E46 M3 S54 Vanos pressure tests

[sapote]

It is actually pretty logical, as you stab the gas pedal the splines more than likely move to adjust timing based on rpm and load change, that uses oil to move the splines which causes the pressure drop inside the unit until the pressure stabilizes again. Having a working acc and pump would just make those dips shorter as oil supply is almost instantaneous.

Disagreed. See post #43 as we had discussed this 2 months ago.

[maupineda]

Disagreed. See post #43 as we had discussed this 2 months ago.

you can hold to your believes anything you want, you are pretty knowledgeable, but don’t have the truth to all things.

and there is no fundament to that post

remember that at any moment of steady state conditions there is a specific volume of oil at pressure, the moment the piston displaces, the volume of oil needed inside the VANOS changes which affects the pressure. Is not a leak, just that more volume is needed which reduced pressure momentarily until more oil is supplied.

[sapote]

and there is no fundament to that post

The video clearly shows the pressure stabilized at about 112, then as engine rev up, it first dipped a bit, not more than 1 bar, then recovered and increased more than initially 112 as rpm increased.

Compared this to the last video which dropped a lot as rpm increased, and this seems like pump had low output rate to supply what used by Vanos.

[Santino]

I have made a new video, when i input gas in a stable fasion the pressure barly drops. i've got slight (10-15bar) dips when i stab the gas pedal.
I think i will leave it as it is now, as the pressure dont drop below 100-105bar

[sapote]

I have made a new video, when i input gas in a stable fasion the pressure barly drops. i've got slight (10-15bar) dips when i stab the gas pedal.

It looks much better now with about 5 bar max dropped as compared to before with bad ACC.

[BBRTuning]

It is actually pretty logical, as you stab the gas pedal the splines more than likely move to adjust timing based on rpm and load change, that uses oil to move the splines which causes the pressure drop inside the unit until the pressure stabilizes again. Having a working acc and pump would just make those dips shorter as oil supply is almost instantaneous.

The video clearly shows the pressure stabilized at about 112, then as engine rev up, it first dipped a bit, not more than 1 bar, then recovered and increased more than initially 112 as rpm increased.

Compared this to the last video which dropped a lot as rpm increased, and this seems like pump had low output rate to supply what used by Vanos.

I was going to post this earlier but decided against it, however now that the thread appears to be going in circles because of these two random videos...

I agree with maupineda here. Driving the Vanos certainly takes some oil volume as well as pressure that is "lost" to the system. The Vanos pump cannot supply enough oil volume to continuously supply the Vanos solenoids. Luckily, the design of the system allows the camshafts to stay in their commanded position with little to no additonal input from the solenoids once that position is reached. Therefore only an initial supply of oil volume is required to move the cams to the commanded position, partially draining the accumulator, but then giving the pump a chance to replenish the reserve supply (similar to an Accusump for your oil system).

Unfortunately these two videos mentioned here are completely useless to compare. The video in post #1 shows pressure at idle, and then the engine is *very* lightly revved to 2000 RPM or so. In this situation the intake cam is likely not moved at all, and the exhaust cam only partially (look at factory DME Vanos target tables in these low-load sites). The 2nd video shows aggressive throttle stabs straight off idle. In this case, both cams are moved significantly, requiring much more oil volume, so of course the Vanos system pressure will drop much more.

Bottom line is, test your system pressure at a hot idle/free rev to determine if supply to Vanos pump or the regulator setting is the issue. If pressure seems to be regulated to a value below spec, adjust regulator. Then, test Vanos system. If system response and leak tests pass, you're fine. The Vanos system test (for the most part) puts MUCH more stress or load on the system than one would experience during normal, or even track, driving. During the test, the cams are driven from full rest to full advance (or retard in exhaust's case) at a relatively low RPM. This is something that almost never happens in actual driving, as the cams are constantly moved across only intermediate values at partial load.

The request for the cam to be driven from one mechanical stop to the other immediately will only ever happen if you suddenly go from 0% to 100% throttle below ~3000 RPM, and in that situation, cam response will be <300 ms (<0.3 seconds). If you do this low RPM stab over and over, AND you have a bad accumulator or weak Vanos pump, you MAY notice some slight reduction in engine torque response due to slower Vanos movement. Otherwise, it's your tune, or it's in your head.

Another way to put it (with data): it takes about 60-80ms to move your foot from 0-100% throttle during an aggressive stab, an additional 100-140ms for the DBW throttle system to open throttle from 0-100% on these cars. That's a total latency of ~150-220ms from when your foot starts to move to when the throttles are fully open, during which the Vanos is already moving to targets. If you have a "lazy" Vanos system that tests at ~300ms, then you're looking at roughly 1/10 of a second between when you reach 100% torque target and you actually get full torque with cams in final position. Additionally, in such a situation, the throttles provide about 75% of full torque, with the Vanos being in correct position accounting for the additioinal ~25%. Even a very astute driver would be hard pressed to notice this 100ms delay from 75 to 100% torque. Trust me, I'm unfortunatlely also all for spending money on things that don't really need fixing (lol), I just don't want a ton of people losing sleep over some issue they're experiencing and go down the Vanos rabbit hole when they don't need to.

[sapote]

Unfortunately these two videos mentioned here are completely useless to compare. The video in post #1 shows pressure at idle, and then the engine is *very* lightly revved to 2000 RPM or so. In this situation the intake cam is likely not moved at all, and the exhaust cam only partially (look at factory DME Vanos target tables in these low-load sites). The 2nd video shows aggressive throttle stabs straight off idle. In this case, both cams are moved significantly, requiring much more oil volume, so of course the Vanos system pressure will drop much more.

