Camshaft Deviation out of range, 2001 Boxster S

[Schnell Gelb]

Here is a Camshaft Deviation situation with a much tighter focus than normal.I have also included the best links I found to help others who find this through Search.This is a 5 chain engine.2001.Boxster S.

The engine is just rebuilt by me. It runs wonderfully well with no Fault Codes, none. Great oil pressure.compression even on all cylinders. New chains,but original tensioners,new wear pads,new IMSB, IMS shaft pinned.

But

Bank 1 Deviation is negative 8 degrees. Bank 2 is much less than 1 degree negative. Spec is max 6 degrees +/-. Deviation is rock solid on both Banks throughout the rev. range(except for normal Variocam change). No Pending or Active Codes.

I recently had Bank 1 Cam Cover and Cams off to rectify an obscure VarioCam issue (Thank you PorscheTech3!). I re-timed the Cam on Bank 1  using the Baum Tools. The tools are excellent but clearly(?) need a degree of finesse in use that I was unaware of.

8 degrees CRK per  Durametric is only 4 degrees at the cam so it is impossible to do a visual check of the slots in the Camshafts to confirm if this is a static cam timing issue or a Camshaft system component failure. So I am resigned to re-do the timing but need reassurance on the precise technique to use before I R&R the Cam Cover again.

Cam Timing Details are in the links at the end of this Post.

Here is the tentative plan that I hope others will be able to correct :

Follow Procedure in links below to lock the Cam with the Baum Tools close to TDC. To get perfect Cam timing, I'll need to very slowly rotate the Crankshaft forward toward TDC. Only when the tools fit perfectly will I  lock the Baum Cam Timing tool. Then I'll try to insert the  TDC Crankshaft Locking Pin.

Knowing that Bank 1 is excessively retarded 4 degrees(cam), I should expect that the Crankshaft Locking Pin will not slide in easily when the Cams are perfectly timed. At this stage I should loosen all the Camshaft Sprocket  bolts. But not remove the (old) Chain Tensioner - right ?

Then the Crankshaft should need rotating 'forward' 8 degrees  until the Crankshaft Locking Pin slides in easily.Then tighten the Camshaft Sprocket bolts. Then rotate many times and re-check.

The Bank 1 Timing Chain Tensioner is still very powerful and seems as 'strong' as Bank 2. When I refitted Bank 1 Tensioner  last time, it required serious muscle to force it upward while delicately engaging the threads. So I assume it is functioning adequately and is not the cause of the out-of-range Camshaft Deviation .I am assuming it is original(90,000 miles).

What other components should be checked ?

I did check the Camshaft Position Sensor for correct fitment and the Reluctor ring for damage during the VarioCam repair.

 

https://rennlist.com/forums/996-forum/594122-how-to-set-cam-timing-on-996-a.html

see Post #7

 

http://www.pelicanparts.com/techarticles/Boxster_Tech/16-ENGINE-Camshaft_Swap_and_Chain_Tensioner/Gp1800.pdf

Good dwg and description of mechanism and parts.

Please add your best links if you have any in your replies so that this may help others with the Deviation issue?

And thanks in advance for any suggestions and corrections.

Edited June 30, 2017 by Schnell Gelb

[Ahsai]

Um, not sure I got it. Since the cams are 8 degrees (crk) lagging behind the crank, don't you need to rotate the crank 8 degrees past TDC before the exhuast cam can be locked by the tool?

 

Regardless, if you are sure the timing chain links offset between the intake and exhaust cams are correct, you should be able to turn the crank and lock it at TDC. Then loosen the sprocket of the exhaust cam then turn it to the proper position using the timing tool?

[Schnell Gelb]

Ahsai, Thanks for commenting I agree with you about the Crankshaft rotation direction to correct the negative 8 degree Deviation issue.

" you should be able to turn the crank and lock it at TDC. Then loosen the sprocket of the exhaust cam then turn it to the proper position using the timing tool? "

But I read from Jake (in the links provided) that he usually sets the cams ,then does the fine adjustment to the crank position, then tightens the cam chain sprocket bolts. I think he has said it is O.K. to turn the crankshaft backwards for this purpose(?). But he always stresses a re-check after turning the engine over many times by hand.

The link spacing between the dots on the sprockets was an anxiety because I don't have the 'gold' links as a reassurance . So now I have a photo of the final position before i replaced the cam cover (last time). The photo is a comfort in the middle of the night when you have an anxiety  attack - was it 7 links or 8 ? There was just enough space to slip a Smart Phone in there to take the photo before the Cam Cover went back on. But I'll re-check anyway.Thank you.

[Ahsai]

There may be other ways but I'm pretty sure the typical way is to lock the crank, then set the cams and lock the sprocket. Of course with the tensioner in place.

 

Also, never turn the crank backwards.

[JFP in PA]

9 minutes ago, Ahsai said:

Also, never turn the crank backwards.

 

+1  On tight clearance interference engines, like these, reverse rotation is a bad idea.................

[Schnell Gelb]

Thanks Guys. I had read conflicting views on reverse rotation. It makes sense to avoid it when you mention the Interference issue.

I hope others doing the Cam Timing will note this because it is very tempting to turn the engine backwards just a little bit instead of locking the Crankshaft and adjusting the Camshaft Sprocket.

[Schnell Gelb]

One point to note is that if you do a camshaft R&R with the engine in place, Bank One is much easier than Bank 2.

The big issue is access - for example the Tensioner for Bank 2 is under the a/c compressor and other tubes/pipes/hoses and fittings interfere.Then there is the Airbox !

A much bigger problem is that it is very difficult to verify the sprockets and chain retain their setting - 7 links apart -  while struggling to refit the cams to the cylinder head.

I used a white paint Marker pen to highlight the 'divots'. My chains did not have different colored links so I marked them on the bench with flourescent green paint Marker.

I suspect some of the large degree Deviation problems may be caused by the chain slipping 1 tooth on one of the sprockets. I think the math works out to roughly a 10 degree Deviation.

If this happens, it is one helluva lot of work to dismantle and verify !!!

Someone did hint that it is better to drop the engine +/- transmission that do this job with the engine in place.... He did have a point I now realize :-).

Oh and btw, Deviation is to be measured only with the engine fully warmed up.

Edited October 23, 2017 by Schnell Gelb