diesel flywheel timing marks

[TylerDurden]

That's the 12^o BTDC mark, right?

[92EcoDiesel Jetta]

That's the 12^o BTDC mark, right?

Yes

[ORCoaster]

I thought green was TDC and the grayish block near the center pointer was the 12 degree tab on the flywheel.  Not true???

[92EcoDiesel Jetta]

I thought green was TDC and the grayish block near the center pointer was the 12 degree tab on the flywheel.  Not true???

The green mark in the video is the 12 degree tab. If I hit the advance button on the timing light, the green tab moves towards the center pointer (towards the radiator). In the video, is my timing too far advanced or too far retarded? I do not hear any nailing but then my hearing is not very good.

I will keep driving it at the current setting and see what the MPG will be, then adjust the IP and see which direction I have to turn it to line up the green 12 deg BTDC mark to the center pointer.

[TylerDurden]

Currently, you can hit the advance button on the light until the mark is centered and it will indicate where the IP is set now.

To set the timing to a desired value,  your timing light should be set to the desired advance minus 12 (since you have a mark at +12). Then turn the IP to center the mark. ( e.g. if you want 15 BTDC, set the light for +3)

[ORCoaster]

Given that the green line is 12 degrees BTDC and you are at that same distance from the center pointer tab in the well I would give a second guess that you are closer to 22 BTDC.  You should be able to roll your advance to figure out exactly when the line for 12 matches the center pointer.  The extra degrees will give you the reading as described by TD.

Should rotate the pump towards the engine to make it line up better and stop nailing as you say it is doing.  I believe it as mine was running +19 for a bit and sounded nasty.  I couldn't even claim its just a diesel!

[libbydiesel]

Press the advance button until the TDC mark is right under the bell housing pointer then look at the reading.  No need for any other marks or math.

[92EcoDiesel Jetta]

Press the advance button until the TDC mark is right under the bell housing pointer then look at the reading.  No need for any other marks or math.

I will try that thanks. Do you know how the advance function works on these timing lights? I assume it puts a incremental delay into the firing of the strobe light as you push the advance button. But it must know when and how much of a delay to put in based on calculation from RPM.

[libbydiesel]

Not specifically.  I would assume it takes the time of the last two pulses, divides by 360, multiplies by the degrees of advance and delays the strobe by that amount of time.

[92EcoDiesel Jetta]

I continue to be plagued by a non repeatable reading in the same spot. The lines are kinda rusty and I did clean them with 400 grit paper but there was still a little bit of rust left. It looked clean enough for a good enough electrical connection. WRONG! I cleaned it some more till it was shiny (for both the clamp and ground) and tried the pulse adapter again and it was much better. I won't call it success until I can get repeatable steady readings.

Note: The inner aluminum circle on the clamp is the ground for the piezo sensor so it must make good electrical contact to the line since the alligator clip ground is clipped to the line next to the clamp. Both have to be clean enough for a good electrical connection.

Anyway this video was taken after the latest line cleaning and with the strobe advanced 4.6 degress, the 12 degree green tab is lined up with the pointer in the opening. So my timing is at 16.6 degree BTDC. It does not sound overly clattery to my ears nor do I hear any nailing. I will get the dial indicator out and get some readings and correspondence to the pusle adapter.

CLICK TO PLAY!

[ORCoaster]

My money is on 95 mm @ 20 degrees BTDC.  Let's see how close I am.  Just looking at my chart of dial mm to degrees BTDC.  That is where I was at the start of my comparison exercise.  I put it back a few degrees just to see what that would do for MPGs.

[92EcoDiesel Jetta]

Why do you think it's @ 20 deg BTDC when the timing light says it's @ 16.6  BTDC?  Am I using the advance feature wrong?

[ORCoaster]

Let me kick myself for that!  Let's just say I think you will be measuring 95 mm on the dial.  You are are 16.6 degrees but even those lights can be off you know.  Get a buddy to measure it with another and you likely will see a different measure.  It's an electronic thing and calibration kills on them.  Good brands have high standards to meet and knock offs, not saying your light is one, but those tools just plain don't measure up.  No pun intended, but it came out anyway.

So measure with a dial indicator and let us know.  My quarter sits on the 95 square.  Just because I think that is where it will be.  Remember my earlier guess of 22 degrees was wrong by nearly 6 degrees. 

[TylerDurden]

I assume it puts a incremental delay into the firing of the strobe light as you push the advance button. But it must know when and how much of a delay to put in based on calculation from RPM.

One degree adjustment might delay strobe by 1/720 pulse interval. Two crank rotations per pulse...

[92EcoDiesel Jetta]

Let me kick myself for that!  Let's just say I think you will be measuring 95 mm on the dial.  You are are 16.6 degrees but even those lights can be off you know.  Get a buddy to measure it with another and you likely will see a different measure.  It's an electronic thing and calibration kills on them.  Good brands have high standards to meet and knock offs, not saying your light is one, but those tools just plain don't measure up.  No pun intended, but it came out anyway.

So measure with a dial indicator and let us know.  My quarter sits on the 95 square.  Just because I think that is where it will be.  Remember my earlier guess of 22 degrees was wrong by nearly 6 degrees. 

I'll see what I get with the dial indicator. I hope you're wrong that these inductive timing lights are all different calibration wise. What good are they if true?

As for your chart on the other thread, you are getting a diesel pulse adapter timing of 15 deg BTDC with the dial indicator timing from 0.70 to 0.80 mm. 0.70 to 0.80 mm is retarded from spec. I thought 12 deg BTDC (as Libby reported the best MPG timing) is obtained with the timing advanced a little beyond spec? Something is not right.