I'll post a piece from an American forum Re- cooling of the charged air.
it's a good read i thought.
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If I'm not mistaken, one of the biggest advantages to s/c porting, besides increased airflow, is a decrease in intake temperature. Temperature, to me anyway, is a little more important. This is probably the main reason for the drop in KR.
If you have an understanding of adiabatic efficiency, I could explain this in more technical terms.
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Simplest definition I could find. For any forced induction enthusiast, this is a good read and important to know.
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Forced induction compresses air, and as a law of physics the temperature of the air increases as a direct counterpart to its compression. A lot of engineering goes into trying to compensate for this fact in supercharging and turbocharging design.
The word "adiabatic" describes a process in which no heat is gained or lost - 100% adiabatic efficiency would be the perfect forced induction device, creating no heat gain whatsoever, probably impossible to achieve ever. And the closest anyone can come yet is around 80% efficiency.
The problem with heat is it defeats the original purpose - the hotter the air, the lower the density possible, and the extra power comes from dense air. Another problem from heat is ignition - the hotter the inlet air, the more tendency the engine will have towards detonation and pre-ignition (knock and ping), which damages the engine, besides diminishing performance. Drivers of blown vehicles tend to keep an eye on the temperature gauge.
The goal of efficient charging is to compress the air and to keep it cool, for maximum power. The cooler the intake charge, the denser the air and the more horsepower produced.
The greater the adiabatic efficiency with which a supercharger compresses air, the less the heat that gets added to the intake manifold. Efficiency is measured by the discharge air temperature at a given pressure. For 6 pounds of boost, a supercharger with intake air temperature of 185 degrees is more efficient than another at 190 degrees. Boost itself is only the measure of pressure the intake air is under, not an indication of the power produced as horsepower.
The Roots blower has the lowest adiabatic efficiency of all the forced induction designs (including the turbocharger, which has to start off with hot exhaust gases to deal with) - generally around 50 percent. The roots type is so inefficient because it doesn't compress the air directly, but delivers uncompressed air which wells into the intake manifold, becoming more compressed, but with additional heat gain from the turbulence and reverse flows of air mixing. Centrifugal superchargers can vary from 60% up to perhaps approaching 80% efficiency, as can turbochargers; both are more efficient at higher rpm, which is another way of calling them more inefficient at lower rpm. The twin screw supercharger normally delivers lower output temperatures, for adiabatic efficiencies of 70-80% across the whole rpm range.
Cooling the air before it goes into the engine has a major effect on performance. Intercoolers are the physical means of cooling the compressed air, radiator-like systems using air or water for cooling. Inter cooling reduces temperature, but reduces boost (pressure) too because of flow restriction as the air circulates through cooling, and also as a direct result of the temperature change itself - again that law of physics. But the net result is compressed (dense) air at a cooler temperature. Cooler air at lower boost will give more power than hotter air at higher boost, because cooler air can be denser than hotter air no matter how much boost you throw at it. Drag racers often use cold water and ice in the intercooler for tremendous power over the short term.
Intercoolers come as air cooled systems and as water cooled systems. Very often the efficiencies of modern chargers permit running without an intercooler especially in street or OEM applications, but for performance uses, in general optimal performance comes from intercooling.
Hope this explains it well enough.
Few questions - S/C Ecotec
just relaying information I received from chiptorque however I do remember louies VN supercharged V6 (charge6) and that was running with a machined down yella terra 20PSI snout and F.I.T. air to air intercooler too
Linear Mode
