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Dawek View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dawek Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2017 at 10:05am
Ok, got it. Just one more question. What is the reason for moving it out of direct exhaust stream? In stock (when before the main cat) it is mounted in direct exhaust stream, right? So what is the reason to move it out of the exhaust stream? (i'm a newbie, so sorry if it is a stupid question)
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Post Options Post Options   Thanks (1) Thanks(1)   Quote essNchill Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2017 at 11:36am
An aftermarket manifold doesn't have a pre-cat, so if you fit one on the 144 and leave the second sensor where it is, the readings will be insane :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dawek Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2017 at 12:29pm
Yeah, i understand that, maybe the question was posed wrong. I was just curious why does the second sensor have to be out of the exhaust stream after it was moved behind the main cat. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote bavs83 Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2017 at 12:34pm
The purpose of the pre cat and cat is to clean up the exhaust emissions. The ECU uses the first lambda to detect how much is needed to clean up. The second lambda checks to see if the precast is working and cleaning up as it should. The ECU will adjust the air fuel ratio to help with this. By removing a precat, your reducing the amount the car can clean. By moving the sensor past the main cat and out of direct stream the ECU thinks both cats are working fine and the engine management light won't come on.
If you keep the lambda I the air stream, it may think the engine or cat is a problem and your enine management light will come on.
Hope this makes sense......there is more science to this but I've just sumarised it
It's not what you drive....It's how you drive!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dawek Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2017 at 1:26pm
Oh, now I get why it should be moved out of the direct stream. Thanks man, I am looking forward to learning more about how all the stuff works. 
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