How does the vanos work?

[Pondy]

My 'new' M54 3 litre has a "double vanos" but I am unsure what it does.
I was under the impression it acts like a VVT and alters the timing to increase something.....is it torque, or BHP?

What revs does the vanos 'kick in'?

I am trying to work out how to drive the car, as it is all new to me. I am used to turbos (diesel and petrol) where it's all about lowdown torque not revs. Revving the nuts off an engine is not something I am used to, so it's a bit worrying TBH.

 

[sars]

If you'd not just insulted B21, he may of mansplained it to you

Yes it is like VVT, the double vanos is for both the intake and the exhaust camshafts to vary the timing of both independently.

 

[Mr Tidy]

Very nicely put sars.

To be fair I didn't notice a big Vanos surge in the M54 engine I had in my E46, or in the 4 BMWs I've had with the N52. But it definitely makes life get exciting in my Z4M after 5,000 rpm.

 

[Pondy]

If you'd not just insulted B21, he may of mansplained it to you

He don't know shite about anything except what he reads on Google. Although I've heard he knows quite a lot about pies!

AND...he started it. Which is bizarre considering I am (apparently) on his 'ignore' list and have been since he had a massive sulk a few years back and re-invented himself.

 

[Pondy]

Yes it is like VVT, the double vanos is for both the intake and the exhaust camshafts to vary the timing of both independently.

Thank you Gorge.

 

[axelleveau]

Vanos is continuously varying cam timing to suit the RPM and to a lesser extent, load. It will not give a kick like VTEC or similar technologies. It does give the engine designer a wider powerband to play with so long story short is that you can get more power by having torque at higher RPM without loosing drive-ability at lower RPM, and of course trade that with NVH, consumption...

 

[sars]

Very nicely put sars.

To be fair I didn't notice a big Vanos surge in the M54 engine I had in my E46, or in the 4 BMWs I've had with the N52. But it definitely makes life get exciting in my Z4M after 5,000 rpm.

Thanks, and that's because the Z4M is lacking in the torque department so it needs the 7800 rpm to get the power

Thank you Gorge.

You're welcome Shirley

 

[Mr Tidy]

Thanks, and that's because the Z4M is lacking in the torque department so it needs the 7800 rpm to get the power

It's because the Z4M is all about using the right gear (which is why you have a manual gearbox in the first place) and revving the nuts off it, rather than plodding about relying on a surge of torque from forced induction.

 

[Usel]

On the M54 the vanos changes at 4k rpm. With a tired or incorrectly functioning vanos you will always have the full power from 4k - 6.8k rpm but it's the engine range lower than 4k rpm that is effected. You lose the low down torque.

If the engine has a big change in power at 4k rpm then it's likely the vanos isn't working correctly. When functioning correctly you should notice a change but it shouldn't feel like a powerband like on a 2-stroke motorbike.

 

[buzyg]

He don't know shite about anything except what he reads on Google. Although I've heard he knows quite a lot about pies!

AND...he started it. Which is bizarre considering I am (apparently) on his 'ignore' list and have been since he had a massive sulk a few years back and re-invented himself.

Pies are important.

 

[buzyg]

I gather before the cam change you get a bit more Torque to help acceleration. Then after the Cam change a bit more HP to help with top speed. As Mr T said you really do feel it in the S54.

 

[sars]

It's because the Z4M is all about using the right gear (which is why you have a manual gearbox in the first place) and revving the nuts off it, rather than plodding about relying on a surge of torque from forced induction.

