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  1. #1
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    VANOS how it works…

    Couple times VANOS has popped up in conversation. I’ve asked questions before but no body answered in detail… but I never started a thread. I’m curious about the specifics.

    The n54 has double VANOS meaning an inner and outer gear on both the intake and exhaust cams which advance or retard about 20 crank degrees or so changing overlap, when the valves open/close.

    Reduced overlap at idle for smoothness
    Increased overlap when cruising for EGR
    Maybe reduced overlap on boost to prevent loosing boost pressure.
    Off boost more overlap increases EGR, cylinder fill and pressures.

    • Is the actual operation variable or just 2 positions
    • What are the on and off boost effects
    • If intake is advanced, is exhaust always retarded and vise versa
    • What’s the time period in transition… how fast can the oil move the gears
    • We know there’s a VANOS event at around 3500rpm at WOT... is this to reduce overlap… ie. Advance exhaust and retard intake.
    If we could reduce overlap wouldn’t this greatly help intake carbon buildup? What would be the effect on performance… cruising may suffer some due to no scavenging and reduced cylinder fill off-boost, but would this be significant?

    I’ve seen a write up for the e39 M5 engine, but this is NA and only intake I believe.

    Anyway curious.

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    Excellent question, hopefully some here can enlighten us on VANOS operation, it's benefits, and the implications of tuning.
    Click here to enlarge

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    Click here to enlarge Originally Posted by Kamal Click here to enlarge
    Excellent question, hopefully some here can enlighten us on VANOS operation, it's benefits, and the implications of tuning.
    Agreed, great thread and question and hopefully someone can give a detailed response.

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    very very interested...hopefully someone knows the details, i've been trying to dig up this info for a while now
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    That last point you bring up about the carbon build up is a good one. I was just reading an article (linked either on here or N54Tech) about the carbon buildup issues associated with DI, and what some MFG's were doing to correct it. It sounded like they were using cam timing to help combat it. It would be interesting to see how that fix impacts performance and efficiency. Any time you change valve events, you affect one or the other, but maybe it's minimal at cruise.

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    2 out of 2 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    Couple times VANOS has popped up in conversation. I’ve asked questions before but no body answered in detail… but I never started a thread. I’m curious about the specifics.

    The n54 has double VANOS meaning an inner and outer gear on both the intake and exhaust cams which advance or retard about 20 crank degrees or so changing overlap, when the valves open/close.

    Reduced overlap at idle for smoothness
    Increased overlap when cruising for EGR
    Maybe reduced overlap on boost to prevent loosing boost pressure.
    Off boost more overlap increases EGR, cylinder fill and pressures.

    • Is the actual operation variable or just 2 positions
    • What are the on and off boost effects
    • If intake is advanced, is exhaust always retarded and vise versa
    • What’s the time period in transition… how fast can the oil move the gears
    • We know there’s a VANOS event at around 3500rpm at WOT... is this to reduce overlap… ie. Advance exhaust and retard intake.
    If we could reduce overlap wouldn’t this greatly help intake carbon buildup? What would be the effect on performance… cruising may suffer some due to no scavenging and reduced cylinder fill off-boost, but would this be significant?

    I’ve seen a write up for the e39 M5 engine, but this is NA and only intake I believe.

    Anyway curious.
    Disclaimer: im not an expert on VANOS systems

    I'll do my best to answer what I can...
    • Is the actual operation variable or just 2 positions
    The actual operation of this system is infinitely variable, for instance the cam phase angles can sweep from (guessing) -10 to +30 degrees. Intake and exhaust phase position angle extremities will vary. They are both moving simultaneously, sometimes in the same direction and sometimes not, depends on how the algorithm was designed for cam control.
    • What are the on and off boost effects
    Heres the thing, when you advance the intake cam you essentially close the intake valve sooner which helps low end power and torque. It also reduces the lobe separation angle. For a naturally aspirated engine, the lobe separation angle is the angle between the intake and exhaust lobe tips if you were to draw a line from the lobe tip through the camshaft centerline.

