TDC Cyl #1 for a 3-chain 996 (2004, 3.6L)

[Domiac]

Right now I am at 360 degrees (TDC #4 just about to ignite).

I am sure that if I rotate another 360 degrees (getting to TDC #1 just about to ignite), I can fit LN Engineering camshaft locking tool again to bank 2 just fine. After this I'd be back on the situation where I am on my first message on this thread:

- cyl #2 intake valves open

- cyl #3 exhaust valves open

=> meaning cyl #6 would fire next, then #2, then #4, then #3 and then #5.

I truly hope this endeavour produces meaningful data to others too :-)

Edited April 12, 2014 by Domiac

[Ahsai]

Let's try to confirm the following and see if I missed anything:

1) LN tool is meant to lock bank1 regardless of 3-chain or 5-chain engine <- confirmed by JFP on your other thread on LN IMSB instruction

2) The half-moon orientation needed before you insert the tool on bank 1 <- confirmed by xmac on 5-chain engine (larger half moon closer to engine block and smaller half moon closer to camcover)

With both of the above you cannot insert the LN tool to bank1 regardless of which TDC. That sounds like a problem by itself since you can't poceed without locking bank1.

Regarding TDC definition, I'm not sure either but if the engine is at TDC (about to ignite) on cyl #1, the valves of cyl #2 and cyl3 are FULLY open, which will exert a lot of force on the camshafts (tend to rotate the cams) and the IMSB side since cyl3 is closest to the IMSB.

On the contratry, if TDC (about to intake) on cyl #1, only valves on #5 and #6 are FULLY open, which will exert less force on the IMSB being far from it. Even though in both cases cams in bank1 will be locked anyway, the latter seems to create less stress to the locking tool hence a safer position and less tendency to rotate.

Edited April 12, 2014 by Ahsai

[Domiac]

Let's try to confirm the following and see if I missed anything:

1) LN tool is meant to lock bank1 regardless of 3-chain or 5-chain engine <- confirmed by JFP on your other thread on LN IMSB instruction

2) The half-moon orientation needed before you insert the tool on bank 1 <- confirmed by xmac on 5-chain engine (larger half moon closer to engine block and smaller half moon closer to camcover)

I believe that both of above are correct.

With both of the above you cannot insert the LN tool to bank1 regardless of which TDC. That sounds like a problem by itself since you can't poceed without locking bank1.

I have only tried to install LN tool to bank 1 once, it might very well go easier to my cams if I rotate another 719 - 720 degrees, getting the lock installed requires some finesse on turning the crank.

Regarding TDC definition, I'm not sure either but if the engine is at TDC (about to ignite) on cyl #1, the valves of cyl #2 and cyl3 are FULLY open, which will exert a lot of force on the camshafts (tend to rotate the cams) and the IMSB side since cyl3 is closest to the IMSB.

On the contratry, if TDC (about to intake) on cyl #1, only valves on #5 and #6 are FULLY open, which will exert less force on the IMSB being far from it. Even though in both cases cams in bank1 will be locked anyway, the latter seems to create less stress to the locking tool hence a safer position and less tendency to rotate.

Yes, compression TDC #1 will have stress on bank 1 as then there are two valves open on bank 1. Overlap TDC #1 on the other hand means there are no valves open on bank 1.

I took the liberty to quote porsche52 "Board Certified Porsche Trauma Surgeon / Cayenne Grief Counselor" from rennlist, hopefully this is OK, here's part of the instructions on how to time bank 2.

"When you are just timing one bank, you must, I repeat MUST know for sure that the other bank (bank 1 in this case) is on TDC compression when you install the bank 2 cams in on overlap!! Cams are installed on OVERLAP (intake is just opening and exhaust is closing) For cyl#4 the camshaft lobes should point away from eachother when on overlap. (FYI, cams are installed on overlap because they are relaxed, no valves open, no pressure on cams for that bank), All you need to do is pull the cam plugs, (little green plugs, at the end of the cam cover) to see how the cams are allocated. When you pull out your green cam plugs, opposite end of camshaft sprockets. So for Bank 1 they will be on the front of the engine, below the alternator etc... for bank 2 they will be on the back of the engine (flywheel side). Once you have the plugs removed, you will see the ends of the camshafts. Rotate engine to TDC , the crank pully is marked "OT" and there will be a notch in the pully that lines up with a casting mark in the engine case the reads " OT Zyl 1". Fix the pully with pin, through hole marked "OT". You are now on either TDC compression #1 or overlap #1. This is why you must pull the green cam plugs. With the crank fixed @TDC, look at the ends of your camshafts for bank 1, If the smaller circular cutouts are pointing away from the engine then it can be said that cylinder #1 is on TDC overlap and cylinder #4 is on TDC compression. If the smaller circualr cutouts are pointing inward toward engine, then it can now be said that cyl #4 is on TDC overlap and cyl #1 is on TDC compression."

