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DP Install: O2 Sensor ground question..
car: 1995 MB PEP M/T, all stock, adding RB catback and coated pettit SS DP
SO! Finally got my pre-cat off 15 minutes ago. grueling process for a newbie! gotta start somewhere. Anyway, examining my high temp ceramic coated DP--it looks like they coated the inner threads on the O2 sensor bung; I remember hearing that they should be left uncoated (and I requested that during the service but, long story, it must have been miscommunicated). I'm assuming the sensor uses the threads as its ground, and I also have read threads about problems when the O2 sensor isn't grounded properly...so: 1)do I have nothing to worry about? or 2)should I ground the O2 sensor separately? -If so, best method of doing so? I have a new in box univ. Bosch with its single wire just curious: 3)would the downpipe even act properly as a ground with its flanges coated as well (i.e. seems like it could not conduct electricity from the block, if coating insulates current) thanks for all feedback |
from what I know single wire O2 sensor actually creates voltage up to 1 volt and that is what is sent to the ECU to determine lean/rich conditions. I know that from the factory there was a ground(s) placed on the exhaust system but I'm not sure if it was for the O2 sensor.
edit: just read something that says it SHOULD ground through the exhaust. |
Exhaust is bolted to turbo(s).
Turbo(s) bolted to exhaust manifold. Manifold is bolted to engine. Engine is grounded. |
The O2 sensor must be grounded. I have no experience with coated downpipes, but I don't think the coating is conductive. I would chase the bung threads to clear off enough of the coating to ensure conductivity by installing and removing an O2 sensor a few times. I would also remove coating around the bolt holes of the flange that bolts to the turbo manifold.
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My DP was coated same as yours. The threads were coated as well. I left everything alone. I have had no problems.
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Originally Posted by Monkman33
(Post 11621656)
Exhaust is bolted to turbo(s).
Turbo(s) bolted to exhaust manifold. Manifold is bolted to engine. Engine is grounded.
Originally Posted by FDHoward93
(Post 11621962)
My DP was coated same as yours. The threads were coated as well. I left everything alone. I have had no problems.
After some searching on other forums (Z28), people with completely coated headers (which also should be grounded in a similar way) have had no problems with their O2 sensor . Considering I got it done by a reputable shop (IRPerformance), and FD howard has reported no problems, I'll give it a shot without shaving anything off. just a little paranoid about all of these potential bad ground issues. If i notice anything bad, i'll update this thread for those interested, also found: E. Electrical Properties Certain ceramics conduct electricity. Chromium dioxide, for example, conducts electricity as well as most metals do. Other ceramics, such as silicon carbide, do not conduct electricity as well, but may still act as semiconductors. (A semiconductor is a material with greater electrical conductivity than an insulator has but with less than that of a good conductor.) Other types of ceramics, such as aluminum oxide, do not conduct electricity at all. These ceramics are used as insulators–devices used to separate elements in an electrical circuit to keep the current on the desired pathway. Certain ceramics, such as porcelain, act as insulators at lower temperatures but conduct electricity at higher temperatures. |
Originally Posted by TpCpLaYa
(Post 11621607)
from what I know single wire O2 sensor actually creates voltage up to 1 volt and that is what is sent to the ECU to determine lean/rich conditions. I know that from the factory there was a ground(s) placed on the exhaust system but I'm not sure if it was for the O2 sensor.
edit: just read something that says it SHOULD ground through the exhaust. |
Originally Posted by TpCpLaYa
(Post 11621607)
from what I know single wire O2 sensor actually creates voltage up to 1 volt and that is what is sent to the ECU to determine lean/rich conditions. I know that from the factory there was a ground(s) placed on the exhaust system but I'm not sure if it was for the O2 sensor.
edit: just read something that says it SHOULD ground through the exhaust.
Originally Posted by Sgtblue
(Post 11622313)
There's a braided metal ground strap running from a bolt on (IIRC) the aft cat flange to chassis.
yup, I am familiar with that ground and Ray hooked me up with a replacement strap, though same issue---with entire pipe including flanges are coated, and if the coat isn't conductive, that ground is only going to affect catalyzation (which appears to be its main purpose at least from the threads ive read) |
With all coated parts (powder, plating, ceramic, hydro dip) current flow or conductivity changes. Our ceramic black coating does add some resistance to current flow. However it's generally not enough to make an issue. In general it's always a good idea to thread chase any coated parts to ensure proper operation of threading hardware. So to simply answer your question, you should be fine. If you are concerned you can remove the coating inside one of the mounting flanges bolt holes to allow for better current flow. You can also thread chase the O2 bung. Ironically the application of anti-seize will also add some resistance as well. However with all honestly when the O2 threads into the bung there is so much surface area your going to get a good ground pretty much no matter what you do. With the hundreds of exhaust pipes we do I have never had a customer have an issue with getting a proper ground with an O2 sensor. Hopefully that answers your question and puts you at ease. If not let me know and I'll do my best to get you going. |
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