Hello everyone, I am wondering if a typical gasoline engine will make more power when the coolant is cold or hot. I know that cold air and fuel is denser and will make more power, but what about the coolant? I have seen 2 theories on this and not much actual testing.
Theory 1- Hot engine makes more power. Heat is energy, keeping as much heat in the combustion chambers as possible will produce the most powerful explosion and therefore the most power. A cold combustion chamber will absorb thermal energy from the explosion, therefore decreasing pressure. Piston rings seal best when at normal temp, increasing compression. Fully warmed up engine has less friction due to proper clearances as well as thinner oil. Hot engine atomizes fuel more efficiently, so more efficient combustion. ECU may limit power with a cold engine for safety .
Theory 2- Cold engine makes more power. Cold head means cooler intake manifold, ports, and valves, therefore a denser charge. A cooler combustion chamber will accept more air and fuel, therefore more power. Ignition timing can be advanced more, making more power.
To make things even more confusing, different people have reported different experiences with this. For example, some people report that they get their best time at the drag strip with an ice cold engine while others say that their ET is better with a hot engine. One person even said that they blew the fuse for their electric water pump at the staging line and their engine was up to 250 by the time they got to the finish line and they broke their record and got their fastest time ever with an overheated engine! Same with the few hot vs cold dyno comparisons I found online.
So what's the reality on the power potential of a hot vs a cold engine? I'm thinking that most engines are probably going to make the most power when running at the temp that they are designed to (fully warmed up but not overheated), but please correct me if I am wrong. Thanks in advance!
Theory 1- Hot engine makes more power. Heat is energy, keeping as much heat in the combustion chambers as possible will produce the most powerful explosion and therefore the most power. A cold combustion chamber will absorb thermal energy from the explosion, therefore decreasing pressure. Piston rings seal best when at normal temp, increasing compression. Fully warmed up engine has less friction due to proper clearances as well as thinner oil. Hot engine atomizes fuel more efficiently, so more efficient combustion. ECU may limit power with a cold engine for safety .
Theory 2- Cold engine makes more power. Cold head means cooler intake manifold, ports, and valves, therefore a denser charge. A cooler combustion chamber will accept more air and fuel, therefore more power. Ignition timing can be advanced more, making more power.
To make things even more confusing, different people have reported different experiences with this. For example, some people report that they get their best time at the drag strip with an ice cold engine while others say that their ET is better with a hot engine. One person even said that they blew the fuse for their electric water pump at the staging line and their engine was up to 250 by the time they got to the finish line and they broke their record and got their fastest time ever with an overheated engine! Same with the few hot vs cold dyno comparisons I found online.
So what's the reality on the power potential of a hot vs a cold engine? I'm thinking that most engines are probably going to make the most power when running at the temp that they are designed to (fully warmed up but not overheated), but please correct me if I am wrong. Thanks in advance!
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