The effect of camshaft changes on vanos timing

[Sajk]

Let me start out by saying that I know enough about tuning old jeep 3.8 V6 pcms with hptuners to be a danger to myself and my engine. That is not much but I understand tuning concepts at least.

So to the question I have a low milage M52tu which has had an M54 3.0 intake manifold fitted for a while and yesterday finally the M54 intake camshaft was fitted. This cam has a little more lift and quite a bit more duration. Its still running the tune I had done for the intake manifold.

As double vanos is continuously variable I would think that the new can profile would throw off the DME calculations?

Does anyone have knowledge in this area?

[BimmerBreaker]

Probably not as much as youd think or expect, youll want a tune to maximize the gains, but even as it is now it should be an improvement over stock. Its doing the same thing upgraded cams do in other engines - it just also happens to have vanos.

[Sajk]

I figured it will need some fuel at WOT when its in open loop because their should be more air but because of the change in overlap I would have thought the DME would be moving the cam at the wrong time. I think I agree with you if it was a difference in lift only but I have absolutely no idea how the DME makes these decisions and based on what sensors. Perhaps the software understands what is going on. I don't know.

Thanks for the reply.

[rf900rkw]

at WOT, 99% of the time there will be no more air. The only time there will be more is when the part you replaced became a restriction. But no matter, the air is measured directly by the MAF. As long you don't exceed the MAF's capability, everytihgn will be fine.

Did you move the cam lobe centerline ? If not, then leave the tuning alone.

[BimmerBreaker]

The O2 sensors and MAF will work together to supply the appropriate amount of fuel for the amount of air going into the engine. The engine tune is not a rigid profile where for X input it gives Y, Z... It looks at the data from the various sensors and calculates the right amount of fuel and timing (and other things), then looks at the O2 sensors to make sure it is combusting effectively and will adjust within certain parameters. If those parameters are exceeded you get a check engine light. In your case the upgrades are not likely to be enough to push you out of the adjustable range of fuel, timing, etc...

What you need a tune for is to adjust vanos maps and other things to take the most advantage of the new cam and intake. You wont see max performance gains until you have it tuned

[328 Power 04]

You can attempt to make a few different VANOS combinations in the tune (make 6-8 tunes with different VANOS settings), and get out on the road and log maf and load using testo. Flash, and repeat.

You do this some 6-8 times, and then choose the camshaft settings that give you the highest maf and the highest load values. Plot in Excel and see your work. You can influence airflow greatly. Even with the exhaust cam a bit.

Fueling won't need to be changed since the air is measured, as long as your fuel tables are fine.


Example of my 4 graphed VANOS settings at WOT, on an M52tub25 with M54B30 manifold as well

Attach301712_20200502_224916.png

At one point, DISA will need very minor corrections too.

[Sajk]

All of that is true in closed loop with a narrow band O2 sensor in the exhaust targeting 14.7afr. In open loop at WOT to my knowledge DME runs the engine based on a set of hard coded tables mapped to airflow. It knows nothing about AFR at WOT because it does not have the hardware to measure it.

[Randy Forbes]

I recently redid a set of Schrick cams in a supercharged engine (originally sourced from VAC). When I contacted them about cam timing, they said, and I quote "we don't send out instructions with our cams."

I took that to imply they're installed straight-up (by the book, factory settings, according to TIS).

[328 Power 04]

All of that is true in closed loop with a narrow band O2 sensor in the exhaust targeting 14.7afr. In open loop at WOT to my knowledge DME runs the engine based on a set of hard coded tables mapped to airflow. It knows nothing about AFR at WOT because it does not have the hardware to measure it.

It still has MAF reading, which will go up if you actually have increased air capacity, and read on a different cell from the fuel tables + WOT modifier. So you don't have to edit fuel values randomly. MAF (and in turn the calculated Load) dictates what fuel quantity will be injected.
A proper fuel table will easily cover your air quantity increase.

[rf900rkw]

All of that is true in closed loop with a narrow band O2 sensor in the exhaust targeting 14.7afr. In open loop at WOT to my knowledge DME runs the engine based on a set of hard coded tables mapped to airflow. It knows nothing about AFR at WOT because it does not have the hardware to measure it.

Your knowledge is incorrect. This isn't a speed-density Honda. The MAF is king. It measures air directly and the DME uses that to add the appropriate amount of fuel. The "appropriate" amount is the base for a given airflow lightly modified by parameters, one of which is the fuel trim tables. In open loop, the tables are used as is in static mode. In closed loop the tables are adjusted in realtime by O2 sensor feedback. The MAF is always used.... well, used unless someone reads some moronic post in the internet about unplugging it "as a test" (it's not). Then, and only then, are the default look-up tables used in an Alpha-N arrangement.

Also worth not is BMW;s of that era were in closed loop mode within a minute of starting, usually less than 20 seconds.

[Sajk]

Thanks for the replies. There are some conflicting options ranging from leave vanos stock to a graph showing that airflow can be greatly influenced.

In terms of my comments on fueling reread my post. I did not say it could not measure airflow in closed loop. I said it could not accurately measure AFR because it does not have the hardware (wideband) to do it. I said the DME runs the engine on a set of hard coded tables mapped to airflow.

Yes I forgot about short and long term trims in my post.

Does not matter if the system is speed density or MAF based. Without a wideband the fueling cannot be accurately verified on the fly.

I do see it going into closed loop super soon after startup.

But are you saying it should stay in closed loop at WOT?

I have never checked this but will do so today.

