Cowhorn

Is it necessary to wait for the water temp to reach a certain point, or is it more important to allow the oil to reach a certain temp before pushing the rpm's above 4K to 5K?

Phil G.

I've heard and read that 180 should be your target prior to revving >4K RPM.

Dro

i believe the oil temp is what is important.

99firehawk

full warm up is 180, oil and coolant temp should be pretty lineaer as the engine is the same temperature all over. Your goal is to have the engine at opeating temperature so all the metal is hot and fully expanded.

Mike Murphy

Jim, as you know, the air-cooled cars don't get any warmer than 170F in sub freezing temperatures. So I consider 170F "warmed up." In the other 3 seasons, the engine will run much warmer, between 190-220F.

In any case, I keep the revs below 4,000 and the throttle less than 50% until at least 170F and 10 minutes of driving. I think it's important to have not just the oil and water up to temperature, but also the heads and block up to temp as well. Full throttle at RPMs under 4000 can still produce maximum heat and I don't want my valves, heads, piston pins and rod bolts to be shocked with a sudden increase in temperature.

Porsche_Smile

i wait until i see the needle at 90 degree.......then it let it rip.....

OCBen

Incorrect.

Oil temperature is always hotter than coolant temperature when the engine is fully warmed up.

It is best to allow the engine to fully warm up before letting 'er rip. That means going by the oil temperature, waiting until it reaches operating temperature.

At normal operating temperatures, the oil temp gauge is pointing at the 9 o'clock position (~ 220 F) and the coolant temp at the 12 o'clock position (~175 F), generally speaking.

99firehawk

linear manes that they will follow the same plot, when the coolant is at opearting temperature the oil will also be at opeatring temperature. the temperatures will be diffrent i never said they would be the same

gpjli2

I always use oil temp>180 deg and then progressively ramp it up.

OCBen

Not sure what you're trying to say there but if you're trying to say that the rise in temperature is linear, then that's clearly incorrect.

Without getting too technical here, when an engine warms up (or any object subject to thermal conduction, for that mattter) it undergoes a transient heat transfer thermal conduction phase before reaching steady-state temperature conditions. During this transient phase temperatures rise quickly, then more slowly as the steady-state temperature is asymptotically approached. On a plot of Temp vs Time, it has the same appearance as Voltage vs Time for an electrical capacitor in an RC circuit during the charging phase.

The opposite is true of an object losing heat during a transient heat transfer condition. The temperature drops quickly and then tapers down asymptotically until it reaches its steady-state temperature.

But in neither case is the temperature changely linearly. In fact, it is exponential in function, based on the exponential function e (e = 2.71828). There is nothing linear going on anywhere during this time.

Also, contrary to what you were saying, the temperatures are not the same throughout an engine in steady-state. The cylinder temperatures are obviously the hottest temps and the water jacket temps at the inlet feed from the radiator are the coolest.

GeoMedic

Parallel follows "the same plot", with minor variants for "dependent" on or "correlated" to that would show different final temps.
Linear means a straight line non-curving line.
Heat transfer certainly is not linear as the rate of change is dependent upon material and gradient... but I think we all see what is trying to be said.

OCBen

Yes, and that would be the temperature gradient across the interface of the two materials exchanging heat.

What it really boils down to (no pun intended) is that the coolant reaches operating temperature within minutes, whereas the oil temperature takes a while longer to reach operating temp, as everyone here has observed for themselves.

And so to answer the original poster's question (if it hasn't already been beaten to death) the engine is considered warm (or at operating temperature) when the oil temp is at operating temp.

Paul S.

At least on my Club Coupe, this is not true. The water temperature rises much faster than the oil temperature. Depending on ambient temperatures, it can take me nearly 10 miles before the oil temperature reading is up to normal operating (fully warm) temperature. The coolant usually gets up to 175-180 in a few miles.

Mike Murphy

Good idea. Because even when the engine is supposedly fully warmed up, the engine will still cycle through a given heat range, depending on load and RPM. An engine just cruising at 40mph at part throttle will be colder than one a full throttle. This can happen even with the engine water temp showing a constant 180F. So the point is, you don't want to shock the engine with high transients of temperature change. Even when fully warmed up, the gas pedal shouldn't suddenly go from 20% to 100%. I prefer a gradual change of increasing RPM and throttle position.