Should i sell my brand new 389

Discussion in 'Ask An Owner Operator' started by kay_ray, Dec 11, 2021.

  1. roundhouse

    roundhouse Road Train Member

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    Technically yes ,
    Because when the pump governor reaches its limit , it reduces the fuel available to the injectors .

    every mechanical injected diesel that came from the factory with a warranty, had an RPM limiting governor in the injection pump .

    most were set around 1800 rpm or so
    I owned a couple of trucks where the pump had been rebuilt and the govonor removed before I bought it
    But there’s really no point in removing it .
    With a 14 or 16 liter diesel , anything above 1900 just damages the engine .
     
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  3. shooter19802003

    shooter19802003 Road Train Member

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    Correct, but that changes upon conditions, so you aren't governing the speed. Your governing power delivery.
     
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  4. Getsinyourblood

    Getsinyourblood Road Train Member

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    These kinds of stories are a sign of things to come. Inflation.
     
  5. shooter19802003

    shooter19802003 Road Train Member

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    It's not technically.....thats how it works. Which was the original point. Which is why I asked the question I did. How did you govern it at a speed. Well, it wasn't. That was just were it tended to settle with the loads that were pulled. I'm just keeping it in context of the original question.
     
  6. Oxbow

    Oxbow Road Train Member

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    The governor restricts engine RPM, not speed. Generator set diesels have governors. I don't think speed is an issue with them. Speed limiters are not governors.
     
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  7. roundhouse

    roundhouse Road Train Member

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    All true
    The mechanical pump has no idea of your road speed in miles per hour ,
    All the govonor cares about is the engine rpm .

    when you go up a hill with your foot in it , once the engine rpm drops below the govonor set level , it resumes 100% fuel, so you get full power.

    your lawn mower has the exact
    Same setup , when you shove the throttle lever to full speed, with no load on it , the engine doesn’t over rev and explode .
    The engine revs to the govonered speed and stays there .
    If you hit some heavy grass, and the rpm drops , then you get full power , but as soon as the engine rpm gets back to the govonored limit , it cuts back on the fuel to prevent the engine from revving to the moon and destroying the engine .

    road speed is variable based on many conditions , wind , hills, cargo weight , and most of all , transmission and axle ratio and tire diameter .

    the engine didn’t know and didn’t care about the road speed . All it cared about was not going above the rpm
    Limit that was dialed into the weights on the pump.

    Most older cars with distributors used weights to control the spark timing advance .

    a mechanical injection pump used the same thing . the faster it spins the further the weights sling out , the further out the sling , the less fuel you get injected .

    the big cam Cummins used the oil pressure to advance the injection timing .
    You’d adjust the injection timing at idle and then adjust how much advance you wanted and the advance was just accomplished by the oil pressure moving the pump timing selector .
     
  8. roundhouse

    roundhouse Road Train Member

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    Lawn mowers are
    The same way

    the available power is not limited by the govonor , just the top speed of the ENGINE

    same with the mechanical diesels
    The top speed of the truck isn’t what the govonor Cares about ,

    it’s the top rpm of the engine that’s controlled . To prevent engine damage .
     
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  9. SmallPackage

    SmallPackage Road Train Member

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    Fuel pump Governors work exactly like @woreout and @Oxbow say. The Cummins PT pump governor was arguably the most simpliest and easiest to “hotrod” of them all.
    That being said you can govern speed by both engine rpms through the fuel pump and overall gear ratios to the rear wheels. Due to extrememly low gears My ‘51 Diamond T is governed at 58 mph at stock set 2100 engine rpm yet the engine can still run at its “hotrodded” governed 2400 rpm. It is purely mechanical and the engine has plenty of steam just not enough leg. In that extra 300 rpm It will not go any faster due to being what is called “gear bound”. But technically I guess that could still be considered just a mechanical speed limiter.
    0D542514-8CEF-4C53-9404-AC4183FB0265.jpeg
    Factory speed governors/limiters in a sense were back in the ancient times too. Lol!
     
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  10. roundhouse

    roundhouse Road Train Member

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    Pics of the diamond T ???
     
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  11. SmallPackage

    SmallPackage Road Train Member

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    E8377A17-BEA3-45B7-9613-9AF63FC6B5AC.jpeg
    This was a few years ago when we drug it out of the barn to start playing with it again. Laying down cardboard boxes and ready to polish the hood and aluminum bumper, radiator, and wheels.
     
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