LC-1 sensor location
Thread Starter
Melting Slicks
Joined: Feb 2002
Posts: 2,285
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From: Crooks SD
LC-1 sensor location
ok... here's my dilemma...
I would assume the WBO2 sensor would need to be installed BEFORE the cats as there is a re-burn process that will remove some of the fuel in the exhaust. However, a very knowledgeable person told me I could put it AFTER the cats. Thus, I would simply remove one of the factory cats and install in that bung. So... WHICH IS IT?
in advance, fellas
I would assume the WBO2 sensor would need to be installed BEFORE the cats as there is a re-burn process that will remove some of the fuel in the exhaust. However, a very knowledgeable person told me I could put it AFTER the cats. Thus, I would simply remove one of the factory cats and install in that bung. So... WHICH IS IT?
in advance, fellas
Race Director
Joined: Sep 2003
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From: Now in God's Country, the Big Sky, Montana!
Cruise-In 7-8-9-10 Veteran
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
No, you need to put it ahead of the cats in order to get an accurate reading. I welded a bung on collector behind the bung for the stock sensors on my LG LTs.
Drifting
Joined: Oct 2004
Posts: 1,384
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From: Southwest Virginia
Well, either place would be the correct answer, it will work in either location. BUT only pre-cat will give you an accurate reading. You will see fairly good readings post cat but the problem is you don't know exactly how efficient the cat is running at any giving time so there is no way to know exactly how close you really are. Some say to subtract like .2 or .7 and that is where your are. That don't work because cat efficiency relies on so many different thing. Cat temp, exhaust gas temp, amount of hydrocarbons in the exhaust, and exhaust gas velocity to name a few. So there is no way to have a magical chart that says this post cat AFR is equal to that pre cat AFR. Yea, you can get a idea of where you are post cat, but the only way to know for sure where you are is to check it pre cat. This all assumes your cats are working of course, if they are there and gutted then any location will work just fine.
Thread Starter
Melting Slicks
Joined: Feb 2002
Posts: 2,285
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From: Crooks SD
Originally Posted by 1 Nasty Z
I also have wondered this because when you take your car to a shop for a dyno tune they just stick the probe in the tailpipe, cats or not they put it in the same place. Sorry this didn't sound too good after I read it again.
That's from the other thread I started... Honestly, I can't see WHY you have to put it in front of the cats based on this reason alone...
So, Cajun, how can dyno shops get away with putting it in the tailpipes?
Race Director
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From: Now in God's Country, the Big Sky, Montana!
Cruise-In 7-8-9-10 Veteran
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
I guess because they compensate in their heads for the differences. Some shops do it, I've seen it. It is just not the most accurate method. The one I look at it is if I'm gonna put the gauge in my car, I'm gonna set it up right to get the best readings possible. That's why I purchased the gauge. I installed it so I can watch my A/F on the track and any spirtied street runs. It doesn't take long to lean out an engine. 
Race Director
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From: Now in God's Country, the Big Sky, Montana!
Cruise-In 7-8-9-10 Veteran
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
Moreover, shops will put it in the tail pipe because they can get a close to accurate reading. This is in there own interest so the engine doesn't blow on the dyno. While they too would much prefer to have it in front of the cats, they are certainly not gonna lift your car up and do it for free.
Drifting
Joined: Oct 2004
Posts: 1,384
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From: Southwest Virginia
Many people running modded C5 don't have cats installed. Probing the end of the pipe is fine in this case. If they have cats then a lot of time the shop has no choice other than probing the end of the pipe. It is not quick and easy to install a bung in the exhaust. It normally requires removing the headers (or pipe) which normally requires removing the entire exhaust, not quick, not cheap. This was exactly why when installing my headers and WB bungs I welded extra bungs in the bottom of the headers as well. Since I planned on running cats I wanted easy access to the pre cat exhaust when I get it on a dyno. Now I can simply remove the plug and screw in a WB sensor or any adaptor needed to hook to their WB equipment. If you are going to do it and have the choice, why not do it right?
