Governors

[Bob_Young]

This is NOT a Pataki rant! /forums/images/graemlins/grin.gif

I seem to recall from my days as a Johnnypopper pilot, that all the gasoline powered tractors I operated had operator throttles that controlled a governor setting. You would set a no load engine speed with with the hand throttle and then the governor would manage the engine throttle in an attempt to maintain engine speed under load. In other words, as the engine bogged down under load the governor would open the throttle on the carburetor to restore RPM.

It was the way tractors worked back then. The upshot was when the engine really did bog down, and you gave it more throttle, you didn't get a whole lot more for your input as the governor already had the engine throttle open in an effort keep things moving.

Running the L4300 and the Ford 4000 diesels, it's dawned on me that they don't act like governed engines. When they bog down under load, there's more power to be had, usually much more, simply by opening the throttle.

Diesels, besides having alot of low-end torque, seem to have a natural resistance to losing RPM. Actually the two go hand-in-hand. It appears this property of diesels permits them to work well in tractors without need of a governor. Anyone know if this is the case or are the diesels governed too?
Bob

 

[Morgan1952]

Bob,
I can't speak for all diesel engines, but, I believe that they all have a Governor. I know that my Kioti does. It works pretty much the same as you described. It is based on engine RPM and attemps to maintain a constant engine speed by adjusting the fuel flow.
Bob

 

[Egon]

Think you will find that almost all tractor engines wether gas or diesel have a govenor. In many cases a set speed is very critical to the farm operation. A govenor will allow this.

It also means the operator does not have to keep an appendage constantly on a speed controlling device as is done with a car unless cruise control is being used.

Any operation requiring steady state operation under varying load requirements will require some form of fuel control.

Egon /forums/images/graemlins/grin.gif

 

[SnowRidge]

The "throttle" on a diesel is actually an RPM request control. The governor controls the amount of fuel injected into the cylinders so that the engine speed matches that of the "throttle" setting. As the load on the engine varies, the governor increases of decreases the amount of fuel injected in order to keep the RPM constant.

Gasoline engines on power equipment (tractors, lawn mowers, pumps, generators, etc.) work the same way, except that the governor controls the real throttle--usually a carburetor's butterfly plate.

Like anything else, there may be some exceptions to the above, but in general, that is how it works.

 

[Bob_Young]

OK, what everyone's said in response makes sense. BUT why, when RPM has dropped on a diesel due to a heavy load (I'm thinking PTO operated implement primarily, but have seen it pulling a plow too), is it possible to bring the RPM back up by opening the throttle? You'd think that if it's possible to do this, the governor would already have done it.

Has it got something to do with the governor's response range?
Bob