wideband o2 after cat ok?
#1
06-14-2006, 09:45 PM
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wideband o2 after cat ok?
Hi, I have an 01 f-150 5.4 with some mods and I am having a hard time finding a muffler shop that will install an oxygen sensor bung in my driver's side header collector, near the factory o2 before the cat. I was wondering if you could get decent air/fuel readings after the cat? Is it possible to remove the secondary o2 and put the wideband o2 there? From what I understand the secondary oxygen sensors are not used by the computer in calculating fuel trims. I know its not going to be as accurate, but aren't dynos that use the tailpipe sniffers getting their data from the same place, after the cats. Has anyone tested before and after the cat with a wideband and know how much the air/fuel reading varies? I want to just unscrew the secondary o2, but leave it plugged in and hang it out of the way. Then screw in the wideband o2 and take some readings. Then when I'm done, screw the factory o2 back in. Has anyone done this? Thanks. 
#2
06-15-2006, 03:09 AM
The rear sensors sees very little change after the exhaust get thru the cats.
This tells the PCM that the cats are doing there job ok.
If the rear sensors swing too much then the cats are nearing end of life and a CEL lamp and code will be set when limits are reached.
This means a wide band at that point won't tell you anything useful when the cats are working good..
This tells the PCM that the cats are doing there job ok.
If the rear sensors swing too much then the cats are nearing end of life and a CEL lamp and code will be set when limits are reached.
This means a wide band at that point won't tell you anything useful when the cats are working good..
#3
06-15-2006, 06:57 AM
Hi.
FYI -
Cheers
Grog
FYI -
Originally Posted by Superchips_Distributor
...
Next - I disagree with claims saying that you cannot get a correct A/F ratio from sniffing the tailpipe - that is absolute hogwash today as far as I am concerned.
Now a number of YEARS ago, we used to feel the exact same way! But that was before proper equipment was designed that allowed that to be done properly. The very LM-1 that Neal brags about is precisely what we use to do tailpipe sniffing, and is EXACTLY what DYNOJET uses in THEIR wideband A/F setup, whether it's mounted in a bung ahead of the cats or up the tailpipe - how's THAT for some reality! It's the exact same Bosch LSU4 wideband O2 sensor, friends. With the properly designed and patented exhaust clamp we use, we easily get repeatable readings within 2-3 tenths of a point comparing with A/f's sampled from welding in a bung AHEAD of the cats (the ONLY other way to compare, not plugging into the O2 socket of a cat!!) to what we get from the tailpipe using the clamp design we use that is based on the venturi principle to get proper airspeed & space sampling. The MAIN thing about sniffing at the tailpipe (which is fine for emissions testing, by the way, though unfortunately being phased out to lower the cost of gear for shop owners) is the type of exhaust clamp used, and knowing the pattern of the oxygen storage of the catalytic converters involved - which also means that whoever is doing the "testing" needs to know this platform very well, including the cat temp override constants & numerous other characteristics, such as how long it takes the cats to dump their stored oxygen at various power levels & exhaust pipe diameters, etc.
Next - I disagree with claims saying that you cannot get a correct A/F ratio from sniffing the tailpipe - that is absolute hogwash today as far as I am concerned.
Now a number of YEARS ago, we used to feel the exact same way! But that was before proper equipment was designed that allowed that to be done properly. The very LM-1 that Neal brags about is precisely what we use to do tailpipe sniffing, and is EXACTLY what DYNOJET uses in THEIR wideband A/F setup, whether it's mounted in a bung ahead of the cats or up the tailpipe - how's THAT for some reality! It's the exact same Bosch LSU4 wideband O2 sensor, friends. With the properly designed and patented exhaust clamp we use, we easily get repeatable readings within 2-3 tenths of a point comparing with A/f's sampled from welding in a bung AHEAD of the cats (the ONLY other way to compare, not plugging into the O2 socket of a cat!!) to what we get from the tailpipe using the clamp design we use that is based on the venturi principle to get proper airspeed & space sampling. The MAIN thing about sniffing at the tailpipe (which is fine for emissions testing, by the way, though unfortunately being phased out to lower the cost of gear for shop owners) is the type of exhaust clamp used, and knowing the pattern of the oxygen storage of the catalytic converters involved - which also means that whoever is doing the "testing" needs to know this platform very well, including the cat temp override constants & numerous other characteristics, such as how long it takes the cats to dump their stored oxygen at various power levels & exhaust pipe diameters, etc.
Grog
#5
06-15-2006, 12:46 PM
Originally Posted by Bluegrass
All that's very nice but he has none of the experience or 'all' your correct hard- ware.
You make a great effort to rub.
You make a great effort to rub.
mustangtw5901 - I use the tailpipe clamp available for the LM-1 wideband. I have it on good authority that it is accurate enough to allow the recorded A/F's to be used in custom tuning.
Temporarily replacing a rear O2 'may' be okay - but I'd defer that to an expert.
