TDC Offset

[97-6.5TD-F]

I am having an issue with my 97 K1500 in which I recently overhauled the engine. I installed a DSG gear drive and phazer, and since the first fire it has rattled loudly like the cold advance is staying on all the time. It is like this even cruising down the highway at cruise speed. It is quiet only when under load like when accelerating.

I performed the tdc offset relearn procedure which seems to have helped slightly. The timing was right around 14* when hot before, now it goes down to around 5 at idle. Only thing is after doing this it is setting a injection timing control code and tdc offset code now. Also what is fairly unusual is that now it seems to advance the timing for a second at each shift point as it gets noticeably louder each shift:confused: .

The tdc offset spec is -.25 to-.75. Mine is right around -2.5. I am wondering if I should adjust it as per factory spec even though I am using the crank phazer?

I talked to the guys who sell this phazer and could almost see the blank look on there face from how they reacted over the phone. Thanks for any advice, Josh.

[gmctd]

IP is advanced - rotate the IP toward the turbo-side so the ESO solenoid is exactly vertical - lock it down - clear all the DTC's - do the ko-ko routine - crank the engine - all DTC's must be cleared B4 timing will reset - ECT must be >170degF B4 timing will reset - I wait till 180deg 2 B sure

TDCO of -1.50deg to -1.94deg is good, but the above will get you back toward -0.5deg.

[Billman]

I had the same issue when I installed Gear Drive. Marked IP before disassembly and lined up after install.

Closest I could get to positive was -2.02. Previously running -1.76. Rattles like hell at -2.02.

Disassembled this week and went 1/8" towards the turbo.

When I reconnect to Tech II, I'm expecting -1.50 range.

[ronniejoe]

There is a two degree advance built into the reloctor wheel of the DSG set up. Some think it is advancing the cam, but it is not.

Here is a shot of the DSG crank gear on top of the factory sprocket/reluctor.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM002033mod.jpg

As you can see, the dot is in the same place relative to the keyway on the DSG gear as on the factory sprocket.

Here's a shot of the reluctor wheel on top of a factory crank sprocket/reluctor wheel combination.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM002038mod.jpg

As you can see, the DSG toothed wheel is advanced compared to the factory wheel.

This is why the injection timing is always advanced when you install the gear drive.

[Billman]

I knew their was advance built-in, thought it was 4*.

Just didn't cross my mind at the time when I was timing the pump.

[DA BIG ONE]

So, Im running the gear drive and my readings are as follows:

Desired injection timing 10.5
Actual injection timing 10.5
TDCO 1.90

Question is, should I still be looking at 1.94 TDCO, or would a lower TDCO be better?

[ronniejoe]

You've already backed the pump off to compensate, if you have -1.90 TDCO. I would leave it alone.

[gmctd]

I remember getting those same results - can you post a pic of the gearset on, idlers in place and timing marks aligning as crank is rotated in normal direction?

[ronniejoe]

http://www.thedieselpageforums.com/photopost/data/500/IM002050mod.jpg

J.D., I had a boss (director of engineering for the division) like you once. He liked to play this game where he would ask questions until the employe couldn't answer one, then walk off triumphantly. With most folks, he usually won after three or four questions. He tried that with me one day on the 250 assembly floor. After thirty minutes and countless questions, he finally asked a question about another engine model...I smiled and he walked off in a huff.

What will it be next?;)

[Kennedy]

So, Im running the gear drive and my readings are as follows:

Desired injection timing 10.5
Actual injection timing 10.5
TDCO 1.90

Question is, should I still be looking at 1.94 TDCO, or would a lower TDCO be better?

If you are reading 1.90 you must have a generic scan tool and the actual value should be 1.94 so I'd leave it or verify with a Tech I or II

[gmctd]

I setup mine in '03-'04, so I've slept some since then, but iirc, the advance in the crankset is due to the camgear offset caused by the unequal-diameter idler gearset - is that not what you've seen?

The question usually comes up when someone is installing the gearset as to how to correctly time the gears, because the marks do not align - a straight-edge to the centerline of the crank and the cam is usually suggested as the best method of ensuring alignment when approaching crank TDC in the normal cw direction.

As you do so many of these setups, you should be able to settle this eternal question once and for all, n'est ci pa?

It is a simple request - a direct frontal head-on pic of the assembled gearset, timing marks as close to alignment as possible, and I would sincerely appreciate your thoughts on the final alignmental results - camshaft to crankshaft to cyl #1 TDC, including the reluctor in the phazer set.

[ronniejoe]

This is the best photo that I have.

http://www.thedieselpageforums.com/photopost/data/500/medium/IM002049.jpg

This probably isn't good enough, but you can see that they align very well...as well as you can align with a chain.

The idler is forced into tight mesh when the engine is running. If they designed the mesh properly, timing should be closer to dead on than with a chain, because of the slight stretch of a chain (even with a new one) and the small amount of clearance in the roller links themselves that allow some extension of chain length when loaded.

The point of this is, there should be no fears of crashing valves into pistons with stock lift cams, as some have made a very big deal about. With a mechanical injection system, there are no significant timing differences at all.

The only difference with these gears is in the location of the four teeth on the reluctor wheel which is read by the crank position sensor. The DSG reluctor teeth pass under the sensor earlier in the cycle than the stock ones do.

Cam timing is unaffected.

[gmctd]

Yeah, it's all coming back to me now - so what do you think - max of +2deg cam by losing the timing chain + the reluctor advance is the 4deg advance everyone mentions, but no documentation ever stated?

[97-6.5TD-F]

So if my tdc offset reading is -2.5 then I have to advance the IP?

It seems to run slightly better after I performed the clean and learn procedure, but now the ses light is on all the time and it rattles loudly during low load. So by the sounds of it I should retard the IP? Or am I confused by the - in front of my offset number?

[ronniejoe]

Move the pump toward the passenger side, then relearn.

[More Power]

So if my tdc offset reading is -2.5 then I have to advance the IP?

More negative is more advanced. You'd need to retard the timing, to get the TDC-Offset more inline with what GM indicates.


max of +2deg cam by losing the timing chain + the reluctor advance is the 4deg advance everyone mentions, but no documentation ever stated?

I think DSG has the info on their web site. I've installed 4-5 of these gear drives. The engine rattles a lot more afterward, if the IP isn't moved. In general, I've needed to retard the IP 3 or more degrees (1/8"+ at the scribe lines) to get the rattle right...

http://www.thedieselpageforums.com/photopost/data/500/DSGGearDrive.jpg

The above shows how I initially set the timing marks. It's easier to get the marks lined up this way. For those who want to see the dots facing each other, simply rotate the crank one complete turn - then the marks will be at 6 & 12 o'clock. The above photo was taken of a gear drive I installed on a 1996 6.5TD.

Jim

[Warren96]

Ronniejoe said it best''move the pump to the passenger side'' just a hair and then relearn, if you are turning it the right (left) way you will see the numbers go down.

[Warren96]

By the way those are awesome pictures RJ ,for a moment I thought I could smell the motor oil!

[97-6.5TD-F]

Finally got the time to sneak it into the shop today and moved the pump approx. .060" to the right (turbo) side. Tdc offset went from -2.47 to -1.7. Less rattling and no more ses light so I am happy.

On a side note is there any way to test the FSD driver? I am going on a 2000 mile road trip tomorrow and am hoping all will be fine :rolleyes: