Cam deviation at 6 after VC pads done
 

Hey guys,

Over the winter I replaced my variocam pads and chains, along with the 3 chain tensioners and various other items. I retimed the engine using the very slick timing tool and rotated the engine several times to verify it was spot on. I hooked up my durametric yesterday after a 1 hour drive to see that bank 1 was at +6 cam deviation at idle, bank 2 is at zero. I did drive the car around and saw at one point that bank 1 was at 3 degrees but at idle it returns to 6.
I did check it last year before the work was done and i was at -9 cold and -6 after a 1/2 of driving. Bank 2 was at zero. IIRC.
Engine has 100K(60k miles) and is very smooth and runs beautifully.

Did i do something wrong?

I need to perform the same work on mine as well. I am interested in how this turns out.

My understanding of the measurements is that they should be taken at idle with the car hot, but should not fluctuate widely with rpm variations unless there's an actuator issue (then you'll see huge variations)

I think there are a few sentiments about these numbers - first is that the trend is more important than the actual number (stable over time vs progressively worsening) and that unless a cel is on then not to worry. Second is that anything greater than 2 deg is enough to start causing mechanical issues (dme changes fuel trims) and should be addressed.

If you know that your pads and tensioners are good, then you're probably fine. You may have a bad sensor and it.might be worth swapping the sensors.from side to side to see if the readings change. If they do you have your answer.

If you swap sensors and still get 6 on bank 1, it may be mistimed. I don't know what the right answer there is though. I say that because one of the main reasons behind the "ignore it unless you get a cel" is because supposedly these cars will come off the line with significant timing deviations, although I've never seen a hard example to quote. 9 is the threshold for the cel, and 6 shouldn't put you in danger of piston/valve damage, so as long as your hardware is good and performance is good you can easily invoke the old "enemy of good" philosophy.

One thing I find fascinating - I know people make a big deal over these numbers, and rightly so considering the consequences of pad failure. With that being said, ROW cars (and that includes those in the fatherland) don't even register cam deviation on bank 2. So clearly porsche never wanted to put much emphasis on these numbers from the get go. Whether that was an oversight though (and you could very well argue that it is) is not clear.

Hope this helps.


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Thanks for the well written reply ike84, I certainly appreciate you taking the time. It seems odd that the timing would be off based on the fact that I used the recommended Porsche timing tool and spun the motor many, many times to verify it was perfect. I have fired both solenoids with my Durametric and both caused the same result, a noticeable change in the idle quality. I'm not sure what else it could be?
The measurements were done hot, at idle.
I have "heard" that it's possible those were the numbers when it came from the factory, not sure I believe it but maybe? I will certainly keep an eye on things.
The car runs so well and so much better than before I did all the work I can't imagine there's an issue, but the number's don't lie...or do they?

What did the pads look like, worn down or not to bad,.?

Have you looked at your fuel trims?
Have you compared fuel trims before the work with after?
Have you compared fuel trims bank1 vs bank2 ?
Positive fuel trim on bank1 could point to the cam timing on that bank not being spot on.





















d

They were well worn.

http://986forum.com/forums/uploads02...1619569022.jpg

Thank you for this, I had no idea I could check it that way. Great idea.

As cam timing gets farther and farther from the Ideal set point (deviation).
The engine will begin to use more fuel.
It may be very slight, but you may see it in the fuel trims.
Since it is four cams and two banks you can compare bank 1 to bank 2.
I think you stated that bank 2 has zero or very little deviation.
If bank 1 is at I think you said 6?? you should see it in positive fuel trims on that bank.
Long term trims is where it will show up.

Blue is right about the trim going rich with deviation. I didn't realize we could check trims on the banks separately. Always more to learn...

Did you try swapping the sensors between banks?

The "factory misalignment" would have been with the timing adjustments, not the cam with relation to the adjustment points, so if they were properly aligned (as you have likely done based on your description) then they should now both be at <2. The factory issue supposedly was.one of attention to detail during assembly. It would be interesting to find out if this was more common in Stuttgart than sweden or vice versa.


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Ike

You have a bank 1 O2 sensor and a bank 2 O2 sensor so you will have bank 1 and bank 2 fuel trim readings.
Another thing you can compare to check cam (valve) timing on a flat six is to compare compression readings from one bank to the other.
Bad cam timing (usually late timing) will show a drop in compression.
I think fuel trims would be a better indicator if the cams are off by just a few degrees.

Wow pretty worn for 60 K miles,..now iam nervous,..I have 90 k.

Mine at 100k wore down to the bottom, broke apart and made the chain somehow jump teeth and subsequently caused valve-to-piston contact. It`s very important to replace these pads in time, they are really poorly made.

What is the time frame to accomplish this if your a rookie. 2 weekends ??

If you do it with the engine in place it`s probably doable in two weekends. I pulled the engine because it had to be torn down completely, but it`s not necessary. Just much easier on an engine stand. First I`d look at the cam deviation values and cut apart the filter or even pull the sump to see how much plastic debris you have accumulated there.

OK..I shall start with that,.I have watched the filter every oil change and I don't see anything alarming But I have never pulled the sump plate, I even do random filter checks, But I still get that noise on a quick start,if I crank it over a couple times first and when it does start I don't really hear what I think is chain rattle noise but My Cam numbers are like 3.4 and 8.2 so I figure it must be that and that is why Iam trying to look at the guides B 4 I pull that engine Bc that noise make me crazy... Thanks for the info,.!!

I would install the revised pressure relief valve and spring while you're at it. Only takes 5 minutes.

I haven't seen anyone really comment on this but I would be curious to know if over time guys running the updated parts have less vc pad wear.

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Which bank has the 8.2???????

Hey blue62, I will ck my notes, Frank

The reason I ask is that it seems as though most cam deviation issues here on the forum are on bank 1.
So I am curious and wondering why the issue favors bank 1.