Leaving the rear one hanging in free air may set codes ...
If you use a LM-1 there is an option to replace an existing O2 with the wideband sensor it comes with, and programming in a transfer function that 'mimicks' the original sensor to the PCM so it doesn't set a code. The LM-1 needs to be connected & running permanently, though.
Hope this helps.
Cheers
Grog
#6
06-15-2006, 01:04 PM
Look, he apparently has the $300 insturment and is looking for a less than proper way to use it.
IMO, might as well guess at the A/F ratio in the absence of experience using it reguardless of all the ways of making up for using it in the tail pipe or some other location.
Next, you will never see me use quotes from any source. It is my personal position that it is being offensive 'much of the time' to do this because it is done when there is a differences of opinion.
I stand on what my original reply says.
If a topic can't be discussed without quoting, it then don't even try with me.
The last time that was done to me the quoted replies were wrong.
I have a recording WB LM and use it on both gas and alky motors.
I love these prople who come on trying to always get around something, then get insulted when it is pointed out.
By the way, I couild care less about what Neal does.
IMO, might as well guess at the A/F ratio in the absence of experience using it reguardless of all the ways of making up for using it in the tail pipe or some other location.
Next, you will never see me use quotes from any source. It is my personal position that it is being offensive 'much of the time' to do this because it is done when there is a differences of opinion.
I stand on what my original reply says.
If a topic can't be discussed without quoting, it then don't even try with me.
The last time that was done to me the quoted replies were wrong.
I have a recording WB LM and use it on both gas and alky motors.
I love these prople who come on trying to always get around something, then get insulted when it is pointed out.
By the way, I couild care less about what Neal does.
#7
06-15-2006, 01:25 PM
WTF ???
Look,
1. I was just trying to help.
2. I use quotes often - saves typing particularly for previously posted, relevant material. Personal preference - same as you are entitled to.
3. Quotes from acknowledged experts like Mike can foster further discussion - both by the expert and by the original requester, who now may contact said expert for help. Opposing views can also foster discussion.
4. I wasn't insulted - I apologized since apparently you were.
5. Did I say I was just trying to help? I was neither being judgmental nor trite, okay?
6. Why are you being so cranky? I've always valued your input and advice.
Cheers
Grog
Look,
1. I was just trying to help.
2. I use quotes often - saves typing particularly for previously posted, relevant material. Personal preference - same as you are entitled to.
3. Quotes from acknowledged experts like Mike can foster further discussion - both by the expert and by the original requester, who now may contact said expert for help. Opposing views can also foster discussion.
4. I wasn't insulted - I apologized since apparently you were.
5. Did I say I was just trying to help? I was neither being judgmental nor trite, okay?
6. Why are you being so cranky? I've always valued your input and advice.
Cheers
Grog
Originally Posted by Bluegrass
Look, he apparently has the $300 insturment and is looking for a less than proper way to use it.
IMO, might as well guess at the A/F ratio in the absence of experience using it reguardless of all the ways of making up for using it in the tail pipe or some other location.
Next, you will never see me use quotes from any source. It is my personal position that it is being offensive 'much of the time' to do this because it is done when there is a differences of opinion.
I stand on what my original reply says.
If a topic can't be discussed without quoting, it then don't even try with me.
The last time that was done to me the quoted replies were wrong.
I have a recording WB LM and use it on both gas and alky motors.
I love these prople who come on trying to always get around something, then get insulted when it is pointed out.
By the way, I couild care less about what Neal does.
IMO, might as well guess at the A/F ratio in the absence of experience using it reguardless of all the ways of making up for using it in the tail pipe or some other location.
Next, you will never see me use quotes from any source. It is my personal position that it is being offensive 'much of the time' to do this because it is done when there is a differences of opinion.
I stand on what my original reply says.
If a topic can't be discussed without quoting, it then don't even try with me.
The last time that was done to me the quoted replies were wrong.
I have a recording WB LM and use it on both gas and alky motors.
I love these prople who come on trying to always get around something, then get insulted when it is pointed out.
By the way, I couild care less about what Neal does.
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#8
06-15-2006, 10:40 PM
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I have the innovate LC-1 wideband kit. So you can or can't install it after the cat, in the factory o2 location? I'm not worried about it setting a code, I can just reset it when I'm done getting the data I need. I just want to measure my air/fuel at WOT to make sure I am running safe, and get some datalogging to Mike T. I can't find a place who will weld the bung in. Every where I go, no one wants to do it. I was browsing the nloc forum and thats where I came across the idea of subsituting the wideband for the secondary o2, so I was wondering if anyone else has done this before and what kind of difference in numbers can I expect. If its only a tenth of a point or two difference then thats close enough for me.
#9
06-19-2006, 01:26 PM
Former Sponsor
Everyone has an opinion on this, which is why we've done the testing that we have and continue to do...........
1.) When doing a permanent install of any wideband on a vehicle, weld the bung in before the cats - the sensor will last longer, and you don't have to worry about being familiar with the initial spike - I.E., pattern of dispersal of the stored oxygen from the cats when initially going thru the transition from idle to heavy throttle.
