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    dual bank O2 sensor solution brainstorm thread

    With the recent advances of both cobb and jb4 being able to control boost for single turbo applications I think the next important step is to solve the pre turbo O2 sensor issue. Being able to run post turbo O2 sensors will make life alot easier for single turbo users. It will vastly extend the life of the O2 sensors as well as allow better spooling more compact manifolds and even cheap options like cast log manifolds. Bimmerboost is home to the AT transflash, the True open flash, and much more. I think if there is any forum that can solve this problem its this one. Think about being able to make 600+whp for under 4k. Think of the children. For just posts a day you can solve the N54 O2 dilemma.
    Turbo lag is the on ramp to the highway which is power.

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    Click here to enlarge Originally Posted by WDBi Click here to enlarge
    With the recent advances of both cobb and jb4 being able to control boost for single turbo applications I think the next important step is to solve the pre turbo O2 sensor issue. Being able to run post turbo O2 sensors will make life alot easier for single turbo users. It will vastly extend the life of the O2 sensors as well as allow better spooling more compact manifolds and even cheap options like cast log manifolds. Bimmerboost is home to the AT transflash, the True open flash, and much more. I think if there is any forum that can solve this problem its this one. Think about being able to make 600+whp for under 4k. Think of the children. For just posts a day you can solve the N54 O2 dilemma.
    I'm a newb. explain why we can't do this right now.

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    We need to really start disassembling the fueling stuff in the roms.

    NickG made it possible on e46 m3 and I'm hoping will we be able to do the same in time.

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    I haven't spent much time thinking about this because I'm still in stock turbo land. That said... can someone clearly articulate the problem? By design the o2 sensors are bank specific, right? Is the issue that you lose o2 sensor feedback from bank to bank, or that bank specific feedback from the o2 sensors is now an average of the 2 banks, so feedback origin is lost?

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    Im not quite sure the exact reason we cant just run post turbo O2 sensors but i know its a problem and i know its preventing n54 guys from getting things like this http://www.spracingonline.com/store/...KIV_Supra/3256
    Turbo lag is the on ramp to the highway which is power.

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    Well... if you have a single turbo, obviously with one output that is the sum of both banks 1 & 2... lets say bank 1 is running perfect but bank 2 is running rich. Your post turbo 02 sensors will, since both banks are merged, read as both banks being slightly rich. DME will pull some fuel until o2 values are in normal range. This could end up with bank 1 running lean (knock city) and bank 2 still running rich, but your averaged post turbo o2 values being just right.

    Just a guess.... sound right?

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    Click here to enlarge Originally Posted by SCGT Click here to enlarge
    Well... if you have a single turbo, obviously with one output that is the sum of both banks 1 & 2... lets say bank 1 is running perfect but bank 2 is running rich. Your post turbo 02 sensors will, since both banks are merged, read as both banks being slightly rich. DME will pull some fuel until o2 values are in normal range. This could end up with bank 1 running lean (knock city) and bank 2 still running rich, but your averaged post turbo o2 values being just right.

    Just a guess.... sound right?
    Makes sense to me but how do other cars run with just 1 O2 sensor?

    I think its more of a making the DME happy thing than a tuning issue
    Turbo lag is the on ramp to the highway which is power.

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    Click here to enlarge Originally Posted by WDBi Click here to enlarge
    Makes sense to me but how do other cars run with just 1 O2 sensor?

    I think its more of a making the DME happy thing than a tuning issue
    By not having individual banks? Making fuel adjustments globally (all cylinders)? It's a step backwards to lose the seperate banks, although it would solve the issue.

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    The way I understand it is the DME reade the 3 banks as 2 separate 3 cylinder motors, just as was describe above if you merge them the DME will not have an accurate picture of which bank or motor is running rich or lean. It sounds to me unless someone can figure out how to make the DME read both banks together its not possible, and to me that sounds like something you would have to reprogram the entire DME for as every table must reference both banks I am assuming. I could be way off, but this is not a problem that will be solved but discovering a hidden port on the solenoids.

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    So as of today, you can either:

    1: Go pre-turbo O2 and keep individual bank control, at the expense of some o2 sensor accuracy and life expectancy.
    2: Go post-turbo O2 and have to figure out how to preprogram the DME or live with severe O2 related issues.

    Between those 2 options I'd rather come up with a way to shield the O2 sensor from the heat and pressure it's exposed to while pre-turbo. That's directly related to me not knowing anything about programming the DME, and being uninterested in learning how to, lol.

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    you have to remember that there are plenty of 1000+hp turbo cars running post turbo O2 sensors.

    @Terry@BMS , @dzenno@PTF Could you elaborate on the specific issue?
    Turbo lag is the on ramp to the highway which is power.

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    Hopefully someone will figure it out. I am sure Terry can explain why they have to be separate. I know it has something to do with pulses between banks.

