Warm Up Time / Oil Temp - When is it ok to cut loose?

[REXman]

Just before you give up, as I am not really fussed what people do with their engines either. But I must correct something your said earlier:
Aircraft engines are not under full load straight away? Prudent pilots warm their engines up. Apart from common sense, owing to there being more at stake, manufacturers require them to do so. I am yet to meet a pilot who starts an aircraft engine from cold and immediately subjects it to full power. It is just not the done thing.

Correct, my GF's brother is a pilot for qantas and he concurs, 'captain. Once your at altitude your cruising also.

PS warming up a car is a good thing. I have warmed up every "street" car I have had, heavily modified engines over 420HP as well as stock cars with just a TMIC, tune and TBE, pushed them hard, but all I ever did was service them well, and warm them up, and NEVER had a problem.

My girlfriend, dad and sister dont warm up there cars.. and they have 20000km, 45000km and 85000km on there cars. And in both the last cars - You can tell cause they now sound pretty of beat.

Where my old MY03 WRX I had for nearly 5.5 years - 70K clicks on it and it purred and thats a SuBie...

Pressure is good, sure, but the oils need to be warm before they operate properly and the properties are realised. And easying on a cold motor is the way.. I dont do it any other way. Some of those photos of other non related cars people put up on the net are just silly.

Where are they from? What really happened? How old are those motors? What are the real causes?

I can say one thing, It aint from warming up.

[Beaker]

I give up. If you guys won't listen to an extremely knowledgable person, WITH credentials (Transporter) and are still arguing, there's no hope for you.

It's your car, so i don't really care. I doubt i'll be buying it off you second hand. The only reason most people know anything about cars is the internet, and some of them seem to think that the little they've read (and pretend to understand) makes them an expert.

Good luck to you.


Oh, and FYI, as a hole heats up, it expands, it doesn't contract. So your crank journal to big end analogy doesn't work, Beaker. If the rod gets hotter than the crank, the clearance increases, not decreases. And there are no "simple" physics in an internal combustion engine, mate. Believe me.

Yeah I guess. 20 years building rally engines, what would I know?

Aircraft engines are always warmed up on the ground, a miss on take off can kill you, a pilot who doesn't warm engines up before take off has a death wish, in addition Aircraft engines have strict hour limits after which they MUST be stripped down and rebuilt. The piston engines used in aircraft are, as a general rule, also much less advanced then modern car engines, a mate flies a reasonably modern plane with a 4 cyl 5L pushrod/OHV Lycoming engine that makes a huge 160hp - hardly what you'd call pushing the envelope of performance. If anything aircraft engines have less in common with a Golf engine then the F1 example used earlier. The example I gave earlier with a big end is exactly the point. When you put a liquid under pressure between two surfaces close together it spreads out and holds those two surfaces apart, if you hold those surfaces a long way apart and squirt a liquid between them it simply flows out along the route of least resistance, by doing that it can't hold the surfaces apart effectivley.


That IS basic physics (surface tension of liquids + thermal expansion of metals)

I won't argue any further as everyone applies their own knowledge to any problem presented and make their own descisions on what to accept as correct, but it's always a mistake to presume the knowledge of others.

[gerhard]

I always like to have my engine nicely warmed up before caning it. I don't mean oil and water, I mean all the metals.

I've lost count of the number of cold siezes I've seen on the kart track - bozos leave the pits with a cold engine and hit anything from 10,000 to 18000rpm (depending on engine type) by the first corner. Most of these engines have 4 studs holding the head to the barrel to the crankcase, and when they seize you can see the 4 marks on the piston where uneven thermal expansion has caused friction and terminal seizure.

[HPSOV]

There is no requirement to warm up the engine on a jet aircraft because they are turbine engines. A completely different scenario to piston. On piston aircraft you MUST wait for the oil temp the get into the green band on the gauge prior to takeoff.

[pologti18t]

I always like to have my engine nicely warmed up before caning it. I don't mean oil and water, I mean all the metals.

