What is an intercooler?
The primary function of an intercooler is to reduce the temperature of the air charge after it has been heated by the turbo and before it reaches the engine. Without an intercooler, the charge air would be less dense, reducing efficiency and power. The same thing can be true if the intercooler becomes inefficient and can no longer dissipate the heat generated by the turbo, an event commonly known as heat soak. The most common cause of heat soak is external weather conditions. A turbocharged vehicle in 100-plus-degree F temperatures becomes sluggish and unresponsive.
If boost pressure is increased, do I need a larger intercooler?
There are a number of variables that don't allow for a simple yes or no answer. Some stock intercoolers typically allow for a moderate boost level increase, while others have the ability to support more aggressive increases. What really determines the need for a larger intercooler is the increase in the amount of airflow (CFM) generated by the turbo. If increases are more than 50 percent above stock, a larger intercooler is recommended.
Will adding a larger intercooler on a stock turbo increase horsepower?
If at any time during acceleration the vehicle's knock sensors retard timing because of low-octane fuel, increased boost, or hot weather conditions, the addition of a properly designed intercooler upgrade can help regain power. This area is tricky, though, because similar results can be seen by running 100-octane fuel or driving in cooler weather. It comes down to one thing:ignition timing makes power-the cooler the charge, the more advanced the timing. There are other limiting factors, but upgrading an intercooler can help maintain power levels and, in some instances, even gain a little extra.
Should I build my own intercooler kit?
If you have a fabrication facility, a dyno, diagnostic equipment and a decent research and development budget, then go for it. What many consumers don't understand when they see the price of an intercooler is the amount of man-hours involved in prototyping and testing, and the tooling costs. Plus the piles of scrapped plumbing, intercooler assemblies and Band-Aids. Even with today's fancy computer programs, it's impossible to get it right first time. Much time and effort goes into making a production intercooler fit and work correctly.
There's also a lot more to designing an intercooler upgrade than just fitting the largest core. There are many factors involved in making sure the core assembly is designed properly. A key factor is determining how long it takes the turbo to fill the entire intake track before boost is delivered to the engine. If the core is too large, it can cause pressure loss and create lag. And it must be placed in such a way that allows for ambient air to flow effectively and therefore reduce temperatures.
Any additional or replacement plumbing has to be designed for precise fit and clearance, while sized accurately to maintain the pressurized system.
Conclusion
Think of an intercooler as an investment. Extensive research is required to make sure it will support current and possible future needs. With decreasing fuel quality and more frequent heat waves, a properly designed intercooler will help reclaim lost power for years to come. Keep in mind that intercoolers may look maintenance-free (and, in most instances, are), but cleaning the core every 15,000 miles to flush away build-up will ensure maximum efficiency.