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    Click here to enlarge Originally Posted by WDBi Click here to enlarge
    you have to remember that there are plenty of 1000+hp turbo cars running post turbo O2 sensors.

    @Terry@BMS , @dzenno@PTF Could you elaborate on the specific issue?
    Um, all cars run the O2's post turbo. Think you are kinda confused on what is going on here. With a single you can run all 4 post turbo if you want, sure throw them in the dp. Problem is everything is merged. As I said the DME is seeing things as 2 separate 3 cylinders. Why do you think I went to all the trouble of building stage 3, because I enjoy trying to stuff double the plumbing in the same space? No because I wanted the DME to work properly with it and not worry about killing O2 sensors every 500 miles. I honestly think this issue is not going to be easily solved if it can be solved at all.

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    Click here to enlarge Originally Posted by VargasTurboTech Click here to enlarge
    Um, all cars run the O2's post turbo. Think you are kinda confused on what is going on here. With a single you can run all 4 post turbo if you want, sure throw them in the dp. Problem is everything is merged. As I said the DME is seeing things as 2 separate 3 cylinders. Why do you think I went to all the trouble of building stage 3, because I enjoy trying to stuff double the plumbing in the same space? No because I wanted the DME to work properly with it and not worry about killing O2 sensors every 500 miles. I honestly think this issue is not going to be easily solved if it can be solved at all.
    When i said post turbo O2 sensors i meant those are the only ones you are using. I understand the whole 2 banks of 3 issue im just stating that all the other big single cars i know of run solely off of O2 sensors in their downpipes
    Turbo lag is the on ramp to the highway which is power.

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    Click here to enlarge Originally Posted by WDBi Click here to enlarge
    you have to remember that there are plenty of 1000+hp turbo cars running post turbo O2 sensors.

    @Terry@BMS , @dzenno@PTF Could you elaborate on the specific issue?
    How any of those cars run closed loop fueling 100% of the time? I think that's the main issue here as much as it would be convenient to have the O2's after the turbo, it's not the best thing when the DME is trying to fine tune everything. Older cars only used the O2 for cruising so it doesn't matter if some of the cylinders are a little off.
    2008 135i - Cobb AP, JB4 G5 w/2Step&FSB, MS DP's, Berk street exhaust, AMS IC, VTT Inlets, UR Intake, ER CP w/Tial BOV, Spec 3+ & Steel FW, CDV delete, Quaife LSD, DSS Axles, M3 control arms, M3 rear SF bushings, M3 Trans bushings, SS brake lines. Pics

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    I have some ideas for it but would take some time to flush out and I'm buried with other stuff right now. When time permits though I'll kick them around and see if anything gels.
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    Wouldn't ProEFI fix this issue? Any full stand alone should fix this right? What is limiting us is wanting to use the stock DME.

    What about a wideband o2 in DP and a split second fuel controller, would the DME would freak out?

    As far as the DME seeing two 3 cyl engines why not just duplicate the signal from the single o2 and have it report back to the DME as if both were identical? Does one bank normally read more lean/rich than another?

    Most supra log style kits are inexpensive as posted above. But they all run a full stand alone unless I am mistaken.

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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    Wouldn't ProEFI fix this issue? Any full stand alone should fix this right? What is limiting us is wanting to use the stock DME.

    What about a wideband o2 in DP and a split second fuel controller, would the DME would freak out?

    As far as the DME seeing two 3 cyl engines why not just duplicate the signal from the single o2 and have it report back to the DME as if both were identical? Does one bank normally read more lean/rich than another?

    Most supra log style kits are inexpensive as posted above. But they all run a full stand alone unless I am mistaken.
    My comments are based completely on my opinion with no factual evidence or documentation to back it up. My thoughts are that the DME goes through a cycle of checking AFR feedback, probably at light throttle cruising in which it adjusts one bank to go richer/leaner while checking for the adjustments to be picked up on the wide band for that bank. If it sees both banks go richer/leaner, it freaks out and now your problems begin. We know from looking in INPA that the DME makes individual cylinder injector compensations. Its much more complicated then you think. Being that we run closed loop fueling, its better that the DME keeps an eye on two sets of three cylinders at a time, your margin for error is going to be a lot less in this capacity.
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    FYI: http://forum.e46fanatics.com/showthread.php?t=967056

    Sheds some light on the e46 application and converting to a single bank.

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    The problem is the DME knows right away when its o2 readings aren't conforming to fuel inputs. Go reverse your bank1/bank2 o2 sensors and watch how $#@!ty the car runs. It varies fueling on each bank based specifically on the feedback from the o2 sensors, and it expects certain results, and its very accurate. When those results aren't seen, it flips out.

    How different are the N55 ECU's and can any of that fueling/O2 code be ported?

