Anybody keep their downstream O2 sensors?

[BrApple]

Brapple has one catalyst monitor in the downstream bung of the Bank 2 header, and he installed a bung for the other catalyst monitor on the up pipe / y-pipe rather than on the Bank 1 header itself.

Neither of these sensors would act as catalyst monitors, of course, so if they were not disabled in the tune then Brapple would need to splice MIL eliminators into them.

He also had to add a bung for his wideband, presumably on the flex pipe ahead of the main cat. [Am I right?]

you are correct.

both down stream sensors are basically where they would be stock. both have mil-eliminators on them.

my wide band is located just ahead of the flex pipe. not currently running any cats but I have one that I could put on.


also there isn't any space to put a O2 bung on the bank 1 header. so the only place would be in the up-pipe/y-pipe in a stock like location.

why would you run your wide band on one bank only?

 

[SoopaCooga]

why would you run your wide band on one bank only?

frankly, the instructions i had for the wideband were specifically for installing it in a stock location, so i never considered other options. i could easily have had a bung added when i had a high flow cat installed. :shrug:

 

[BrApple]

frankly, the instructions i had for the wideband were specifically for installing it in a stock location, so i never considered other options. i could easily have had a bung added when i had a high flow cat installed. :shrug:

interesting. I know the LC-1 has instructions that tell you how to wire it in inplace of a stock sensor, but it also comes with a bung so that it can be installed on its own.

 

[BurritaSVT]

Recommend installing to both banks that way if one banks goes lean you will see % rise in A/F tp warn you to stop. Joey

 

[SoopaCooga]

u said u have ur wideband currently at the same spot i have mine. so it'd get its values from only one bank right? wouldnt it be more accurate placed further back so it reads from both?

sorry i missed your post. you are correct. alternatively, you could get a second wideband as suggested by BurritaSVT, but of course that means putting more money into the car.

 

[BrApple]

here is the pic of how I have the Bank 1 lower O2 sensor installed. For bank 2 they are bothO2 sensors are like stock. wideband it in the exhaust just after the flexpipe before where the cat would be and the catback.

As you can see I did have it furthur down but it was in a bad spot. I scrapped over something and it ripped up the header wrap and bent the sensor. so when I had everything out a few weeks ago to replace the wastegate gaskets again I had another bung installed.

 

[SoopaCooga]

I wonder, Brapple, if the upstream sensors would be more accurate if they were moved to your downstream sensor locations. Doing that would allow the sensors to read the A/F for the entire bank and not just the middle cylinder of each bank. onder:

Would you be interested in trying that and sending Joey a log so that he can see if there is any noticeable difference? If it proved to be more accurate, then you would have helped everybody with MSDS headers to have better running motors. :shrug:

 

[98_C-SVT]

Super glad Fredericksburg VA does not have emissions. They just put palm over tailpipe to find any leaks and thats it. :laugh:

 

[SoopaCooga]

My wideband is bad. At least that's what Joey keeps telling me. He says it should be reporting 14.8 at idle when STFT = 1.00 but instead the wideband is reporting 14.2. I don't know what to do. I confirmed that the sensor sends a 5.0 V signal when in free air. I checked that the wiring was correct and that there was minimal signal degradation (0.005V). At this point I don't know whether to buy another sensor, buy another controller, or plot a hundred data points on a graph in order to recalc the formula for converting voltage to A/F. :help:

 

[BAD SVT]

My wideband is bad. At least that's what Joey keeps telling me. He says it should be reporting 14.8 at idle when STFT = 1.00 but instead the wideband is reporting 14.2. I don't know what to do. I confirmed that the sensor sends a 5.0 V signal when in free air. I checked that the wiring was correct and that there was minimal signal degradation (0.005V). At this point I don't know whether to buy another sensor, buy another controller, or plot a hundred data points on a graph in order to recalc the formula for converting voltage to A/F. :help:

hey soopa. widebands dont sit @ one spot @ any point in the workings of the car. @ idle, ur wideband should be moving. i think what joey is saying is that it should go back n forth between ~14.2 and ~14.8 @ idle depending on ur boost level.

