<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tepid1 &raquo;</TD></TR><TR><TD CLASS="quote">Dude.... you are off in your understanding of what compression is and how it affects power.

Not true.

Partially true.... Displacement helps more than compression due to the fact that you can add more fuel to a larger bore than you can a smaller.... thus creating more power. Compression does not affect spool like you think it does.

Higher compression is not more heat energy. There is the same amount of energy in a 10:1 car as there is in a 9:1 car as long as you maintain all the same variables. The 10:1 makes more power, not because of more air, but because is decreases the volume of the area in which the "explosion" occurs which in turn increases piston velocity and yields more power.

Now with the heat aspect....

You are essentially creating more thermal effeciency. The thermal efficiency is a measure of how effectively the engine converts the heat-generating potential of the fuel, when burned with an appropriate amount of air, into mechanical power. In order to appreciate a higher CR you need to also look at the ER, or the expansion ratio as well.

The Expansion Ratio (ER) is what occurs as the piston moves down the bore on the power stroke rather than what happens as it moves up on the compression stroke.

Here is a cool example:



Now so far you should be able to see why more compression makes more power. It is not solely because the charge is squeezed harder and the resulting combustion pressure is increased, but also because the higher expansion ratio allows more energy to be extracted from the original high-pressure charge.

CR and the correct cams go hand in hand. If you don't understand CR then you probibly don't understand the true benefits of a good cam.

So in a nutshell.... raising the CR increases torque, and consequently power, throughout the rpm range. Because raising the CR increases thermal efficiency, it brings about an increase in fuel economy. If a longer duration cam is installed, raising the CR at the same time can be worth considerably more than these two moves considered separately. When the CR is raised, peak combustion pressures are increased. And since cylinder pressure equals torque, that's a good thing. A rule of thumb for typical production engines is that combustion pressure is equal to the CR times 100. This tells us that, from a 10:1 engine, we would expect to see about 1,000 psi of peak combustion pressure. </TD></TR></TABLE>

Here's the true beauty and purpose of honda-tech right here. Actual educated facts.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tepid1 &raquo;</TD></TR><TR><TD CLASS="quote">Dude.... you are off in your understanding of what compression is and how it affects power.

Not true.

Partially true.... Displacement helps more than compression due to the fact that you can add more fuel to a larger bore than you can a smaller.... thus creating more power. Compression does not affect spool like you think it does.

Higher compression is not more heat energy. There is the same amount of energy in a 10:1 car as there is in a 9:1 car as long as you maintain all the same variables. The 10:1 makes more power, not because of more air, but because is decreases the volume of the area in which the "explosion" occurs which in turn increases piston velocity and yields more power.

Now with the heat aspect....

You are essentially creating more thermal effeciency. The thermal efficiency is a measure of how effectively the engine converts the heat-generating potential of the fuel, when burned with an appropriate amount of air, into mechanical power. In order to appreciate a higher CR you need to also look at the ER, or the expansion ratio as well.

The Expansion Ratio (ER) is what occurs as the piston moves down the bore on the power stroke rather than what happens as it moves up on the compression stroke.

Here is a cool example:



Now so far you should be able to see why more compression makes more power. It is not solely because the charge is squeezed harder and the resulting combustion pressure is increased, but also because the higher expansion ratio allows more energy to be extracted from the original high-pressure charge.

CR and the correct cams go hand in hand. If you don't understand CR then you probibly don't understand the true benefits of a good cam.

So in a nutshell.... raising the CR increases torque, and consequently power, throughout the rpm range. Because raising the CR increases thermal efficiency, it brings about an increase in fuel economy. If a longer duration cam is installed, raising the CR at the same time can be worth considerably more than these two moves considered separately. When the CR is raised, peak combustion pressures are increased. And since cylinder pressure equals torque, that's a good thing. A rule of thumb for typical production engines is that combustion pressure is equal to the CR times 100. This tells us that, from a 10:1 engine, we would expect to see about 1,000 psi of peak combustion pressure. </TD></TR></TABLE>

Google engineering ftw.

http://www.popularhotrodding.c...ratio

 

Yup