[rf900rkw]

No, we did not lsay it stays in closed loop, IE aiming for 14.7. What we are saying is the DME uses the MAF to read the exact amount of air going in, measured on a per cylinder-stroke basis, at all times and adds exactly the correct amount of fuel for that air within the needed parameters.WOT parameters are different than cruise, but it's not a flat lookup table based on no inputs like you keep saying. All your changes for "more air" will only effect the top of the rev range, and can easily cause less air in the areas you drive the most. VE is a real thing, and the BMW engineers understand it a hell of a lot better than I do, and I understand it a lot better than most. The gains you get will be less than the gains made by lowering the intake air temp by 20 degrees. The DME doesn't need a retune every time a cold front passes through, it won't need one for this.

[Sajk]

Thanks for your reply Randy.

You still miss my point. Stock tuning is arrived at by testing all over the planet along with mathematical modeling for a given engine HARDWARE configuration and thus can be relied on in a vast variety of circumstances and geographies.

This is because the maths done by the DME around the commanded and measured AFR via the narrowband O2 sensor which oscillates around 1 volt (I think its one) has been tested and verified with wideband sensors in real world tests.

A narrowband is hopelessly inaccurate either side of 14.7 and so the computer adds and removes fuel as the voltage jumps above and below the measurement point of 14.7.

When you change the HARDWARE configuration of an engine all the previous tested assumptions in the Dme software go out the window. It might be commanding a certain AFR but it has absolutely no way of knowing if it is achieving it because it only has a narrowband.

When we went through tuning pain with my supercharged wrangler (speed density I know) the tune from the blower manufacturer was commanding between 11.5 AFR and 12 which is pretty safe for a non decompressed engine at the boost level being achieved. After trouble with detonation I purchased and innovate wideband and found that despite what the narrowband was saying for the current hardware configuration the PCM was actually achieving and AFR in the 15s. I was lucky it did not go boom

After asking for opinions here because I was not sure it was worth spending money on a tune revision here i contacted Active Autowerke who tuned this Z and I data logged this morning with the innovate tailpipe sensor in place.

With the m54 intake only we were targeting and achieving 12.5 to 12.8 AFR which is normally aspirated max power. This morning when I logged after the cam install its achieving 13.2 to 13.5 AFR so a retune is needed which was confirmed by them.

BTW when I first started tuning with this engine the data logs showed it did indeed continue to target stoichiometric 14.7 even at WOT but I did not check if it was in closed loop.

By no means am I experienced or particularly knowledgeable in this stuff. I am a software engineer of some 40 years experience measuring computer and network performance and modern vehicles have in excess of 1 million lines of code running. Trust me. If you did not right the code you are not an expert.

Once again thanks for your response.

[328 Power 04]

13.2 afr is perfectly fine, and will actually make slightly more power, than richer.
Even bmw documentation says that they make the best power at 12.8-13.4ish.

[Sajk]

Thanks for the input. I really don't understand why this is so contentious. I know there are thousands (millions?) of people who know more than me that's why I am asking.

What I was asking was specific to VANOS timing when the camshaft profile is changed.

I don't know the answer to this and in this thread there are opinions ranging from do nothing leave it stock to a graph from 328 power showing that airflow is greatly influenced. So there is no consensus in this thread alone.
EDIT

When I looked at the BMW documentation today I find this. So BMW seem to move the VANOS differently on M54 3.0 intake side with 240 intake cam vs M52TU with 228 intake cam.

In. /Exh. In spread. Exh spread


M52B28TU X3 X3 - MS42 228°/228° 80° to 120° -80° to -105°


M54B30 X3 X3 - MS43. 240°/228° 86° to 126° -80° to -105°



All I have said on AFR is that at WOT the DME cannot accurately measure AFR because it does not have a wideband and when you change the engine hardware you need to do this.

The target air/fuel ratio is set to a constant value in all areas where the engine may operate during WOT. This helps reduce the confusion associated with trying to hit a moving target when correcting the airflow model. A table of MAF breakpoints at WOT can again make calculating corrections easier. RPM is added to correlate dyno and PCM data points.

[328 Power 04]

All you have to do is get out there and test and log on a cool morning. Even the bmw settings, they highly depend on engine displacement (re: comparing to m54b30).
So the best thing is to create your own settings. They'll be close or similar to stock, but the timing of the transitions, plus some minor changes can help.

Been there 5 years ago. Using MS43 settings is not optimal.

After you get your airflow maximized as best as possible, then calibrate fueling. No reason to go through fuel yet.



Additional question... Where are you getting that the fuel table is an afr table? It's not. (Unless wording didn't make it clear)
You should NOOOT be changing the MAF calibration at all. You should be changing the fuel injection pulsewidth (injection time table).

[Sajk]

Its a wording thing. I am not changing anything as I don't have the tools or the knowledge on this platform. On the Chrysler platform I would have changed pulse width to fatten it up.

I am just trying to learn and your comments are appreciated very much.

I have a new flash from the tuner tonight they say with some vanos changes to improve mid range torque with the new cam timing and lift so I will see how that goes.

[328 Power 04]

Fun fact, I've had such inconsistent experiences with Active Autowerke in the past, that I would not be dealing with them. It was at least 10 years ago, but still.


Most will say MS42 is the forgotten child, but this isn't true at all. It's a very capable DME, and tuning isn't a mystery on it.

Personally I'd run this at 0.88-0.90 if not running any boost.

[Sajk]

Thanks for the advice.

I loaded the new tune last night. Will give it a day or so to adapt and then data log. Will post the lambda results here. No boost.