Warm Up

[F6L913]

Hello everybody.

How many time do you warm up the tractor, combine,... engine before work?
Abd after a hard work, do you wait 5 or 6 minutes to "breath" the engine?

Nedd the modern transmission a warm up before high load?

[kenjar]

Hey F6L913,

I always let mine run for awhile before putting it to work, especially during the winter months.
Most operator manuals recomend letting turbocharged engines cool down prior to shutting them off.

[eppie]

I never pull the throtttle open to high rpm when i just started the engine. I let it warm up to at least 60 C before putting it to work, and 70 C before i use the maximum performance of our engines.

Warming up engines is very important.
The crankshaft bearings are slide bearings. Slide bearings dont use bullets or pins to roll over, but the oil prevents the both bearing rings from metal surface contact. When the engine oil is cold, it is thick, and it will not reach all engine parts. The principle of an oil lubricated slide bearing is hydrodynamic lubrication. It uses the same principle as waterskiing. The speed has to be high enough to reach the level of floating.

When I just have started, I dont run high revs. The oil flow has to start up, in order to reach the head and that takes about 10 seconds, depending on the viscosity of the oil, and how worn the bearings are.

Besides, a Diesel has high compression and combustion pressures, up to 40 bar. Gasoline fueled Otto engines have pressures to 20 bar, due to lower compression ratio. This means a Diesel is quite heavy constructed. The pistons are since the second world war, all made of alumina. Alumina grows more, when heated, than normal steel. All this means that you have to warm up your engine slowly, so that the heat is distributed through the whole engine. Then, you reduce the risk of cylinder and head cracks due to internal material tension. This tension is caused by heat, what makes the material shrink or expand unevenly if there is a temperature difference over the piece of material.

Turbo engines mostly have hotter engine oil. The turbocharger runs at about 15,000 rpm max. When the engine just starts, it takes some time for the oil to reach the turbo bearings, since it is high mounted, and lubrication is extremely important for parts with such a high speed. Letting your turbo engine cool before you stop it, reduces also risk of cracks because of higher engine temperature, and when the oil cools, it's getting thicker, and it wont drain to the motor carter so quickly. so when you start it again, there will be more oil left in the turbo.

About the tranny: I think not. It uses roller bearings, so the right oil conditions are less important. I think overheating of tranny oil is more harmful than cold oil, ince hot oil is thinner than cold, so the camwheels can 'wear through' the oil film. This problem will be strongest in Vario transmissions.

Good Goan, Renze

[leemsutton]

Le tit idle for up to 5 mins before i even move it generally, although sometimes you cant do that and I notice that our Case 5150's are useless until they warm up.

Cooling down - about 3 mins to let the turbo slow down etc.

Lee

[Laapa]

I have noticed in the past how som epowershift-transmissions on large tractors are very heavy to operate if not given a sufficient warm-up.