I've lost count of the number of cold siezes I've seen on the kart track - bozos leave the pits with a cold engine and hit anything from 10,000 to 18000rpm (depending on engine type) by the first corner. Most of these engines have 4 studs holding the head to the barrel to the crankcase, and when they seize you can see the 4 marks on the piston where uneven thermal expansion has caused friction and terminal seizure.

But thats a 2 stroke engine. They can seize when they overheat as well
Not sure what the relevance is to a 4 stroke engine with a sump full of oil.

[logger]

There is no requirement to warm up the engine on a jet aircraft because they are turbine engines. A completely different scenario to piston. On piston aircraft you MUST wait for the oil temp the get into the green band on the gauge prior to takeoff.

Nah mate. you should know better than that.

RB211 Engine warm up requirements (before takeoff)
-when engine has been shut down for more than 1.5 hours: run engine for at least 5 minutes
-when engine has been shut down for less than 1.5 hours: run engine for at least 3 minutes
-use a thrust setting normally used for taxi operations
-engine oil temp must be above the lower amber band before takeoff

I know from experience that with cold turbine engines in cold ambient conditions you can get oil filter bypass activating until the eng oil warms up. Of course some operators may not choose to apply the manufacturers recommendations

[gerhard]

The relevance is the rate of expansion of the piston comared to the metal around it.

2 stroke vs 4 stroke is no different in that regard, a sump full of oil vs oil in the fuel is also a non-issue.

Yes it's probably more dramatically evident in a 2 stroke that can rev to 22,000, but the fact is the pisron expands faster than the surrounding metal. Just like in your 4 stroke with a sump full of oil that only revs to 7000 or so, which can also destroy itself when overheated.

[Transporter]

When you put a liquid under pressure between two surfaces close together it spreads out and holds those two surfaces apart, if you hold those surfaces a long way apart and squirt a liquid between them it simply flows out along the route of least resistance, by doing that it can't hold the surfaces apart effectively.


That IS basic physics (surface tension of liquids + thermal expansion of metals)

I won't argue any further as everyone applies their own knowledge to any problem presented and make their own decisions on what to accept as correct, but it's always a mistake to presume the knowledge of others.

Hmm..., for that occasion we have additives in the oil.

Besides, everyone of us is warming up engine properly, anyone who drives on public roads is warming up engine in the way that is sufficient for the engine to last looooong time, unless he really stole the car. Just as well that we're in Australia, I can't imagine guys for how long I would have to be warming that engine up during winter in country like Canada?



I suppose that every one of us has different perception to what does it mean to drive gently or fast from cold.

[dave_r]

If you spend $45K on a car, drive it how you like, but anyone who thinks it isn't damaging it to flog it cold is kidding themselves.

I will do what I like as I have on all my previous cars, but after a start up in the garage, backing out, leaving the court and getting around a few corners, its plenty ready for a thrashing. Just avoid me on carsales if it's an issue.

I've lost count of the number of cold siezes I've seen on the kart track - bozos leave the pits with a cold engine and hit anything from 10,000 to 18000rpm (depending on engine type) by the first corner.

I never thrashed my watercooled rotax until it was at the right temp, but not the same thing as a Golf engine!

[gerhard]

I never thrashed my watercooled rotax until it was at the right temp, but not the same thing as a Golf engine!

Same here - the Rotax stayed below 10,500 until it was warm enough - at Oakleigh about 2 laps was enough. Still a lot of revs, but the nikasil barrel coating and the relatively slow revving rotax helped prevent those engines from seizing. The RESA was probably the worst for cold-seizing but gave more thrills than the Rotax Max. The Rotax would stop accellerating by DPE corner, whereas the RESA kept going till time to brake

Different to the Golf engine - I still say no different. Theyre both piston in bore compression engines which get hot when running.

Another reason not to thrash when too cold is the mixture the ECU feeds in - even though the GTI runs pretty rich AFR all the time, it still runs richer when cold. This provides more unburnt petrol to wash that oil off the side of the bores.