Thread: Regrounding the O2 Sensor

My $300 fluke does not read it accurately enough, its just something that needs to be a specific meter to read in the mili or micro ohms.

I would assume all motors with a plated Stainless Steel header will benefit, not just SR20's. Its just the fact that it is not a GOOD ENOUGH ground to get the best readings possible.

The more people that do some tests the better. From VE's to DE's to GA's, we will benefit from the results.

You are correct Mr-4-door-sr20de & Squirtz... This is a Stainless Steel grounding issue and it applies to all cars with 3-wire O2 sensors (odb1 or odb2). Stronger and accurate O2 signals are all transmitted with better grounds; otherwise some signals never make it... I do believe (and testing shows it too) that the newer/faster types of O2 sensors will benefit OBD2 cars more (ecu processor is faster and can read all of the incoming faster O2 signals).

Calum ecu's are modded OEM ecus with daughter boards and improved mapping.. This mod is to improve the signal strength to any ECU (modded or not). As a added benefit, the 4-wire O2 sensor is also faster and will send more signal pulses (thimble vs planar). Also, the heater element reaches operating temperatures in 10 seconds (old type takes about 3-5 minutes!!) but the ODB1 ECU cant take advantage of this due to the 3 minute Air Regulator cycle at startup.

Your $3 DVM probably dont have the ohm setting necessary to see a difference but your car's ECU definitely will.. And your gas mileage should also improve due to ecu actually receiving signals & more of them..

AGAIN, if your car has a Stainless Steel Header AND a 3-wire O2 sensor, then this mod will improve the quality of the O2 signal to the ECU. NO OTHER component is impacted.. Side effect benefits are smoother idling (due to the ECU is now receiving data and can improve the A/F mixture) and better gas mileage (O2 sensor accurancy signal improvements). The only mod differences between Car Mfgs (US, Japanese, German, etc) is determining the correct equivalent 4-wire O2 sensor replacement with the same voltage and signal ranges as the original OEM sensor (I cheated and called the Bosch techs).

Well, I dont believe it!!! I actually passed the Md Emissions test for the 1st time ever with my NX today!!!

Car setup:
- Reinstalled the 4-wire O2 sensor (grounded on the Intake Mani w/the MAF reground)
- EGR blockoff kit installed but reinstalled the AIV (adds fresh air to the exhaust)
- Set timing to 13 degrees
- Set idle to 750 rpm at operating temp
- Cleared the Calum ECU relearn (so settings takes effect immediately)

Drove car to inspection station (approx 15 miles), kept car running while waiting in line (so it wont cutoff), and they tested the car... It freaking passed ! ! !

Moral: You can pass emissions with a NX2000 if you set it to run like crap!! I will be removing the AIV, resetting the timing & idle, and resetting the ECU to get it back to normal operating power settings..
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Your Fluke DVM has the settings required to actually see the differences..
Give me a call and we can discuss how to setup the DVM and how to perform some tests.

Congrats Scotty!

Very interesting too

Awesome news, Scotty! I was pondering re-installing my AIV for testing, and I think I will do just that.

For others following the thread, I am running the Bosch 4 wire 15727 sensor on the front position of the SSAC 2.5" header, and I can confirm this is a worthwhile mod for the OBD I highport. Using Conzult to monitor O2 sensor output, and rich/lean condition, the voltage oscillates appropriately during the mode II test, and drivability is great!

Darrin

so it's just stainless that has the problem right?

cause i have a ceramic coated header

Well is it the Stainless core? Plus I don't think anything else will be quiet as good as a ground at your ECU ground

Darrin,
Adding the fresh air back into the exhaust, installing the regrounded O2 sensor and rolling back the timing & idle, did the trick for me. I was soooooo surprised to actually pass!!

Good luck on your testing!!

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Dont know about a ceramic covered head.. Like Vadim says, if its has stainless steel under the ceramic, then you have the same grounding problem. But if its just steel or aluminum, you should be fine using your 3-wire sensor (especially if your sensor is not old)..

Reinstalling the AIV allowed me to pass MD emissions testing with S3 cams.

Great Bill.. How's it going? Havent talked to you in a while...

So my decision to put it back for the smog test was a good one. I really didnt expect the car to pass and was gathering receipts for the $450 waiver.

Btw Bill, the 4-wire O2 testing result is starting to look real good. The signal is super strong and accurate. My mpgs are improving to around 30mpg. The bogging is better but still there. Im resetting my car this weekend. Thinking of checking my A/F ratios again after all of the changes made since I last checked; replaced cams, some lifters and a few shims. So, let me know if you are free in the next few weeks. I need to run-through a few more tanks of gas without any engine changes before I do the test.

This will be my final check before closing this thread and doing a complete howto writeup with my findings, mpg & idle improvements, and A/F mixture changes.
LMK your availability..