Very interesting - I had not seen that yet, but will have to keep it in mind in the future. It would be interesting to put the old batteries back and do some testing - actual operating voltage, ripple voltage, etc...
Thanks: 6
Likes: 13
Very interesting - I had not seen that yet, but will have to keep it in mind in the future. It would be interesting to put the old batteries back and do some testing - actual operating voltage, ripple voltage, etc...
Hey TimOriginally Posted by AccurateDiesel
Since you've brought this back up, I've got a theory...could be wrong though.
6.7 Cummins mapping shows me that injection pulses are limited based on voltage. I'm think in Drew's case with voltage drop he was maybe losing his pilot shot, thus slowing the POI to the point it was too late for a proper/incomplete burn thus the blue smoke. ??
The Cummins Whisperer!John 3:16, Romans 10:9-10...Tuning for the Heart and Soul.
Interesting thought! Late injection timing is definitely a common cause of blue smoke! Sure would be nice if the PCM would flag a low voltage code before or when it got to that point!
As you can see from the screen shot, after you drop below 11 volts you start loosing pulses. Now this is MCC, what really happens could not be said without data logging.
The Cummins Whisperer!
Had to edit my last post. My laptop won't insert a full sized image on the forum for some reason but my Tapatalk app will.
The Cummins Whisperer!
Interesting - hard to imagine he was running anywhere near that voltage with the alternator turning (but as you stated we don't know OE strategy).
Agreed. He should have had 12.5 volts at least with alternator spinning. Wonder if the ECM accepts a strategy prior to startup?
The Cummins Whisperer!
I'm betting it takes its initial strategy at key on/diag scan before starting then some of the mapping changes with conditions. I would expect that there is alot still going on in the computer that we don't have access to via MCC or EFI. That map is based off of voltage, but what good is voltage without current? With the batteries being weak I'm betting it was low current and possibly not enough amps going thru the batteries from the alternator that was the cause. Thinking back on it, the days that I remembered to turn off all accessories, and shut my door quick, battery saver stuff, I had a quicker crank/start and normal smoke. If I had to get in and out of the truck a few times, or left my cell booster on, it made crank and start slow, and I'd have my excessive grey smoke.
Posting Permissions
Register To Reply
Bookmarks