After reading Ahsai's last post and porsche52 comments, I am quite confident that also on a 3-chain variocam engine, to perform IMS work, one must:

1) Crank clockwise until overlap TDC #1 is seen

- cyl #1 exhaust has just closed, cyl #1 intake is just about to open

- cyl #6 exhaust open, cyl #5 intake open

- bank 1 smaller circular cutouts are pointing away from the engine (or when looking at bank 1 and intake camshaft is above and exhaust camshaft is below, then smaller circular cutouts are on the left side, larger cutouts on the right side)

2) Lock bank 1

Once again, this means compression TDC #4 and overlap TDC #1.

I am glad we got this figured out, special thanks to Ahsai! I'll mark this message as a solution after few days, unless someone feels my logic is flawed.

The image on this message shows the "360" column which we are looking for.

PS. A small amendment for Ahsai's last message. On a variocam engine, intake is only max. 2mm open at any given time, exhaust goes always up to 10mm. One would need to activate variocam somehow manually if you wish to get 10mm opening for intakes. Then again, it would seem to be impossible to activate variocam "manually" in such way that you would get intake valve travel to 10mm as there is no oil pressure when the engine is not running.

Edited April 18, 2014 by Domiac

[Domiac]

I moved my crank tiny bit past TDC #1 overlap (see the image), otherwise it was impossible to lock camshaft 1. Once I managed to lock my camshaft 1 without excess force, I gently tapped the crank counter-clockwise just a tiny bit so that I could lock my crank using the lock pin. Hopefully I did not do something stupid as one should never move crank counter-clockwise. However the travel was very small, perhaps 1 degrees. Then I locked camshaft 2 with my fabricated tool, used metal sheets to install it quite tight because the original width was not exactly like the original. Popped cam1 tensioner out (yes, there was a pop once it comes out) and then I removed the IMS tensioner (no pop), both look good but I'll post pictures of these later. After that I took the IMSB flange out, which was really easy to remove. Finally using the fabulous LN Engineering tools, I removed IMSB, it also came out quite easy. I had however a habit of spraying small amount of lubrication to IMSB for several days before I took these actions today. Every day I got darker stuff out from IMSB until finally I got only clean oil, could be that this has helped me to remove IMSB more easier.

The good news is that IMS looks perfectly aligned, old bearing looks like new and there really was no particles or such on the IMS area. Borescoping revealed simply clean oil 360 degrees, top, bottom, left, right and inside the IMS. There was some tiny crud on the bearing but looked like really old oil and the amount was really small. IMS had plenty of oil inside which I vacuumed carefully with a clean pipe just in case, even though everything looked really clean.

Thanks for JFP (once again!), xmac and especially Ahsai for debugging my logic :-)

Edited April 13, 2014 by Domiac

[Ahsai]

Well done and mystery solved! :)

Edited April 13, 2014 by Ahsai

[Ahsai]

BTW, I think this tool should be able to id TDC compression (whistle sound) and TDC overlap (no sound)....could have solved your dilemma instantly :)

http://www.bavauto.com/fland.asp?part=9710

Or you can just connect a pressure gauge at the spark plug hole to achieve the same.

Edited April 18, 2014 by Ahsai

[Domiac]

BTW, I think this tool should be able to id TDC compression (whistle sound) and TDC overlap (no sound)....could have solved your dilemma instantly :)

http://www.bavauto.com/fland.asp?part=9710

Or you can just connect a pressure gauge at the spark plug hole to achieve the same.

I considered buying a similar tool but decided not to. I might be old school, but I think it is nice to feel the piston movement through a plastic or wooden stick when you are moving the crank. Also it is best to understand how crank pulley angles work and check the correct angle from the pulley too. Stock 996 crank pulley contains marks for every cylinders TDCs. My dilemma was not that much of finding TDC compression or TDC overlap, it was more of understanding which one, overlap vs compression, I should find before proceeding with my IMS upgrade :beer:

In my case it was easy to understand overlap vs compression as I had exhaust and intake parts completely off, I could see the valves easily. If somebody for any reason needs to find out TDC overlap or compression, simply set cylinder to TDC and screw a hose to sparkplug hole. If it leaks already with very little amount of pressure (e.g. 10PSI), you are on TDC overlap and your exhaust valves are open. If it does not leak, then you are on TDC compression. A leak down tester would show a drastic difference between these two.

Thanks!

[Schnell Gelb]

For a simple way to confirm TDC Overlap vs TDC compression use  Leak down Tester.

The Whistle needs a simple mod to use if the engine is in the car(Boxster)

Details here:

 

Edited September 30, 2017 by Schnell Gelb