[3000GT MR]

Some of you know i've been working really hard on getting Bosch ADV lambda sensors working on the n54. It hasnt been an easy road but they have been running in my car for a few months and a few thousand miles now.13.0:1 to 20.0:1 was cake walk. Figuring out that BMW uses a different equation for every lambda richer than 13.0:1 was the biggest PITA. Im on revision 83 of my excel spread sheet if that means anything. Theres over 16 tables and im down to the very last few. During this time i wanted to point out a few things about
our AFR's and what you think they are actually reading vs what your seeing. I copy and pasted this from another forum so it may seem a little out of text.

The reason for trying to get these sensors to work is mainly for ST users but effects all of our cars. Our WB's werent made to operate in the exhaust preturbo where pressures can increase 60+psi. The readings get skewed and if you ever look at a ST log above 20 psi youll notice right off how wavy and inaccurate it is and how much the actual reading jumps around. Bosch makes a sensor specifically to work in these conditions. I have already tested and proven the success of them i just now have to finalize a few things before its publicly available. I'll eventually port all the testing and results here but for now they are else where on another forum if your interested. Anyways,

Just some random tuning tips.

Since AFR's have been a hot topic recently i figured i'd shed some light on actual AFR's vs what we are seeing. After browsing the 16+ or so tables that control lambda i got to the end where there is correction factors for both lean and rich modes vs Pressure. The DME compensates for pressure in the exhaust (yes even post turbo) due to the back pressure from the cats and exhaust system. The table is pretty small since there isnt a 2:1 ratio of boost pressure.

When i finish up my lambda testing for the Bosch ADV sensors these tables will be modded for different AFR and boost settings. It should be the very last thing for me to test before i release the final results. They are not a proportional so it makes it difficult to have just 1 table. If you have Stock turbos (catted or non-catted), or Hybrids non-catted, then i wouldnt worry about this.

Notes:
-Even with this correction the LSU 4.9 sensors still have over a 15-20% (ADV's are in the 3% range) deviation swing above 15psi EGP. All vehicle will give different results. Make sure you take proper precautions when making any changes.
-I have also proven that what the AEM WB AFR gauge displays is not nearly as accurate as what it logs. The + and - swings caused by pressure bumps may equal out by the end of the tail pipe or halfway through the exhaust but it is not what the ratio is burning inside the cyl.

These are the typical AFR's in current OTS maps. I used 2:1 as the boost to back pressure since that is more or less the ideal number

Lambda .880-.810 is the transition the DME goes from considering it lean to rich. Its a very grey area because certain criteria needs to be me for the switch. I suggest tuning richer than 12. @Terry@BMS is this why your high power maps are set to 11.9? did you have anomalies going leaner? There is a separate calculation for leaner than 12 but like i said its a grey area. I added 12.3 in there so you could see how the tables turned.



Target in DME....................Actual
30psi
12.3.................................12.2
11.9.................................12.02
11.7.................................11.93
11.5.................................11.84
11.3.................................11.75
11.0.................................11.6


25psi
12.3....................................12.1
11.9....................................12.02
11.7....................................11.78
11.5....................................11.7
11.3....................................11.6
11.0.................................. 11.46

20psi

12.3.................................11.98
11.9.................................11.77
11.7..................................11.66
11.5..................................11.55
11..3.................................11.44
11.0................................ 11.28

Sorry i should have explained this a little better, i was in a rush trying to leave work plus im already a scatter brain and im not that good at putting thoughts down to paper as words.

Long story short, As you pressurize exhaust gas the the WB o2's readings become skewed. This is because of the different matter being compressed. This is not a sensor issue, its just physics. The DME has in place a table that compensates this to a point. So if the DME sees X amount of boost it knows that the back pressure should be X through testing. So what it does is use these multiplication factors based off the sensors manufacturer to get the AFR back in check. IE if you were targeting 11.7 @25psi boost with a 2:1 boost to EGP then your actual AFR is around 13.10-13.20. So the DME uses this multiplication factor to richen the AFR so that the target 11.7 is actually 11.7. As you richen the mixture the more lean it reads. The stock map was set to 10.8:1 so it required A LOT of correction. Hence why its not "that bad" considering what we are doing with them. Theres also a separate equation for lambdas leaner than .810-.880. This isnt BMW specific its strictly physics. If our engines were N/A and we stuck O2's pre turbo we would end up with a absolute tuning nightmare. To be honest we lucked out big time. A number of variables could have thrown these numbers off a lot more. Everything from Factory AFR's, stock cat and exhaust restrictions, work around AFR corrections that were based off specific cells which is a work around for other platforms. The stars really had to align for us to be as successful as we have.

