Some (slightly advanced) questions about VANOS...

[anom3]

In my quest to figure out whats causing this bloody grinding noise during my cold starts I spent a good part of last evening learning about how the BMW VANOS works and what it does. For the most part, I have it figured out. An overall simplification would be simply a hydraulically "moved" piston that advances / retards timing based on whatever the ECU reads the conditions to be (RPM mainly, but a few others as well).

I do however have a couple of slightly advanced questions that I am unable to find answers to. I'm thinking that its a safe bet that even tho the S65 VANOS is not a high pressure system like most other VANOS, the same principles as BMW's high pressure VANOS should apply.

So, onto the questions:

a) I have read a number of posts stating that during engine start, VANOS does not really come into play. Correct?

b) If "a" is correct, is this to say that whenever the motor is turned off, the position of the piston is "reset" to a "default" position?

c) If "a" is correct, how quickly after engine start does the ECU start advancing / retarding timing using the VANOS?

d) If the vehicle is in neutral, but RPM is raised (eg: via the gas pedal) to 3000 or even 6000RPM, will the ECU start adjust timing via the VANOS? Or does the ECU need the vehicle to be "under load" (eg: in gear) to start adjusting the timing?

That's it for now, and I apologize if my understanding is incorrect or terminology is off, but I'm a newbie at understanding all of this. Bare with me

[isherdholi]

Originally Posted by anom3

a) I have read a number of posts stating that during engine start, VANOS does not really come into play. Correct?

I always thought VANOS is always in play. This is what moves the camshafts isn't it?

Sorry if that's totally wrong.

[anom3]

well its the gears that move the cams, yes.

but as far as advancing / retarding the timing (the inside gears of the vanos) thats what im curious about.

Originally Posted by isherdholi

I always thought VANOS is always in play. This is what moves the camshafts isn't it?

Sorry if that's totally wrong.

[FRFNUGN]

You said you did some digging, so I don't know if you've seen this or not, but it's pretty informative. I think the one answer you're after is:
"At zero pressure, a locking pin (2) also holds
the VANOS unit in the normal position or
engine start position."

So that would imply that during start, VANOS does not actuate the cams but rather keeps them at their zero position. Once engine run speed is reached though (idle) and oil pressure is sufficient, they are used to go into cold mode (which everyone seems to love to code out). You can hear when they change and cold mode ends, and they go back to normal mode (though still actuating as required for best performance).

[termigni]

is this E46 M3 related question?

[///M3Fresh]

going based on my E46 hands on with Vanos/cam/timing experiance: ( I would imagine its the same for the S65)

To answer them in order:

a) Correct, at start up there shouldnt be any vanos in play. the cam timing does not adjust as its all RPM based.

b) Since a is correct, to answer simply, No. It just goes back to where it should be once the RPM's drop under the vanos actuation parameters.

c) I cant give you a specific RPM range but my educated guess Vanos wouldnt kick in until ~3k rpm ++. Meaning really once you feel that spike in TQ (you should get an idea of it from driving your car) give or take 500 revs that when vanos is advancing/re-tarting timing.

Again this is all going based on what i know from working on my S54 and other locals near me. I am sure there are differences but the mechanics are the same.

TL: DR- Vanos works under RPMS and after a certain rpm its kicked on.

[anom3]

Thank you both very much for the informative pointers. On my mobile now so its a bit hard to follow up but wanted both of you know i have read the answers and will follow up as soon as back at my workstation. As for if this is E46 related, no, E92, but I'm guessing much of what applies to the high preasure VANOS will apply to the low pressure one as well as they are similar in function and made by the same manuf. thx.

[anom3]

My first question right away would be... And i know this is one who only someone internal to bmw or bensian (spelling i know...) can answer for sure... As the VANOS doesnt come into play at cold start... How about lets say 30 seconds after cold start if the motor is allowed to idle with out any 'user' input eg. Gas pedal.

Edit : re read your anawer... So some adjustment in timing does take place until rpm settles where it needs to idle.

