bazhart
Barcelona
- Joined
- 20 May 2009
- Messages
- 1,343
Good question and interesting answers - and nice to know some people are interested in the longevity of their cars - but the most important thing is not the coolant or oil temperature but the temperature of the internal engine components and their effect on expansion rates and running clearances.
True the oil temperature guage will give a clue when the engine is not hot enough for spirited driving - but if you drive relativley carefully until you see it reach the top temperature and then screw it - the internals will receive shock expansion and incorrect clearances for a while which endanger long life and performance. Pistons (for example) expand and only reach the right shape after gradual temperature rises. If they are suddenly subjected to a change of driver aggresion/mood they initially provide too much piston clearance for the increased gas pressure and "blow by" increasing surface oil temperatures and increasing friction, thrust loads and wear - potentially seizing a piston.
These issues you may regard as thermal stress and the engine will perform best when they are all at the right temparature which takes at least 20 minutes of gradually increasing the amount of throttle you are using and the revs the engine is reaching.
Setting off modestly from cold and over 5 minutes gradually increasing throttle and revs is good, but equally never sudddenly decide to turn into a F1 driver in an instant or you will shorten the life of the engine - instead react as if you are learning a circuit, gradually increasing the throttle and revs over a period of what would be on the track say 5 laps or perhaps 10 miles on the road. This is one of the reason racing engines have quite short lives because you do not get the opportunity to properly warm them up during a "warm up lap" before exposing the engine to rapid temperature rises.
The consequences of not doing it gradually enough are, castings cracks, premature piston wear, poor gasket sealing and potential failures etc.
Anyone who has had the experience of enjoying a spirited road drive for perhaps a couple of hours (say through Scotland or to Le Mans etc) may have noticed how very quiet the engines become after about 45 - 60 minutes and this is when finally the whole package has reached the best sizes and running temperatures from quite fast road work over a long period.
Most owners will adopt the attitude that it doesn't matter to them because it will still outlast their ownership and it is a future owner who will experience the resulting problems - but as internals become more critically designed for light weight, and good ecconomy with performance - those limits are often reached sooner than expected if owners couldn't care less about their engines.
Baz
True the oil temperature guage will give a clue when the engine is not hot enough for spirited driving - but if you drive relativley carefully until you see it reach the top temperature and then screw it - the internals will receive shock expansion and incorrect clearances for a while which endanger long life and performance. Pistons (for example) expand and only reach the right shape after gradual temperature rises. If they are suddenly subjected to a change of driver aggresion/mood they initially provide too much piston clearance for the increased gas pressure and "blow by" increasing surface oil temperatures and increasing friction, thrust loads and wear - potentially seizing a piston.
These issues you may regard as thermal stress and the engine will perform best when they are all at the right temparature which takes at least 20 minutes of gradually increasing the amount of throttle you are using and the revs the engine is reaching.
Setting off modestly from cold and over 5 minutes gradually increasing throttle and revs is good, but equally never sudddenly decide to turn into a F1 driver in an instant or you will shorten the life of the engine - instead react as if you are learning a circuit, gradually increasing the throttle and revs over a period of what would be on the track say 5 laps or perhaps 10 miles on the road. This is one of the reason racing engines have quite short lives because you do not get the opportunity to properly warm them up during a "warm up lap" before exposing the engine to rapid temperature rises.
The consequences of not doing it gradually enough are, castings cracks, premature piston wear, poor gasket sealing and potential failures etc.
Anyone who has had the experience of enjoying a spirited road drive for perhaps a couple of hours (say through Scotland or to Le Mans etc) may have noticed how very quiet the engines become after about 45 - 60 minutes and this is when finally the whole package has reached the best sizes and running temperatures from quite fast road work over a long period.
Most owners will adopt the attitude that it doesn't matter to them because it will still outlast their ownership and it is a future owner who will experience the resulting problems - but as internals become more critically designed for light weight, and good ecconomy with performance - those limits are often reached sooner than expected if owners couldn't care less about their engines.
Baz
