Looking for advise on pilot injection

[longcummins]

I am in the process of trying t build a tune that will work with my (CNG) system that I run on my truck. CNG = (Compressed Natural Gas) . I am trying to disable pilot injection above 1500 rpm so that I am not burning the energy available from the cng that is wasted in the pilot injection. I wanting the injection to take place only in or within the main pulse injection kind of like the older 12 valves with only a single injection event {above 1500 rpms). I have tried to set the pilot injection to 0.00 above 1500 rpms but when I do that I get multiple codes that come up and it runs pretty ruff. Any thought or input appreciated.

[2007 5.9]

Need to add main timing to offset the reduction in pilot timing..these engines need a minimum timing to run properly.

[longcummins]

I am still trying to get this figure out so what do you suggest + 10.0 + 15.0 % more over stock settings ? Any idea where I should start and what would be maximum to not go over?

[mpdtune]

Look at your stock pilot injection table. Basically you're trying to make it run like a 12 valve motor, just one injection event. They run static timing of around 12 degrees.

[longcummins]

So a minim of 12 degrees of timing then and that should make it stable then correct?

[2007 5.9]

12* of main is too much on a 07.5-current piston design at idle. Look in the 7-9* area

[longcummins]

Thanks you 2007 5.9 , I certainly cant afford to melt down a piston while trying to save money on fuel cost.

[2007 5.9]

And you don't want to run 7-9* static all the time...you still need to adjust timing as rpm rises...much like a regular tune.

[longcummins]

Yes sir that's what I was thinking, just down low in rpm where I am disabling pilot and low in mm3 correct?

[2007 5.9]

Yes, I run 7-9* at idle and just off idle I begin to ramp timing up.

[longcummins]

Thanks again Les you are a great help on this forum.

[mpdtune]

Don't be afraid to play with it some. The CNG is acting as the new pilot injection, in theory. Made need more or less to allow it time to react in the cylinder.

[longcummins]

I now have about 20 miles on it with the timing adjusted and now I get no codes so I am good for now. Thanks for the input guys it's appreciated.

[longcummins]

Actually with the pilot turned off at 1400 rpm and above, the CNG can't burn until the start of the main injection. Their is no spark for it to do so until primary injection.

[computerjlt]

interesting, how much CNG is used. is it a set amount or does it vary by rpm/load?

I've seen natural gas used on big industrial diesels to offset using as much diesel or fuel oil (i was reading a lot of these papers to learn more about diesel combustion and cylinder pressures and how everythign ties together). i've never seen it used in a passenger vehicles except for CNG and LPG conversions that were popular years back.

[longcummins]

The best advice I can give you computerjlt is to go to cummins forum. Go to alternative fuels and lubricants section. Look up cng in a diesel to start with and a couple others there in that section and read a couple pages it should answer some of you questions.

[mpdtune]

You might try using a much smaller pilot injection to ignite the CNG. That way it would be burning before the main event, should give more complete combustion of the diesel.

[longcummins]

I have been running the stock setting on pilot until last weekend. I now see a lose in mileage running with out pilot injection. The rattle from the injectors was driving me nuts also without pilot. Now I am back to running the pilot injection set to factory spec.