If you are going to run higher than 6psi you typically need to have some type of intercooler. The more you increase the boost, the hotter your intake temperatures get. The hotter the temperatures get, the more prone to detonation and knock you are.
According to the Ideal Gas Law (PV = nRT) anytime a gas is compressed, its temperature rises.
Let's say at 10 psi your turbo produces about 180F delta increase of the temperature. This means if you have 90F ambient (at the air filter), at 10 psi you'll get about 270F at the turbo outlet.
Since the temp goes up about 180F over ambient. If a 67% effective (poor) IC were present, the charge temp would drop about 120F.
Should I get the uber big intercooler?
The size of the IC or pipes has absolutely nothing to do with throttle response, or boost response. If you can calculate how long it takes for X amount of CFM to fill the volume in the intercooler, then you're thinking too hard. The flow is so great relative to the volume of the intercooler and pipe and distance involved in whatever sort of plumbing you utilize that these factors have virtually zero influence. Larger ICs do have greater pressure drops. If a 2psi drop exists, then the turbo is pushing 14psi, but only 12psi exits. This can effect spool time simply because the extra 2psi you need to add might take just those extra few RPMs to reach.
The efficiency (effectiveness) of the IC has two basic factors (longer tube & internal flow)
The longer the tubes in the core, the greater the effectiveness. However, The heat rejection tapers off with longer and longer tubes. For example, 25" long runners calculate, and measure, to be about as efficient as one can get… near 96/97%. Suppose you double the tube length, you may or may not be able to get that extra 3 or 4%. The limit of an excellent intercooler lies between 18 and 24 inches.
The second factor is the internal flow area of the core. The more area, the less the pressure loss in getting the air charge through the core.
The measure of proper intercooling clearly lies with the ability to remove heat and not lose boost in the process.
Most people will tell you to use the largest intercooler you can fit. While you want the largest surface area possible, there are other things to consider when sizing an intercooler:
- Do not block a lot of airflow to your radiator. (The air passing through the intercooler will be hotter than in front of it)
- Match the intercooler size to the engine's airflow for the most efficient system.
- Too big of an intercooler wastes your money…the efficiency increase of utilizing runners longer than 18-20" is minimal at best.
- Keep pressure drops across the core to a minimum, 1.5 psi at full boost max.
- Quality can make up for size. A better conducting cooling medium, such as aluminum, will increase the drop in temperature.
- Mount the intercooler so it can get the most air that passes over the fins.
- Seal the intercooler and direct the airflow to increase efficiency.
- 6-7 sq. in. of internal flow per 100BHP
1: the intercooler heats the airflow to the radiator…if you fill the entire mouth, the radiator will not work as effiecent, so you my have awesome air intake temps, but your water temps & cooling system could be compromised.
try to get as much airflow to both the IC and radiator, so seal the top area by the hood-latch, try a scooper from below and block the sides of the mouth so air is forced to pass through either one.
With all that said, I'd go for an intercooler that didn't fully block the radiator (or had provisions to scavenge airflow from below directly onto the radiator), had somewhere around a 18-24" long core, and had enough internal airflow to support your given HP range.