Bushy

I have run a pretty wide range of timing in mine...the thing displays the symptoms the guys have described...
One thing to always keep in mind is the cylinder pressure issues....the more the advance the higher the pressures...
You may never have any problems but you just may be the unlucky one so keep it in mind.
I also saw a drop in overal boost numbers...not huge but certainly obvious on the gauge.
Smoke does clean up, the throttle response is noticably better and when shutting down the engine all but stops dead in it's tracks...signs of higher timing....

As for towing, I wouldn't be too afraid to bring the timing up a bit...you really are in the "ok" zone with this if you use good sense..
Remember, the earlier trucks ran between 1.35mm and 1.40mm plunger lift. Ours are 1.25mm lift in "stock" condition so you're ok with this as long as you don't go wild....
As the timing goes up the boost drop is not the only thing that changes...you will see a decrease in overal torque too...not alot but some....this makes a difference when you tow so bringing your timing up to about 1.35mm - 1.45mm lift is WELL inside the safe zone. In terms of degree's, no I don't know the corresponding values...never been able to find em or do the math...
but, aim for about 15.5* - 16* advance if you use the degree method...again well inside the safe zone for most of us, 'specially if we have some upgrade nozzles in the truck.


pb...

cLAYH

I'm set at 15* timing on my rig with stock injectors. I'm thinking about rolling my timing back some next towing season to help with the water temps. With the load I pull I can hit the "H" mark fairly easily.

Blowndodge

So good Pastor, you think my 1.7mm timing is the reason my truck runs substantially hotter when towing?

That the Cummins would have "less" torque with more advance is the exact opposite I thought would happen. On gas engines which I raced for 10 years, the more advance timing we could get away with gave quicker ET's and more torque on the dyno but a little less horsepower and a 2-3 MPH reduction in speed through the traps.

Theory was that with the timing advanced as far as we could take it, the cylinder pressure was high and allowed for a shorter shift because of the extra torque but as revs got higher, we were fighting against this advanced because of the burn starting sooner, fighting against the piston, pushing in back down.

Where do you think I should have the timing set for all around use with my signature? When I reset the timing, stock was at about 1.12mm and the truck was lathargic.

Brad

FerranRico

Well, last Friday I set my timing at 1.45mm advanced.., since it is a newly rebuilt pump, I didn't know what to expect.., but true to form as ya'll been saying.., I had the following symptoms towing a 10K load.., Jeep and trailer...
1. Boost followed the fuel pedal, it would fast peg at 30 lbs with no effort..
2. Temperature hovered before the H if I went faster then 65 mph.. (I don't trust my Banks tach.. as it shows 1K rpm at around 65 mph).
3. Seemed that it had no torque on hills, slowing down to 45-50mph..
4. Black Smoke was heavy when heavy on the pedal, and white smoke at at idle..
I'm gonna set it back to the factory setting on the plate of 1.25mm, or maybe 1.3 and see how it does..

wannadiesel

If you are white smoking at idle, you need more advance or you have a bad injector.

FerranRico

Hummnn.. injectors are the High Horse kind.. less than 2 yrs old.., the timing is waay advanced.., something else must be wrong.., does the wastegate have anything to do with it?

wannadiesel

Nope, it's not the WG. If you have big injectors, you need a good bit more timing than stock.

Underpsi

I don't really understand why people keep saying that. When I put my PODs in I didn't touch the timing and I still haven't and it seems to run really good, although I didn't notice a big difference with them. Not like I was hoping for anyways

G1625S

From the good pastor hisself---a while back but always relevant

''Firstly, the earlier trucks actually had a factory timing set value as high as 1.40mm (this is using the plunger lift method.)
So, the factory timing setting ranged from 1.25mm to as high as 1.40mm.
The reason for the changes were primarily due to emissions requirements...this plus the addition of the intercooler helped to deal with those requirements and made it necessary to lower the injection timig for emmissions reduction.

Now, the stock timing value for our later model trucks was/is 1.25mm plunger lift. This addresses emissions and middle of the road timing advance to accomodate the onset of fuel injection into the cylinder.
As you may know raising the timing on any of the trucks will help improve the general responsiveness, smoothness of idle, lower smoke and so forth....even with stock injectors.

When you upgrade your injectors, they usually have a higher "bar" value...that is the pressure at which the injector releases it's fuel charge into the cylinder. Since a higher bar value means it will take longer to reach release pressure you need to set the injection onset sooner, or, advance the timing to accomplish this....the higher the bar the higher the timing setting.
Normally the best all around value is approx. 16-17* advance....note this is in "degrees" not mm plunger lift.
If you have your pump set using the plunger lift method then you'd be aiming at roughly 1.55 - 1.60mm as your advance value.

