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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Single Turbo Kit Interest Still?



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      02-08-2013, 05:48 PM   #45
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Quote:
Originally Posted by Jake@PTF View Post
The problem lays in logic control. Separating the widebands after the turbo requires rewriting the logic of the DME to allow both banks to fuel identically because they will be seeing identical mixtures. This means they need a way to actually change code on the ROM and not just tables. While it is great to talk about - its a very different thing to be successful. Cobb has a lot of custom code for many different things in their flash. Things written to allow them to do things the dme did differently or limited or didn't want happening to limit power output. I hate sounding like a pessimist but its experience talking and knowledge of what is going on - not just hating. I love ETS. I use their products on multiple platforms for 700+hp applications.
Jake has a lot of experience in this platform as well as other platforms. We will have to see how this test goes over the next couple of weeks. If it's not successful we always have twins right?

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      02-08-2013, 06:03 PM   #46
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Always wondered when this would pop back up as an option. I think everyone would love to see more options, the viability really comes down to, can you change the way the DME operates on the ROM side of the software. Do you have that capability? If not, then it may be best to wait for the ProEFI or watch you make some twins. It would be nice to have a stock DME run POST o2 sensors. Reminds me of the work PEIC300 is doing on the E46 DME for their single project.
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      02-08-2013, 06:55 PM   #47
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I am curious why one couldn't run two sensors into the downpipe rather then split them just run 2 separate sensors. Does it go into some type of fuel trimming loop when they read the same? This is some of the tests we are going to be performing over the next couple of weeks.

Michael
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      02-08-2013, 08:42 PM   #48
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Quote:
Originally Posted by ETS Michael View Post
I am curious why one couldn't run two sensors into the downpipe rather then split them just run 2 separate sensors. Does it go into some type of fuel trimming loop when they read the same? This is some of the tests we are going to be performing over the next couple of weeks.

Michael
This is exactly the problem HPF ran into. They had to separate the flow until after the sensors in order for the thing to run right.
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      02-08-2013, 10:21 PM   #49
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Quote:
Originally Posted by ETS Michael View Post
I am curious why one couldn't run two sensors into the downpipe rather then split them just run 2 separate sensors. Does it go into some type of fuel trimming loop when they read the same? This is some of the tests we are going to be performing over the next couple of weeks.

Michael
The DME has logic in it that they work on a somewhat opposite pulsating trim. Basically - if they are post single turbo - they will read identical to each other since it will be flowing through a single exhaust (the turbine housing) before splitting back up. Since the DME will see identical readings it will "freak out" and enter wierd trimming modes. Without the opposite pulses that they get when separate the DME will not fuel properly. You would have to change the logic of the DME so that the sensors would be okay being identical.

This among other things are on the list of "to-do's" at Cobb. They do A LOT of custom logic and coding on top of just accessing and changing tables. Time is the issue and Jason and Josh are both working very hard to keep on top of as much as they can and delegate projects when needed.
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      02-08-2013, 11:58 PM   #50
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Michael, let me know if you need another car to work on. Has all the required upgrades for a big single already.
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      02-09-2013, 06:44 AM   #51
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Quote:
Originally Posted by Jake@PTF View Post
The DME has logic in it that they work on a somewhat opposite pulsating trim. Basically - if they are post single turbo - they will read identical to each other since it will be flowing through a single exhaust (the turbine housing) before splitting back up. Since the DME will see identical readings it will "freak out" and enter wierd trimming modes. Without the opposite pulses that they get when separate the DME will not fuel properly. You would have to change the logic of the DME so that the sensors would be okay being identical.

This among other things are on the list of "to-do's" at Cobb. They do A LOT of custom logic and coding on top of just accessing and changing tables. Time is the issue and Jason and Josh are both working very hard to keep on top of as much as they can and delegate projects when needed.
I read up on this a while back trying to understand the logic. I believe this is part of their (BMW-Bosch's) way of ID'ing individual cylinder combustion health. That is they superimpose a low level coded pulse of fuel/timing onto each cylinder's ordinary fuel/timing every so often and then look for its signature variation out of the O2 sensors for the appropriate bank. I am not sure how they de-correlate it but they can then infer what is going on in each cylinder by time windowing or some other signal processing logic. So you'd capture the coded pulse and then everything near it time wise would contain info on that cylinder. Somehow they tease out the info.

It is there for a reason and a paper I read seemed to imply it was for some obscure CARB emissions requirement either in place now or was thought to be coming soon regarding individual cylinder combustion monitoring. I guess the point is before trying to spoof this it would be good to know why it is there.

