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Fuel tuning c8.3 p7100 F800

Discussion in 'Trucks' started by John V, Aug 28, 2021.

  1. John V

    John V Well-Known Member

    Joined:
    Jun 25, 2019
    Messages:
    83
    Location:
    North Carolina
    Hey, does anyone have experience fuel tuning a cummins 8.3 with a p7100 injection pump? Interested in modest power gains, but I also don't want to break my driveline. It's in a 1995 F800 with a FS6206A eaton roadranger (nominally rated to 600ft-lb) and a meritor RS-21-230 two speed axle. The cummins is factory rated to 210hp (not sure on torque). It'd be great to see what an extra 30-50hp feels like climbing these western north carolina hills loaded with logs.
     
  2. Delmer

    Delmer Senior Member

    Joined:
    Jan 4, 2013
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    WI
    Easy enough to look up the procedure online. Same pump as lusted after by the older Cummings diesel Dodge crowd, and you can turn the pump the same way they do with the same results.
     
    DB2 likes this.
  3. Birken Vogt

    Birken Vogt Charter Member

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    Location:
    Grass Valley, Ca
    I'd be more concerned about melting the little engine down. Acceleration from stop lights is one thing, grinding up a hill loaded is something else. My general advice is to leave it stock and make profit to buy a bigger truck later. The minutes you save climbing a hill (it goes just as fast everywhere but hill climbing) are not likely to be worth it if you break the engine.

    That being said, if somebody can figure out the CPL on this engine, it might be capable of more horsepower in its current configuration or by changing some hard parts. But the pistons are likely to be a limiting factor. Cummins built it like they did for a reason.
     
  4. mekanik

    mekanik Well-Known Member

    Joined:
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    Location:
    Canada's Northwest
    I used to work on Cummins 8.3 Marine engines for a water taxi company.
    They were rated at 350HP. Head gasket coolant leaks and piston failures
    were ongoing. Three boats one with twin engines kept me busy.

    To time the pump on a high HP engine you need a pressure pump to spill time it.
    The #1 injector is removed and TDC is verified with a dial indicator. I used a
    degree wheel attached to the damper with magnets. Fuel is pumped into the
    fuel pump inlet at approximately 300PSI A short piece of fuel line is put on the
    #1 fuel pump delivery port. Fuel will squirt from the line into a container. Back
    the engine up about 45 degrees or more BTDC and slowly bar it in direction of rotation
    as you reach the timing spec on the data plate the fuel from the injector line
    should slow to drip every few seconds.

    I used to retard the timing on them 2 degrees to clean up some of the smoke at idle
    and when cold.
     
    Truck Shop likes this.
  5. Truck Shop

    Truck Shop Senior Member

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    Max factory hp settings I've seen {Ford L8000 series/ FL 70 Freightliner with 8.3 is 250 hp.} for on highway.
     
  6. Birken Vogt

    Birken Vogt Charter Member

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    Grass Valley, Ca
    I've seen Ford 7.8s that were 270 HP. I don't know about mechanical 8.3s but electronic ISC 8.3s could go a bit over 300 HP and run very reliably. But it all depends on the CPL of that particular engine I think.
     
    Truck Shop likes this.
  7. Truck Shop

    Truck Shop Senior Member

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    I think it really boils down to what the engine is spec'ed for. Most common fleet engines
    hang in the 250 hp range. Plus special options.
     
  8. Bluox

    Bluox Senior Member

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    Jun 20, 2010
    Messages:
    1,427
    Location:
    WA state
    When you go over 250 hp there are internal changes pistons, injection oil cooler and so forth .
    The big problem is cooling on larger hp motors.
    Then there is the problem getting a pump shop to turn up a pump they won't set them up different than the pump tag.
    the mechanical truck engines ran up to 330 hp for fire trucks but they smoked when cold.
    Bob
     
  9. thepumpguysc

    thepumpguysc Senior Member

    Joined:
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    Occupation:
    Master Inj.Pump rebuilder
    Location:
    Sunny South Carolina
    I’ve done it a GAZILLION TIMES both on and off the test stand but I wouldn’t venture to explain it to someone..
     
    Coaldust and Truck Shop like this.
  10. John C.

    John C. Senior Member

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    Location:
    Northwest
    Maximum horsepower ratings are dependent on duty cycle types. A truck engine has intermittent full power runs while a genset can have 100% loads for long periods of time while a main propulsion boat engine can have a high horsepower but a very low duty cycle. When I was working on engines a lot, I would put the output as close to the maximum factory rating as possible. If the customer wanted more, he signed a piece of paper acknowledging his desire and the possible ramifications of that. The factories generally set the output in the middle or lower on the range. The rebuild guys with access to a dyno usually set the screws at the low end of the range and many times I would get told to go and adjust it. If they didn't have access to a dyno, it was almost always low. Keep in mind this was mostly on dozers and wheel loaders where good operators could tell when something wasn't pulling proper by the gear that they were in.
     
  11. gwhammy

    gwhammy Senior Member

    Joined:
    Nov 21, 2013
    Messages:
    362
    Location:
    missouri
    Put an exhaust temp gauge in it. On the 5.9 you really want to keep 1200 or under pulling. I do timing by pinning the pump and using a degree wheel on the crank. I've seen 8.3's in tandems do fairly good with the right trans and gears.
     
  12. Coaldust

    Coaldust Senior Member

    Joined:
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    Cargo Tanks, ULSD, RUG, Methanol, LPG
    Location:
    North of the 60
    John V has a cool old Ford.
    It’s looking pretty cool!
    Juicing up his pump.
    Let that turbo spool!
     
    John V likes this.