Mag #63 conflicting information

[brods]

On page 82 we are told that added rail pressure does not give mileage gains and is “problematic to injector and injection system durability”. Then on page 110 we are lead to believe that increasing fuel pressure will increase mpg by 7%. Joe, whats the straight poop?

 

[Joseph Donnelly]

In theory, it would seem that increasing rail pressure would help mileage, as noted on p. 110. In practice, neither Marco Castano (owner, MADS electronics/developer of Smarty), Mark Chapple (owner of TST, Cummins engineer for 33 years, developer of Power Kit and PowerMax products), nor I have seen any clear, verifiable mileage increase from raising rail pressure above the stock Cummins curve. Power adders do “cheat” the truck's overhead console report of fuel mileage, giving falsely high readings because fuel is being added that the computer doesn't know about. Mark told me he did see a nice torque increase in the 900-1300 rpm range from added rail pressure that was not achievable to the same extent by adding injection duration. As with some other products and approaches to modifying turbo diesels, “YMMV” in internet slang, or “your mileage may vary. ”

 

[ENafziger]

On some very highly instrumented test engines that I've dealt with, it seems that for the most part, more power is required to drive the cp3 harder for increased pressure than is gained from better atomization.

--Eric

 

[brods]

Thanks for the replies. So what about injector life? Is any increase in pressure over stock safe? Is it relatively safe to ramp up rail pressure faster while staying under the factory maximum? Or is injector life inversely related to pressure, ie more pressure = shorter life even at the lower pressures?