 

[SoopaCooga]

hey soopa. widebands dont sit @ one spot @ any point in the workings of the car. @ idle, ur wideband should be moving. i think what joey is saying is that it should go back n forth between ~14.2 and ~14.8 @ idle depending on ur boost level.

yes, thanks, i know they oscillate. the point i was making is that mine bounces between 13.6 and 14.4 whereas Joey expects it to bounce around 14.8. mine is reading richer than that, but Joey says it should not be. Joey says when the STFT = 1.0 then the A/F is at stoich.

 

[BurritaSVT]

Gary don't worry about the wideband I will do the offset if you are reading 14.2 at idle on a average I will add .6 to any WOT run don't go blow any money use a dyno to back up your sensor that way you get your numbers along with verification. I need the load datalog and once I get that and it seems close I will turn on your adaption. Please do not spend money till we know for sure I will do my own offset here. joey

 

[SoopaCooga]

Gary don't worry about the wideband I will do the offset if you are reading 14.2 at idle on a average I will add .6 to any WOT run don't go blow any money use a dyno to back up your sensor that way you get your numbers along with verification. I need the load datalog and once I get that and it seems close I will turn on your adaption. Please do not spend money till we know for sure I will do my own offset here. joey

Thanks. I'm just concerned that the the offset alone won't fix it, know what I mean? I started plotting points on a graph, and I ended up with this equation: 2.3*V+9.5. I want to hear what PLX tech support has to say. it would be great if somebody local would be willing to let me borrow their wideband to confirm that mine is FUBAR'ed so I know it's the sensor and not something else.

 

[SoopaCooga]

Now this is interesting:

All pump cell wideband sensors are pressure sensitive. They should not be placed where the working gas pressure is much above or below atmospheric pressure, otherwise different calibration curves must be used for best accuracy.

This white paper lists several more environmental factors to consider when installing a wideband:

Other environmental conditions likely to cause a shortened sensor life include:

• Operating the sensor hotter or cooler than its optimal heat range
• Placements where condensation is likely to enter the sensor during warmup or operation. Bosch recommends
  orientations where the leads point up from the horizontal by at least 10°.
• Operation in a confined space where heat soak can occur, resulting in elevated
  sensor body temperatures and subsequent failure of flexible insulation. Operating
  sensors vertically will exacerbate this situation so, in confined spaces, We suggest
  you position the sensor away from the vertical by at least 15°.
• Using the sensor unpowered when in an exhaust stream. The sensor should be
  powered from a controller whenever it is exposed to exhaust gasses.
• Excessively rich environments (Lambda 0.75 or richer) will cause more rapid
  contamination than stoich (Lambda=1.0) operation. Lean and even free-air
  operation is usually not a problem.
• Excessive oil consumption will rapidly contaminate and physically clog the sensors
  internal structure. Bosch recommends oil consumption of less than 1 quart/1000 miles.
• Sensors are designed to be powered when the vehicle is started – this minimizes
  the risk of thermal shock.

 

[BurritaSVT]

Now this is interesting:



This white paper lists several more environmental factors to consider when installing a wideband:

well there you go you need to relocate the sensor after the turbo backstream reducedd heat and clean the sensor with some carb cleaner while you are at it.

 

[SoopaCooga]

Joey, I would think the same thing, except that you got BADSVT dialed in, and he has his wideband in the same place. :shrug: It's still worth a shot...

my wideband is also in the lower part of one of the headers. thats why i have both downstreams behind the cat. which reminds me... u said u have ur wideband currently at the same spot i have mine.

 

[SicSE]

Better late than never...

Without the sensors I got DTCs (of course) for bad sensor heater circuits, and the car would then operate in open loop (i.e. limp) mode.

Open loop is not limp mode. Limp mode is utilized when there is a potentially engine-damaging situation, most commonly a type-A misfire, or overheating condition. In limp mode, the fuel strategy will be "Open loop - fault". However, there are numerous other issues that will put the fuel strategy into open-loop fault, but NOT initiate limp mode.

