question on nebraska test results

[Roto]

I am looking at the test for tc55 for example and it says 48 HP at 2700 rpm's and 42 hp at 2800 rpm and 11 hp at 2938. whay does Hp go down with higher rpm and gal/hr goes down. why dont they go up? It seems backwards form what it should be.


Mike

 

[daTeacha]

Engines are designed to maximize torque and/or hp at whatever rpm the engineers anticipate the tractor being run at for a particular use. Usually, the torque maximizes at a good pulling rpm and the hp at a good PTO rpm. Exactly how they accomplish it varies, but involves compression ratios, fuel flow, intake and exhaust flow dynamics, internal friction in the engine, and a bunch of other stuff that others are far more qualified to address than I am.

 

[whitetiger]

I am looking at the test for tc55 for example and it says 48 HP at 2700 rpm's and 42 hp at 2800 rpm and 11 hp at 2938. whay does Hp go down with higher rpm and gal/hr goes down. why dont they go up? It seems backwards form what it should be.


Mike

High idle for this tractor is 2950 ERPM with no load on the PTO. When the dynometer load is increased, it takes 11 HP load on the PTO to pull the engine down 12 ERPM to 2938 ERPM simulating a light load.