Why a governor

Discussion in 'Trucks [ Eighteen Wheelers ]' started by MustangPeterbilt, Aug 22, 2016.

  1. MustangPeterbilt

    MustangPeterbilt Bobtail Member

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    Hello. I understand the basics of a diesel engine, but one thing I don't get is why you need a governor in a diesel engine and not in a gasoline engine if in both you control the speed with the throttle and in both engines the load can change. Can someone help me understand this better.
     
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  3. Old Man

    Old Man Road Train Member

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    A governer is just a rpm limiter.
    Your gasoline car has one, just mash the pedal when in park and it will hit the limiter.
     
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  4. BoxCarKidd

    BoxCarKidd Road Train Member

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    You Tube Detroit Diesel run a way.
    We are talking Peterbilts here not Mustangs.
    The parts are large and the forces are also. A crankshaft turning a 4000 rpm has rods that go from 0 to 8000 and back to 0 and 8000 RPM speed each revolution. They can not stand it.
    Now are you talking engine speed or road speed?
     
  5. x1Heavy

    x1Heavy Road Train Member

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    Engine speeds must be governed to protect the engine.

    There is a top RPM in which a heavy truck Deseil will give you and no more than that.

    If you exceeded the RPMs willfully you stand a risk of having the crankshaft fail across most of, if not all... your main bearings surfaces which wil grenade your very expensive Truck engine which will probably have you buy the trucking company a replacement. 30K I think is the going rate for one.

    Car engines are gas same with pickup truck suvs etc those things rev higher but many new cars made today have a governor, and also a nanny speed limiter to take away everything you got at a certain speed.

    The only engines I recall working in my day which had a governor but did not really have one was the old Macks, those things would be turned over at 3200 RPM or higher. Burying the rig in 100+ while speeding.

    Many companies speed govern the trucks now and virtually all of them RPM Govern the engine.

    Engines have gotten much slower in the last 40 years or so in which I can recall. Such as top RPM 2300, then 2150 and some lower to around 1950 or even less. You really only shift between say ... 1250 and 1500 tops.
     
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  6. peterd

    peterd Medium Load Member

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    Without a governor a diesel engine will just continue increasing RPM's till it blows up. I was a diesel mechanic before I started driving a truck.
     
  7. Diesel Dave

    Diesel Dave Last Few of the OUTLAWS

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    What about those tractors trucks they use for sled pulling, those turn some pretty high rpm's, @SmokinCAT has a Cummins that sees pretty high revs....
     
  8. peterd

    peterd Medium Load Member

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    They would still have a governor. The governors can be set at higher RPMs. 30 years ago the company I worked for used to go to the truck drag races once a year. We used to enter a cabover Freightliner with an 8V71 Detroit Diesel that I had installed N80 injectors with the RPM opened up to 3200 RPM. The truck was doing the 1/4 mile in under 18 seconds.
     
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  9. Majestic 670

    Majestic 670 Heavy Load Member

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    2150 in the Pete Caterpilla tops...,Bubba
     
  10. SmokinCAT

    SmokinCAT Road Train Member

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    When a diesel governors out at set throttle point or max rpm it pulls fuel, when load returns it compensates without additional throttle.

    Not sure why this is a big issue?
     
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  11. DustyRoad

    DustyRoad Road Train Member

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    ECM Governors manage the dynamic power rating of torque and horsepower associated wth RPM. Two main functions are to boost the power range in low gears and control top speed in high gears by limiting rpms.

    Modern engines are digitally controlled by a microprocessor for maximum performance. The performances are engine load specification for power, for off road or fuel economy, for highway. Truck engines are tuned via a ECM, that allows user settings based on what the owners prefer. Typically the transmission plays a role in the configuration of speed limiters using sensors through communication data links.

    With autos....the factory sets the performance rating to meet guidelines set by CAFE.

    CAFE @ http://www.ucsusa.org/clean-vehicles/fuel-efficiency/fuel-economy-basics.html#.V7vieU4pDxA

    Most modifications outside of a dealer will void the warranty on smartway certified engines.

    Add to that, the codes to do a upgrade at a dealer must come from a password protected download site managed by the factory technical support group.

    Cummins has many engine configurations ranging from 375 hp to 650 hp....a dealer can spec a truck for heavy haul, off road or highwsy use.


    10-4 good buddy.....
     
    Last edited: Aug 23, 2016
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