I have an AAN with a 7A exhaust cam installed and the car has just recently started to run again after a couple of years. It runs fair, but there are a few issues that we are trying to sort out.
Eric Fluhr has always been suspicious of the cam installation and he thinks that we have it wrong. His suspicion stems from the fact that the timing marks do not line-up perfectly with the plane of the head. They are lined-up horizontally, but they are raised just a bit as you can see in the photo. Based on some tech that I got from the S-Car list (Ned Ritchie and a post from Keith Maddox come to mind), Ken Fluhr and I feel like it's set correctly.
So, what would a "tooth off" look like? What would the failure mode be? The car starts and runs pretty well (though I feel it's down on power) and there is no bangy-bangy of valves, so we can't be off by much.
I have no idea if this is related or not, but it's timing related, so I'll throw it out. My car is throwing a 2111 (RPM sensor open or short circuit, defective sensor & cables, metal fragments on flywheel teeth.) If the sensor was bad the car shouldn't start. Any tips on what to look for here? Any common fixes associated with this code? Mockry's site didn't have much about it.
11-04-2004, 08:06 AM
<center><img src="http://www.bufkinengineering.com/cams2.JPG"></center><p>Have you verified that the RPM sensor and the Crank position sensor are both working correctly off the flywheel pin and teeth respectively?
11-04-2004, 08:16 AM
If either of those don't work, the car won't start. However, I am throwing a 2111, so SOMETHING isn't quite right with the RPM sensor. We plan to inspect it next. We will make a visual inspection of the flywheel and check RPM sensor grounding and wiring.
maybe two even and each cam needs to come in towards center one more tooth. Look at James's pics and note the cam lobe also, they are both pointing more inwards, laying more horizontal thank yours. Though I may be nuts!
Maybe you are getting that code because you do have the base cam/crank timing off? I would get those cams to line up better like James's and then give her a whirl.
That will surely make you run down on power as well. I found some damage to the damn crank on my motor which allowed for the base timing to be off and when I fixed that up it made a world of difference in power.
11-04-2004, 08:33 AM
...that makes it look spot-on with how yours is done. You can tell the slight difference is from the angle the photos were taken from (your photo taken from steeper angle).
11-04-2004, 08:38 AM
I was drawing the line and it wasn't quite lining up. I can't see the exhaust side of the head so its hard to tell.
I did notice that the chain and its associated teeth are quite different on the exhaust side.
But, it could just be that with a slight counter clockwise rotation of both cams, they dots will align.
11-04-2004, 09:14 AM
noticed that when doing timing belts and other timing related parts nothing ever seems to line up 100% on the mark. On more than several motors I've lined up the flywheel at TDC and the vibration dampener mark/cover arrow don't line up 100%, nor does the cam pulley and head arrow line up 100%, sometimes it's off enough to make me try one tooth difference and then go back, just to be sure. The cam pulley on my AAN seems to sit slighly counter-clockwise in the arrow on the valve cover when the flywheel is at TDC, though if I jump the belt back one tooth and adjust the mark goes far beyond the arrow on the valve cover. I've noticed this on 10v's, 16v's, 8v's alike.
11-04-2004, 09:32 AM
11-04-2004, 09:48 AM
Most often the alignment seems to be "between teeth", or a half tooth off. Can be a little disconcerting.
11-04-2004, 09:55 AM
11-04-2004, 10:03 AM
My car is also only pulling 10 inHg at idle and I think that would also support the car not making full compression because of incorrect timing.
I'm satisfied that we need to have another look and perhaps try again. Thanks for the tips, guys!
11-04-2004, 10:14 AM
that would be a good indicator too that base timing may be off. If you fix it soon then you can tell us how fast she is:)
11-04-2004, 10:26 AM
11-04-2004, 06:50 PM
11-04-2004, 08:18 PM
<center><img src="http://pictureposter.audiworld.com/83502/camtiming.jpg"></center><p>Sorry to yell but c'mon guys, count the teeth. From the photos view, the exaust cam needs to be rotated counter clockwise one tooth. Looking at my drawing, #1 is the timing mark location on the sproket, count up to #7, then start counting across the chain till you get to #7 of the other sproket. The "bad" one has 11 links between vs. only 10 on the "good" one.
11-04-2004, 09:18 PM
If it had come just an hour earlier, it would have saved the 45 minutes the three of us stood around tonight, staring at the cam markings and deciding if we should move it or not. The vote split, but based on the earlier evidence and the experience of Alex and the others who weighed in, I swung the vote (it's my car after all) and we clocked the intake cam one tooth.
The adjustment fixed everything. Idle is now rock solid, the engine pulls 17 inHg at idle (which fixed the brake vacuum booster problem I thought I had), O2 gauge is now behaving properly, the car is quieter(?), and oh yeah, holy crap my car is blazing fast! I jumped on it in 2nd and it pulled so hard and fast, I think I made a little pee-pee. Seriously, it transformed the car. Still, only one week left until the track event and we can't rest on our laurels; lots of work still left to do.
Thanks for the advice fellas. The I5 forum has its first legit success story. I trust Alex enough to have followed his advice, but it was Brian who really made an excellent point by reminding us not to get too focused on one thing (in this case, the cam markings), when the answer is otherwise right in front of us. We deserved the yelling. Good illustration, too!
11-05-2004, 05:30 AM
11-05-2004, 06:10 AM
11-05-2004, 06:25 AM
11-05-2004, 06:47 AM
11-05-2004, 10:54 AM
... and the problem would have been more obvious if you replaced the cam chain with new. The problem with worn cam chains is that you can make it appear you are in 'time' wtih slop when you are actually a tooth out. That is the biggest difference between your cam pic and James B's IMO.
Any vertical movement in the chain, replace with new. With a new chain, you can barely get the cams to sink in the journals. Then you don't at all need M5BMW excellent index overlay to know it's not indexed.
Ned and I had many discussions on cam timing of DOHC audi motors. I argued that with a new cam chain, the -0- are cut exactly in half by the lower cam journal. All bets are off if the cam chain is sagging from miles. As a rule, I like to do the chain at the TB service. On the 20vt, it usually needs it by then. IME, idle gets much better too, especially on the N/A 20v cars.
My technique on the 20vt motors is to line up the indexes level (Hey you can use that laser level line for S&G - looks just like those pics) on the bench with the cam chain attached, then drop the cams in the journals. Then if the intake cam wants to roll over onto the next lobe (sound familiar?), let it, cuz ultimately the alignment of the two cams doesn't change.
HTH and my .02
QSHIPQ Performance Tuning
11-05-2004, 11:12 AM
I consider that another valuable lesson learned and archived for the future. Worn chains might be the cause of some of the disinformation I came across the first time around. Anyway, more signs of a healthy, helpful forum. Thanks for the tip, Scott.
11-06-2004, 11:30 PM
My engine bay, at about 210k. Always run fully synthetic (so i was told)