Timing a 1994 turbo diesel

[miked]

Hello All
I bought a 1994 2wd extended cab turbo diesel a little over a month ago. And after having it safetied, I have been driving it for the last couple of weeks to get a feel for how it runs.
This truck came with stock size exhaust and no other modes that I can see.

Today I decided to check the timing on the engine. As I was having more smoke at cold start then I thought it should have and even though it has more power than my naturally aspirated truck had, it just did not seem quite right to me.
I have a Chinese made diesel timing light I picked up from princess auto here in Canada and had never used it before. It seems to be working well. Other than, the advance wheel is touchy to use, but once you get it set it worked well.

My first reading, at 2000 rpm and 0 advance, showed the timing mark 3/4 of the way to the top hole in the bracket.
After a number of adjustments, I ended up at around 4 to 5 degrees advanced, using the centre of the bottom hole as my guide.
This rotated the injection pump about .200 thou. As per my vernier.

I am struggling to move it more, as the injector lines are binding. I loosened the line nuts that I could reach, and that got me to where it is now.

Are there any more tricks to gain the last few degrees needed????
If you see any errors in the way I timed it also let me know.

The différance in drivability even at that setting is very noticeable. Where before if I was a 50 mph if I tried to increase to 60 mph it would always kick down the transmission. It had me cursing the tranny as being the problem. But on my test drive tonight, it would smoothly accelerate from 50 to 60 mph with ease and no downshifting unless I punched it. Tomorrow morning I will see if the cold start smoke will be less also.

Thanks

 

[IDIBRONCO]

You can remove the line that comes into the back of the pump from the filter and then use a crowfoot to loosen the lower lines that you can't reach otherwise.

 

[Black dawg]

You wont gain much if anything if you are at 5 now. I time all turbo motors to between 4 and 6 degrees.

 

[miked]

Thanks idi bronco and Black Dawg,
I will have to pick up a set of crowsfoot wrenches for the future.
I was trying to go to 8 Degrees as per the manual but sounds like it is not needed.

 

[IDIBRONCO]

Engines with a turbo seem to like slower timing for some reason. Of course that's also not chiseled in stone. If you're happy with how it runs right now, I'd say to leave it. You can always mess with it later if you want to.

 

[miked]

I will leave it for now. This truck ran noticeable better after I finished timing it. Shows that having the timing checked on an old pump can be worthwhile.
I am interested in the possible reasons turbo motors might like slower timing though.

 

[miked]

A footnote,
for all of you with a burning desire to know whether the timing change got rid of my cold start smoke cloud.
It did, no smoke at all now.

 

[IDIBRONCO]

I am interested in the possible reasons turbo motors might like slower timing though.

I can't even make a guess on that part.

 

[KansasIDI]

I can't even make a guess on that part.

My guess is because retarding the timing moves the combustion heat back, putting more heat into the exhaust and less into the piston itself. This is why some say ‘EGTs are just a number’

Moving that heat into the exhaust will spool up the turbo better, more heat moving is more energy moving. And with more exhaust force, the turbo will in turn push more air into the engine, an ingredient for better power.

 

[miked]

Thank-you for that explanation.
You have given my old brain something to play with.

 

[Nero]

I'm willing to bet it was something emissions based during cold starts.

 

[KansasIDI]

I'm willing to bet it was something emissions based during cold starts.

That is definitely a factor as to why they might be set back from the factory, but the reason they would run a little better with less timing would pertain to where the heat peaks at…

 

[XOLATEM]

the reason they would run a little better with less timing would pertain to where the heat peaks at…

I know that this thread is months old but that is one good explanation and gets my thinking in that direction...answers like that reflect a pretty deep understanding of the combustion efficiency and resultant power dynamics...

I greatly appreciate this kind of education...

Along with this theory...

Moving that heat into the exhaust will spool up the turbo better, more heat moving is more energy moving. And with more exhaust force, the turbo will in turn push more air into the engine, an ingredient for better power.

This is an answer that I can get my head around...

Thanks much.