On cold start at idle, the fuel strategy should be open loop. Once it reaches a certain operating temp, it should shift to closed loop. Stomp on it driving down the road and it should switch to open loop-drive. And as mentioned above, certain faults will put it into open loop-fault.

in the state of nevada, u r allowed a maximum of 2 incomplete ecu cycles.

Any non-green state will have federal emissions standards. Under federal emissions, you can have two incomplete emission monitors and still pass.

And someone mentioned the P1000. P1000 is just a code indicating that all the monitors have not completed since the last PCM reset. It is not a monitor, but just a DTC, and you will get it everytime you pull codes as long as any of your monitors are incomplete.

I am thinking about possibly splicing two sensor harnesses into one sensor so that I only need one downstream sensor but can plug it into both sockets so that the PCM is happy. Kinda crazy but it should work...

Let me know if you get this to work and how you do it. I thought it would be as simple as splicing wires together but it didn't work out that way for me.

If both of those check out then I am going to relocate the EGR to the down pipe or even the flex pipe. Now I need three bungs on the flex pipe! That thing is gonna look like Neo in The Matrix! LOL

Definitely relocate it. If your EGR tube is plumbed before your turbo, the backpressure created by the turbine is going to give you more EGR flow than the PCM wants, when it wants it, and possibly even some flow when the PCM doesn't want any.

I wonder, Brapple, if the upstream sensors would be more accurate if they were moved to your downstream sensor locations. Doing that would allow the sensors to read the A/F for the entire bank and not just the middle cylinder of each bank.

Since the PCM regulates fuel for the entire bank based on feedback from the O2, it IS best to have it located after all the cylinders on that bank merge.

The biggest problem with having the O2 sensor in only one header primary is that if you develop a lean condition in another cylinder on that bank, the PCM won't see it in the A/F and won't make the necessary fuel adjustments to keep things from eventually melting in the lean cylinder. Conversely, if you develop a rich condition in the one cylinder that IS monitored, the PCM will pull fuel from the whole bank to get it's desired reading from the O2, possibly making both of the other cylinders on the bank dangerously lean.

 

[SoopaCooga]

Better late than never...

thanks for confirming my understanding.

The biggest problem with having the O2 sensor in only one header primary is that if you develop a lean condition in another cylinder on that bank, the PCM won't see it in the A/F and won't make the necessary fuel adjustments to keep things from eventually melting in the lean cylinder. Conversely, if you develop a rich condition in the one cylinder that IS monitored, the PCM will pull fuel from the whole bank to get it's desired reading from the O2, possibly making both of the other cylinders on the bank dangerously lean.

right, but did anybody with MSDS headers move their upstream sensors after the collector? i am willing to bet that nobody has moved them or at most somebody like DemonSVT or warmonger. i wonder how significant the loss of accuracy is when relocating them 12" further from the exhaust port?

my new wideband sensor arrived today, so we will see tomorrow whether or not that solves my wideband accuracy issue.

 

[SicSE]

right, but did anybody with MSDS headers move their upstream sensors after the collector?

I moved my bank 1 O2 in my SHM's from the cylinder #2 primary to after the collector. Does that count?

i wonder how significant the loss of accuracy is when relocating them 12" further from the exhaust port?

Personally, I'd be surprised if there is any difference in accuracy.

 

[SoopaCooga]

SicSE, you're cool just by owning SHMs! i tried to get a set of those a few years back.

Personally, I'd be surprised if there is any difference in accuracy

Well, you're collectors are much further than mine from the exhaust ports. I have read that for an accurate reading, the wideband should be located 40" - 60" from the exhaust port (or after the turbine in my case). The narrowband is more heat tolerant, so it doesn't need to be 40" away from the exhaust port, but there must be some threshold distance beyond which the accuracy of the sensor is grossly off.

Today I had sensor bungs added to my NPG flex pipe: one before the cat for the wideband and one after the cat for the monitor. Hopefully my PCM will be delighted by the change. I also bought a new wideband sensor to see if that makes any difference. This car is fueled by money, not gasoline.