[desertman123]

Originally Posted by jonwilli

Does that not depend on how the ECU uses the sensor 1 data? If the ECU only changes fuelling for cylinders 1, 2 and 3 from sensor 1 would it matter if it data from the sensor was at the merge or just in cylinder 2 location?

Yeah there would be a difference in reading 1 cylinders vs 3. You'd get less frequent data points (since you're seeing 1/3 the number of combustion events, per unit time) and a lesser mass flow (weight of the exhaust passing by the sensor per unit time). Now how much this stuff actually matters to the DME I don't know.

Originally Posted by jonwilli

The guys running superchargers are having problems with AA headers as sensor 1 location is away from the engine block and results in a delay between sensor reading to changes in the fuelling confusing the ECU. The supercharger must be exasperating any issues that the NA tune may have? Could it not be that this O2 sensor location is optimised for N52?

Hassmachine discovered the DME (MSV70/80) DOES have an adaptation for O2 sensor delay. I know some of the supercharged guys were having issues as well because ESS wasn't up to the task for digging through the DME to fine tune these values. Check out BPC's work with the supercharger.

Shouldn't be anything software won't be able to fix. For my custom tune, he looked at the O2 sensor feedback data from the Euro S54 and interpolated their values over to MSV80. There were a few other variables in the mix though - Euro MAF delete & MILVS mainly.

Originally Posted by jonwilli

The ARMA N52 headers had O2 sensor 1 locations in the same location as the OPs and guys in Oz had no issues with the car running smoothly with those headers.

Can you link a thread?

[jonwilli]

Originally Posted by desertman123

Can you link a thread?

https://www.1addicts.com/forums/show....php?t=1066291

I wonder if Hassmachine knows how the DME uses the pre cat O2 sensor readings for fuelling? i.e. is fuelling for cylinders 1, 2 and 3 exactly the same as it is using the cylinder bank O2 readings or is the DME clever enough to interpret changes in O2 reading to each individual cylinder.

I'd be interested in this as I have ARMA headers (based in UK need RHD) and I had the sensor 1 after the merge previously and had idle hunting. I have now moved the O2 sensor to the bung by cylinder 2 and 5. Would like to know what is the optimum location for a smooth running engine and to keep emissions low.

[Wally_84]

Originally Posted by jonwilli

https://www.1addicts.com/forums/show....php?t=1066291

I wonder if Hassmachine knows how the DME uses the pre cat O2 sensor readings for fuelling? i.e. is fuelling for cylinders 1, 2 and 3 exactly the same as it is using the cylinder bank O2 readings or is the DME clever enough to interpret changes in O2 reading to each individual cylinder.

I'd be interested in this as I have ARMA headers (based in UK need RHD) and I had the sensor 1 after the merge previously and had idle hunting. I have now moved the O2 sensor to the bung by cylinder 2 and 5. Would like to know what is the optimum location for a smooth running engine and to keep emissions low.

I have exact same questions . Was hoping for Hassmachine or Axiom to chime in.
If only Just Pete would still be with us...
Nevertheless I also have aftermarket headers and as your ARMA mine are also having two O2 ports on 2 and 5 cylinder whereas AA and Supersprint have them located in the merge section.
Does it, and how it matters is beyond me.
I remember I have read somewhere in here that o2 post cat sensors are responsible for fuel mixture.
But are they still after the tune? Mine second sensor (behind the cat) on 3-6 cyl throw’s a code 2C7F without CEL (because tune disabled it) but I don’t know if that have any impact on power.
Car runs great at idle and in high rpm’s .

Here is post with more info about the subject: https://www.e90post.com/forums/showt...php?p=23708670

[jonwilli]

Originally Posted by Wally_84

Here is post with more info about the subject: https://www.e90post.com/forums/showt...php?p=23708670

Which locations do you currently have the pre CAT O2 sensors in? Those are the sensors that influence AFR.

I think the post CAT O2 sensors only check that that CAT is in place and operating correctly. You will probably get post CAT errors even with sports CATs as they restrict flow less.

[Wally_84]

Originally Posted by jonwilli

Which locations do you currently have the pre CAT O2 sensors in? Those are the sensors that influence AFR.

I think the post CAT O2 sensors only check that that CAT is in place and operating correctly. You will probably get post CAT errors even with sports CATs as they restrict flow less.

You are sure that post cat o2sensors don't affect AFR ratio?
So everyone with the headers and tune (AA or BPC) have post-cat 2C7F errors in INPA?