Originally Posted by ///M3Fresh

going based on my E46 hands on with Vanos/cam/timing experiance: ( I would imagine its the same for the S65)

To answer them in order:

a) Correct, at start up there shouldnt be any vanos in play. the cam timing does not adjust as its all RPM based.

b) Since a is correct, to answer simply, No. It just goes back to where it should be once the RPM's drop under the vanos actuation parameters.

c) I cant give you a specific RPM range but my educated guess Vanos wouldnt kick in until ~3k rpm ++. Meaning really once you feel that spike in TQ (you should get an idea of it from driving your car) give or take 500 revs that when vanos is advancing/re-tarting timing.

Again this is all going based on what i know from working on my S54 and other locals near me. I am sure there are differences but the mechanics are the same.

TL: DR- Vanos works under RPMS and after a certain rpm its kicked on.

[FRFNUGN]

Originally Posted by anom3

My first question right away would be... And i know this is one who only someone internal to bmw or bensian (spelling i know...) can answer for sure... As the VANOS doesnt come into play at cold start... How about lets say 30 seconds after cold start if the motor is allowed to idle with out any 'user' input eg. Gas pedal.

Edit : re read your anawer... So some adjustment in timing does take place until rpm settles where it needs to idle.

Regarding answer "C" in the post above yours - there is no RPM range in which VANOS kicks in, it's not VTEC. Your edit (as quoted here) is correct. When valve timing adjustment is required for engine performance, it happens. Cold mode operation (just after starting, starting being cranking and first firing, i.e. ~1-3 seconds) requires valve timing adjustment to more quickly heat up the catalyst, so VANOS is operated. Regardless of RPM, VANOS can be operated, but that doesn't necessarily mean it is. It's all based upon calibration for whatever performance BMW was trying to achieve (whether it be load control at that point, or emissions, or temperature management).

[anom3]

Understood.

So by the looks of it, a start sequence looks as follows:

0) "Cold Start" or "Start" pin "enabled" in VANOS gears (Butchering this... but I mean the gears them selves are in "cold start" mode via the pin in each gear).

1) Starter spins

2) Ignition takes place

3) ECU decides, yep motor is firing on its own, we can start adjusting timing via VANOS __if needed__ (condition based... whatever these conditions may be). At this point the cold start / start pin is "withdrawn" (somehow? hydraulically?)

Edit : The "cold start" / "start" pin I speak of is the "locking pin" that holds the vanos at normal (default) position. I understand now that it appears this pin works on oil pressure : Have pressure? Pin withdrawn and thus VANOS can be used to adjust timing (if needed / conditions are right)... No pressure (motor off)? Falls into "locked" position, thus forcing the VANOS to "default" mode.

---

Once again, sorry about my terminology...

---

Originally Posted by FRFNUGN

Regarding answer "C" in the post above yours - there is no RPM range in which VANOS kicks in, it's not VTEC. Your edit (as quoted here) is correct. When valve timing adjustment is required for engine performance, it happens. Cold mode operation (just after starting, starting being cranking and first firing, i.e. ~1-3 seconds) requires valve timing adjustment to more quickly heat up the catalyst, so VANOS is operated. Regardless of RPM, VANOS can be operated, but that doesn't necessarily mean it is. It's all based upon calibration for whatever performance BMW was trying to achieve (whether it be load control at that point, or emissions, or temperature management).

[///M Power-Belgium]

http://prodcds.bmwuniversity.com/lib...0%20Engine.pdf

[///M3Fresh]

Originally Posted by FRFNUGN

Regarding answer "C" in the post above yours - there is no RPM range in which VANOS kicks in, it's not VTEC. Your edit (as quoted here) is correct. When valve timing adjustment is required for engine performance, it happens. Cold mode operation (just after starting, starting being cranking and first firing, i.e. ~1-3 seconds) requires valve timing adjustment to more quickly heat up the catalyst, so VANOS is operated. Regardless of RPM, VANOS can be operated, but that doesn't necessarily mean it is. It's all based upon calibration for whatever performance BMW was trying to achieve (whether it be load control at that point, or emissions, or temperature management).

Again I have not looked at the design of the S65 VANOS( had not had the reason to, yet, knock on wood) but simply going off the S54 that I know.

I mentioned the VANOS actuating on or off purely due to the high pressure oil required to operate the system, I would imagine that at idle the pressures are not what they would be say 3-4k RPM's more then idle? again this is how I comprehend the VANOS, at least in the S54/S85.

