Engine noise diagnose assistance - Possible vario cam actuator/pad/chain issue?
 

First of all thank you to everyone taking the time to read and reply, I appreciate your thoughts.

Background: 2001 S, 53k miles, Fabspeed exhaust, tune (I believe done by fabspeed, it happened 2 owners ago). The tune is possibly ROW, but I do not know for sure. The reason this believed is because it does not have the normal amount of emissions monitors. I have owned it for a bit more than a year and 1/2 and replaced the AOS when i got it. So far as I know no other major work has been done (original IMS assumed, no chain guide replacements, etc). I noticed a small amount of brown plastic in the filter last oil change from the vario cam pads. It was my second oil change since owning the car and the first I did not see any plastic, but I do not know how long the oil was in it that time. Other then that the car was running like a champ.

I have been monitoring my camshaft deviations since I found the plastic (this past fall) and they seem to sit around:
Camshaft 1: -0.74 (this does increase to 1.60 or a bit more as it warms up and then goes back down)
Camshaft 2: -9.27

Now the problem / question:
I was out for a nice drive a couple of weeks ago, enjoying a corner probably in the 4-5k rpm range in 2nd, some g-forces but nothing crazy, let's call it 60% of what the car could do in that corner. I noticed mid corner the engine seem to take on a different sound. The intoxicating whale sounded more like a Subaru (Not picking on flat 4's, that is just the best way I can think to describe it).

I drove it home 8-9 miles cautiously. It is possible it had lost some power, but given how gingerly/cautiously I was driving it, it is more likely just my perception. If there was a change it was not big.

I finally got out today (work has been insane for a bit), put it in service mode and checked the intake for obvious leaks and the exhaust (just a quick check, nothing detailed, the car is still on the ground). So while I can't discount a leak in the intake / exhaust, I do not see any evidence to point me in that direction.

My concern of course is the vario cam actuator / guides and chain. I am far from an expert on these systems but am hoping that this video I took will help show the data in a way that someone here might see something if there is an issue

I had planned to try to get through the season and then replace the vario cam pads along with a pro-active ims / clutch /etc. But I think i might have to do that a bit sooner possibly.

Note: at the beginning of the video I say crank angle, but meant to say cam...

Hopefully this drive link works:
https://photos.app.goo.gl/eJM9qYHyqL1TrkUg8

Thoughts? Do you the noise is related to the vario cam system? It seems to start right @ 2500 rpm when the angle changes. (Although it seems to disappear a bit or become harder do separate from the normal engine sound as I went up the rev range). Do the actual cam angles appear normal in the sense of where they start, when they change, etc ?

I stopped at your cam2 deviations & the brown plastic you found in the oil. -9 is out of spec by a good amount. 6+/- is what is in the FSM. That much difference you should be throwing codes.

With these 2 items screaming at you, it isn't something you want to "get through the season"

I say all this at the same time I have a car with bad deviations that I think is the cam tensioner pads. It goes in the shop Monday to be looked at, verified and replaced.
Video/audio closer to the engine without commentary would help, but that ticking noise does sound like chain noise.

oh, and you should be checking it at idle after it has been warmed up (20 minute drive).

Thank you!

And yes, I know (trying not to drive it more than i need to at the moment)

I have a similar noise at 2500 rpm after a full engine rebuild, but I haven`t found out yet what`s causing it. One thing I tried to determine the bank where it`s coming from was that I disconnected the connector for the variocam solenoid on both sides one at a time, but the rattle didn`t change substantially either way. So I`m not sure actually if it`s related to the variocam. You can try this test on yours too, the connectors are easy to access even on the road. If I put the covers back on it`s barely audible. My cam deviations are fine, -3 and 0.

That isn't going to do anything. The chain rubs along the pads at all times. All it will do is verify if the solenoid is working or not and only at certain rpm's/

I made another video hopefully with better sound: https://photos.app.goo.gl/nESH5um2LB7S11LN6

Since the sound is more pronounced when (or maybe even not present until) the vario cam actuators activate, perhaps unhooking them as Homeoboxster suggests would add a clue if the noise goes away? (the additional tension of actuation is required to cause it)

Coming full circle to what I know I have to deal with anyway could it be that part of the pad broke away and the noise is the chain hitting/rubbing part of the metal support as it is actuated and the angle changes, but when it is not actuated it is riding on what is left of the pad?