    This angle basically gives you an idea of how much overlap between the intake and exhaust valve events there will be. The overlap of the camshaft allows the exhaust gases to scavenge intake into cylinders. Again, for a naturally aspirated engine this is key for making power with only atmosphere pressure.

    Boosted engines are different, they dont need as much overlap or nearly as much duration because they have turbos to cram air in the cylinders. So, for boosted VANOS applications you would probably not see huge swings in cam angles like you probably would on an S65 that needs to retard the intake cam continuosly up to redline to allow for more and more lobe separation angle for top end power.

    A boosted engine doesnt use inertial packing as much as an NA engine does. But that doesnt mean it cant use VANOS. Its just that boost masks the advantages of VANOS.

    • If intake is advanced, is exhaust always retarded and vise versa
    See above, it's not always cut and dry like that. A high revving NA engine will see a greatly different cam phasing routine programmed into the ECU than a low RPM boosted engine like the N54. The physics of both engines are very different, one engine only has atmospheric pressure and the other has as much pressure as you want at any RPM, so the VANOS maps will be different.
    • What’s the time period in transition… how fast can the oil move the gears
    Very fast, the cams phase almost instantly. Oil pressure is at somewhere around 60-80 psi, so the phase changes happen fast ( I dont have a number sorry)
    • We know there’s a VANOS event at around 3500rpm at WOT... is this to reduce overlap… ie. Advance exhaust and retard intake.
    For the N54 the upper RPM VANOS changes which kick in about 4200 RPM are probably to retard the intake cam (this is typical for almost all engines, intake cam gets retarded for high RPM inertial packing).

    Low RPM vanos changes promote better spool probably by advancing the exhaust cam to open exhaust valve earlier to move the turbos.



    I wouldnt want any manufacturer to build a program that phases the cam to reduce carbon buildup, this just shows the engine was poorly designed and they are sacrificing optimal cam phasing for carbon buildup problems.


    EIDT: I'm sure evolve could better answer all these questions.


    EDIT:

    heres a good link

    http://www.tildentechnologies.com/Cams/CamDesign.html
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    Click here to enlarge

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    Disclaimer: im not an expert on VANOS systems

    I'll do my best to answer what I can...
    • Is the actual operation variable or just 2 positions
    The actual operation of this system is infinitely variable, for instance the cam phase angles can sweep from (guessing) -10 to +30 degrees. Intake and exhaust phase position angle extremities will vary. They are both moving simultaneously, sometimes in the same direction and sometimes not, depends on how the algorithm was designed for cam control.
    • What are the on and off boost effects
    Heres the thing, when you advance the intake cam you essentially close the intake valve sooner which helps low end power and torque. It also reduces the lobe separation angle. For a naturally aspirated engine, the lobe separation angle is the angle between the intake and exhaust lobe tips if you were to draw a line from the lobe tip through the camshaft centerline.

    This angle basically gives you an idea of how much overlap between the intake and exhaust valve events there will be. The overlap of the camshaft allows the exhaust gases to scavenge intake into cylinders. Again, for a naturally aspirated engine this is key for making power with only atmosphere pressure.

    Boosted engines are different, they dont need as much overlap or nearly as much duration because they have turbos to cram air in the cylinders. So, for boosted VANOS applications you would probably not see huge swings in cam angles like you probably would on an S65 that needs to retard the intake cam continuosly up to redline to allow for more and more lobe separation angle for top end power.

    A boosted engine doesnt use inertial packing as much as an NA engine does. But that doesnt mean it cant use VANOS. Its just that boost masks the advantages of VANOS.

    • If intake is advanced, is exhaust always retarded and vise versa
    See above, it's not always cut and dry like that. A high revving NA engine will see a greatly different cam phasing routine programmed into the ECU than a low RPM boosted engine like the N54. The physics of both engines are very different, one engine only has atmospheric pressure and the other has as much pressure as you want at any RPM, so the VANOS maps will be different.
    • What’s the time period in transition… how fast can the oil move the gears
    Very fast, the cams phase almost instantly. Oil pressure is at somewhere around 60-80 psi, so the phase changes happen fast ( I dont have a number sorry)
    • We know there’s a VANOS event at around 3500rpm at WOT... is this to reduce overlap… ie. Advance exhaust and retard intake.
    For the N54 the upper RPM VANOS changes which kick in about 4200 RPM are probably to retard the intake cam (this is typical for almost all engines, intake cam gets retarded for high RPM inertial packing).

