I'm looking to put a WB02 in my 92 LT1. Do I use a single sensor on just one side, in an X-Pipe at the union, or dual sensors? Any advice appreciated. I'm just at the point of looking at different systems and getting some prices.
TIA

 

I think most people use just one due to cost.

 

I am still running cats (RT aftermarket at least). If I use the extra bung behind the cat for the WBO2 will it affect the accuracy?

 

You need to install the bung BEFORE the cat in order to get proper readings since the CAT will affect accuracy.

The ideal setup would be to run dual WBO2's so you can adjust bank-to-bank mixures and identify any bank-specific problems.

Practically, as stated above, a single one is fine for us normal people. Even most professional dyno tuners rely on a single WBO2.

I have a Techedge unit (one of their older ones) installed in an extra bung immediately after the header collector on the driver's side. My unit doesn't do logging, which really stinks. I'd strongly recommend getting one with the ability to log data against at least RPM and ideally MAP. That will give you the ability to determine where your fuel map needs to be adjusted.

 

Does the cat affect the accuracy enough that I should'nt just move the ECM's (heated) O2 sensor behind the cat to free up the bung in front for the WBO2??

BTW, my dyno guy just sticks the sensor in the tailpipe and never asked whether I have cats or not. Do I need to find another dyno shop?

 

The new accel 77063 (I'm pretty sure that's the part number anyway) is a dual channel wideband kit with datalogging and multiple outputs. Might be something you want to look into. It's expensive though. Pricing wasn't available when I bought my wideband but I'm sure it's in the $1000-$1200 range.


-Justin

 

Well, let's think about that for a minute...

A typical equilibrium chart for combustion gas OUT of an Engine looks something like this:
http://www.megamanual.com/PWC/emissions.gif

Typical gas composition OUT of the Cat Converter is whatever you read off a smog test:
for example, < 50 ppm HC & < 0.25 % CO. The gas composition OUT of the cat is NOT
the same as the gas INTO the cat; a new equilibrium state is reached after the cat's
(oxidation) reactions.

Also, a typical cat has air pumped INTO it to promote HC/CO oxidation. Thus the O2
reading AFTER the cat has no relation at all to the equilibrium conditions after the
Engine's combustion chamber.


From those facts, it seems safe to conclude that placing an O2 sensor AFTER a functioning
cat converter makes no sense at all, in terms of ENGINE control.

For a detailed discussion of WB-02 sensors (Nernst Cells) you might try this site:
http://www.megamanual.com/PWC/



In terms of datalogging, I believe Dataq still sells their small A/D converter box for ~$30,
including software. Last I looked they had upgraded it to 10-bit resolution, and it still
had 4 inputs, with 240 sample/sec recording. That makes it a vastly superior tuning
recorder to anything I've seen on the comercial UEGO units. There's a pic of an old Dataq board
on my CF site. HTH

 

Thanks, that is very helpful. Now does that mean when I go for a Dyno tune and the guy shoves a WB02 in the tailpipe, I'm getting garbage AFR readings? He doesn't correct for the cats in any way, or even express interest in knowing if they are there.

 

Not necessarily, it may not be the most accurate but at WOT the amount of gases flowing through the CAT and what the sensor reads at the tail pipe, should be very close. Because of the high flow conditions at WOT the CAT cannot process all the fuel blowing past it so if you see say a 12.5:1 AFR at WOT the difference in reading it at the tail pipe or at a test point before the CAT should be no more than a tenth or so.

 

Another stupid question, can I replace my current O2 sensors with wideband units, and wire them into the harness so they do double duty for logging and the engine management function, or are the signals incompatible?

TIA

 

Allowing that I don't know anything about your Dyno shop I can't offer an opinion.

However if I were paying for testing services I'd expect the technician to be able to explain
how his testing equipment works; provide documentation on the manufacturer's calibration
methods for that equipment; and have written records of the calibration history of the gear.

Numbers produced from uncalibrated gear (or by an untrained operator) are only numbers.


tj makes a good point though - at WOT the cat won't reach equilibrium, so the measurement
error will be mitigated for that condition - assuming the meter is calibrated in the first place.


However I spend most of my tuning time looking at part-throttle and transient fueling. Those
are the conditions that govern 'drivability' - and for those, a sensor before the cat is necessary.
Sampling at the collector is where a WB and a fast recorder show up ignition and fuel problems.


Then again, my cars spend most of their lives at part-throttle on the street, and need to pass
smog. If I were building a car to run only at WOT the objectives might be different. JMHO

 

Yes, that is where I'm coming to, I need to focus more on part throttle tuning instead of just being focused on max power at a band where I spend relitively little time. Hoping a lot of reading and data from a WBO2 will help here.

 

I just purchased and installed a FAST dual wide-band set up that even allows you to record runs. Really nice set up for cheap. I purchased it through MuscleMotors.com. Was in the are of $430 shipped.

 

Are the O2s in 94-96 allready wideband?

 

Pretty sure they are plain heated narrowband devices. I ended up getting a setup that has both a wideband and narrowband output that allows me to use a single sensor to log and feed the ecm.

 

In response to the question about 94-96 sensors, they are regular 1.0V narrow band sensors. Very few cars run 5.0V widebands from the factory.

The two most common sensors are the Bosch and NTK.

 

Thanks people

 

In order to tune using the WB, you'll need to run O/L otherwise the ECM will continue making adjustments to fueling based on the NB input.
Also will need to disable EGR and CCP.

 

I'm very new to all this, but I mostly bought the WB to see what my AFR looks like in C/L, to see it it needs more work there. I expect my tuner to get the PE mode stuff right based on the dyno measurements, but I've been blind as far as what the mixture looks like running down the highway.

 

If you are running C/L, the BLM is the indicator you want to use, not the WB.The reason a WB is used for WOT tuning is that 1) the NB works in a very narrow range for AFR, optimized for Stoich., 2) at WOT, the AFR required is outside the range of the NB accuracy parameters and so the ECM is interpolating the PW required for achieving the commanded PE AFR. How accurate that ECM is depends on how close the C/L is to the magic 128 BLM. The ECM uses the last BLM before entering PE in order to calc how much longer the PW should be for WOT.
So, if your BLM is higher than 128, the ECM will interpret that the motor is running leaner than it should and actually enrichen the WOT AFR by a corresponding amount. All you guys that get your cars dyno tuned need to make sure the BLMs are locked at 128 before modifying the WOT AFR. Or make certain the BLM is at 128 or below before entering PE. Otherwise, the AFR will vary depending on whether the last BLM was below or above 128. When I go to the track I load a bin with my BLMs "locked" at 128 so the ECM doesn't modify my WOT VE parameters.
So scranage, if you are going to use the WB to tune your PT, then you'll need to run O/L. The VE table will not necesarily look the same depending on if you have tuned to 14.7AFR or a use the BLMs. Its one or the other.
For a nube this is probably clear as mud, but you'll get it like the rest of us have.