Determining safe timing limits ?

[2007 5.9]

Are the post injections started relative to the start of main or from the end of main ?

If you make the pilot long and close to the main, will the ECM allow it to run into the main, creating one long injection ?

There are minimum delays set from end of pilot to beginning of main and end of main to beginning of post.

As long as those values are never changed, you can't have one big event.

[someguy]

One word to answer your question definitively...

Dyno

I don't think a dyno will indicate when you've reached a safe timing limit. A dyno will show (at full throttle) when adding timing stops adding power. The timing at max power may still have cylinder pressures in excess of what the engine will take.

[2007 5.9]

So then back to your original post...you'd need to install pressure gauges in all cylinders.

Hp curves, sounds, and all around engine attitude will let you know.

If your not sure...I'd suggest a private tuning session with somebody who knows how to tune appropriately.

[2007 5.9]

How does one know what the "Safe" pressure limit is??

Cummins won't release this info...

[DoghouseDiesel]

I don't think a dyno will indicate when you've reached a safe timing limit. A dyno will show (at full throttle) when adding timing stops adding power. The timing at max power may still have cylinder pressures in excess of what the engine will take.

Nope, you can see exactly when you've reached the saturation point for timing on the dyno, you just have to know what you're looking for.

You'll see it on the dyno before you hear it in the motor.

And no, the dyno is not just for WOT / Max Power.

Tunes are built based on the engines build, not one size fits all. What I have my engine timed at would blow a stock engines head gasket on the first pull.

Safe pressures are, again, based on the engines build. A stock motor vs a motor with a 12V crank, Carrillo rods, .100" taken off the top of the pistons, heavy duty rod bolts, etc., will handle different pressures.

And yes, timing values vary with RPM's.

No need for a scope, the values are right there......unless you're tuning Smarty style.