    Low RPM vanos changes promote better spool probably by advancing the exhaust cam to open exhaust valve earlier to move the turbos.



    I wouldnt want any manufacturer to build a program that phases the cam to reduce carbon buildup, this just shows the engine was poorly designed and they are sacrificing optimal cam phasing for carbon buildup problems.


    EIDT: I'm sure evolve could better answer all these questions.


    EDIT:

    heres a good link

    http://www.tildentechnologies.com/Cams/CamDesign.html
    This is the closest we have gotten to an answer so I tip my hat to you good sir.

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    Thanks DBFIU!!
    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
    I wouldnt want any manufacturer to build a program that phases the cam to reduce carbon buildup, this just shows the engine was poorly designed and they are sacrificing optimal cam phasing for carbon buildup problems.
    I think part of BMW's focus was EGR, cat warm up, etc. So some optimization in performance may also reduce carbon build up. Overlap is probably more of a cause then cc ventilation.

    Cobb ATR should have the VANOS tables unlocked and we will learn more about when, how the cams are phased.

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    Messing with Vanos is like black magic...it is infinitely variable, and all it takes is one table off by a digit or two to cause a CEL or surge/lag in power.

    Given the issues that we have with them now (especially the earlier build N54s), I wouldnt mess with the Vanos units until they actually stop failing. Frustration gets pretty heavy when you go out for a day of road racing and have nothing but a limp mode at every turn...

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    2 out of 2 members liked this post. Yes Reputation No
    This is all I Got:

    VANOS VALVE/CAM TIMING SYSTEM IN BMW’s


    VANOS is a combined hydraulic and mechanical camshaft control device managed by the car's
    DME engine management system.

    The VANOS system is based on an adjustment mechanism that can modify the position of the intake camshaft versus the crankshaft. Double-VANOS adds an adjustment of the intake and outlet camshafts.

    VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, reducing fuel consumption and exhaust emissions.
    Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed.


    VANOS significantly enhances emission management, increases output and torque, and offer better idling quality and fuel economy. The latest version of VANOS is double-VANOS, used in the new M3.

    VANOS was first introduced in 1992 on the BMW M50 engine used in the 5 Series.

    Here's how it works:


    In overhead cam engines, the cams are connected to the crankshaft by either a belt or chain and gears. In BMW VANOS motors there is a chain and some sprockets.

    The crankshaft drives a sprocket on the exhaust cam, and the exhaust cam sprocket is bolted to the exhaust cam. A second set of teeth moves a second chain that goes across to the intake cam. The big sprocket on the intake cam is not bolted to the cam, for it has a big hole in the middle. Inside the hole is a helical set of teeth. On the end of the cam is a gear that is also helical on the outside, but it's too small to connect to the teeth on the inside of the big sprocket. There is a little cup of metal with helical teeth to match the cam on the inside and to match the sprocket on the outside. The V (Variable) in VANOS is due to the helical nature of the teeth. The cup gear is moved by a hydraulic mechanism that works on oil pressure controlled by the
    DME.


    At idle, the cam timing is retarded. Just off idle, the
    DME energizes a solenoid which allows oil pressure to move that cup gear to advance the cam 12.5 degrees at midrange, and then at about 5000 rpm, it allows it to come back to the original position. The greater advance causes better cylinder fill at mid rpms for better torque. The noise some people hear is the result of tolerances that make the sprocket wiggle a bit as the cup gear is moved in or out.


    Double VANOS

    Double-VANOS (double-variable camshaft control) significantly improves torque since valve timing on both the intake and outlet camshafts are adjusted to the power required from the engine as a function of gas pedal position and engine speed.

    On most BMW engines that use a single VANOS, the timing of the intake cam is only changed at two distinct rpm points, while on the double-VANOS system, the timing of the intake and exhaust cams are continuously variable throughout the majority of the rpm range.


