The Effect of Replacing O2 Sensors - Results

The Convert

Captain
Jun 4, 2017
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I've had a bit to eat and drink today, and am yet to drop a deuce this evening. So, I'll have a look see at those posts of yours you recommend.
 

matreyia

Major
Apr 19, 2017
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I've had a bit to eat and drink today, and am yet to drop a deuce this evening. So, I'll have a look see at those posts of yours you recommend.

Remember to save it for the post Dr. Superior. You really must think you fucking great. Holy shit... the comments I have been reading from your past posts. Just...holy shit.
 

matreyia

Major
Apr 19, 2017
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Twisted tuning is the only good decision you've made this far. Personally, I think you should just sell your car though. Your candle doesn't quite burn bright enough for this platform I'm afraid.

Why is that Convert? Why is Twisted a good decision?
 

The Convert

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Jun 4, 2017
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Why is that Convert? Why is Twisted a good decision?
from what I have seen on the forums, and from his posting, he genuinely seems like he cares about trying to meet the customer's goals without putting their motor at unnecessary risk with overly aggressive timing tables and tuning beyond the limits of the map sensor.
 

matreyia

Major
Apr 19, 2017
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from what I have seen on the forums, and from his posting, he genuinely seems like he cares about trying to meet the customer's goals without putting their motor at unnecessary risk with overly aggressive timing tables and tuning beyond the limits of the map sensor.

So you have his tune?
 

The Convert

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Jun 4, 2017
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No, but he is someone I would be willing to talk to about tuning my car if I was in need of a tuner.
 

langsbr

Captain
Apr 5, 2017
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They aren't, except for when you have to have them because of emissions. I have a Twisted tuning tune, and am very happy. Justin is a true professional and tunes on many platforms, not just BMWs.
 

langsbr

Captain
Apr 5, 2017
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Unless the UPS truck hits a pothole and kills the engine.
 
Nov 8, 2016
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NY
Actually its a pretty well known fact, that 02 Sensor's after about 60k-100k miles of use are extremely "lazy". Even though they might not trigger a CEL, doesn't mean they're no longer effective in giving the DME a proper AFR Reading.

An improper 02 Sensor reading can cause a bunch of issues. Most of the time, nothing major. The worst usually being a CEL light to be triggered, but poor running, starting, idling, engine efficiency, and fuel economy will usually always suffer as an 02 Sensor gets old and gives out slow reacting and slightly incorrect readings to the DME, which is what causes the issues/problems i outlined above.

I would say anyone on here with a N54/N55, etc with above 80k miles, would absolutely benefit from a 02 Sensor Replacement. That being said, if you're not going to replace with OEM Bosch (02) Oxygen Sensors, than you might have better rtesults with the older 02 sensors,. than cheap off-brand replacements, just for the sake of replacing them...

Off Topic: My old DD was a 2001 Mazda Protege 2.0L DOHC 16V 4CYL - Automatic. The car only had about 130HP , but was a great car for a DD. Very Comfortable, super reliable, parts very easy to get; any parts store. Also as far as servicing goes, nothing was required except regular maintenance, in the 4 years I've owned it. Basically a great DD.

However, after woning it for the 4 years, i started to notice the MPG go down pretty steadily arpund the 3yr mark. So i did a tune-up, since it needed it anyway. Car definitely ran better with new plugs/wire/coils/filters/pcv valve/Trans Serv/Etc..
I was hoping to get the near 30mpg highway mileage i was used too, back, but it was still lacking and probably only went up 1-2 mpg, to about 24mpg highway & light mixed town driving.

So i thought about it some more and figured that with 95k miles at the time, the 02 sensors, were probably ready to be changed.
So I found out that Bosch was OEM manufacturer for the 02 sensors, and after reading the forum..
Everyone suggested just changing the 1st 02 Sensor, in-line, from the engine. The reasoning being is that, this is the sensor that controls the AFR for the ECU, and the 2nd 02 Sensors is used mostly to compare the two sensors and make sure the Cat is doing its job. Cleaning up the exhaust to the proper standards set by the ecu.

So i ordered the OEM Up-Stream 02 sensor and installed, and what do you know... The car ran better, had more power, was more peppy, and most importantly, I was able to get OVER 30MPG highway/light in town driving..


So I know this was a long post, but anyone that understands the basics of how an ECU for a fuel injected car uses it sensors to calculate the amount of necessary fuel needed.. It makes perfect sense that a Old, Tired, Slow, and Inaccurate 02 sensor's, especially on the Up-Stream's of each Bank (Bank 1 & Bank 2), will make a noticeable and in some cases a drastic difference if new 02's are installed.

That being said, even before reading this thread ive been planning on replacing my two UP-STREAM 02's in the near future. I dont feel like it's necessary to replace the Down-Stream 02 sensors's, especially on a Tuned Car, with DP's, bc theyre basically not doing anything at all. Thne Tune or Piggyback is just showing the DME what it wants to see from the two Down-Stream 02's, as to not trigger a CEL, which would happen , if all you did was remove the DP's and did nothing else on the DME Tuning Side.

