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Thread: 6.7 injectors in a 5.9

  1. #1
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    6.7 injectors in a 5.9

    With 5.9 injectors only being rated to 160Mpa, and 6.7 injectors rated at 180Mpa, would it be worth it to run 6.7 injectors in a 5.9 so you can run more pressure? Im not exactly asking about flow through the injector, obviously I can throw nozzles on and get more flow. Im more asking if the added pressure would help atomize fuel through the nozzle?
    2004.5, built 48re, Fass lift pump, s364.5 with a s483 compounds, ARP studs, 103# valve springs, 110hp injectors, 669hp 1075ftlbs

  2. #2
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    More pressure will absolutely better atomize fuel and will also push more fuel out for the same given time. If running 180MPa is a concern you can upgrade fuel lines, PRV, the rail pressure sensor and rail. As a side note, stock 6.7 injectors flow a fair bit more than stock 5.9 injectors

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    Aside from having bad injectors I was able to get the 6.7 injectors running quite well in a 5.9. Never did finish getting them dialed right in though. To really make a difference in getting them running good you need access to parameters only available through user defined parameters and since HPT restricts what you can access through user defined parameters I?m not sure if HPT will allow accessing all you need

  4. #4
    It's my understanding that 6.7 injectors require more voltage as well as the 6.7 cp3. The voltage issue is what i understand keeps them from ever being able to be tuned properly.

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    I had no issue getting them tuned. Ran well for me with the right changes with a custom bin file. Was done on a 2005, all stock other than the 6.7 injectors

  6. #6
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    Im a light duty diesel tech and ive seen a lot less injector issues with 6.7 injectors than the 5.9. Reliability would be an improvement, and of course performance with the right tuning. Jim, you say they flow a fair bit more than 5.9, any idea what kind of power numbers stock 6.7 injectors can support in a 5.9?
    2004.5, built 48re, Fass lift pump, s364.5 with a s483 compounds, ARP studs, 103# valve springs, 110hp injectors, 669hp 1075ftlbs

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    Power level difference between the two I?m not exactly sure on

  8. #8
    Id definitely be interested in hearing more results and how you achieved them. I know the 6.7 injectors are much tougher and rarely fail.

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    The truck they were in had a failed FCA, stuck full open which means potential pressures higher than the stock rail pressure sensor reads, couple that with a 300 mile drive, the injectors took large abuse along with the cascade overflow valve and rail pressure relief valve. I replaced the cascade overflow valve and PRV and was able to get pressure building again in the high pressure fuel system, over the injectors did have a very slight leak to them. Running stock duration table and rail pressure for the 5.9 injectors but with the 6.7 injectors it was very smokey under load. With some interpolation I remapped the duration table to that from a 2008 6.7, cleaned the heavy smoke under load right up. Startup wasn?t super great along with idle. Took some reworking of the rail pressure correction tables, cranking timing and fueling and cranking rail pressure to get it smoother and starting up nicely. All sorts of injector voltage and current settings had to be changed along with some other combustion management parameters. Rolling on 35? Toyo Open Country M/T?s I was pulling in over 19mpg on highway driving with a NV5600 transmission. Most info you can find where people try 6.7 injectors in a 5.9 say mileage is worse and blah blah blah. Hell, I don?t think over 19mpg is worse with those kinds of tires. It ran smooth, started up good, good fuel mileage, pulled good although didn?t spend a whole lot of time in the upper end of the fueling, ran clean. Unfortunately injectors ended up sticking open and ended up wrecking the motor, coolant would very rapidly drain into the crankcase O.O