Thumper3

Please tell me what alloy they use that reverses what you have stated previously. There is a difference between a different RATE of expansion and REVERSE expansion.

You stated that the metal shrinks when cold and expands when hot in our engines, claiming the "gaps" are what cause damage to the engine. Assuming that the alloys in the F1 cars are different and expand at a different RATE, that still does not change the fact that they must EXPAND from heat, and if they are already seized when cold, how do they expand and then move? If you stop and examine what you are saying you would be able to see the flaw.


Again, I have no idea what science class you took in school. Claiming that a fluid will flow at EXACTLY the same rate at temperatures hundreds of degrees apart because it is "designed" to work at those temperatures is incredibly illogical. Yes, it will work (flow) at those temperatures, that does not mean that the laws of thermodynamics and fluid dynamics has been changed. There certainly is an issue of having too much flow (although your example actually goes toward viscosity and breakdown, but hey) but that has no bearing on what we are talking about. Let's stay within the discussion before casting about wildly.

Since we are talking about a fluid at 0 degrees in the real world and at 100+ degrees in the real world we should examine that fluid in THOSE conditions to prove our point shouldn't we?

The simple laws of physics state that a thicker fluid, as you said, will need more energy to flow, since the oil pump is not variable speed based on cold (and is still limited by the lines and channels used to transfer it) it will take longer to flow the oil at a thicker viscosity (when cold) then when thinner. This extra time is when the poorly lubricated engine is damaged.

It does not matter if you understand or except oil viscosity, the universes will enforce it just the same.

Joe85STi

http://www.reizendemoke.be/techniek/...e/conrodgt.gif

Please reference 3 and 4 in the picture. These are the rod bearings which connect the pistons to the crank shaft. Because F1 cars rev so high, these bearings have a much tighter tolerance and are also made of different alloys than the crankshaft itself. When these bearings cool and shrink, they get smaller and grab onto the crankshaft. Could also be cylinder sleeves shrinking more than the Pistons. The whole point, is metal expands when warmed, agreed?


I didn't say the flow would be the same, I am saying the decrease in flow is negligible at those temperatures. It has been thoroughly tested by engine manufacturers as well as oil companies. The flow rate of our oil at 0° is more than ample to provide protection.

Another consideration I haven't brought up is carbon buildup. Our engines being direct injection are very susceptible to carbon build up. The way the engineers at audi have tried to limit it is by having the engine run a little hotter than normal in an attempt to burn the carbon off before it has a chance to solidify. The longer you keep the engine running cold, the more carbon gets caked up.

StumpJumper

-7f here this morning

damned right I warmed up my car

m444

46F here this morning. Car in garage at 55F, warmup 30 to 45 seconds. Depends on your situation and local Temp.

moto-one

FYI; Oil pumps are a positive type pumps and flow the same volume at any temp. There is an increased load on the motor to drive the pump at thicker viscosity. There are pressure relief valves and thermal control valving that also control the flow. The faster the flow rate of the oil the more heat is extracted (doesn't matter if it's 5w or 50w). The galley design with in the engine and where it start it's flow and finishes has a lot to do with how a motor is meet to warm and control an even expansion rate of all parts (moving and stationary or fixed) Now the coolant is a different but same idea only most coolant pumps are centrical pump, unless you have an electric thermostat control pump. (Audi does not use them)

Mark.



Mark.

tna3

Even in the coldest weather in Boston by the time I pull out of the driveway on to the road the car is idling below 1k. I prefer not to waste gas idling in the garage. I just shift below 2k rpms for the first 2 miles or so then drive normal. I won't race the engine until the temp needle is about half way. This is probably the happy middle between the extremes of opinions found in this post. You definitely pay at the pump for cold idling. The big brother comment is silly.

Joe85STi

You've got to remember also that the cold start, car idling at 1500 rpm for 10 seconds, has nothing to do with warming the engine, it does that to warm the catalytic converter, that's it, strictly for emissions. If you get a tune, you can get that feature disabled.

Tna3, I hope you're not "racing" your engine right when the coolent temp gets to the middle. When the coolent gets to temp, the engine oil is still not close to being warmed up yet. I'd suggest you find someone near you with a vag-com and enable the oil temp display.

In the dead of winter, when my coolent temp gets to the middle, the oil temp isn't even registering yet, doesn't start reading until it's above 140°. I wait until it gets above 180° before I start revving above 3k, which takes another 10 minutes after coolent gets up.