Originally Posted by ///M Power-Belgium

http://prodcds.bmwuniversity.com/lib...0%20Engine.pdf

This is a good link with a lot of info, but OP is trying to find answers to steer him towards what could be going wrong with his VANOS.

[FRFNUGN]

Originally Posted by ///M3Fresh

Again I have not looked at the design of the S65 VANOS( had not had the reason to, yet, knock on wood) but simply going off the S54 that I know.

I mentioned the VANOS actuating on or off purely due to the high pressure oil required to operate the system, I would imagine that at idle the pressures are not what they would be say 3-4k RPM's more then idle? again this is how I comprehend the VANOS, at least in the S54/S85.

This is a good link with a lot of info, but OP is trying to find answers to steer him towards what could be going wrong with his VANOS.

For everyone's clarity, the S65 VANOS is different from the S54/S85 in that it uses normal (low) oil pressure instead of high oil pressure, which is why it shouldn't matter what RPM you're at. I posted the relevant PDF (VANOS section only) earlier in the thread so that OP didn't have to wade through that entire engine breakdown (though it is a pretty awesome source of info for all the other systems too).

[M3 Pilot]

VANOS, MIVEC, VVTI, etc, (Variable timing) should not be confused with VTEC, which has an addition cam lobe.

[BPMSport]

Originally Posted by anom3

In my quest to figure out whats causing this bloody grinding noise during my cold starts I spent a good part of last evening learning about how the BMW VANOS works and what it does. For the most part, I have it figured out. An overall simplification would be simply a hydraulically "moved" piston that advances / retards timing based on whatever the ECU reads the conditions to be (RPM mainly, but a few others as well).

I do however have a couple of slightly advanced questions that I am unable to find answers to. I'm thinking that its a safe bet that even tho the S65 VANOS is not a high pressure system like most other VANOS, the same principles as BMW's high pressure VANOS should apply.

So, onto the questions:

a) I have read a number of posts stating that during engine start, VANOS does not really come into play. Correct?

b) If "a" is correct, is this to say that whenever the motor is turned off, the position of the piston is "reset" to a "default" position?

c) If "a" is correct, how quickly after engine start does the ECU start advancing / retarding timing using the VANOS?

d) If the vehicle is in neutral, but RPM is raised (eg: via the gas pedal) to 3000 or even 6000RPM, will the ECU start adjust timing via the VANOS? Or does the ECU need the vehicle to be "under load" (eg: in gear) to start adjusting the timing?

That's it for now, and I apologize if my understanding is incorrect or terminology is off, but I'm a newbie at understanding all of this. Bare with me

Stumbled across this thread, thought I'd give some technical details:

The ECU has both cold and warm vanos maps for the inlet and exhaust camshafts.

There is a engine temperature dependent characteristic "KL_KH_VAN_DELAY_TMOT"
which delays the VANOS target position interventions after engine start. Also, the catalyst heating system must complete its cycle, and motor temperature be less than or equal to the threshold K_KH_VAN_TMOT_MAX to activate VANOS operations.

The DME does monitor cam position on engine turn off, and has variables which determine oil supply to the VANOS units. The VANOS operation is quite complicated, 200+ pages on how it's controlled by the DME with tons of diagrams. Even to the extent of mentioning rattling! When there is no pressure, a locking pin holds the vanos unit in the normal/engine start position.

To answer question C - when revving in neutral with no load, the VANOS units aren't varying the camshaft timing - both in cold and warm operation. Camshaft movement by the VANOS unit takes place the most under load/higher relative filling. The inlet camshaft moves much less than the exhaust camshaft at lower loads

Here is an example of the targeted inlet cam position when cold. It is more or less the same in these areas when warm as well:

Hope this helps some..

[Disturbed]

I'm new to these BMW's so forgive me if this is common knowledge.

Is it possible to tune VANOS? As in tuning with no overlap below 3000rpm and then progressive overlap happening between 3000-4000rpm?

I would think by now there would be some way to control that to give the engine more low end.

What about with aftermarket cams? I would think you could get a pretty big cam to idle decent and make big power uptop.

What I haven't seen is any kind of veritable lift system.


On a personal note....I like the choppy cold idle and wish it did it all the time. I used to have a Viper that had a crower stage 1 street cam and I dropped the idle down to 650rpm....it lopped so much the car would rock at idle...loved that.