Admittedly the higher bar value represents mere micro seconds delay (retardation) but it is best to advance the timing for some of the other reasons noted above...one thing that comes from the advance is the fuel charge is beginning sooner, at a more correct position and that in turn impacts on the combustion onset, peak rise and, end of the burn cycle.
This allows the entire combustion process to start/peak/end well within the most efficient crank rotational position.... it also does something else as a byproduct...it raises cylinder pressures as well...that is good and bad but is another topic...

I hope that is some help....and, I'm open to corrections if I've overlooked anything here guys...

pb....''

Underpsi

thanks for posting that. WHy would you lose boost and torque then if its better?

G1625S

This is a tough one to explain. It makes sense in my head, but I've typed this about 5 times and it still doesnt' read right, but here goes...

Boost is partly a function of how fast the turbo is spinning. Turbo speed is determined by the flow of hot exhaust over the turbine wheel. Spinning up the turbo at low RPM with hot exhaust is what gives the percieved low end 'grunt' of these engines when the timing is set per-factory. By advancing the timing, more of the hot combustion gasses that would otherwise be expelled to spin the turbo are contained in the cylinder for a better burn. The resulting exhaust coming out of the manifold is now cooler and slower moving, slowing the spool of the turbo---hence the sluggish low end. Boost will be down across the board since the timing we're messing with by moving the pump is static. The up side is a better burn and higher horsepower in the mid and upper RPM range. There are many inter-related factors that come into play other than what I've noted. Anyone who'd like to add a detail or correct me, please step in. Tuning is always going to be a series of compromises with mechanical injection, since you can't really tune on the fly.

FerranRico

OK.. I get it.. sort of..
But... when with 2.5 mm stock setting and a stock pump I could get it up to 80 mph towing 10K lbs and the temp dummy gauge marked only half way...
and now with hP injectors and a pump with tapered fuel rod and 3k rpm spring, at 4.5 mm advance it gets up to HOT at 65 mph?
What gives?????
The only reason that I went with the upgrade pump was that I was getting 8 mpg ALL-the-Time..., towing and not-towing..., so I thought the old pump was crapping out...

G1625S

I'm going to venture a guess that a soulution will be hard to find because you changed so many variables at once. Next, when you say it gets 'HOT at 65'' arou you talking about the dummy temp gauge? If so, this follows suit because with the added cylinder pressure of advanced timing comes higher water temps as the cooling system tries to pull all that heat from the head and block. Even if your timing bump is directly proportional to the different injectors, you're still making more power with the bigger sticks and fresh pump, so there's gonna be more heat...All this really doesn't address why your un-bombed truck would run 80 with a load and now you can't. Again, with all the variables that changed at the same time, it's hard to nail down...How much tuning have you done with the AFC housing? I've heard that the aftermarket fuel pins dump a lot of fuel early on, which is good for hot-rodders, but bad for steady-state pulling. Here's a quick and dirty trick to see if you simply need to tune the pump better: Take the line that feeds manifold pressure to the AFC off. Plug the hole in the maifold so you don't have a boost leak. If you're fussy, plug the AFC housing to keep dirt etc. out. Now hitch up the wagon and see what happens. If you notice considerably lower temps, you'll know that some AFC tuning is in order. Are your temp problems mostly coolant, or are your EGT's out of whack too? After reading back through this, I'm beginning to suspect maybe your cooling system is not up to the task of cooling your new power. Still, if it would pull 10k @80 before the changes, I'd have to guess that should not have changed and that some simple tuning is in order. Don't be afraid to mess with the timing, just be sure to mark the start point. Every truck is different, so just tinker and find out what works for yours---and report back here when you do so we can all learn something!

FerranRico

Thanks for the reply, I'll give your suggestion a try...
The only thing that's changed is the new fuel injection Bosch pump.., it's had the high output injectors for a couple of years and they did increase the performance with the old pump and temperature wasn't afected.., it had lot's of power and ran cool (half way on the the dummy temp gauge) however the truck only got 8 mpg all the time..
So I decided to change the injection pump to see if the mpg's would get better.., as I kept hearing that most others get about 18-20 mpg's...
Being that the pump is "new" I haven't done anything with the AFC housing, which i wouldn't know how to anyway.., or what it is??
But I'm open to try anything...
I really appreciate the help guys.. I do...
Thanks

FerranRico

Ohh.. forgot.. the EGT's are slightly higher too, not too much.., I get around 800-900 degress (post turbo sensor) at 65mph, which I guess is about 1100 degs on the exhaust pre-turbo? It used to run about 700-800 (post turbo) before with a load and at 70-80 mph.
The tranny temp stayed at an even 180 degs, which indicated to me that it wasn't working extra hard..., before it used to get up to about 230 when climbing with a load...
It was just the engine temp that skyrocketed..