tartar

While I'm waiting for a replacement cam shaft position sensor to arrive, I started thinking (doubting) the chain link roller 15 count positioning as it relates to the cams "timing arrows" alignment. Although there are definitely 15 chain link rolls in between the cam cap arrows, at TDC (cylinder #3 at its highest position with crank shaft pin inserted), my links always align themselves in the "valleys" as the picture below clearly shows.

http://www.flickr.com/photos/targuevara/7294775806/http://www.flickr.com/photos/targuevara/7294775806/ by http://www.flickr.com/people/targuevara/, on Flickr

In addition, the intake cam gear "timing notch" is not aligned smack in the middle of the corresponding cam cap "timing arrow" (it's ever so slightly towards the inside). I also noticed that the cam chain tensioner in bank 1 goes up much higher than the one in bank 2 while at TDC. Although to be fair to the bank 2 chain tensioner, bank 1 chain tensioner never had its oil squeezed out of it with the VAG cam chain tensioner tool. How many hand cranks does it take before the cam chain tensioner refills itself with the proper amount of oil in order to apply the correct tension to the chain?

Can I still be off 1/2 a tooth or is it possible that the cam chain tensioner is failing and not providing enough tension to the chain in bank 2?

I may be just paranoid and that the cam chain tensioner in bank 2 is supposed to be at this height/tension whenever the engine is at its TDC, but a knowledgeable person's input would definitely help out a lot in clarifying this situation to a "noobie" grease monkey as myself.

Huskerbob

Before I pulled my cams on the driver's side I marked and counted the rollers. 15 exactly but it takes some creative eyeballing. With the crank locked and #3 at TDC the cam chain had some slack in it but I was still able to count 15 rollers. Not sure if that helps but when I reassemble I will recount just to make sure.

divil

I am not sure, sorry! It looks to me as though the cam cap mark, the notch and the chain roller on the left are all lined up perfectly. But on the right, the sprocket notch lines up almost perfectly with roller no. 14, while the cam cap mark is about halfway between 14 and 15. No way could I count this as "15" going by that picture, no matter which marks I use - but then I realize you can see the real thing more clearly and from different angles.

I would put this down to differences in the tensioner's adjustment, and if I had to guess I'd say you're good.

Which side is this in the pic above? I'm assuming it's the driver's side.

It might be worth putting 1 more roller between the marks and give it a few turns. Clearly that would put the timing marks at quite an angle (you can just see the tip of the sprocket tooth to the right of the intake timing mark...this is where the mark will be!). Looks like too much to me. But maybe turning it over will give the tensioner a chance to line it up better - if it doesn't, you'll know you were right when the pic was taken.

A useful tip (IMO) is: put one roller directly over one of the sprocket notches (as close as you can). Mark it with white-out, then count 15 from there, inclusive, and mark number 15 in the same way (regardless of how it lines up). Then as you make adjustments, it will be much easier to see when it's lined up correctly.

Huskerbob

If you look at the picture in this thread taken from the Bentley it appears as though the you have to sort of lean a little to get the one mark (on the left of the picture)to line up. It looks a bit slanted to me and that's the way mine looks when I count 15 rollers. The notches and the arrows line up so I think I'm good. 16 on the passenger side and 15 on the driver.

Huskerbob

Here is that shot from the Bentley, thanks Prospeeder, and look at the left side how the highlighted mark sort of leans left and the one on the right is straight up. That's how I counted mine.

divil

Fair enough...when I counted mine I thought I was pretty much looking at them straight. But I must have factored in this angle without realizing it.

tartar

I'm gonna play some more with its position while waiting for the cam position sensor to arrive. I feel that the driver's side chain, gears, and cap arrows are not at their optimum timing position right now.

TO BE CONTINUED...

Prospeeder

you cant turn the engine over by hand to refill the tensioner, the engine must be running with full oil pressure. It will make some awful awful noises for 5 or 10 seconds but it quiets down as soon as the tensioner fills up. as far as how your marks are, i see that from time to time. I wouldnt worry about it. Some slight chain stretch or the way the tensioners are cause the marks to not line up perfectly.

tartar

Thanks for the tip! I'll leave it alone for now.

SloopJohnB@mac.com

One way to look at it is that there are two aspects to the timing chain position. First are the cams positions. The cam sprockets have to be aligned with the timing marks on the camshaft bearing caps.
Second, the timing mark on the passenger side intake cam tang lines up with the valley of the sprocket/tooth.

There are an equal number of rollers on both sides, but the driver side is tooth to tooth with 14 rollers between teeth while the passenger side is 14 rollers from the timing tooth on the exhaust cam with the 15th tooth being IN the valley of the two intake cam sprocket timing teeth on either side of the sprocket timing mark.

This is probably crystal to audi engineers but it sure seems stupid to anyone else in the logistics industry where we would demand identical intake and exhaust sprockets, identical number of rollers between teeth, and the camshafts ground/manufactured to the correct timing specs when assembled. OTOH, it could well be that Audi preferred to have identical intake and exhaust camshafts for both banks with this type of construction making up the minor difference in timing chain alignment. It sure looks like the intake cam sprocket on the passenger side is a different part than the intake cam sprocket on the driver side.