My headers:

[jonwilli]

Originally Posted by Wally_84

You are sure that post cat o2sensors don't affect AFR ratio?
So everyone with the headers and tune (AA or BPC) have post-cat 2C7F errors in INPA?

Again good for others to chime in but I think you can code out the checks on the CATs with a tune so you don't get errors.

What brand are your headers? Have you installed them with pre CAT sensors in the cylinder 2 and 5 locations? Any issues?

I did ask Bob at BPC who is tuning my car which location on my ARMA headers he would recommend (with photos) and no response on it. I assume that means it doesn't really matter knowing his communication style.

[rjahl]

Originally Posted by jonwilli

https://www.1addicts.com/forums/show....php?t=1066291

I wonder if Hassmachine knows how the DME uses the pre cat O2 sensor readings for fuelling? i.e. is fuelling for cylinders 1, 2 and 3 exactly the same as it is using the cylinder bank O2 readings or is the DME clever enough to interpret changes in O2 reading to each individual cylinder.

I'd be interested in this as I have ARMA headers (based in UK need RHD) and I had the sensor 1 after the merge previously and had idle hunting. I have now moved the O2 sensor to the bung by cylinder 2 and 5. Would like to know what is the optimum location for a smooth running engine and to keep emissions low.

Put it this way, there is a timing factor for the location of the O2 sensors. Some cars have the sensor further downstream and the sensor feedback system uses a different timing value.

I'm pretty sure the sensor bungs should be at the collector and not on a single pipe as shown. The tune should adjust the feed back timing or sensor distance.

Use good headers and a good tuner and you won't be guessing.

I would not recommend headers without a matching tune. My two cents.

[Blueeyesredpanda]

I know this is not where you got yours from. But this vendor is selling the same one as you bought, which is the one you SHOULDN'T have bought:


https://www.aliexpress.com/item/Cust...f-9396251024a9


The one you SHOULD have bought:
https://www.aliexpress.com/item/JKVK...f-9396251024a9

Take a look at the O2 sensors location

[gT-BMW]

hey those headers look cool, I just say SEND IT youll notice top end opening up. well atleast for me it was noticeable gain because i put it on a 325i.

why is 02 sensor location important? Is it for mpgs? Cause when i installed my AA headers my mpg reduced to 25-26 from 28-31mpg. now after installing the 3im with bimmerlabs tune im lucky to get 23mpg which everybody around here says its normal.

[jonwilli]

Originally Posted by Blueeyesredpanda

I know this is not where you got yours from. But this vendor is selling the same one as you bought, which is the one you SHOULDN'T have bought:


https://www.aliexpress.com/item/Cust...f-9396251024a9


The one you SHOULD have bought:
https://www.aliexpress.com/item/JKVK...f-9396251024a9

Take a look at the O2 sensors location

But is it not supposition that the second set O2 sensor location is better? I have Pm'd Hassmachine to see if he knows for certain from his knowledge of the ECU whether the location makes any difference at all. As I mentioned BPC did not seem phased where the pre CAT O2 sensor was located in my headers for their tune.

[bimmerclad]

Well guys I took it to a shop and they'll try to get it done tomorrow. I'll update with what they did and if they're any good!

[Wally_84]

Have you done stock dyno run?
Without it there is no way of knowing how those ebay headers are performing.

[hassmaschine]

Sorry for not responding to this thread (and PM's / emails) but sometimes things take a back burner.

Anyway, regarding headers. Yes, O2 positioning, and the number of cylinders sampled, is extremely important. No, the N52 doesn't adjust individual cylinder trims - however, you could do that (if you had the data), there are built in maps for that. By default it only adjusts the 2 banks based on the pre and post cat sensors.

But on headers that only sample 1 cylinder, not only is the *rate* of samples much lower, you are missing out on whatever average is built into the 3 cylinders, and you still haven't adjusted for the 'time lag' problem. Also, I know for a fact that BMW calibrates the 2 banks differently from the factory, so the averages do matter.

Regarding the *distance* aspect. It is actually very important - the N52 uses a high speed, fast adjusting wideband feedback loop. It actually runs closed loop all the time (except for a few seconds at cold start). Past engines ran open loop at WOT, but the N52 does not. The MAF will help mask the poor wideband feedback with the messed up sensor positioning, but that does not mean it doesn't matter. The N52 was designed to run with no MAF from the factory - it was added on after the fact, mostly for emissions reasons IMO.

