Pilot qty coolant temp adjust and multiplier is a limiter?!

[arinkuddy]

So I noticed that the truck would rattle when cold more so then when warm even when I upped the pilot qty. Come to find out the actual pilot qty was lower then my base table was but when it warmed up the actual pilot was following my base table. So I stared messing with the Pilot Quantity, Coolant Temp Adjust and Multiplier. It seems to me that it is actually a max limit on pilot qty. I did a test and set the adjust to 2 mm3 and the multiplier to 1 across the table and what do you know i get a max of 2 mm3. At start up it did shoot to 7 mm3 but I think thats probably due to an unseen table having to do with coolant temp at idle because it stops at 60 deg. I don't if im the first to discover this or if its common knowledge, but I couldn't find any info on this.

I was on tune 2
17669

The log
17670

[GMPX]

Interesting findings, it never really made sense to me the multiplier on the timing adjust tables, but if it being used as a limiter then where they have a mult of 5 it is essentially being disabled from limiting based on what you've found.
It may be that what happens is the ECM is choosing the lowest result of the tables to run with, so if table (a) has 3, table (b) has 10, table (c) has 6, then table (a) wins.

[arinkuddy]

I bet that's what is happening either way the description isn't accurate. So you think the pilot timing adjust acts the same way? By looking at the maps I would say they have to. If I wanted to test the actual pilot timing you would have to subtract the logged main timing from the logged pilot timing and that would give you your deg before main event correct?

[GMPX]

I bet that's what is happening either way the description isn't accurate.
You'll find that happens, this isn't an exact science what we do, this is not an official Cummins tuner after all.


So you think the pilot timing adjust acts the same way?
It might, I can't say for sure though, logic would suggest the same rule (or concept) would apply.

[arinkuddy]

You'll find that happens, this isn't an exact science what we do, this is not an official Cummins tuner after all.

Ya I understand, its an impressive tool but just a minor flaw that could easily be fixed.



So I tried the same idea using the pilot timing adjust and multiplier and that as well acts like a limiter. Also 5 deg of pilot timing across the board shuts off pilot injection in the upper rpm, scared me at first :shock:

[GMPX]

The shutting off of the pilot might also be a function where the ECM has calculated it is going to occur too close to the main pulse therefore it disables it.

[arinkuddy]

Ya that's what I figured happened... The truck didn't seem to care much that the pilot timing was low except for that.. I still don't have a good grasp on what to do with pilot timing