Well, the chain rubs along the pads with different pressure since when the variocam actuates the pressure on one side of the pad increases while on the other side decreases, in other words one side of the chain loosens while the other becomes more stretched, which would explain while the rattle happens to occur right when it actually changes. But in mine it didn`t make a big difference in terms of noise, just the performance dropped.

At some point you will have to replace the pads anyway because they are falling apart. If you want to get an idea about how long it will last you can inspect them with a borescope if you have one.

[QUOTE=bg305;635176]I made another video hopefully with better sound: https://photos.app.goo.gl/nESH5um2LB7S11LN6

Yeah, looks like it happens right at the changeover. And it`s very similar to the rattle in mine. Can you also hear it when the engine covers are back on?

I agree, I know they need to be replaced.

I just also had a few pieces that did not add up (deviations while horrible, had not changed from before the sound started) and I like to make sure as best I can that am fixing the right problem (I have little doubt of that at this point).

[QUOTE=Homeoboxter;635180] I only had it running the one time before and it was all buttoned up. That's when I said it almost sounded like a subaru... best way I can describe it. The engine just sounded "ruff" not the usual smooth song it sings.

I honestly thought it might be an exhaust header or exhaust leak when I heard it in the car driving with the cover on.

Well, having the pads replaced wont hurt anything (provided done correctly).

If you are attempting to isolate a sound.
Use an automotive stethoscope, or a length of hose.
Hold one end of the hose to your ear then move the other end of the hose around the engine to locate the sound.
Ok I know access can be difficult.
Also if it only happens at certain RPM's then you need a helper.
But it is actually very effective.
If the sound is Vario Cam chain,pad related you should be able to isolate the sound to which bank it is without to much trouble.

Looking at your Cam angles it is showing a 25 Degree change at change over.
25 Degree change in Cam angle when the VarioCam actuator triggers is spot on.
I forget what RPM that is supposed to happen but somewhere around 1500 RPM is when they kick in. Then back out at around 5500 RPM.

For the actuator kicking in at I remember 1500 rpm too, but actually on the first video the changeover is clearly at 2500. The description (see the copies of the book) of the variocam in this thread clearly states 1500rpm though:

https://rennlist.com/forums/996-forum/557016-how-variocam-and-variocamplus-works-a-primer.html

Perhaps that section is referring to the 968 hence the confusion? :confused:

Another thing that people fail to consider when using common OBDII readers is the refresh or sample rate of the reader. Durametric, Foxwell, (I have both) whatever. I don't think the sample rate is all that fast.
For example when looking at O2 sensor signals on the Durametric the sample rate (across the bottom of the graph) is in frames over time. Frames per minute IIRC.
A Pico or a good Snapon scanner like a Versus the sample rate is in milliseconds.

So I think the slower sample rate of the common OBDII reader has an affect on the info they display.
Also the more sampling you are trying to do the slower the sample rate becomes.
Your going to get a faster sample rate looking at one 02 sensor signal then you are when looking at all four.
If your looking at cam angle on both banks, Cam deviation, RPM,
Your going to get a much slower sampling or refresh rate then you would get when just looking at RPM alone.

I don`t know, he was revving up the engine quite slowly, definitely in the second range...

[QUOTE=bg305;635182] I can barely hear anything when the covers are back on. But when I was test driving the car after the rebuild I had the same noise at 2500 rpm. I couldn`t really find the source so I kept using it to see if it gets worse. It`s over 3000 miles now and I think it actually got better, I can`t hear it any more. I`ll double check it though with the covers off. If you want to do the solenoid disconnect test you can reach the left one through behind the driver seat, and the right one from above. You`ll have the CEL on, just FYI.

I am pretty sure the activation is happening around 2500 (honestly looks more like 2800), and it seems to stop at 6k rpm. Perhaps there are differences between the 2.5/2.7 and the 3.2 as the red line if different, etc... I did try searching a bit on google I found some threads like this one: http://986forum.com/forums/performance-technical-chat/72342-camshaft-deviation-gurus.html which seem to have the same crossover for an non plus variocam 3.2.

I am also really curious why i do not have a CEL related to the 9.27 on bank 2

Now the big question, find an indy or do it myself :). If i do it the engine is coming out. Anyone know if scissor style lifts offer enough clearance to get the engine out of the middle? And I mean the clearance between the lift and motor, not the height. I think I need more than 26 in high. My worry is that the scissor lift itself will be in the way of getting the engine out.