Increasing fuel delivery volume: mm3 vs. uS

[2006Cummins]

When increasing fuel delivery volume does both the mm3 and uS need to be increased, or can just uS be increased? Just wondering since it seems that some only increase uS, but others comment on mm3. Will not increasing the mm3 limit the volume delivered? Thank you.

[GMPX]

I remember with the Duramax when people were changing the pulse uS table only it threw off the MPG reading in the cluster, so I think it became the norm to get more fuel via the MM3 tables instead, then if you still need more then look to the pulse table.
The commanded mm3 values can be thought of as just a reference point for the Pulse uS table which is the final decision point on how long the injector will be open, so think of it controlling what pulse time will ultimately be used.

[2006Cummins]

I think I understand. I'll take a look at the tables again to be sure. Thanks!

[AdamRRT]

So are you saying to be sure we are maxing out the flow at that duration before increasing duration?
Won't that potentially result in higher rail pressure? I guess it depends upon if one overrides the other.

[GMPX]

The commanded mm3 table can almost be thought of like a throttle response table on an LS1 with ETC, pedal vs blade opening, except on a Diesel of course it's pedal to commanded fuel.
The Cummins is a little different to the Duramax because the throttle response table is (I'm sorry to say) quite crude in that it's pretty small, but it does the job. Comapre it to a Duramax which has far greater control on the response due to the table size. Cummins addressed this in the 6.7L as the throttle table is much bigger.
As you are coming from a gas world, you can almost think of the pulse table as an injector flow table on a gas motor. You can make drastic changes to fuelling on a gas ECM by just altering the injector flow table(s), but it's not really the way to do it, it's more a 'base' setup table matched to the engine injection hardware.
I am by no means a Diesel tuner (far from it), but my logic tells me that if you have a stock fuel system then the pulse table isn't where you should be changing things, do it via commanding more mm3 if you want more power. But again, it's a little tricky on the Cummins because you don't get that finite control on the throttle vs mm3.

[THEFERMANATOR]

I remember with the Duramax when people were changing the pulse uS table only it threw off the MPG reading in the cluster, so I think it became the norm to get more fuel via the MM3 tables instead, then if you still need more then look to the pulse table.
The commanded mm3 values can be thought of as just a reference point for the Pulse uS table which is the final decision point on how long the injector will be open, so think of it controlling what pulse time will ultimately be used.

I know for an LB7 that it normally will only fuel to say 89MM3 of fuel, but you can go into the throttle and torque tables and get to 100MM3 of fuel which is as high as it goes in the tune. To go to more than that you have to go in and increase the pulsewidth for each MM3 of fuel setting. So say you get 100MM3 of fuel at a 1400 pulsewidth with 160 rail pressure, then 2800 pulsewidth would give you 200MM3 of fuel. So you woulkd go in and make 100MM3 of ffuel in teh fuel table be 2800 pulsewidth. Now when teh ECM thinks it's injecting 100MM3 of fuel it is actually injecting 200MM3 of fuel. I know this is how DMAX tuning is done on LB7's and LLY's, haven't played with an LBZ or newer yet.