Cummins Smokeless Tune
Hi everyone, I have a 6.7 truck that has 250% injectors. I am having a hard time getting it to stop smoking during moderate acceleration/cruising in the low boost areas. It's not heavy smoke its light smoke that never goes away. On surface streets I can drive it smoke free if I
Massive injectors like those are difficult to clean up. Air mass entering the engine, pulsewidth, timing, rail pressure, list goes on with things that need to be finely tuned with those injector sizes. Getting air/fuel ratio matched up throughout the rpm and load range will be crucial for getting a clean tune. The ecm does calculate a theoretical AFR, logging that combined with a real AFR gauge plugged into the exhaust really helps with tweaking the pulsewidth table.
I'm not sure why my first post got cut off but so far I have had best results with timing. I brought Main timing into the -3 to -4 range and it drastically reduced smoke output in these areas. When doing that I had to bump up pilot quantity a little bit because it started popping. I tried advancing main timing and I did not have positive results cleaning up the smoke, negative timing has worked the best. I pulled pulse width and that did not have a noticeable effect on smoke, it just made the truck feel a bit more sluggish. As for rail pressure it is around 150-180 MPA in these areas. Right now I would say that 95% of the smoke is gone in the cruising areas.
Pulsewidth is the definition of what the flow characteristics are of the injectors, just randomly lowering pulsewidth is same as putting on a blindfold and just start tossing darts while spinning in a circle, hence the mention of using the ECM’s calculated AFR and logging real AFR and adjusting till they match up as close as you can get or could always pay for a flow test for the pulsewidth table.
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