Injector Balance ?

[icemanjc1]

Yesterday I recorded a run file for the first time to get an idea of how it works, plus I'm trying to pin point an injector problem. Anyway, what should I be looking for on the balance rates between injectors? 5 of them show between 0.3 to -0.7mm3 and one shows 1.0 mm3 with a max of 1.6 mm3. Any ideas?

[Dmaxink]

Typically on our dmaxes they would start white smoke after 3 mm3. I would say yours are in check

[FUBAR]

So what exactly are we looking at per say. Total cubic millimeters of fuel that an injector is flowing "x" amount of time? Or the difference in mm3 of fuel between the average of other injectors? I got confused when I seen 4450mm3 on the last ScanTool version and now am only seeing 0.3mm3-1mm3 etc... Just a little insight would be appreciated.

Thanks,

[Dmaxink]

Honestly i dont know "technically" what would be considered out of rate...but i can say under 3.5mm3 we have not had any knocking or white smoke. I have not had a dodge come through yet with bad sticks so i cant speak from that standpoint yet,,,im sure les or zach may be able to hint on this a little harder. But i can say +/- under 3mm3 i would not worry about unless it is knocking or blowing white smoke.

[FUBAR]

Thanks, I can appreciate the tolerance on real world conditions what would be out of tolerance, i.e. 3 mm3 or more, but is that 3 mm3 fuel per stroke or what? Doesn't make since comparing it to 10 mm3 - 100+mm3 of fuel per stroke based on tune tables. I'm just trying to under stand the "x" mm3 of fuel value in the injector balance rates.

Thanks,

[2007 5.9]

Thanks, I can appreciate the tolerance on real world conditions what would be out of tolerance, i.e. 3 mm3 or more, but is that 3 mm3 fuel per stroke or what? Doesn't make since comparing it to 10 mm3 - 100+mm3 of fuel per stroke based on tune tables. I'm just trying to under stand the "x" mm3 of fuel value in the injector balance rates.

Thanks,

On my '07, I'm seeing roughly the same values as you are. However I am still uncertain of the meaning if the values. I am used to seeing a balance rate listed in a % value to indicate cylinder contribution.

~Les

[Dmaxink]

I would assume given it would take say 10mm3 (dont know off top of head for cummins) to idle and we have 6 cylinders you would estimate each cylinder would have to give say 1.66 mm3 of fuel to make it idle correctly and hit our desired 10mm3 (or 12, 15, ect. whatever a cummins idles at)...if this desired flow per cylinder is out of rate, for example positive, then it would be flowing too high of a rate say 6+mm3 over the necessary 1.66mm3 for that cylinder...likewise lower than the desired the 1.66mm3 say -6mm3 ..then the injector would be flowing that much less than the 1.66mm3 desired. I'm not the best of explaining myself but this is my understanding to how the ECM puts a value to the flow rate. I could be wrong but it made sense in my head :-)

Edit: Also the value ex. "1.66" is not shown in any of the tables for idle...it is what im assuming the ecm would explect to see per cylinder and the +/- values you see in the balance rates is what is above, or under the 1.66mm3. Again, im not sure what mm3 it idles at so likewise if it is 15mm3 at idle we would estimate each cylinder to be 2.5mm3.. If rates are 100% in check then it will show up as "0"..if it is over or under the estimated mm3 number it will be +/- that much.
Hope this helps, and this is just my theory

[FUBAR]

That definitely gives me something to rationalize when I go look at it again. Thanks

[Dmaxink]

Someone may correct me because i may be wrong, but it is the only way i can make sense of how the ecm would know how to put a value to it is by a pre-defined 'factory assumed' mm3 value and given the desired mm3 at idle would be 10. they would divide that value by the 6 cylinders equaling 1.66 and that would be our pre-defined value.

[FUBAR]

I just logged balance rates idling and here's what I came up with. Average mm3 to idle is 9.4mm3 Take that divide by 6 cylinders and you get 1.57mm3 per cylinder. Now here's the log of the cylinders...
#1 -1.0mm3 Flowing actual 0.57mm3
#2 0.0mm3 Flowing 1.57mm3
#3 -1.2mm3 Flowing 0.37mm3
#4 -1.2mm3 Flowing 0.37mm3
#5 3.5mm3 Which I hope is not going bad (no symptoms yet) Flowing 5.07mm3
#6 -0.02mm3 flowing 1.55mm3
Now, all the "negatives" (meaning flowing less than commanded per cylinder) add up to 3.42 mm3. All the Flowing actual values add up to 9.5mm3 which what the log said it was commmanding.

This definetly helped me understand this now. I just wonder if the other "negative" cylinders were compensating for the cylinder flowing too much?

-Andrew