So what made the S54 good was that that gentle rise and fall curve between 2500 rpm, to 7800 rpm with a peak of 269 lb.ft at just under 5000 rpm. That span of 40 lb.ft of torque lasts over 5300 rpm, giving you that linear-ish acceleration through a gear. And I guess by the time you get to 6000 rpm, you're in the sweat spot for the next gear. There's no doubt that the S54 is a legend of an engine, but by the time it was retired in 2008 the world had really moved on. And that's where we come to the B58, it in no way feels like it is forced induction, that double vanos that made the S54 great, makes the B58 truly outstanding, it has a torque curve that makes the S54's look like a rather severe mountain that's not very tall! and it does everything else better to boot. The S54 only ran in three cars, it has a few known issues and it wasn't even a new design in 2000 either, whereas the B58 is used so extensively you can find it in any model where it will fit, is reliable, is less stressed and requires very little maintenance. And the pièce de résistance, that artificially flat torque curve 1600 rpm to 4600 rpm and 369 lb.ft, and the manual gearbox gives you a similarly linear acceleration feel as the S54, just with an extra 100 lb.ft all the way from 1000 rpm, and there's no M premium either, so there

 

[bigwinn]

This conversation reminded me:

 

[Mr Tidy]

To be honest I'd probably prefer a B58 engine in a daily driver, but my Z4 isn't my daily driver!

And this is the bit that put me off "that artificially flat torque curve 1600 rpm to 4600 rpm and 369 lb.ft,".

At the end of the day we've both got what we want.

 

[MikeyH]

Oh my god, I just fell asleep reading this

 

[Zedist]

Everyone has explained what effect it has but no-one has yet explained ‘how it works’. ?

 

[Mr Tidy]

Maybe this will help. https://bimmertips.com/bmw-vanos-basics-explained/

 

[sars]

And this is the bit that put me off "that artificially flat torque curve 1600 rpm to 4600 rpm and 369 lb.ft,".

That's like saying your fake Picasso is better than my fake Van Gogh, they are both artificially created torque curves by the vanos affect.

Everyone has explained what effect it has but no-one has yet explained ‘how it works’. ?

Apologies, imagine that you can alter how much the intake or exhaust valves open and decide at what point they start to open and close relative to, but independent from, the position of the piston. In a conventional system this is relatively fixed and no fine tuning at different rpm, load or fuel feed can be achieved. So hopefully you know what suck, squeeze, bang & blow is without being rude, If you thus open the inlet valves later in the suck cycle, there is an improvement in suction at lower rpm (an improved fuel fill of the cylinder), this creates more torque but only works at lower rpm's. Also in a conventional system with fixed valve positions there is an overlap between the exhaust valve closing and the inlet valve opening and at high rpm's there is the inevitable blow back into the inlet manifold, this decreases the efficiency of the engine and thus torque/power at high rpm's, these are just two examples of the how, there are many more.

 

[Zedist]

That's like saying your fake Picasso is better than my fake Van Gogh, they are both artificially created torque curves by the vanos affect.


Apologies, imagine that you can alter how much the intake or exhaust valves open and decide at what point they start to open and close relative to, but independent from, the position of the piston. In a conventional system this is relatively fixed and no fine tuning at different rpm, load or fuel feed can be achieved. So hopefully you know what suck, squeeze, bang & blow is without being rude, If you thus open the inlet valves later in the suck cycle, there is an improvement in suction at lower rpm (an improved fuel fill of the cylinder), this creates more torque but only works at lower rpm's. Also in a conventional system with fixed valve positions there is an overlap between the exhaust valve closing and the inlet valve opening and at high rpm's there is the inevitable blow back into the inlet manifold, this decreases the efficiency of the engine and thus torque/power at high rpm's, these are just two examples of the how, there are many more.

Thank you for the comprehensive explanation, but what I was actrually asking was, how does all this become manifested in the M54 engine? What mechanical process occurs? I can see that the M54 has a big lump on the front whereas the N52 has two inset solenoid valves. Given all the threads on here talking about replacing seals in the vanos unit on the M54 I asume there is a mechanical movement somewhere. So how does it work?

 

[smorris_12]

Think of a traditional camshaft where there's a big gear nailed to the end of the shaft. Everything is rigidly fixed together. The gear is driven by the cam chain and the cam lobes open valves at the same position every time the crank goes round. Cam variators like VANOS work by removing that rigid connection in the camshaft and instead let the gearwheel move up to (something like) 15 degree from that fixed position. This changes the timing (sometimes called phasing) between crank and cam shafts and this is A Good Thing.