How close to the cat. can the WB go? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-13-2010, 05:06 PM   #1
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Default How close to the cat. can the WB go?

I want/need to install a wideband bung in my supercharged car.
I searched around & found lots of posts saying away from the engine, in front of the cat.
I have the FM Butterfly brace & the blower in place & all the other excuses why I really don't want to remove the downpipe.
I'm wondering if its safe? to install the bung in the neck of the cat. There is about 3" there between the coupling & the body of the cat.
If that location is ok, I can slide the cat out the back to get the job done.
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Old 05-13-2010, 05:09 PM   #2
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I dont see any reason why that would be a problem in fact, many factory vehicles have the O2 sensor in that location
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Old 05-13-2010, 05:17 PM   #3
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+1, shouldn't be a problem since you are doing as advised and placing it before the cat. Only problem I can see is that the Cat does not last as long at the midpipe. So if the CAT decides to crap out you are going to have to weld in a new bung all over. This assumes OEM replacement.
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Old 05-13-2010, 05:19 PM   #4
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Its good to place away from turbo before the cat.
you want to place it away from the turbo and before cat.

what was your question again
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Old 05-13-2010, 05:20 PM   #5
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My one concern was that the cat heats up pretty good.
Due to the exaust flow, no problem when running, but what if I do 20 hard laps then stop. Will the heat kill the sensor or am I over thinking this?
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Old 05-13-2010, 05:21 PM   #6
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You want it before the cat so you see the real mixture, not after the cat have burnt up more gas.

You want it away from the turbo so the high EGTs don't lessen the longevity of the sensor.
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Old 05-13-2010, 05:23 PM   #7
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Quote:
Originally Posted by 18psi View Post
Its good to place away from turbo before the cat.
you want to place it away from the turbo and before cat.

what was your question again
I thought the subject explained the question pretty well?
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Old 05-13-2010, 06:15 PM   #8
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Quote:
Originally Posted by StarGehzer View Post
My one concern was that the cat heats up pretty good.
Due to the exaust flow, no problem when running, but what if I do 20 hard laps then stop. Will the heat kill the sensor or am I over thinking this?
yes
Quote:
Originally Posted by StarGehzer View Post
I thought the subject explained the question pretty well?
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Old 07-21-2010, 12:14 PM   #9
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What is the relationship between the distance away from the turbo and the o2 readings? Would the AF ratios still be accurate the further it is from the turbo? I am planning on relocating my wideband from the stock narrowband location to the exhaust, but that seems REALLY far away from the engine. But of course, if the exhaust gas velocity is fast enough than there's no lag to worry about.
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Old 07-21-2010, 12:20 PM   #10
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problem is heat and degradation of sensor.
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Old 07-21-2010, 01:17 PM   #11
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AFRs will still read the same as long as it's still before the cat. I don't think there would be an issue with delay but somewhere in the software is an adjustment for that too.
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Old 07-21-2010, 01:35 PM   #12
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I installed my wideband in the stock o2 location,
Removed the stock narrowband o2 sensor, installed wideband o2 sensor, wired it all in.
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Old 07-21-2010, 01:42 PM   #13
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I tried this. In back of the cat, he ignored it. A foot in front was no problem but moving it to within 3" he attacked it, and chewed one of the wires.
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Old 07-21-2010, 09:36 PM   #14
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Quote:
Originally Posted by rleete View Post
I tried this. In back of the cat, he ignored it. A foot in front was no problem but moving it to within 3" he attacked it, and chewed one of the wires.
Hah. I see what you did there.

But in all seriousness, typically you want it a bit back from the turbo to maximize the life of the O2 sensor.
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Old 07-21-2010, 09:42 PM   #15
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and the op has a supercharger and not a turbo, I would put it in stock location and run o2 simulation to the computer off the controller
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Old 07-22-2010, 04:28 AM   #16
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Use a heatsink pas er the manual and put it in the stock location. Irll be fine.

Mines been there for 5 years and many trackdays.

Similarly my mate has a Greddy same LC1 with a heatsink and in the stock location, again no issues.

Install it properly, use a heatsink use the stock location and stop worrying about it.
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Old 07-22-2010, 12:06 PM   #17
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I'm using an MP62 on my NB. My LC-1 is in the stock location with the narrow-band sensor removed. I'm also running without the heat-sink and it's been fine since October last year.

My sensor is also second-hand so it's had lots of miles on it.
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