Tom @ Fast Forward
06-09-2006, 09:55 AM
I was talking to a couple of you over the last couple weeks about why the stock radiator is marginal. I said "in the old days" the engines used to be considered 25-30% efficient but thought that todays engines were much better. I was wrong. :) Found this today.
3. Ratings of Efficiency
There are many different ways to find the efficiency of an engine, and many different parts of an engine that you can rate the efficiency.
Thermal efficiency is the percentage of energy taken from the combustion which is actually converted to mechanical work. In a typical low compression engine, the thermal efficiency is only about 26%. In a highly modified engine, such as a race engine, the thermal efficiency is about 34%.
Mechanical efficiency is the percentage of energy that the engine puts out after subtracting mechanical losses such as friction, compared to what the engine would put out with no power loss. Most engines are about 94% mechanically efficient.
This means that for a stock engine, only 20% of the power in fuel combustion is effective.
That means 80% goes into heat that the oil and water have to cool. When you double the WHP, that is a LOT of extra heat for the stock radiator to compensate. Especially when it is somewhat marginal to begin with. At least out here.
3. Ratings of Efficiency
There are many different ways to find the efficiency of an engine, and many different parts of an engine that you can rate the efficiency.
Thermal efficiency is the percentage of energy taken from the combustion which is actually converted to mechanical work. In a typical low compression engine, the thermal efficiency is only about 26%. In a highly modified engine, such as a race engine, the thermal efficiency is about 34%.
Mechanical efficiency is the percentage of energy that the engine puts out after subtracting mechanical losses such as friction, compared to what the engine would put out with no power loss. Most engines are about 94% mechanically efficient.
This means that for a stock engine, only 20% of the power in fuel combustion is effective.
That means 80% goes into heat that the oil and water have to cool. When you double the WHP, that is a LOT of extra heat for the stock radiator to compensate. Especially when it is somewhat marginal to begin with. At least out here.