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Pilot/Post Injection Fuel Economy Tuning

Practical Diesel Tuning

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Greetings,

So far I have advanced my Main Timing so that approximately 50% of the fuel is injected BTDC. I also increased my fuel pressure slightly in the cruising areas. This has lead to a little over 1 mpg increase on the highway. Looking to see if anyone has dabbled in decreasing or moving pilot and post injection for the sake of fuel economy in a Duramax, specifically an LML.

The Cummins guys seem to turn it down/off quite frequently but it does not seem as common with the Duramax. Personally I could care less about the noise. Looking to increase efficiency. I dont mind buying DEF its cheaper than fuel.

From a few articles I found it looks like more pilot is better for acoustics but a smaller well placed pilot injection leads to better efficiency of the Main Injection. Thanks for the help.

Sounds like a fun project. I don't know the answer, but for what it's worth, the options you stated of reducing or skipping it are the things I'd give a shot. I'd say you're on a logical path and it also sounds like you've already confirmed a gain from other changes, so I think you have all you need to test and find out yourself.

Someone else might shortcut to the answer, but figuring this sort of thing out is the fun part, and I love to see that you have the tools to do so.

I agree it is fun. Decided to disable Post Injection first. I kept it active from 800 to 1400 rpm in the lower fueling areas in Mode 0 and the Transition tables. I kept it with the idea of helping spool the turbo. It seems during normal acceleration I do have slightly higher fueling rates. I suppose the ecm is compensating for the lack of Post and injecting it in the Main Event. Butt dyno says its the same power as before. Will have to log some more to tell the difference during normal acceleration.

During Cruising I did not seem to notice any fueling quantity changes. It does run slightly cooler though. Will not do well for passive regens if you still have a DPF installed. The DIC says the truck is getting better MPGs. Although we all know how accurate those are. Will need to put more miles on the truck and continue to log to see what the results are.

Excellent work! Great job performing iterative tests, logging, identifying how the control systems react.

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