"sniffer" out of tail pipe?
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From: Collinsville, IL
"sniffer" out of tail pipe? i was just curious how accurate it is when the "sniffer" is put in the tail pipe vs. the 02 sensor hole? i have been told air fuel ratios are usually about 0.8 off when doing this, meaning that the guage will read 0.8 leaner than what it really is. my tuner used this method and i feel that it is running a little rich. my plugs always come out a little more than dark brown, but not like total black.
Kind of a crap-shoot, how far up the pipe, how much exhaust
out-flow vs reversion and so on. I wouldn't put any credence
in any given correction factor. Just jam it way up in there until
the idle reading quits changing and hope for the best.
out-flow vs reversion and so on. I wouldn't put any credence
in any given correction factor. Just jam it way up in there until
the idle reading quits changing and hope for the best.
We run quite often with one in the tail pipe for the dyno graph and one in the car for logging that is hooked up in the collector, or down pipe for a turbo car. They usually only vary by about .01-.04.
I personally don't trust the one in the tailpipe at all - I have seen them be off by a full point when I have tested them against mine in the collector. It is especially bad for idle and part-throttle tuning. And a catted app will be off even more... I always put my wideband sensor in the collector when tuning...
Thread Starter
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From: Collinsville, IL
I personally don't trust the one in the tailpipe at all - I have seen them be off by a full point when I have tested them against mine in the collector. It is especially bad for idle and part-throttle tuning. And a catted app will be off even more... I always put my wideband sensor in the collector when tuning...
Thread Starter
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Joined: Apr 2007
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From: Collinsville, IL
would it be better for me to buy my own wideband and hook it up to a stationary guage in my car and compare that to my tuners methods with the sniffer in the tail pipe/hp tuner program? the tuner i went too didn't give me a $500 tune. i paid about half of that and i was satisfied with the before and after results of the car. he spent a few hours with me and that is what i paid for.
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Hate to break it to ya'll, but there's virtually no difference in the WOT. Under WOT, the cats aren't working anyways, so the results will be the same. The only difference will be if you're using 2 different WBs, as in different name brand, that may have different accuracy.
Just as a preface, or postface LOL, I've used both up stream and down stream widebands, as well as a 5 gas analyzer. So, regardless of the WB accuracy, ya can't get much more accurate than a calibrated 5 gas.
Just as a preface, or postface LOL, I've used both up stream and down stream widebands, as well as a 5 gas analyzer. So, regardless of the WB accuracy, ya can't get much more accurate than a calibrated 5 gas.
I use the tailpipe along with the one in a primary O2 location for almost every car on the dyno. This is a DJ224 (this sensor in the tail pipe: http://www.lsxtune.com/shop/product_...roducts_id/646) and an LM1 in an upline bung, usually a front, that also uses a Bosch sensor (cheaper VW connectorized unit here: http://www.lsxtune.com/shop/product_...roducts_id/345) and I get *CONSISTENTLY* 0.3-0.5 AFR LEANER from the tailpipe unit than my LM1. Perhaps there is something different with our arrangement, but I look at it OFTEN.
This is at WOT. Our tailpipe unit is useless for light throttle / idle.
This is at WOT. Our tailpipe unit is useless for light throttle / idle.
I use the tailpipe along with the one in a primary O2 location for almost every car on the dyno. This is a DJ224 (this sensor in the tail pipe: http://www.lsxtune.com/shop/product_...roducts_id/646) and an LM1 in an upline bung, usually a front, that also uses a Bosch sensor (cheaper VW connectorized unit here: http://www.lsxtune.com/shop/product_...roducts_id/345) and I get *CONSISTENTLY* 0.3-0.5 AFR LEANER from the tailpipe unit than my LM1. Perhaps there is something different with our arrangement, but I look at it OFTEN.
This is at WOT. Our tailpipe unit is useless for light throttle / idle.
This is at WOT. Our tailpipe unit is useless for light throttle / idle.
There's more to the steady state upstream versus downstream, but I gotta go. Maybe I'll post from home tonight.
I'll back this up. I've tried this no less than 20 times typically when a wideband starts throwing a fit I'll move it around and see whats going on. The graphs ALWAYS overlay each other. The Innovate tail pipe sniffer is fantastic and works pretty well even at idle just about everything. The dynojet pump tail pipe sniffer is much more problematic and I have actually packed it away (do not use it anymore).
Same thing about cats. Everyone always says it will read leaner after the cat at wide open.. That is bogus. Its a big mass balance problem.. Its a rich mixture, no more oxygen is being introduced so nothing is "burning" in the cat, what goes in = what comes out.. period.