On the other hand I may be completely full of shit.
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      02-09-2013, 11:48 AM   #52
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Quote:
Originally Posted by ajsalida
Quote:
Originally Posted by Jake@PTF View Post
The DME has logic in it that they work on a somewhat opposite pulsating trim. Basically - if they are post single turbo - they will read identical to each other since it will be flowing through a single exhaust (the turbine housing) before splitting back up. Since the DME will see identical readings it will "freak out" and enter wierd trimming modes. Without the opposite pulses that they get when separate the DME will not fuel properly. You would have to change the logic of the DME so that the sensors would be okay being identical.

This among other things are on the list of "to-do's" at Cobb. They do A LOT of custom logic and coding on top of just accessing and changing tables. Time is the issue and Jason and Josh are both working very hard to keep on top of as much as they can and delegate projects when needed.
I read up on this a while back trying to understand the logic. I believe this is part of their (BMW-Bosch's) way of ID'ing individual cylinder combustion health. That is they superimpose a low level coded pulse of fuel/timing onto each cylinder's ordinary fuel/timing every so often and then look for its signature variation out of the O2 sensors for the appropriate bank. I am not sure how they de-correlate it but they can then infer what is going on in each cylinder by time windowing or some other signal processing logic. So you'd capture the coded pulse and then everything near it time wise would contain info on that cylinder. Somehow they tease out the info.

It is there for a reason and a paper I read seemed to imply it was for some obscure CARB emissions requirement either in place now or was thought to be coming soon regarding individual cylinder combustion monitoring. I guess the point is before trying to spoof this it would be good to know why it is there.

On the other hand I may be completely full of shit.
So with this theory the cylinder bank individual runner lengths would have to be in the algorithm for that cylinder. If any aftermarket change in runner length for that cylinder would throw off the timing of the pulse capture. Sounds legit.

T
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      02-09-2013, 12:30 PM   #53
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Quote:
Originally Posted by Mangler View Post
So with this theory the cylinder bank individual runner lengths would have to be in the algorithm for that cylinder. If any aftermarket change in runner length for that cylinder would throw off the timing of the pulse capture. Sounds legit.

T
It could be calculated automatically upon startup or something. There would be many factors in determining the speed at which a pulse would arrive at an o2 sensor, rpm, temperature, waste gates, etc.
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      02-09-2013, 12:34 PM   #54
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To make things even more interesting- since the factory o2's are post turbine, that certainly has to effect things if you are trying to time the exhaust pulses down stream in a preturbo o2 design that also has WAY less back pressure.
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      02-09-2013, 01:13 PM   #55
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Quote:
Originally Posted by Mangler View Post
So with this theory the cylinder bank individual runner lengths would have to be in the algorithm for that cylinder. If any aftermarket change in runner length for that cylinder would throw off the timing of the pulse capture. Sounds legit.

T
Yeah it'd really be just an advanced method of fuel trimming each cylinder mainly for emissions purposes but the usefulness for performance is obvious. The point is, and you bring up runner length, there's a load of assumptions in here that one would be wise to understand before breaking out the welder.

I do not know for a fact what they are doing, the papers and patents I was looking at were older. But they seemed to imply impending CARB/EPA rules for individual cylinder emissions monitoring capability. Wideband sensor + DI and some signal processing makes that possible.

Obviously another part of the whole algorithm is individual injector modelling. I mean I read about this and said since when? But you have to ID injectors now and hand off that model to the ECU or it won't run right.

In control theory terms there's something called system identification, or system ID. Basically modeling the dynamics of part of the system being controlled so you can anticipate responses better. This can be done on line (like with coded pulses), off line and then inserted into the algorithm (like with injector ID'ing), or just part of the hard coded algorithm and not explicitly called out (like maybe runner length). It is good to know which one of these cases something you are messing with is and how it is reflected in the architecture.
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      02-09-2013, 01:26 PM   #56
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Quote:
Originally Posted by Fully_Bolted View Post
To make things even more interesting- since the factory o2's are post turbine, that certainly has to effect things if you are trying to time the exhaust pulses down stream in a preturbo o2 design that also has WAY less back pressure.
Yes this was exactly the thing that made me think they couldn't possibly be doing this, but then I kept reading and it looked like they were. The HPF folks seemed to discover this empirically the hard way. However if I remember correctly it is only key to keep the streams read by the first O2 sensors for each bank separate, as Shiv did, and somewhat close to the exhaust port in terms of length not so much that it is pre or post turbo. So who knows lot of mystery here.

If you think about it you can still hear clear exhaust pulses out of an exhaust, so even after getting scrambled by a turbine wheel (or wastegate) and six cats there is a distinct acoustic signature for each cylinder in terms of information content available. So I would bet the times series read out of an O2 sensor still has distinct info available for reading out of each cylinder's combustion byproducts.

I doubt any of this is going on all the time, there are probably fixed steady state or cruise conditions that kick off a measurement/ID cycle.
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      02-09-2013, 01:52 PM   #57
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Depends on price
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in for more info on writing to the ecu
+1 to both of these.
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