Can someone explain to me the "Intercooler Efficency" in this link?

[irn__man]

http://www.roadraceengineering.com/eclipsetech/icflowcharts.htm

I'm looking at getting the Griffin 24" x 10" or 20" x 10" and weld the HKS Endtanks on. I figured I can make a decent intercooler for about $500.

But I am still confused with the flowcharts that RRE has on their site.

thanks
iron

 

[DrZiplok]

The charts make the assumption that an intercooler cools by transferring heat from the charge air to the ambient air, and so they plot the ratio of cooling (Tin-Tout) to difference to ambient (Tin-Tambient).

Unfortunately, this isn't how an intercooler works. The body of an intercooler is a heatsink; on a boost run you dump heat from the charge air into the body of the intercooler, and it's the thermal mass and efficiency of this transfer that is interesting at this phase.

Then when you're off the boost, the intercooler bleeds heat off to ambient, and also back into the charge air. The efficiency of these transfers is also interesting.

What puts the "intercooler is a radiator" assumption to death is that the rate of heat absorption during a boost phase is far greater than the rate at which heat can be drained by ambient airflow.

This is one reason why bar-and-plate makes better intercoolers than tube-and-fin; the bar-and-plate construction involves a lot more metal, giving the resulting intercooler much more thermal mass.