Bosch LSU 4.9 and NGK NTK's for our car are identical. They were both made to the exact spec. They both have a deviation in 15-20% at 1bar of EGP. This means that no matter how you play the pressure table you could still have over a point or two swing in actual reading. Some people have burnt up Bosch's and had better luck with NGK's etc, Thats probably just manufacturing issues. I have had over 30K miles on ST's and have seen old sensors last 20k and new ones last 5k.

The ADV sensors are much more accurate and consistent in exhaust pressure so that with the combination of the pressure compensation tables equals a very accurate true reading. Thats the overall reason for this project as a whole. However i wanted to bring this to light so that you know what your trying to actually targeting when you tune your AFR table.


Enjoy and tune safe

[terryd5150]

Excellent post.

[JDuke335i]

^^^^ +1

[135Pats]

How the F are only two people interested in this?

These are huge developments for post-turbo wideband use.

[Jeff@TopGearSolutions]

Originally Posted by 135Pats

How the F are only two people interested in this?

These are huge developments for post-turbo wideband use.

Definitely an interesting read but there are only a bunch of upgraded turbo guys compared to the majority being stock turbo, which this won't affect.

Also I'm not sure how much of the majority know the flaws of the AFR or even know what this means. Haha.

[3000GT MR]

Originally Posted by 135Pats

How the F are only two people interested in this?

These are huge developments for post-turbo wideband use.

Pre-trubo

Originally Posted by Jeff@TopGearSolutions

Definitely an interesting read but there are only a bunch of upgraded turbo guys compared to the majority being stock turbo, which this won't affect.

Also I'm not sure how much of the majority know the flaws of the AFR or even know what this means. Haha.

Well when everyone buys these Chinese $3k ST kits they'll learn real quick. But then again if your buying a $3k ST you probably wont have the supporting mods to make any type of power safely anyways.

IDK why my engine blew up. It was only 30psi with a single fire hose meth nozzle

[1BADM3]

Originally Posted by 3000GT MR

Some of you know i've been working really hard on getting Bosch ADV lambda sensors working on the n54. It hasnt been an easy road but they have been running in my car for a few months and a few thousand miles now.13.0:1 to 20.0:1 was cake walk. Figuring out that BMW uses a different equation for every lambda richer than 13.0:1 was the biggest PITA. Im on revision 83 of my excel spread sheet if that means anything. Theres over 16 tables and im down to the very last few. During this time i wanted to point out a few things about
our AFR's and what you think they are actually reading vs what your seeing. I copy and pasted this from another forum so it may seem a little out of text.

The reason for trying to get these sensors to work is mainly for ST users but effects all of our cars. Our WB's werent made to operate in the exhaust preturbo where pressures can increase 60+psi. The readings get skewed and if you ever look at a ST log above 20 psi youll notice right off how wavy and inaccurate it is and how much the actual reading jumps around. Bosch makes a sensor specifically to work in these conditions. I have already tested and proven the success of them i just now have to finalize a few things before its publicly available. I'll eventually port all the testing and results here but for now they are else where on another forum if your interested. Anyways,

Just some random tuning tips.

Since AFR's have been a hot topic recently i figured i'd shed some light on actual AFR's vs what we are seeing. After browsing the 16+ or so tables that control lambda i got to the end where there is correction factors for both lean and rich modes vs Pressure. The DME compensates for pressure in the exhaust (yes even post turbo) due to the back pressure from the cats and exhaust system. The table is pretty small since there isnt a 2:1 ratio of boost pressure.

When i finish up my lambda testing for the Bosch ADV sensors these tables will be modded for different AFR and boost settings. It should be the very last thing for me to test before i release the final results. They are not a proportional so it makes it difficult to have just 1 table. If you have Stock turbos (catted or non-catted), or Hybrids non-catted, then i wouldnt worry about this.

Notes:
-Even with this correction the LSU 4.9 sensors still have over a 15-20% (ADV's are in the 3% range) deviation swing above 15psi EGP. All vehicle will give different results. Make sure you take proper precautions when making any changes.
-I have also proven that what the AEM WB AFR gauge displays is not nearly as accurate as what it logs. The + and - swings caused by pressure bumps may equal out by the end of the tail pipe or halfway through the exhaust but it is not what the ratio is burning inside the cyl.

These are the typical AFR's in current OTS maps. I used 2:1 as the boost to back pressure since that is more or less the ideal number

Lambda .880-.810 is the transition the DME goes from considering it lean to rich. Its a very grey area because certain criteria needs to be me for the switch. I suggest tuning richer than 12. @Terry@BMS is this why your high power maps are set to 11.9? did you have anomalies going leaner? There is a separate calculation for leaner than 12 but like i said its a grey area. I added 12.3 in there so you could see how the tables turned.



