Muscle Mustangs & Fast Fords
Forced Induction - Why Boost It?
Everything you've ever wanted to know about forced induction on your fast Ford.
The hot side of a turbocharged system refers to any piping or component that circulates exhaust gas. Typically, the hot side of a system contains the exhaust manifolds, the manifold-to-turbocharger piping, and the turbocharger's downpipe. Because the hot side deals with extremely hot exhaust, it is typically built from stainless steel tubing (mild steel is also used in some budget-friendly systems) and should either be coated, wrapped, or routed in a way that reduces underhood temperatures. The hot side is hot—hence the name.
A downpipe connects to the turbochargers turbine outlet and transfers spent exhaust gas from the turbocharger to the atmosphere. On a typical street car, the downpipe will connect to a traditional exhaust system, and route spent gasses alongside the bottom of a Mustang and out the tailpipes. In race cars, the downpipe usually just dumps exhaust directly out of the engine bay or through a hole in the front fender. This looks cool and sounds awesome, but isn't always legal, so check the rulebook before cutting a 5-inch hole in your front bumper. Or don't and send us pictures! Either way, downpipes are normally constructed out of stainless steel (it's on the hot side!), although racers looking for the ultimate weight savings have experimented with aluminum downpipes.
As you can probably guess, the cold side (inlet) of a boosted system deals with any piping or component that circulates compressed air through the system. This includes any piping that feeds the inlet of the turbocharger or supercharger, any piping from the compressor side of the turbocharger or supercharger, the intercooler (if one is present), and any piping connecting to the throttle body or carburetor. Because temperatures on the cold side are relatively low (compared to the exhaust), the tubing is generally aluminum, which saves weight and efficiently transfers heat. The cold side of a system is usually held together with silicone couplers and clamps. If you start "missing some boost," check the couplers first.
Intercoolers provide a way to reduce the temperature of the inlet air after it has been compressed, but before it reaches the combustion chamber. Compressing air heats it (sometimes a lot)—and hot air is bad air, as any racer will tell you. The hotter the inlet air, the less dense it becomes (which is bad for performance since less oxygen is present), and the more prone the engine will be to detonation. This is an unfortunate part of the Ideal Gas Law (we'll save you the science lesson), but the heat created from compressing air must be dealt with if you're looking to optimize your boosted Ford. To cool compressed air, many forced-induction systems rely on an intercooler, which is simply a device similar to a radiator that transfers heat.
Air-to-air intercoolers are the most popular for turbocharged street cars, and rely on the transfer of cool air over the small aluminum fins to pull heat away from the compressed air within the tubes. Air-to-water intercoolers rely on a similar principle in that they pull heat from compressed air, although an air-to-water system uses water (or coolant) to enable the transfer of heat. Stock Ford systems found on SVT vehicles use an intercooler with a heat exchanger to reduce the heat in the intercooler cooling system.
Low Boost, Pump Gas, No Timing
This common phrase can be heard around any racer, tuner, dyno queen, or forum jockey, and it is meant to downplay the current performance of the car in question. "Yeah, and that's only on low boost, pump gas, and no timing—it's got a lot more in it!" This is usually followed by the owner/driver/tuner either actually turning it up and breaking something or leaving it exactly as is for the rest of time. Never trust this statement.