Le Mans Master
Joined: Oct 2005
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From: Location : Location :
Originally Posted by SpeedyZ
Many people running modded C5 don't have cats installed. Probing the end of the pipe is fine in this case. If they have cats then a lot of time the shop has no choice other than probing the end of the pipe. It is not quick and easy to install a bung in the exhaust. It normally requires removing the headers (or pipe) which normally requires removing the entire exhaust, not quick, not cheap. This was exactly why when installing my headers and WB bungs I welded extra bungs in the bottom of the headers as well. Since I planned on running cats I wanted easy access to the pre cat exhaust when I get it on a dyno. Now I can simply remove the plug and screw in a WB sensor or any adaptor needed to hook to their WB equipment. If you are going to do it and have the choice, why not do it right?
I should have done that when I put my LG's in 
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Melting Slicks
Joined: Mar 2003
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From: Macomb MI
There are different type of wide-bands. Most tail pipe sniffers are 3 or 5gas analyzer's that use a different technique to obtain the 02 content that most current heated 02 sensors.
Second, the wide-band will work pre or post Cat, with a minimal difference in readings, especially off idle. Preferred location is pre cat post turbo in "normal" applications.
Now, in your case there is a significant issue in that the back pressure created by the turbo skewing the measurements of the Bosch 4.x sensors (and any other charge pump 02). The amount it will skew the reading is dependant upon how much back pressure is present. But, Typical boost of 6-7 psi is 1 full air fuel point, but can be much higher.
I will attach the pertinent information as well.
Phil
Second, the wide-band will work pre or post Cat, with a minimal difference in readings, especially off idle. Preferred location is pre cat post turbo in "normal" applications.
Now, in your case there is a significant issue in that the back pressure created by the turbo skewing the measurements of the Bosch 4.x sensors (and any other charge pump 02). The amount it will skew the reading is dependant upon how much back pressure is present. But, Typical boost of 6-7 psi is 1 full air fuel point, but can be much higher.
I will attach the pertinent information as well.
Phil
Drifting
Joined: Dec 2005
Posts: 1,720
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From: East Hampton CT
I have an LC-1 on order and a set of LG Street headers (pro longtubes I believe...street from the collector back). The connection pipes came with 02 bungs already welded on there so I can just slap the wideband in there and get a nice reading after the headers....however my reason for writing....
I noticed the factory bung on the LG's seems to be mostly in front of one of the header pipes...wouldn't that skew your factory 02 readings? I mean instead of reading all 4 equally like the OEM manifold, you're basically getting 80% of the reading from one header. If that one plug/injector/wire/etc is off...it'll throw the whole deal off, won't it?
I noticed the factory bung on the LG's seems to be mostly in front of one of the header pipes...wouldn't that skew your factory 02 readings? I mean instead of reading all 4 equally like the OEM manifold, you're basically getting 80% of the reading from one header. If that one plug/injector/wire/etc is off...it'll throw the whole deal off, won't it?
Supporting Tuner
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From: ================== Houston, Texas www.englandgreen.com ================== Necessary Evil™ __________
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St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14
Originally Posted by RoadRebel
There are different type of wide-bands. Most tail pipe sniffers are 3 or 5gas analyzer's that use a different technique to obtain the 02 content that most current heated 02 sensors.
Second, the wide-band will work pre or post Cat, with a minimal difference in readings, especially off idle. Preferred location is pre cat post turbo in "normal" applications.
Second, the wide-band will work pre or post Cat, with a minimal difference in readings, especially off idle. Preferred location is pre cat post turbo in "normal" applications.
Team Owner
Joined: Apr 2001
Posts: 54,204
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From: S.W. Ohio. . . . . . NRA Life Member
Originally Posted by SpeedyZ
Well, either place would be the correct answer, it will work in either location. BUT only pre-cat will give you an accurate reading.
However, a very knowledgeable person told me I could put it AFTER the cats.
Last edited by Mike Mercury; Jun 8, 2006 at 07:49 PM.