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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    Wouldn't ProEFI fix this issue? Any full stand alone should fix this right? What is limiting us is wanting to use the stock DME.

    What about a wideband o2 in DP and a split second fuel controller, would the DME would freak out?

    As far as the DME seeing two 3 cyl engines why not just duplicate the signal from the single o2 and have it report back to the DME as if both were identical? Does one bank normally read more lean/rich than another?

    Most supra log style kits are inexpensive as posted above. But they all run a full stand alone unless I am mistaken.
    The question is why? The more banks you have that the DME can monitor the more adjustability you have. Having all cylinders in one bank is fine if you can make each cylinders environment very close, Like say a NA I6 with equal length headers and velocity stacks where the flow difference is very minimal. But with a turbo engine with an intake manifold that doesn't equally distribute the flow perfectly so the more you can monitor and adjust each bank the smoother and better the engine will be. Race engines they are trying to monitor and adjust for every cylinder why go back to making adjustments across the board.
    2008 135i - Cobb AP, JB4 G5 w/2Step&FSB, MS DP's, Berk street exhaust, AMS IC, VTT Inlets, UR Intake, ER CP w/Tial BOV, Spec 3+ & Steel FW, CDV delete, Quaife LSD, DSS Axles, M3 control arms, M3 rear SF bushings, M3 Trans bushings, SS brake lines. Pics

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    Click here to enlarge Originally Posted by WDBi Click here to enlarge
    you have to remember that there are plenty of 1000+hp turbo cars running post turbo O2 sensors.
    This issue is specific to the N54 platform and to the N54 DME. There are not plenty of 1000hp cars running post turbo O2 sensors with this problem. This DME is very advanced compared to the ancient crappy one in the Supra.

    My opinion on the matter is that this issue won't be solved with a simple flash tune with some tables adjusted. It's going to be something more similar to having your DME upgraded at the dealer; a major reflash. Maybe there's a way to fool the ECU, though that is difficult. Or hoping an affordable ECU alternative arrives on the market; the ProEFI is just way too overpriced for the market.

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    Once there are enough people hacking on the ROM this may be as easy as changing a few memory pointers so only one O2 is used and turning off the CELs for the extra O2 you don't hook up anymore (or just tie them up somewhere). I really think this is being overthought. You'll have to accept the car won't run as well with just one O2, so in the end you may have to run richer than you might get away with using two O2.

    But, I also have to ask, why are you not running twinscroll on your singles and keeping them separate? Honestly I bet the O2 sensors are fine to stay preturbo. If people aren't popping them now running 16psi in our tiny stock turbines... I'm sure the pressure and temperature are pretty awful already just on tuned stock turbo cars.

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    Click here to enlarge Originally Posted by Freon Click here to enlarge
    Once there are enough people hacking on the ROM this may be as easy as changing a few memory pointers so only one O2 is used and turning off the CELs for the extra O2 you don't hook up anymore (or just tie them up somewhere). I really think this is being overthought. You'll have to accept the car won't run as well with just one O2, so in the end you may have to run richer than you might get away with using two O2.

    But, I also have to ask, why are you not running twinscroll on your singles and keeping them separate? Honestly I bet the O2 sensors are fine to stay preturbo. If people aren't popping them now running 16psi in our tiny stock turbines... I'm sure the pressure and temperature are pretty awful already just on tuned stock turbo cars.
    This post is pretty confusing. First off I am not sure you have been keeping up with what is going on in the N54 world. But to catch you up, yes there are people running singles with the banks separated (single and twin scroll) and running o2's pre-turbo, they are killing them VERY quickly. O2's are never meant to run pre-turbo that are not designed for that kind of heat. Also what you are saying about the stock turbos is also semi confusing, the O2's are of course run post turbo so the heat they are seeing is much lower then what pre-turbo O2's would see. The entire point of this thread is to try to figure out how to run a single and get the O2's back post turbo to keep from killing them, while the DME can control them as the car was only supposed to have one bank.

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    Click here to enlarge Originally Posted by Freon Click here to enlarge
    But, I also have to ask, why are you not running twinscroll on your singles and keeping them separate?
    That is how the current ST kit does it unless I am mistaken. A big snake of tubing. Expensive to fab even with a jig I imagine.

    The reason for the discussion is so we can use an inexpensive cast log style manifold and have single turbo set ups for under 4k like the supra guys have. Throw on a QSV and call it a day. Least that is my understanding.

    The N55 only has one set of 02s unless I am mistaken. How different is the intake manifold? I can't find any pictures online...Obviously one would prefer as much information and one o2 per cyl.

    I agree ProEFI is too expensive(to me) and currently isn't even working and you can't buy it for this platform.


    What about a cast style twin scroll manifold with the o2s as they should be? like this:

    Click here to enlarge

    Instead of this:

    Click here to enlarge
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