In case you didn’t already know, when you compress air it heats up. You’ll notice this when you let air out of a tire, and the air coming out is much hotter than the ambient air. The whole point of a turbocharger is to force compressed air into your engine which allows for more fuel, and ultimately more power. There is one problem, however, hot air can cause detonation. For this reason, almost all turbocharged vehicles use an intercooler.
The job of the intercooler is to take the air that the turbocharger has compressed, and cool it down to a reasonable temperature. This can either be done with an air-to-air intercooler design, or liquid cooled intercooler. A liquid cooled intercooler has much greater cooling potential, but the liquid will eventually become too hot unless an auxiliary radiator is used. For this reason, most intercoolers you’ll find on turbocharged vehicles use an air-to-air design.
To keep production costs down often times the OEM intercooler is fairly small. It will typically get the job done, but as soon as you start increasing boost pressure or adding bolt-on modifications, the intercooler can hold you back. Adding a larger intercooler without any tuning will not really add any power. The charge air temperature will be lower resulting in denser air, but the larger intercooler can add a slight amount of drag which can somewhat negate any power gains.
The real magic of installing an aftermarket intercooler is the ability to run a more aggressive tune without running into detonation. A larger intercooler is also less susceptible to heat soaking which means you can stay out on the drag strip or race track longer without losing power. To put it simply: no, a larger intercooler will not really add any horsepower to your car. It does, however, give you much more wiggle room for a more aggressive tune without the risk of harming your engine.
It should be noted, however, that too large of an intercooler can actually do more harm than good. If you have an extremely massive intercooler, you will cause more turbocharger lag and more drag inside the whole system. Luckily you will almost never run into this problem as spacial constraints will force you to run an intercooler that typically isn’t too much larger than the factory unit.
This was a really brief run-down on this topic, and there is a ton of information we had to leave out to keep this short and sweet. If you really want to nerd out on this topic, we suggest checking out some automotive forums. If you’re curious about what aftermarket intercooler is right for your car, give us a call at 1.480.966.3040 or email us at email@example.com.