Ok, engines are more efficent than ever.
Engines are also running at a hotter temperature than ever.
Given a perfect Carnot, the greater the temperature difference and the greater the volume change, the more work is produced.

If modern engines are rejecting so much heat and need such great cooling capacities, how are we getting more efficency out of an engine? Are we not just rejecting the extra heat created by the greater temperature difference?

 

The extra heat allows for a more efficient fuel burn.



That, and computers.

 

Not sure I can agree with you there. An internal combusion engine coolant temp has always run 180-220 degrees.

Computers, fuel injection, stronger materials, lighter materials, auto transmission improvements, have all improved efficenty.

 

Where's Kevin or Justin when we need them?

I'll give it a shot.

They are running hotter, and they are more efficient (partly because of the higher operating temp). They are actually rejecting less heat running at 220 degrees than in the old days when engines ran at 180 degrees.

The extra cooling capacity is there for a few reasons, not all of which apply in all cases. First off, when was the last time you had a car overheat? Used to happen all the time even on new cars with factory cooling systems. People won't put up with it anymore, so the cars have bigger cooling systems. Also, almost every new car has A/C, meaning that the air coming into the radiator has been preheated, so you need more cooling capacity. Engine compartments are very tight these days, meaning less airflow. Finally, because engines are more efficient, they are getting more power out of the same size engine. More power means more heat to get rid of. Just look at the cooling system on an '06 CTD compared to an '89. Double the power means you need a bigger cooling system for the same basic engine.

 

Smaller sized engines also need larger cooling systems.

The engine block can also be called a heatsink. The larger your block, the more heat it will dissipate by itself.

a 200HP 3.0L V6 needs less of a cooling system than a 200HP 2.0L I4.

 

the more heat you loose from various sources, the less heat becomes work.
higher exhaust temperatures, higher temperatures under the hood, higher water temperature, combine this with more electrical loads, I dont see how fuel economy can improve. Afterall, there is only so much heat per gallon of fuel.

 

How do you explain how my 200HP I-6 has a bigger cooling system then both of those engines combined?




phox

 

I would think that the larger the block, the more it would act like a heatsink, and would require a larger system to disapate that heat before meltdown.

 

Dodge over engineers everything.

 

**Cough** Third-gen-lift-pump **Cough**

 

I read something recently that said in round numbers that 33% or the heat does work, 33% goes to the cooling systems, and 33% goes out the exhaust. Of course you recover some of the exhaust heat by running the turbo unlike super chargers that use engine power.

 

Engineers have been working for years on a ceramic composite "adiabatic" engine that has no cooling system whatsoever. The payoff is greatly improved thermal efficiency - more of the fuel energy is used for useful work, not rejected to a cooling system that no longer exists. Within limits of materials and lubricants, the hotter an engine can run, the more efficient it should be since less heat is rejected (lost) to the cooling system.

Rusty

 

Part of the reason the ngines run hotter (diesels anyways), is to reduce emissions. They retard the timing, and that increases the EGTs.

Advancing the timing will...

Decrease exhaust temperature
Increase cylinder temperatures/pressures
Increase fuel economy (yes, economy is better)
Increase your output of NOx (a pollutant)
Decrease your output of Hydrocarbons (a pollutant)
Increase the amount of black smoke at peak torque

http://dodgeram.org/tech/dsl/FAQ/timing.htm

 

Because the cooling system was sized so you could run at 200HP all day long without it becoming heat saturated and overheating. Try doing that with one of those little V6's with a smaller cooling system.