Did you know?

  • Thread starter Thread starter TURBO (@)....
  • 43 comments
  • 1,915 views
Duke
Are you being dense on purpose, or do you really not understand this?

Brakes generate heat through friction when they are applied. That's how they stop the car - they transfer kinetic energy into thermal energy.

A radiator, on the other hand, does not generate more heat while in motion. In fact, it is a heat exchanger, which is designed to cool the liquid by radiating waste heat into the air via the coils and fins of the radiator housing.

The radiator, being a heat exchanger, is entirely dependent on airflow through it in order to carry the waste heat away from the coolant. Otherwise, it simply heats the air in the immediate vicinty more and more until it loses efficiency and the car overheats.

This is why cars have fans - to guarantee a continuous supply of fresh cool airflow through the heat exchanger.
Click to expand...

WOW, great explanation, i really learned something :/ So i should be red lining my car through every gear right? I need to keep up to speed to keep the temparature down. Dont sound right.
 
RobcioPL
WOW, great explanation, i really learned something :/ So i should be red lining my car through every gear right? I need to keep up to speed to keep the temparature down. Dont sound right.
Click to expand...

Brakes and engines are completely different. Dunno how they got in here...
 
iceburns288
Brakes and engines are completely different. Dunno how they got in here...
Click to expand...
I mentioned it because they heat up under extreme driving...........just tried showing a example, since they to get cooled..............
 
What im trying to prove is, the engine temperature will be higher under driving, then the car standing there.
 
Duke's explanation is correct. F1 cars, for example, are not designed for long periods of idling. They are designed to use the air passing over the radiators to cool them. That's why a restart can see other cars failing from overheating.
On the other hand a car under load does generate more heat than a car idling, but the amount of air being pushed through the radiators is more than enough to compensate for this.
 
RobcioPL
What im trying to prove is, the engine temperature will be higher under driving, then the car standing there.
Click to expand...
Well, you're having a hard time proving it because it's simply not true.

If the cooling system is functioning, the block temperature will be cooler even when running hard, so long as the car is moving. Yes, the engine when screaming along is generating much more waste heat than it is at idle... but the increased airflow through the heat exchanger/radiator (not just over the block, though that helps too) will compensate.
 
To further back up Duke's point, note that air is a great insulator when it's not moving (think of how insulation works--it traps stagnant air). The radiator functions by convection--heat exchange through moving air--so with the air stagnant, it will essentially not function at all, meaning all the engine's heat is retained in the cooling system.
 
Ever wonder why your car can overheat at the lights on a hot day? Yet wont when your driving on the freeway.

Airflow and cooling make a MAJOR difference.
 
In fact, if you're stuck in traffic on a hot day and your car begins to overheat, the first thing you should do is put it in neutral and fast idle the engine at a few thousand RPM. This keeps the coolant flowing and the increased fan speed (on a car with a mechanically-driven fan) pulls more air through the radiator, allowing better overall cooling.
 
RobcioPL
What im trying to prove is, the engine temperature will be higher under driving, then the car standing there.
Click to expand...
The higher the rev's the more the engine is working so the more heat the engine will generate. Depending on the car, weather conditions, speed your traveling ect (that's speed your going, not rev's), the the heat may increase faster than the radiator can cool them. However, leaving you car running at a standstill means theres no air flow cooling down the radiator, so you cars temperature WILL increase. Running at higher rev's may increase it depending on the car and weather ect, but running at a standstill WILL increase it. Driving like your meant to, not over revving the engine, will not overheat the car unless you have a problem with your cars cooling system.
 
Duke
In fact, if you're stuck in traffic on a hot day and your car begins to overheat, the first thing you should do is put it in neutral and fast idle the engine at a few thousand RPM. This keeps the coolant flowing and the increased fan speed (on a car with a mechanically-driven fan) pulls more air through the radiator, allowing better overall cooling.
Click to expand...
Right, but how many cars on the road today have mechanically driven fans? Even trucks have electric fans now, if I'm not mistaken...

I have often wondered why you don't see electric water pumps on new cars...it frees up a few HP and would offer great coolant flow regardless of RPM...
 
think of it this way why would an engine use more gas at idle than cruising???? um lets see most cars idle in the 500 range most cars cruise in the 2000 range which do you think would use more gas??
 
Duke
Well, you're having a hard time proving it because it's simply not true.

If the cooling system is functioning, the block temperature will be cooler even when running hard, so long as the car is moving. Yes, the engine when screaming along is generating much more waste heat than it is at idle... but the increased airflow through the heat exchanger/radiator (not just over the block, though that helps too) will compensate.
Click to expand...
I know what you are saying, but, the internal temperature of the engine being pushed hard, will move up.
 
RobcioPL
I know what you are saying, but, the internal temperature of the engine being pushed hard, will move up.
Click to expand...

Unless their is sufficent cooling.

Ever stuck your head out the window at 60mph?, Ive ridden a dirtbike at 70mph and the amount of wind is crazy.

Say you redlined it for 1min at 40mph in a gear, the engine will get hotter much more quickly than if you were redlineing at 120mph in a different gear.
 
Back