tbyrne
09-30-2008, 12:36 PM
Some info from ProCharger about why intercoolers are important -
http://estore.websitepros.com/stores/2081904/catalog/intercooling_chart.gif
The Fundamental Solution
All non-intercooled superchargers operate with an intake manifold temperature in the general range of 115° - 200° above ambient (outside air) temperature at 8 psi. At the same boost level, an Intercooled ProCharger operates at only 28° above ambient! This tremendous advantage from cooler air is just like the difference between driving your car on a cold winter's day vs the blistering heat of summer! Thats a real advantage that yields real performance. It helps to understand that no supercharger alone will ever begin to match the system efficiency of an intercooled supercharger system. This is simply because compressing air creates heat, as dictated by the laws of physics (Boyle's Gas Law). Even in the case of "perfect compression" (100% adiabatic efficiency, which is physically impossible without an intercooler - see chart), air temperature would increase by approximately 71° at only 8 psi, while the lower (40-80%) efficiencies of all non-intercooled superchargers produce substantially higher temperatures. Intercooled ProCharger systems are the fundamental, OEM solution - because not only is less heat created when the air is compressed, the majority of this heat is actually removed through intercooling.
The bottom line is that intercooled boost is substantially more powerful and safe for your engine than hot, non-intercooled boost. Now that technology has developed to the point that gear-driven superchargers are powerful enough to reliably blow through an intercooler, it simply doesn't make sense not to intercool, especially for fuel injected applications running pump gas. In fact, for high compression engines or continuous duty applications, such as marine or towing, intercooling is absolutely essential for reliability.
In basic terms, compressing air creates heat, while intercooling removes heat. The illustration above may help to further explain the tremendous impact of intercooling upon supercharger system efficiency and engine intake temperatures.
Benefits of Intercooling
Greatly Reduced Intake Temperature. An 85° - 200° drop in air temperature (dependent upon application) results in a more dense, powerful fuel/air charge, greatly reduces exposure to detonation, and virtually eliminates the "power fade" felt in back-to-back runs and extended pulls without intercooling
Full Timing
This reduction in temperature allows you to run factory (or close to factory) timing, and avoids the substantial horsepower loss inflicted by excessively retarded ignition timing
More Low-End Boost and Horsepower
The intercooler also acts as a passive wastegate, flattening the boost curve at higher rpm's and allowing more boost to be dialed in at lower rpm's
An Expanded Power Band
Full timing and forced induction keep the engine pulling hard to the redline
More Boost
Not only will you experience the above benefits at any boost level, you can also safely run substantially more boost when intercooled!
Reliable High Performance
Clearly, the only type of performance that matters is reliable performance, and detonation is the single biggest threat to engine reliability. The boost range for reliable performance, without detonation, can be determined by looking at the type of supercharger technology being considered, and the compression ratio of the motor. With a lower compression ratio, an engine can safely handle more boost, everything else being equal. Similarly, if the temperature of the compressed air is lower, an engine will have a much higher detonation threshold (the point at which fuel ignites without a spark), and will be able to safely handle more boost. The chart below helps to illustrate how the overall efficiency of the entire supercharger system can be increased by both leading edge supercharger efficiency and the use of intercooling. Simply locate an engine's compression ratio at the bottom of the chart and trace upwards to determine the maximum reliable boost level. The amount of heat produced (adiabatic effiency) by each supercharging technology is what determines the boost limitation. While gear-driven centrifugal is clearly the superior supercharger technology, it is also clear that the biggest benefit comes from intercooling. These calculations assume moderate timing, 92 octane pump gas, and a good supply of fuel to the cylinders. As mentioned previously, detonation is the single biggest threat to engine reliability. It is heat and detonation that cause blown head gaskets and burned pistons, not boost. Achieving maximum performance from a given engine while avoiding detonation requires the right combination of intake air temperature, timing and fuel quality. For example, without intercooling a stock 5.0 with 9.5:1 compression ratio can only hold 5-6 psi of boost before detonation becomes a problem. The only way to safely run more than 6 psi of boost and still make a meaningful increase in power without an intercooler is by using racing fuel to avoid detonation. Many companies also employ "band-aids" such as ignition retard and larger injectors to run 8-9 psi on pump gas, but the resulting increase in performance is only marginal (since both of these band-aids suboptimize) and detonation is frequently still a problem.
Detonation
We've all heard of this, but what is it? Detonation, or engine knock, occurs simply when fuel pre-ignites before the piston reaches scheduled spark ignition. This means that a powerful explosion is trying to expand a cylinder chamber that is shrinking in size, attempting to reverse the direction of the piston and the engine. When detonation occurs, the internal pneumatic forces can actually exceed 10x the normal forces acting upon a properly operating high performance engine. Detonation is generally caused by excessive heat, excessive cylinder pressure, improper ignition timing, inadequate fuel octane or a combination of these. Of the previous, excessive heat is usually the culprit. As an engine is modified to generate more power, additional heat is produced. Today's pump gas will only tolerate a finite amount of heat before it pre-ignites and causes detonation. Although forced induction engines usually produce far less heat than comparable naturally aspirated high compression engines, the cylinder temperatures in intercooled engines are radically cooler yet. It is rarely boost that causes detonation, just unnecessary heat. An intercooler is such a natural solution for forced induction, that in almost every OEM application, intercooling is part of the package.