Compare videos on post #32 (dropped about 30bar) and post #64 (dropped about 5 bar) and they both from the same car with same rpm reving rate. The poster said the pressure still dripped down after replace ACC: "Finally i have replaced a new ACC bottle for the vanos, it still dips pressure whem hiting the gas, but never drops below 100bar (i have operating pressure at 115bar now)"
115 -100 = 15 bar dropped max
and this is why I said it's mystery. Post #64 video look normal.

[BBRTuning]

The blips in the video with the larger pressure drop sounded much longer duration and more aggressive, but it could just be the video. Either way, I don't think these types of comparisons are very useful. It would be better to do a very repeatable test (such as the actual Vanos system test) at the same oil temperature each time and watch pressure drop then, to really be able to learn anything from it.

I certainly think it's a good idea to check and adjust the regulated Vanos pressure if one suspects an issue. The key-off bleed-down test also does seem to be a decent indicator of Vanos Accumulator condition. Trying to compare different videos of blipping the engine with your foot is less useful.

[Santino]

The blips in the video with the larger pressure drop sounded much longer duration and more aggressive, but it could just be the video. Either way, I don't think these types of comparisons are very useful. It would be better to do a very repeatable test (such as the actual Vanos system test) at the same oil temperature each time and watch pressure drop then, to really be able to learn anything from it.

I certainly think it's a good idea to check and adjust the regulated Vanos pressure if one suspects an issue. The key-off bleed-down test also does seem to be a decent indicator of Vanos Accumulator condition. Trying to compare different videos of blipping the engine with your foot is less useful.

I agree, as an autor of these videos its hard to compare pressure drops for this gas blips, as when i input gas agressive the drops are much more significant then, when aplied in a steady fasion (more compared to road use)

[Arinb12]

I'm having similar issues with this

I have tried to run a vanos test and it has told me to check the pressure regulating valve and or the solenoid (solenoid has been checked and has no issues, nor does the block which has been cleaned and is all free moving)

I ran the pressure tests above and my results are very strange

On cold engine, I have the following video. The car was left a couple of days and then the valve and tester fitted.

revving the engine reduced the pressure as seen in video

It had a nice 115bar pressure and the leak down was not too bad, but not great

After the above video the car was still cold, I restarted it after leakdown finished and the following video was the next read out. (Assume oil was more viscous after a couple mins of the previous video)

Pressure super low! I tried to adjust the regulator valve and it did nothing, I ran out of adjustments.

I let it warm up and tried to adjust again, only thing I could do was back it out and reduce pressure not increase it to 115 bar; it was the same as the below video for both the cold restart and warm engine (more viscosity to oil)

Revving the engine increased pressure significantly only for the load time

This happened on all subsequent tests too


The attached photos is my vanos test results

any advise is appreciated. I have just rebuilt the vanos with new seals. I have new sprocket bolts, new chain guide, solenoid block is clean and free moving, solenoid pack has been continuity tested to confirm no cold solder joints, the disc is the redrilled standard that it came with.

Thanks for the help, I'm assuming ACC or regulator but not sure, also heard about an oil filter between vanos and body that may get blocked?

[Arinb12]

Edited to remove

[maupineda]

Your problem is not the accumulator nor the regulating valve, but your VANOS pump, which once the oil is warm, does not generate pressure. this is due to either a worn-out pump shaft, a worn-out disc, or incorrect tolerances of the radial pistons.

I had the same problem, in my case, the issue was the pump disc, I had to source another OE disc, have it redrilled, and the problem was solved.

to anyone doing VANOS work, I now advise to always measure pressure BEFORE as well as run a DIS/ISTA test, and if all is ok, leave it alone. if you feel you need to fix the play with the exhaust tab, then just make sure you redrill the original to your car disc.

I am more than sure this issue with the disc is present in many cars, just people do not test for it, also, low pressure does not necessarily mean the VANOS test will fail as when the rpms rise the pressure rise to a point where there is enough of it to actuate the VANOS splines. however, it is pretty upsetting to know you have a non-confirming system LOL

in your case, your VANOS does fail as the pressure is too low and causes the response times to be too slow.

EDIT: on the Z4M VANOS test is done at 2k rpms, on the E46 M3 is done at 1500 rpms, so it is more sensitive to low pressure as at 1500 there will be less pressure if your pump fails to be at 115 bars at idle.

[Arinb12]

I failed the vanos test prior to this due to timing issues at the first part. I decided to rebuild new seals before refitting the vanos after timing. My disc is the original but has been drilled by the previous owner?

Could it have worn out that much that it no longer produces enough pressure??

What part is the pump shaft? And what part of this disc could be worn?

What are my options now?

[thegenius46m]

I failed the vanos test prior to this due to timing issues at the first part. I decided to rebuild new seals before refitting the vanos after timing. My disc is the original but has been drilled by the previous owner?

Could it have worn out that much that it no longer produces enough pressure??

What part is the pump shaft? And what part of this disc could be worn?

What are my options now?

Interesting you are having issues with the original disk. I'm in the process of swapping vanos units because my original is not producing enough pressure at all with a besian redrilled disk oe disk from years ago. I have been told the tolerances of all these components can get looser as the mileage rises so it's possible. I picked up a 60k mile unit and had dr vanos drill the holes on the same disk I sent out. My car also has a brand new genuine bmw oil pump, chains, and guides so if that doesn't get me back to spec something is wrong lol.

You also could have a bad regulating valve on the solenoid body. If that doesn't fix it, get an entire vanos unit with the same oil pump disk and just change everything.

[Arinb12]

Low mileage ones are like gold dust in the UK unfortunately!