Target in DME....................Actual
30psi
12.3.................................12.2
11.9.................................12.02
11.7.................................11.93
11.5.................................11.84
11.3.................................11.75
11.0.................................11.6


25psi
12.3....................................12.1
11.9....................................12.02
11.7....................................11.78
11.5....................................11.7
11.3....................................11.6
11.0.................................. 11.46

20psi

12.3.................................11.98
11.9.................................11.77
11.7..................................11.66
11.5..................................11.55
11..3.................................11.44
11.0................................ 11.28

Sorry i should have explained this a little better, i was in a rush trying to leave work plus im already a scatter brain and im not that good at putting thoughts down to paper as words.

Long story short, As you pressurize exhaust gas the the WB o2's readings become skewed. This is because of the different matter being compressed. This is not a sensor issue, its just physics. The DME has in place a table that compensates this to a point. So if the DME sees X amount of boost it knows that the back pressure should be X through testing. So what it does is use these multiplication factors based off the sensors manufacturer to get the AFR back in check. IE if you were targeting 11.7 @25psi boost with a 2:1 boost to EGP then your actual AFR is around 13.10-13.20. So the DME uses this multiplication factor to richen the AFR so that the target 11.7 is actually 11.7. As you richen the mixture the more lean it reads. The stock map was set to 10.8:1 so it required A LOT of correction. Hence why its not "that bad" considering what we are doing with them. Theres also a separate equation for lambdas leaner than .810-.880. This isnt BMW specific its strictly physics. If our engines were N/A and we stuck O2's pre turbo we would end up with a absolute tuning nightmare. To be honest we lucked out big time. A number of variables could have thrown these numbers off a lot more. Everything from Factory AFR's, stock cat and exhaust restrictions, work around AFR corrections that were based off specific cells which is a work around for other platforms. The stars really had to align for us to be as successful as we have.

Bosch LSU 4.9 and NGK NTK's for our car are identical. They were both made to the exact spec. They both have a deviation in 15-20% at 1bar of EGP. This means that no matter how you play the pressure table you could still have over a point or two swing in actual reading. Some people have burnt up Bosch's and had better luck with NGK's etc, Thats probably just manufacturing issues. I have had over 30K miles on ST's and have seen old sensors last 20k and new ones last 5k.

The ADV sensors are much more accurate and consistent in exhaust pressure so that with the combination of the pressure compensation tables equals a very accurate true reading. Thats the overall reason for this project as a whole. However i wanted to bring this to light so that you know what your trying to actually targeting when you tune your AFR table.


Enjoy and tune safe

I would be a set ASAP.

[135Pats]

Originally Posted by 3000GT MR

Pre-trubo

Derppp. I need more coffee

[3000GT MR]

I have a few ADV retro kits available, They are limited supply. They are a must have for any ST owner. No more burning up sensors on a monthly basis!

http://www.e90post.com/forums/showth...4#post19704124

[bradsm87]

This is excellent work. I love seeing things like this advance.

Just a note: Let's say with turbo x targetting flat 25psi, boost to exhaust backpressure is about 1:1 as you reach full boost and ends up at 3:1 at redline. It varies between turbos but the % difference between say 4000rpm and 7000rpm follows a similar pattern. It generally increases a lot with revs rather than tied to a boost level. BorgWarner MatchBot is the best tool for calculating this.

[3000GT MR]

Originally Posted by bradsm87

This is excellent work. I love seeing things like this advance.

Just a note: Let's say with turbo x targetting flat 25psi, boost to exhaust backpressure is about 1:1 as you reach full boost and ends up at 3:1 at redline. It varies between turbos but the % difference between say 4000rpm and 7000rpm follows a similar pattern. It generally increases a lot with revs rather than tied to a boost level. BorgWarner MatchBot is the best tool for calculating this.

You bring up a good point. I did testing at various boost levels and came up with a good boost to correction factor table to get you close. Luckily these sensors can tolerate a much wider range of pressure before readings become skewed. This in conjunction with my mAmeas*gain*theoretical EGBP (simplified) calculator you can get a correction factor based off your PR and boost setting. The pressure comp tables for both gains will be available in an upcoming XDF release. Terry will be implementing pressure comp specific to these sensors like he has for the OEM ones on the JB4. I gave him all that he needed to have a active and dynamic range compensation. For the Flash only guys rescaling X-Axis will give better resolution for your particular boost setting.