Tom
http://estore.websitepros.com/stores/2081904/catalog/intercooling_chart.gif
The Fundamental Solution
All non-intercooled superchargers operate with an intake manifold temperature in the general range of 115° - 200° above ambient (outside air) temperature at 8 psi. At the same boost level, an Intercooled ProCharger operates at only 28° above ambient! This tremendous advantage from cooler air is just like the difference between driving your car on a cold winter's day vs the blistering heat of summer! Thats a real advantage that yields real performance. It helps to understand that no supercharger alone will ever begin to match the system efficiency of an intercooled supercharger system. This is simply because compressing air creates heat, as dictated by the laws of physics (Boyle's Gas Law). Even in the case of "perfect compression" (100% adiabatic efficiency, which is physically impossible without an intercooler - see chart), air temperature would increase by approximately 71° at only 8 psi, while the lower (40-80%) efficiencies of all non-intercooled superchargers produce substantially higher temperatures. Intercooled ProCharger systems are the fundamental, OEM solution - because not only is less heat created when the air is compressed, the majority of this heat is actually removed through intercooling.
The bottom line is that intercooled boost is substantially more powerful and safe for your engine than hot, non-intercooled boost. Now that technology has developed to the point that gear-driven superchargers are powerful enough to reliably blow through an intercooler, it simply doesn't make sense not to intercool, especially for fuel injected applications running pump gas. In fact, for high compression engines or continuous duty applications, such as marine or towing, intercooling is absolutely essential for reliability.
In basic terms, compressing air creates heat, while intercooling removes heat. The illustration above may help to further explain the tremendous impact of intercooling upon supercharger system efficiency and engine intake temperatures.
Benefits of Intercooling
Greatly Reduced Intake Temperature. An 85° - 200° drop in air temperature (dependent upon application) results in a more dense, powerful fuel/air charge, greatly reduces exposure to detonation, and virtually eliminates the "power fade" felt in back-to-back runs and extended pulls without intercooling
Full Timing
This reduction in temperature allows you to run factory (or close to factory) timing, and avoids the substantial horsepower loss inflicted by excessively retarded ignition timing
More Low-End Boost and Horsepower
The intercooler also acts as a passive wastegate, flattening the boost curve at higher rpm's and allowing more boost to be dialed in at lower rpm's
An Expanded Power Band
Full timing and forced induction keep the engine pulling hard to the redline
More Boost
Not only will you experience the above benefits at any boost level, you can also safely run substantially more boost when intercooled!
Reliable High Performance
Clearly, the only type of performance that matters is reliable performance, and detonation is the single biggest threat to engine reliability. The boost range for reliable performance, without detonation, can be determined by looking at the type of supercharger technology being considered, and the compression ratio of the motor. With a lower compression ratio, an engine can safely handle more boost, everything else being equal. Similarly, if the temperature of the compressed air is lower, an engine will have a much higher detonation threshold (the point at which fuel ignites without a spark), and will be able to safely handle more boost. The chart below helps to illustrate how the overall efficiency of the entire supercharger system can be increased by both leading edge supercharger efficiency and the use of intercooling. Simply locate an engine's compression ratio at the bottom of the chart and trace upwards to determine the maximum reliable boost level. The amount of heat produced (adiabatic effiency) by each supercharging technology is what determines the boost limitation. While gear-driven centrifugal is clearly the superior supercharger technology, it is also clear that the biggest benefit comes from intercooling. These calculations assume moderate timing, 92 octane pump gas, and a good supply of fuel to the cylinders. As mentioned previously, detonation is the single biggest threat to engine reliability. It is heat and detonation that cause blown head gaskets and burned pistons, not boost. Achieving maximum performance from a given engine while avoiding detonation requires the right combination of intake air temperature, timing and fuel quality. For example, without intercooling a stock 5.0 with 9.5:1 compression ratio can only hold 5-6 psi of boost before detonation becomes a problem. The only way to safely run more than 6 psi of boost and still make a meaningful increase in power without an intercooler is by using racing fuel to avoid detonation. Many companies also employ "band-aids" such as ignition retard and larger injectors to run 8-9 psi on pump gas, but the resulting increase in performance is only marginal (since both of these band-aids suboptimize) and detonation is frequently still a problem.
Detonation
We've all heard of this, but what is it? Detonation, or engine knock, occurs simply when fuel pre-ignites before the piston reaches scheduled spark ignition. This means that a powerful explosion is trying to expand a cylinder chamber that is shrinking in size, attempting to reverse the direction of the piston and the engine. When detonation occurs, the internal pneumatic forces can actually exceed 10x the normal forces acting upon a properly operating high performance engine. Detonation is generally caused by excessive heat, excessive cylinder pressure, improper ignition timing, inadequate fuel octane or a combination of these. Of the previous, excessive heat is usually the culprit. As an engine is modified to generate more power, additional heat is produced. Today's pump gas will only tolerate a finite amount of heat before it pre-ignites and causes detonation. Although forced induction engines usually produce far less heat than comparable naturally aspirated high compression engines, the cylinder temperatures in intercooled engines are radically cooler yet. It is rarely boost that causes detonation, just unnecessary heat. An intercooler is such a natural solution for forced induction, that in almost every OEM application, intercooling is part of the package.
Tom