I personally would not run a header that only samples 1 cylinder per bank knowing what I know about the feedback loop. Otherwise, the longer distance to the sensor issue on headers that put the O2 sensor at the collector (further away from stock manifolds) can be tuned out. I have had recent success with a MAF delete tune and headers by adjusting a bunch of parameters in the O2 feedback loop - long term fuel trims down to 3% vs maxing them out and leading to poor fuel economy and drivability problems.

I have run my own car without a MAF as a DD for almost 2 years now without any issues but I have stock manifolds. Given how much easier it is to delete the MAF than to install headers (and deal with emissions), I know what my choice would always be..

[Biginboca]

hassmaschine what is the benefit of a MAF delete? Seems like the cars are easier to throw parts on with a MAF it kind of adapts to changing parameters. With it deleted you are stuck doing a dyno tune and then need to constantly redo that tune as changes are made, correct?

Like if it was possible to keep MAF with the SC wouldn’t the SC pulley changes that CobraMarty is experimenting with work out easier? (Im thinking the DME would see the added airflow of boost changes and adapt instead of doing a bunch of dyno tunes for each pulley.)

[hassmaschine]

You are still thinking like the MAF delete makes it run in open loop - it does not. It still runs in closed loop like before, so if there is more air it will give you more fuel. This is a factory mode that was run stock on many thousands of cars sold all over Europe.

All of the fueling is closed loop / target based on the N52 - so unless there's a different lambda target you want at full load, there's no reason to re-tune anything. When I first did the MAF delete I wasn't even sure it was working because it sounded exactly the same at startup (no weird idle, hunting, etc).

As far as the SC, interestingly I think it's definitely possible to make the MAF work with the SC - but ESS couldn't. I'd guess it's the same reason their MS45.1 supercharger tune was completely broken. But on the other hand, it's not really necessary - it was *designed* to not need a MAF, and IMO it's one less failure point. Keeping in mind ESS borrowed my idea for the euro based tune when their old "cut the MAF wire and run it in limp mode" trick wasn't working so well..

[atmosphericM]

To be clear, the only benefit to the MAF delete is the fact that you no longer have the MAF sticking into the air stream which would cause turbulence / restrict flow into the motor?

Interesting to read and learn about the timing issues with the O2 sensors. I'm still afraid of headers on N51 because I keep reading about idle issues. Maybe we are getting close...

[hassmaschine]

less restriction, smoother drivability at low speeds (I can literally idle in 1st and 2nd gear, stop and go traffic is like driving an automatic), no possibility of a MAF failure. It feels more responsive too.

It's such an easy & cheap mod, definitely one of my favorites. the MILVS are fun but man, that install was a giant pain in the ass.

[nsjames]

as always hass shows up and drops knowledge.

it's very interesting that the MAF was a factory add on.

was the throttle body the same way? because the valvetronic and throttle body always seemed real dumb. More gains to be had if you simply deleted everything in the intake tract and just let valvetronic do it's thing. Better yet if you don't need a MAF or the TB, can someone just bolt ITBs to the head and let the engine management do it's thing?

[jonwilli]

Originally Posted by nsjames

as always hass shows up and drops knowledge.

it's very interesting that the MAF was a factory add on.

was the throttle body the same way? because the valvetronic and throttle body always seemed real dumb. More gains to be had if you simply deleted everything in the intake tract and just let valvetronic do it's thing. Better yet if you don't need a MAF or the TB, can someone just bolt ITBs to the head and let the engine management do it's thing?

I have the throttle body is a backup to cut the engine if required

[Phyrexia]

Originally Posted by jonwilli

I have the throttle body is a backup to cut the engine if required

If the valvetronic motor breaks, and you don't have a throttle body, you'd lose all throttle control. So the TB is there as a backup to the valvetronic motor.

[hassmaschine]

yes, not only that, but valvetronic is programmed by default to go to full lift in the event of a limp mode / failure. So if the eccentric shaft sensor failed the car would go straight to WOT.. not good.

You could use ITBs, of course - but think about that. If you're deleting the throttle, and installing ITBs, you still have a throttle.

Straight trumpets would be really easy, but there would be zero failsafe. I suppose you could reset the lift to max out at 1000rpm or something, but man that would suck if you were on the freeway or something.

[nsjames]

derp, I suppose I meant just trumpets, but the idea is so foreign to me that ITB seemed the only appropriate thing.


I mean, who needs a fail safe when you could here all 12 of your intake valves opening and closing at 8K RPM?

worth it.