When people see discrepancies its almost 99% of the time due to temperature. A wide band will read differently if its cold or very hot.
Lastly, I recommend all shops to periodically test their widebands. I personally keep a "new in box" wideband to test the one I'm currently running. If it differs I change them out and check the new with the next in line. I put a wideband in the trash about once a month. I started this a long time ago when I was tuning and a car wasn't going like I felt like it should. Timing wasn't ending up where I wanted and the car in general was not responding how I felt it should. When I changed the wideband the AFR changed instantly 1.5 points. You walk a dangerous line if you do not have a spare on hand that you know is fresh and good.
Same thing about cats. Everyone always says it will read leaner after the cat at wide open.. That is bogus. Its a big mass balance problem.. Its a rich mixture, no more oxygen is being introduced so nothing is "burning" in the cat, what goes in = what comes out.. period.
When people see discrepancies its almost 99% of the time due to temperature. A wide band will read differently if its cold or very hot.
Lastly, I recommend all shops to periodically test their widebands. I personally keep a "new in box" wideband to test the one I'm currently running. If it differs I change them out and check the new with the next in line. I put a wideband in the trash about once a month. I started this a long time ago when I was tuning and a car wasn't going like I felt like it should. Timing wasn't ending up where I wanted and the car in general was not responding how I felt it should. When I changed the wideband the AFR changed instantly 1.5 points. You walk a dangerous line if you do not have a spare on hand that you know is fresh and good.
The problem is the LM1 and the calibration routine. When you manually calibrate the sensor you get much better results OR you just could let the cal resistor do its job, if you ever read the datasheet on a Bosch LSU4 you'll realize that the cal resistor is a blessing in disguise
The problem is the LM1 and the calibration routine. When you manually calibrate the sensor you get much better results OR you just could let the cal resistor do its job, if you ever read the datasheet on a Bosch LSU4 you'll realize that the cal resistor is a blessing in disguise
It's not like the cal resistor updates itself as the sensor ages... AND, it can't be the LM1 (the discrep) because my AFX has gone in the mix a few dozen times as well and that is with a much more hardy NTK sensor. I have had several high HP SC'd cars that got the LM1 in B1, the AFX in B2 (NTK sensor) and the tailpipe is a given just because it's there and the results are the same.
Heck I have had the LM1 in B1S1 and the AFX in B1S2 and I get about 0.1-0.2 difference between the NTK sensor and a new Bosch in the S1 spot. The tailpipe pickup just consistently reads leaner where I'm at.
Maybe you don't have a good tailpipe sniffer. I'm telling you.. No difference.
Take your DJ one and put it in the exhaust somewhere then put it back at the tail pipe. Think about, how could it? Its rich mixture so no more fuel is able to be burnt unless you add o2 somehere in the exhaust.
Take your DJ one and put it in the exhaust somewhere then put it back at the tail pipe. Think about, how could it? Its rich mixture so no more fuel is able to be burnt unless you add o2 somehere in the exhaust.
Maybe you don't have a good tailpipe sniffer. I'm telling you.. No difference.
Take your DJ one and put it in the exhaust somewhere then put it back at the tail pipe. Think about, how could it? Its rich mixture so no more fuel is able to be burnt unless you add o2 somehere in the exhaust.
Take your DJ one and put it in the exhaust somewhere then put it back at the tail pipe. Think about, how could it? Its rich mixture so no more fuel is able to be burnt unless you add o2 somehere in the exhaust.
I honestly don't doubt that if I move the sensor to a front bung that it will read more in line with the AFX and LM1, but I didn't think that's what this thread was about.
The whole dealio with Catalytic Converters is this, in a nutshell. Their whole job in life is to store and release oxygen. The whole premise of the rich lean rich lean switching in closed loop is to assure the Catalyst bed is given a good dose of oxygen. Under cruise state, this works great. If anyone has ever done any pre/post cat O2 sensor testing using an o-scope, you'd understand where I'm going.
During cruise, the left over HCs and CO are split, and recombined with O2 to form CO2 and H2O. Of course you get some left over HCs, O2, CO as well as NOx, although the NOx is further reduced in the reduction bed of an oxidation/reduction cat.
Under WOT, none of this take place as the storage and release simply can't function because of nothing more than the shear volume of exhaust.
During cruise, the left over HCs and CO are split, and recombined with O2 to form CO2 and H2O. Of course you get some left over HCs, O2, CO as well as NOx, although the NOx is further reduced in the reduction bed of an oxidation/reduction cat.
Under WOT, none of this take place as the storage and release simply can't function because of nothing more than the shear volume of exhaust.
So you haven't tried it then? You have 2 variables and no control. Move the same sensor/controller before and after the cat.