timing chain elongation curious results - Page 3 - PeachParts Mercedes-Benz Forum

Brian Carlton · #31 11-23-2011, 11:37 PM

Quote:

Originally Posted by fochs

In re-reading the thread, I think it's fairly obvious what I meant when I described the numerical values in terms of referent. Between you and Mr. Carlton having what, 36-37 thousand posts, I would assume you would recognize the referent, as any number on a scale of degrees must have a referent. Then again, I have just witnessed several of your posts. I find your justification to be passive-aggressive crap, in the classic sense (look it up). I'm just trying to fix my car. (gesture)

..........oh, just ignore him.............he gets crochety around 10:00 p.m. or so..........

I wouldn't "gesture" him, however............he can be quite an asset to you.

leathermang · #32 11-24-2011, 12:45 AM

Quote:

Originally Posted by fochs

..... When I tried to time my ip using the bubble method, 24 degrees to the right of ot as viewed looking down from the front of the car was seriously out of whack. black smoke no power etc. I know it is not as accurate as we had discussed on a different thread, but it was repeatable several times. I have tried the drip tube method, and got no fuel at the attempt and do not know why.

" not as accurate ".... it is not accurate at all... may be repeatable..but has no physics relation to the instructions in the FSM...which are based on the consistency of the volume of the size of a drop of the same fluid from one time to another.
If you tried the drip tube method...and it did not work you need to figure out why it did not work and correct that. MB specifies that method because it automatically compensates for several areas of potential wear in the injection system and gives you a fail safe place to start. IF YOU FOLLOW their instructions.

fochs · #33 11-24-2011, 02:08 AM

Quote:

Originally Posted by leathermang

" not as accurate ".... it is not accurate at all... may be repeatable..but has no physics relation to the instructions in the FSM...which are based on the consistency of the volume of the size of a drop of the same fluid from one time to another.
If you tried the drip tube method...and it did not work you need to figure out why it did not work and correct that. MB specifies that method because it automatically compensates for several areas of potential wear in the injection system and gives you a fail safe place to start. IF YOU FOLLOW their instructions.

I do believe that the drip tube is the way to go. I followed the instructions to the letter. At the action, fuel squirted from the drip tube upon application of the drip tube, but nothing came out during rotation. I did observe the fuel to be somewhat foamed coming out of the drip tube and had bled the filter. I have replaced the fuel hoses from the primer pump and will replace the pump on Friday. I used the bubble method thinking it might get me in the ballpark.

Stretch · #34 11-24-2011, 08:48 AM

This is what I understand from reading through this rapidly growing thread...

You can consistently perform the "2mm lift method" and read a value of 19 degrees off of the graduated scale at front of the crankshaft.

I assume you are reading this value after top dead centre ATDC => this means that when looking at the graduated scale the zero is to the RIGHT hand side of the pointer which is pointing at 19 degrees.

Please correct me if this is wrong!

(EDIT => please see the next two posts to see why the word right is in bold and capitals)

You have an OM616 engine with an as yet unknown cam code.

So here's my first question. Can you read the cam code on the back of the camshaft? You need to get your head right round the back of the camshaft to see it => stuff your head between engine and firewall! Alternatively use a mirror...

According to the table at the top of chapter 5-215 in the non turbo W123 FSM you can see that you should have a code 02 06 or a 10

If you have a 02 or 06 then from the data you've provided the chain elongation from new would be 19 degrees minus 11.5 degrees = 7.5 degrees of "elongation" (crappy expression sorry - but you know what I mean)

If you have a 10 code camshaft then from the data you've provided (notice the small print?!) the chain elongation from new would be 19 degrees minus 9 degrees = 10 degrees of "elongation"

Does this help?

Brian Carlton · #35 11-24-2011, 09:01 AM

Quote:

Originally Posted by Army

I assume you are reading this value after top dead centre ATDC => this means that when looking at the graduated scale the zero is to the left hand side of the pointer which is pointing at 19 degrees.

Please correct me if this is wrong!

The engine spins clockwise, forward looking aft.

From looking downward toward the pointer, this would be to the right.

If you are looking for 19ATDC, 0 must first pass the pointer before 19 gets there. Accordingly, the zero must be to the right hand side of the pointer.

Stretch · #36 11-24-2011, 09:19 AM

Quote:

Originally Posted by Brian Carlton

The engine spins clockwise, forward looking aft.

From looking downward toward the pointer, this would be to the right.

If you are looking for 19ATDC, 0 must first pass the pointer before 19 gets there. Accordingly, the zero must be to the right hand side of the pointer.

Thank you Brian - I just spat my cup of tea out when I realised my own mistake!

