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motor order

motor order

motor order


Somebody could help to understand the motor order?

Thank you so much.



Quelqu`un pourrait m`aider a comprendre l`ordre du moteur.


Escola Politécnica
Universidade de São Paulo

RE: motor order

If you mean first engine order as related to harmonic vibrations, then it is simply the cyclic frequency of the crankshaft.  

For example, something that happens with a frequency w=(engine order 2) has a frequency of 2*engine speed, and thus happens twice for every rotation of the crankshaft.

RE: motor order

There is a lazy shorthand we use to describe speeds and vibrations throughout the car, based on ivymike's explanation. Typically we use E for crankshaft speed, D for driveshaft speed, and W for wheel speed.  Then the camshaft turns at 0.5E, the pistons cause 2E 4E etc due to short conrods, tyre out of balance causes 1W, diff whine would be at 13D, UJs cause 2D 4D etc. The astute engineer will notice that there is a fixed ratio between these different speeds, in many circumstances.  

The rule of thumb on a 4 stroke is that if there is a half in the vibration (eg 3.5E) then it is usually to do with cylinder to cylinder variation in the firing process, or inertial stuff from the valvetrain. Typical causes are flexibility in long shafts causing timing errors or resonances. For instance, the camshaft in an I6 causes 1.5 order in the combustion process, because each cam is effectively delayed as you go down the camshaft away from the gear. The solution in that case is obvious, of course.


Greg Locock

RE: motor order

Thanks Greg and ivymike, thank you very very much.

Best regards from Brazil


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