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Engineering/Technical Ask technical questions about cars. Do you know how a car engine works? |
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10-17-2011, 12:46 PM | #1 | |
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Oxygen Sensor Question
I am going to be replacing my entire exhaust system with a custom high-performance setup. One part that I always was unsure about is the O2 sensor. I know what it is, I know what it does (Wikipedia is very helpful). The only thing I can't seem to find out is if I can run without it? And if it helps at all, I am going with an exhaust system that does not have a catalytic converter.
I realize that the check engine light will come on, but I'm getting an OBDII cable to reset it. I am trying to get as much performance out of this exhaust as possible and I don't care about emissions or increased fuel-usage. The thing is, I do care about my engine. If the lack of an O2 sensor is guaranteed to harm my engine, I'll probably install one. Also, in my stock setup it has two O2 sensors. One on the headers and a second one after the cat. conv. If I have only one O2 sensor (on the headers), will it still be the same? From all I've gathered, the second one is basically just to tell you if your cat. conv. is bad/going bad. Thanks in advance for any help! |
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10-17-2011, 01:01 PM | #2 | |
The Big Meaney
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Re: Oxygen Sensor Question
Your O2 sensor is what tells teh computer how to mix the fuel. it's absolutely necessary. Try to locate it in teh same place as stock on teh new exhaust, so it can measure teh exhuast properly. The after cat O2 sensor is, as you surmised, there to tell the computer whether the cat is working properly. it can be removed or made non-functional and it wont' affect how the car runs at all. BUT, as you guessed, it will set off the check engine light. You can reset it, but it will keep coming back on every 60 miles or so. A better idea is to use it, but instead of just putting an O2 senosr bung in the exhuast downstream and deal with it, you shoudl use a spark plug anti-foul device in the O2 sensor bung, drilled out to allow the O2 sensor to mount, maybe doubleing up on it. What this does is to take the rear O2 out of the exhaust stream so it reads as though the proper amount of work is being done by the no longer existing catalytic converter.
http://www.google.com/search?hl=en&r...d&spell=1&sa=X these links show how that's done. Out of curiosity, why not use a high flow catalytic converter in the exhaust? It can work liek a muffler/resonator and they are rather cheap from Magnaflow (I used a pair of Magnaflow high flow cats in my BMW and removed the mufflers for a high performance exhaust that is still clean)
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10-17-2011, 03:13 PM | #3 | |||
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Re: Oxygen Sensor Question
Quote:
When reading about OBDII tweaking software, I have heard that if you do tweak the ECU, it will basically reset itself with information gathered from the sensors. If the sensors are gone, the ECU can't change what you have already changed. I am going to go sensor-less on the custom air-intake that is soon-to-be-built. Let me just say this: I hate sensors and computers in cars. I don't want the ECU making decisions for me. I want to make the decisions in my engine. It would be nice if things were manually, mechanically adjustable, but modern cars rely so much on computers. Traction/stability control? Hate it. Which is why I'm glad my car doesn't have it Quote:
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10-17-2011, 03:32 PM | #4 | |||
The Big Meaney
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Re: Oxygen Sensor Question
Quote:
Quote:
Seriously these days there's little reason to go back to carbs and non catalyst equipped systems to get the power you want. And just saying "I want my car to run dirty and innefficiently" isn't really a good enough reason.
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10-20-2011, 04:03 PM | #5 | ||
Master Connector
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Re: Oxygen Sensor Question
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If you hate modern computer controlled engine management systems, and the massive benefits they offer in terms of performance, reliability and efficiency, then sell your car and go buy something from the 60s or 70s. Removing the O2 sensors will not do good things and the car will not very well. What ever you read about the system staying closed loop will only apply to some engines, and staying closed loop is not for them. It's intended to get the car home should something fail. Driving it long term could lead to a wrecked engine, as it will run to rich, or to lean both of which can be fatal in different ways. The O2 sensor is there to tell the computer how rich or lean the fuel mix is, and adjust it accordingly, it's fundamental to the engine running properly.
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10-24-2011, 10:16 AM | #6 | |
The RustBuster
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Re: Oxygen Sensor Question
I certainly prefer things to be simpler as well, but I do like the ECU's capability of helping to diagnose problems.
Not that I'm condoning this, but if you're gonna delete the O2 sensors then you might as well delete the cats, too. This for the simple fact that running an OBD-controlled car without sensors will cause it to run in open-loop mode, which is a richer fuel delivery. The excess fuel gets into the cats and overheats them because it is trying to eliminate them from the exhaust. This causes them to melt inside and become plugged, ruining performance and destroying a pair of expensive cats. You can run the upstream sensors but delete the cats and downstream sensor(s). An ECU reprogram or wiring trickery would be needed to counter the missing sensor, but you'd get reasonably efficient performance and free-flow exhaust.
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