Forced Induction

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"Forced Induction" is the pairing of your favorite engine with a turbocharger or supercharger (sometimes nitrous). It involves spinning a tiny fan attached to an exhaust driven fan (turbo) or belt on the front of the engine (S/C) that blows pressurized air into the engine, which we know as "boost." More air and more fuel means more bang and more power! The two best ways of adding power are adding displacement and/or adding boost. We're a fan of both at XAT, particularly the turbo. Let us show you why...

Here's the quick version:  

+: Boost comes on sooner
+: More power in the lower RPM range
+: Easier to install
+: More compact overall package
-: Less peak power than a turbocharger
-: Less boost control
-: Less flexibility of where it can be mounted

+: Most efficient way to make more power on an engine
+: No regenerative costs (like having to refill nitrous bottles)
+: Uses "free" energy; doesn't take power from the engine to make more power
+: Boost can be precisely controlled "on the fly" with a boost controller
+: More flexibility with mounting/placement
+: Works as a muffler
-: Needs a constant oil supply from the engine
-: "Turbo lag"/transient response/boost threshhold
-: More piping/crossover piping required on V and horizontal engines
-: Needs more parts to work, higher initial cost

What's better, a supercharger or a turbocharger? This is a hotly debated topic, as even OEM companies go back and forth on this. For instance, Audi traditionally uses a turbo on their V6s, briefly went supercharged, and is now back to using turbos instead. Meanwhile, Volvo is using both at the same time on their engines, as is VW on some of their 1.4 liter engines!

Supercharging is typically more common on USDM (United States Domestic Market, anything offered for the USA) V8s, particularly the positive displacement "roots" and "screw" type superchargers. These run directly off of the engine's belt drive and tend to have instantaneous boost with none of the "lag" typically turbos are known for. They're also easier to install on V or horizontal engines. Their downside is that they have a low efficiency rating and quickly heat soak the intake. This is bad for performance, as an engine with cooler, denser air will make more power and is further away from predetonation/knock. One compromise between a turbo and an S/C is a centrifugal supercharger, which is belt driven but uses the compressor side of a turbo. These have much better thermal efficiency, but still many of the drawbacks of a supercharger, such as the small power losses of having to spin the supercharger. The faster you spin a supercharger, the more power it takes to do so. The majority of superchargers do not use the engine's oil supply, but do have their own that still needs regular servicing. A supercharger doesnt need a boost controller or wastegate, but if you want to run more boost, you have to swap out the drive pulley. This ultimately limits how much boost you can run.