Maybe, I should add this, for those who don't know.

Inside the wideband sensors, the element is made of ceramic. The ceramic element has an electric heater strip. It uses that heater to raise the temperature of the sensor to greater than what it expects the EGT to be. That way, by varying the current to the heater, it can maintain a controlled constant temperature, while the EGT varies. When the wideband starts up, it begins ramping up the temperature of the sensor element to the target temperature of 1200F. This might take 10 to 30 seconds. The idea is to keep the rate of temperature change slow enough as to not fracture the ceramic. Hitting the hot ceramic with a blast of air ( and, usually some water ), that is more than 1000F degrees colder than the element, causes a VERY fast temperature change ( thermal shock ). The stress from the fast temperature change exceeds the tensile strength of the element. And, cracks form. Initially, a crack may not "hit anything vital". But, like a windshield crack, once they form, they spread, over time. And, eventually they either hit an electrical trace. Or, they can cause an air leak that ruins the calibration, and, gives bad data.

So, "preheating the sensor" is, pretty much, Russian roulette.

The marketing guys at the wideband controller manufacturers like to brag about how quickly their gauges will show an AFR value, after powering on the gauge. This is dumb. Brag about how well you control the sensor temperature. Although, that is hard to demonstrate.

[1970ss8.1]

I am a big fan of PLX. Very accurate and easy to interface. You can take an old narrow band and cut the plug end off leaving a pig tale. Install the wideband where the narrow band goes and use the wire from the wide band to send the narrow band signal to the PCM. When done tuning just put the narrow band back in and plug it back in. I really like the options of data logger, gauge, and IPhone to view the gauge. It also tells you the health of your 02 sensor.

[2therock]

A good (PLX) wireless wide band setup is nice. If I had to do it again I would forgo the pillar pod eye candy thing.
My truck looks bone stock but for the pod thus giving my lite sleeper mode away.
No pod mounting or cable routing.
Once the truck was dialed in I basically never looked at them again. I use HPT scanner to log and check.
Doing a WOT run staring at the pod is not an option.

[kingtal0n]

So, "preheating the sensor" is, pretty much, Russian roulette.

The marketing guys at the wideband controller manufacturers like to brag about how quickly their gauges will show an AFR value, after powering on the gauge. This is dumb. Brag about how well you control the sensor temperature. Although, that is hard to demonstrate.

It's a curious thing, because in the manual for wideband sensors they often tell not to run the engine when the wideband is turned off.

So you have the manual saying to warm the wideband up before you use it,
and you have the people on the internet saying to not warm up the wideband,

In the end I think both things are true, and the way the manual gets around telling people not to shock the sensor is by telling them to install the wideband far from the turbine (or far from a high temp exhaust components)

This way if you pre-warm the sensor then start, the exhaust is so far from the sensor it doesn't get a shock.
I've mounted my widebands around 3 to 4 feet from the turbine on many long-term installations, many friend's cars, never had an issue using AEM's cheapest version.
Not even a bad sensor, ever (except maybe when the widebands FIRST came out I had an innovative and it killed a couple), and its been over 100 cars and 20 years.

[dr.mike]

Both things are not true.

It's a curious thing, because in the manual for wideband sensors they often tell not to run the engine when the wideband is turned off.

This is a common misunderstanding of the Bosch spec. Where they said : ?The sensor must not stay in the exhaust gas stream when it is not heated or when the control unit is switched off.?

What they were trying to get across ( according to the Bosch engineers, themselves ) is that the sensor should not be left, for extended periods, unheated, in a running exhaust; so that it will not accumulate carbon deposits ( which the heater burns off, before they can adhere). This was probably borne out in the original German, with a more precise translation for the word"stay".

They clarified it here:

5.2 Use without control unit
The sensor might stay in the exhaust gas stream for a short time also if
the control unit is not connected. Connect and disconnect only, when the
control unit is switched off.


They make the point crystal clear, here:

4.3.2 System measures:
- Never switch on sensor heating resp. control unit before engine start.
- Delay of sensor heater start or reduced heater power (see section 1.6)
emphasis mine.

There is no ambiguity, here. Bosch 100% says NO to preheating the sensors. Plus, Dr.Mike says:
"I have, personally, intentionally, used the pre-heat/cold-start method to destroy multiple sensors in testing. Including examining ceramic elements, under a microscope, after varying numbers of cold starts. "

The reason for mounting the senors further downstream in high EGT application is to avoid large temperature swings that the controller can not compensate for, using the sensor's heater. When the EGT exceeds the target temperature, the controller loses control of the sensor. As it can only heat, not cool, the element.

Having the sensor further downstream will not help in the start-up thermal shock case. It may, actually, be worse. As more condensed water vapor will hit the hot sensor, than would, normally. That water having been already past the sensor's original location.

Lastly, only the X-Series AEM and the Innovate controllers know when they have a fractured sensor. You can be running a completely trashed sensor on most controllers and, just get bad data. Unless you test the sensors, you never really know. I posted the procedure for that, in some thread, a while back.

Basically, the only real way to know if a sensor is good is to compare it's free-air oxygen % reading to the value that it SHOULD have, given the sensor's factory calibration resistor, and, the current atmospheric conditions.