I didn't manage to log in again quick enough to save face - bugger...

Brian Carlton · #37 11-24-2011, 01:44 PM

Quote:

Originally Posted by Army

Thank you Brian - I just spat my cup of tea out when I realised my own mistake!

I didn't manage to log in again quick enough to save face - bugger...

Anytime.

It's quite easy to get the orientation reversed in your mind.............I have a suspicion that the OP has the exact same problem. His figures are as expected for a worn chain but are on the opposite side.

fochs · #38 11-24-2011, 03:14 PM

This picture is from the diy on this site. My result is on the other side of the scale to the right of the OT stamp. My 616 differs in tab/ tach sensor placement, but hey, just like that, Bob's your uncle!
Happy Thanksgiving some, Happy Thursday others!

Brian Carlton · #39 11-24-2011, 06:49 PM

Quote:

Originally Posted by fochs

This picture is from the diy on this site. My result is on the other side of the scale to the right of the OT stamp. My 616 differs in tab/ tach sensor placement, but hey, just like that, Bob's your uncle!
Happy Thanksgiving some, Happy Thursday others!

Thanks for the photo.

If you are definitely on the opposite side, then you're clearly BTDC.

So, that leaves some other error in the procedure. The intake valve cannot be open by .080" at a point that is 15BTDC.

You are certain that you have the intake valve...........not the exhaust valve?

leathermang · #40 11-24-2011, 10:31 PM

Army , I appreciate you using the term ' elongation' as that is correct and it has taken a while to get people to use it regularly... the term ' stretch' is not correct but used to be the norm. Nothing is stretching in the chain.. the pins and stuff are wearing causing it to be longer....

Stretch · #41 11-25-2011, 11:33 AM

Quote:

Originally Posted by Brian Carlton

Thanks for the photo.

If you are definitely on the opposite side, then you're clearly BTDC.

So, that leaves some other error in the procedure. The intake valve cannot be open by .080" at a point that is 15BTDC.

You are certain that you have the intake valve...........not the exhaust valve?

I thought of that too but it is just as "bad" in my opinion to have any valve opening just before the piston reaches top dead centre - be it the exhaust valve or the intake / inlet...

I am very uneasy about this - I hope fochs has a go at removing the bolt on the camshaft pulley to see if there is an offset key in there despite the bicycle chain nightmares he's been having.

Stretch · #42 11-25-2011, 11:36 AM

Quote:

Originally Posted by leathermang

Army , I appreciate you using the term ' elongation' as that is correct and it has taken a while to get people to use it regularly... the term ' stretch' is not correct but used to be the norm. Nothing is stretching in the chain.. the pins and stuff are wearing causing it to be longer....

Wow that had me scampering back through my posts to see if I had sinned! I hope I haven't...

I must say I have problems with the way in which elongation is measured - I don't like to think of elongation as a change in angular position. I intuitively think of elongation as a linear thing - which I suppose is where the will to call it stretch comes from. Yes yes 14 Hail Mary's etc

leathermang · #43 11-25-2011, 11:48 AM

Army , I was just referring to you saying "degrees of "elongation" (crappy expression sorry - but you know what I mean)"....because it more accurately describes the physics than ' stretching' which so many used to call it.... so I am glad you use it.
At some level on tech discussions it does help to have standardized nomenclature to help get to the actual problems as efficiently as we hope to...
If it helps... visualize the chain laid out straight on a table.. so it is linear in its increased length... does that help ? LOL

Stretch · #44 11-25-2011, 12:01 PM

Quote:

Originally Posted by leathermang

... visualize the chain laid out straight on a table.. so it is linear in its increased length... does that help ? LOL

I do that already and it doesn't help!

I need to do a little project and work out how much elongation 10 degrees in a linear sense actually is... then I'll be a happy man 'cos I can then smugly say that's only X mm you can work it out from the following equation...

Brian Carlton · #45 11-25-2011, 12:17 PM

Quote:

Originally Posted by Army

I thought of that too but it is just as "bad" in my opinion to have any valve opening just before the piston reaches top dead centre - be it the exhaust valve or the intake / inlet...

Correct me if I am mistaken, but it's probably likely that the intake valve starts to open just before TDC on the exhaust stroke. This "overlap", if you will, compensates for the fact that the air mass needs some time to accelerate and travel.

However, it certainly doesn't start opening at an estimated 35BTDC based upon his data.

after further reflection, there is no possibility of the exhaust valve being mistaken for the intake valve in this issue, simply because the exhaust valve starts to open slightly before bottom dead center and there would be no indication whatsoever on the damper.