E46 M3 S54 Vanos pressure tests

[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]

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.

[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]

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.

[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]

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]

It's a mystery why vanos pressure dips as rpm shoot up; could be that the pump disk has abnormal leaking rate with low output rate. Stock disk and 4 pistons?

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.

[Santino]

It's a mystery why vanos pressure dips as rpm shoot up; could be that the pump disk has abnormal leaking rate with low output rate. Stock disk and 4 pistons?

Yes the disk and 4 pistons inside it are stock, only drilled to a smaller diameter to avoid breaking the tabs.
edit after 7 hours pressure still holds at 60bat
i will be taking out the vanos unit to polish it outside, so in anycase will check the disk more thourogh for wear

[sapote]

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)

It's a mystery why vanos pressure dips as rpm shoot up; could be that the pump disk has abnormal leaking rate with low output rate. Stock disk and 4 pistons?

[sapote]

. I even thought about getting the S62 accumulator that has a builtin solenoid to keep pressure until next start but thought it was just unnecessary and too much hazle to adapt.

It shouldn't take long for the vanos pump to build up pressure in the ACC before driving, so I'm not sure why the need to have shut off solenoid. This is useful for the SMG as it save the electric pump wear and tear, but vanos pump runs all the time anyway.

[maupineda]

I also replaced the accumulator and I hold now pressure too after engine shutdown, though I did not test for how long, but before it dropped to zero pretty much immediately. I even thought about getting the S62 accumulator that has a builtin solenoid to keep pressure until next start but thought it was just unnecessary and too much hazle to adapt.

[Santino]

Not normal. I believe it dropped (as the DME changing the VANOS timing when rpm changing) because there is no accumulator pressure reserve in the old tank with empty N2 gas. Need a new ACC bottle.

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)
But the leek down is now great, previuos it took a minute to reach 0, now it drops to 60bar after turning off, and keeps this pressure for 2 hour now as i write this.
Figured it could be helpfull for the comunity

[Arinb12]

Results from my Vanos tests carried out recently, (UK custom guage kit off EBay).
Its somewhat more thorough than the one I'd posted out back in 2016, where I had faults causing v low vanos oil pressure and Ive defined some simple benchmarks, this so that with others data, we could look at establishing indicators that can help us determine whether our systems are at full health.
Am keen to get your feedback (and data points) to work this one further up, please comment.

Could you tell me how you attached this. I got the parts you linked to. Do I just replace the bolt, retain the washers and use some PTFE on the guage threads?

[Santino]

If the gauge was connected to the oil filter lid then the reading may not be the same as where the stock oil sensor. Interesting to see the measured pressure at the sensor on the oil filter housing.

it was connected to the blank oil supply, next to the oe pressure sensor

[sapote]

regarding the oil pressure i found info that it should peak at 4 bar so it apears that mine is showing 1bar higher pressure on idle ore on revs

If the gauge was connected to the oil filter lid then the reading may not be the same as where the stock oil sensor. Interesting to see the measured pressure at the sensor on the oil filter housing.