2.) Once the stored oxygen has been dispersed from the cats, with good equipment there is little difference in lambda readings pre or post cat - now of course there are going to be those with all kinds of opinions who are going to crap all over that, and I really don't care - let 'em. That is why we test. We have in fact tested this difference numerous times using just about anything from Horiba meters to low-cost LM-1's to you name it - and found, with fresh and/or calibrated (in the case of the LM-1, a very nice feature) sensors, that the difference is minimal on pump gasoline.
The primary problem comes from those who do not maintain their air pumps on dyno's like Dynojet's for example - which require a change of the air filter every 8 hours, and replacement of the reed valve every 60-90 days, depending on level of activity and what they have been exposed to - we don't use those air pumps. Many times we have seen our customers send in a dyno "reading" showing 18:1 A/F's, and then we dyno that same vehicle 2 hours later on the same fuel and find that it's a nice save 12.3:1, for example - due to things like a broken or damaged reed valve in the air pump.
Another issue comes in when using different fuels, where the stoich point is not known and/or cannot be entered.
Something I like about the low-cost LM-1 is that it's the only one we see that properly allows ongoing recalibration of the sensor, instead of just depending on those "self-calibrating" sensors that are basically trimmed to a standardized value - and if they always ran at stoich, that would be fine, but when these sensors are routinely subjected to significantly richer than stoich A/F (lambda) values, not being able to recalibrate the sensor as the LM-1 does potentially present a problem.
Another point - "tailpipe sniffing" - for years we told people to *never* do that, simply because we were not happy with any of the existing clamp designs at the time, as many of us know how the speed of air gets slower the closer you sample to the wall of the exhaust tubing, etc., etc. We do find that the LM-1's tailpipe clamp works well, and once again, in testing, (and we always recalibrate the LM-1 each time we use it when using an LM-1 in testing), we find little difference to a reading pre-cat versus the LM-1's reading up the tailpipe once the hammer is down, so to speak. Of course, we frequently replace sensors as well.
Everyone has their own preferences - when we do it, in our environment, with our experience & methods, we get good results - whatever anyone else has to do to get results they feel comfortable with is purely up to them - I'm not about to take on any debate on this, everyone needs to do whatever makes them happy. And any customers of ours who have concerns about this are welcome to call us to go over this.
1.) When doing a permanent install of any wideband on a vehicle, weld the bung in before the cats - the sensor will last longer, and you don't have to worry about being familiar with the initial spike - I.E., pattern of dispersal of the stored oxygen from the cats when initially going thru the transition from idle to heavy throttle.
2.) Once the stored oxygen has been dispersed from the cats, with good equipment there is little difference in lambda readings pre or post cat - now of course there are going to be those with all kinds of opinions who are going to crap all over that, and I really don't care - let 'em. That is why we test. We have in fact tested this difference numerous times using just about anything from Horiba meters to low-cost LM-1's to you name it - and found, with fresh and/or calibrated (in the case of the LM-1, a very nice feature) sensors, that the difference is minimal on pump gasoline.
The primary problem comes from those who do not maintain their air pumps on dyno's like Dynojet's for example - which require a change of the air filter every 8 hours, and replacement of the reed valve every 60-90 days, depending on level of activity and what they have been exposed to - we don't use those air pumps. Many times we have seen our customers send in a dyno "reading" showing 18:1 A/F's, and then we dyno that same vehicle 2 hours later on the same fuel and find that it's a nice save 12.3:1, for example - due to things like a broken or damaged reed valve in the air pump.
Another issue comes in when using different fuels, where the stoich point is not known and/or cannot be entered.
Something I like about the low-cost LM-1 is that it's the only one we see that properly allows ongoing recalibration of the sensor, instead of just depending on those "self-calibrating" sensors that are basically trimmed to a standardized value - and if they always ran at stoich, that would be fine, but when these sensors are routinely subjected to significantly richer than stoich A/F (lambda) values, not being able to recalibrate the sensor as the LM-1 does potentially present a problem.
Another point - "tailpipe sniffing" - for years we told people to *never* do that, simply because we were not happy with any of the existing clamp designs at the time, as many of us know how the speed of air gets slower the closer you sample to the wall of the exhaust tubing, etc., etc. We do find that the LM-1's tailpipe clamp works well, and once again, in testing, (and we always recalibrate the LM-1 each time we use it when using an LM-1 in testing), we find little difference to a reading pre-cat versus the LM-1's reading up the tailpipe once the hammer is down, so to speak. Of course, we frequently replace sensors as well.
Everyone has their own preferences - when we do it, in our environment, with our experience & methods, we get good results - whatever anyone else has to do to get results they feel comfortable with is purely up to them - I'm not about to take on any debate on this, everyone needs to do whatever makes them happy. And any customers of ours who have concerns about this are welcome to call us to go over this.