    With double-VANOS, the opening period of the intake valves are extended by 12 degrees with an increase in valve lift by 0.9 mm.


    Double-VANOS requires very high oil pressure in order to adjust the camshafts very quickly and accurately, ensuring better torque at low engine speeds and better power at high speeds. With the amount of un-burnt residual gases being reduced, engine idle is improved. Special engine management control maps for the warm-up phase help the catalytic converter reach operating temperature sooner.

    Double-VANOS improves low rpm power, flattens the torque curve, and widens the power band for a given set of camshafts. The double-VANOS engine has a 450 rpm lower torque peak and a 200 rpm higher horsepower peak than single-VANOS, and the torque curve is improved between 1500 - 3800 rpm. At the same time, the torque does not fall off as fast past the horsepower peak.


    The advantage of double-VANOS is that the system controls the flow of hot exhaust gases into the intake manifold individually for all operating conditions. This is referred to as "internal" exhaust gas re-circulation, allowing very fine dosage of the amount of exhaust gas recycled.

    While the engine is warming up, VANOS improves the fuel/air mixture and helps to quickly warm up the catalytic converter to its normal operating temperature. When the engine is idling, the system keeps idle speeds smooth and consistent thanks to the reduction of exhaust gas re-circulation to a minimum. Under part load, exhaust gas re-circulation is increased to a much higher level, allowing the engine to run on a wider opening angle of the throttle butterfly in the interest of greater fuel economy. Under full load, the system switches back to a low re-circulation volume providing the cylinders with as much oxygen as possible.

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    sweet man, the more info the better, thanks for sharing it
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    If you really want to see how it works, hook up an OBD2 scanner with advanced BMW functions, and data log on the dyno or the street. It will give you part of the picture....you'll very quickly begin to realize it's a 4 D map controlling them in the least....as in the cam movement isn't proportional to RPM alone.

    Neel knows more about this from a real world perspective than anyone else I know....but most of what I've learned was from doing my own research on the dyno and in the shop with a timing wheel....
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    Now, the question "moi" has about VANOS is obviously my high RPM misfire related...is it possible in any way that anything to do with VANOS relates to intermittent misfires in the high RPMs and that there is no error codes stored about the vanos, just misfire code on one specific cylinder (cylinder 5)..

    Given how the DME controls it by varying oil pressure, what would happen with VANOS operation if there was an oil leak anywhere...

    not sure if this is an appropriate thread for this discussion but I don't see why not...understanding failures a lot of times makes for a better understanding of the system itself..

    given N54 vanos "changeover" event happens around 4300rpm, and given that the misfire on my car whatever boost I run doesn't occur if I go WOT at 4500rpm or above, only occurs if going WOT below 4.5k rpm, do you think VANOS/oil pressure could be at play here...and if yes, in what way...
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    VANOS tuning is one big reason I like standalones in race cars and swaps. No worries about CELs or anything like that, and you have a lot of freedom to find what works best for a particular motor. The technical information presented here is fairly good; I don't have a lot more to add except for a few points:

    1. Like anything else, the answer is ON THE DYNO. Intake manifold design, exhaust, turbochargers, etc can all change the fluid dynamics of your motor, NA or otherwise, that will change the optimal point of VANOS activation.

    2. Turbocharging tends to mask some VANOS power benefits, but only on boost. There's definitely a lot to gain in low-end torque and therefore spool-up in using VANOS.

    3. Response times vary by system - this is really what makes higher-end standalones stand apart. To have the proper base-duty cycle tables, well sorted PID loops and other tools to optimize its response, you will be amazed at how accurate the cams track the target. I typically see errors of less than 1 degree even when the cam moves 30 degrees in 100 RPM during a dyno pull.

    -Neel
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    30 degrees within 100 rpm, holy $#@! that fast response...
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    Above my head, but i'll try to understand.

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    30 degrees within 100 rpm, holy $#@! that fast response...
    Yeah, I'm working on a Mitsubishi EVO10 today and I wish it had 1/4 of the BMW's response.
    Neel Vasavada
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    Los Angeles, CA 90064
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