Some Places are stricter than other's. I noticed as lot of overseas guys (Germany, UK, Italy, Etc), use High-Flow Dp's, rather than Catless Dp's b/c of stricter emission's laws and Inspections..

Also dont forget that piggyback tuner's using Auto-Tune do rely on Data from the First two 02 sensors for AFR data, so if this data is incorrect or too slow to respond, you won't have a clean and efficient Auto-Tuned Map.

Higher Efficiency = Cleaner/Complete Burn = Less Heat = Smoother Running = More Fuel Efficiency= More Power!!!
 

matreyia

Major
Apr 19, 2017
1,780
711
0
Ride
335i e93
Actually its a pretty well known fact, that 02 Sensor's after about 60k-100k miles of use are extremely "lazy". Even though they might not trigger a CEL, doesn't mean they're no longer effective in giving the DME a proper AFR Reading.

An improper 02 Sensor reading can cause a bunch of issues. Most of the time, nothing major. The worst usually being a CEL light to be triggered, but poor running, starting, idling, engine efficiency, and fuel economy will usually always suffer as an 02 Sensor gets old and gives out slow reacting and slightly incorrect readings to the DME, which is what causes the issues/problems i outlined above.

I would say anyone on here with a N54/N55, etc with above 80k miles, would absolutely benefit from a 02 Sensor Replacement. That being said, if you're not going to replace with OEM Bosch (02) Oxygen Sensors, than you might have better rtesults with the older 02 sensors,. than cheap off-brand replacements, just for the sake of replacing them...

Off Topic: My old DD was a 2001 Mazda Protege 2.0L DOHC 16V 4CYL - Automatic. The car only had about 130HP , but was a great car for a DD. Very Comfortable, super reliable, parts very easy to get; any parts store. Also as far as servicing goes, nothing was required except regular maintenance, in the 4 years I've owned it. Basically a great DD.

However, after woning it for the 4 years, i started to notice the MPG go down pretty steadily arpund the 3yr mark. So i did a tune-up, since it needed it anyway. Car definitely ran better with new plugs/wire/coils/filters/pcv valve/Trans Serv/Etc..
I was hoping to get the near 30mpg highway mileage i was used too, back, but it was still lacking and probably only went up 1-2 mpg, to about 24mpg highway & light mixed town driving.

So i thought about it some more and figured that with 95k miles at the time, the 02 sensors, were probably ready to be changed.
So I found out that Bosch was OEM manufacturer for the 02 sensors, and after reading the forum..
Everyone suggested just changing the 1st 02 Sensor, in-line, from the engine. The reasoning being is that, this is the sensor that controls the AFR for the ECU, and the 2nd 02 Sensors is used mostly to compare the two sensors and make sure the Cat is doing its job. Cleaning up the exhaust to the proper standards set by the ecu.

So i ordered the OEM Up-Stream 02 sensor and installed, and what do you know... The car ran better, had more power, was more peppy, and most importantly, I was able to get OVER 30MPG highway/light in town driving..


So I know this was a long post, but anyone that understands the basics of how an ECU for a fuel injected car uses it sensors to calculate the amount of necessary fuel needed.. It makes perfect sense that a Old, Tired, Slow, and Inaccurate 02 sensor's, especially on the Up-Stream's of each Bank (Bank 1 & Bank 2), will make a noticeable and in some cases a drastic difference if new 02's are installed.

That being said, even before reading this thread ive been planning on replacing my two UP-STREAM 02's in the near future. I dont feel like it's necessary to replace the Down-Stream 02 sensors's, especially on a Tuned Car, with DP's, bc theyre basically not doing anything at all. Thne Tune or Piggyback is just showing the DME what it wants to see from the two Down-Stream 02's, as to not trigger a CEL, which would happen , if all you did was remove the DP's and did nothing else on the DME Tuning Side.

Some Places are stricter than other's. I noticed as lot of overseas guys (Germany, UK, Italy, Etc), use High-Flow Dp's, rather than Catless Dp's b/c of stricter emission's laws and Inspections..

Also dont forget that piggyback tuner's using Auto-Tune do rely on Data from the First two 02 sensors for AFR data, so if this data is incorrect or too slow to respond, you won't have a clean and efficient Auto-Tuned Map.

Higher Efficiency = Cleaner/Complete Burn = Less Heat = Smoother Running = More Fuel Efficiency= More Power!!!


I can personally confirm your findings on my e93 and on my 2004 MPV. Both benefited from replacing all the sensors. More power, better throttle response, and shifting transmission points.
 

veer90

Lieutenant
Nov 16, 2016
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West Nyack, NY
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e90 335i 6MT
On N54s all 4 O2 sensors affect fuel trims and fuel economy, and they DO take a shit around the 100k mile mark causing rough running, O2 codes, and bad MPGs. This info is from me speaking with a BMW master tech. I also changed my O2 sensors when I hit 100k and noticed a significant MPG improvement. For me it was about a 20% improvement, but I also wasn't getting 12 mpg before.
 
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