CP3 Conversion on LML - Tune Help Needed

[bmax0517]

Hey guys, I'm new to tuning but I'm trying to give it a shot on my truck. I have a 2014 LML Duramax 3500, and recently did a fleece CP3 conversion, as well as new injectors, fuel/return lines, lift pump, etc. The pump I went with was a stock CP3 for an LMM so the FCA wasn't tuned or anything. Before I did any tuning, the truck drives alright until about 4th gear where it experiences heavy surging. Rail pressure is all over the place, but only under throttle (you can coast at high speeds without any shaking).

Using efi live I changed the Desired Flow Vs Current table to match what Fleece has on their website, and thats the only change I made. When I flashed it, there's two issues:

1.) The truck can't seem to maintain desired rail pressure. I get the P0087 low rail pressure code, and if you try to crank it after driving for a bit it has a hard start every time.

2.) The surging DOES go away at high speeds, but only for a while. I drove it about 100 miles yesterday and around 30-40 miles in, the surging returns and stays. Is there something that could be making the tune default back to normal?

I've spent weeks trying to learn everything I can on this so I'm pretty desperate for help, any input is appreciated. Thanks

[Tech1340]

Can you Post your tune before the CP3 and after the CP3 with the surging along with a log.

[JnJSpdShop]

Would need a datalog and see what you are working with

[bmax0517]

Can you Post your tune before the CP3 and after the CP3 with the surging along with a log.

Would need a datalog and see what you are working with

Sorry for the delay, wasn't able to get some logs done until today. Here are both the stock tune and the CP3 converted tune, as well as logs for each:

https://drive.google.com/file/d/1NHF...aD1tP5OPzODSd9

You'll notice the only change in the modified tune is the Desired Flow vs. Current table. In the log, you can see the rail pressure in the modifed tune is about half of the desired at idle/low speed, which would make sense why the truck has trouble starting on this tune. With the stock tune, the rail pressure keeps up pretty much the entire time. I wasn't able to get a decent log on the surging at high speeds, since like I said, it goes away when you first apply the tune but comes back eventually. I would at least like to figure out this rail pressure issue to start

[bmax0517]

I updated the file and added a new log that includes fuel flow and current. If it helps, the current value fluctuates the same way the rail pressure fluctuates when the truck surges, but only then. Otherwise current is static as normal.

Anyone have any ideas on this??

[Lennydmaxguy]

Since you are using a LMM pump, the flow vs current table should match what the LMM trucks had stock rather than the Fleece table. The table they give is for the pumps they sell if you buy the complete kit from them with a pump.

Here's your file with a rough interpolation of the stock LMM flow rate: https://drive.google.com/file/d/1phJ...ew?usp=sharing

[bmax0517]

Since you are using a LMM pump, the flow vs current table should match what the LMM trucks had stock rather than the Fleece table. The table they give is for the pumps they sell if you buy the complete kit from them with a pump.

Here's your file with a rough interpolation of the stock LMM flow rate: https://drive.google.com/file/d/1phJ...ew?usp=sharing

I don't know how I missed that, thank you! The values you gave me fixed the low rail pressure. I guess I assumed the table they gave was for a standard CP3 since they provide a kit with a regular pump and one with a 10mm pump. But seeing how high the numbers in there table are, I guess it was probably for the high power pump after all.

If I wanted to fine tune the surging a little bit beyond that, are there any other tables I should look into altering? Or would it just be slight changes flow vs. current table? I assume this would be by building a similar table in the scan tool and logging all the actual current values over time

[Lennydmaxguy]

I don't know how I missed that, thank you! The values you gave me fixed the low rail pressure. I guess I assumed the table they gave was for a standard CP3 since they provide a kit with a regular pump and one with a 10mm pump. But seeing how high the numbers in there table are, I guess it was probably for the high power pump after all.

If I wanted to fine tune the surging a little bit beyond that, are there any other tables I should look into altering? Or would it just be slight changes flow vs. current table? I assume this would be by building a similar table in the scan tool and logging all the actual current values over time

You should be able to fix it with just that table. I guess try little changes at a time and hopefully you can see a definite improvement with higher or lower numbers.