An internal combustion engine works by mixing fuel and air and igniting them, whether by spark in a gasoline engine or by compression in a diesel engine. A turbo is essentially an exhaust-driven pump that pushes more air into the cylinder. Add in extra fuel, and the resulting explosion has more force, which increases power. Automakers are turning to turbochargers in order to build more efficient cars, but this also opens the door to tuners. Getting more out of these engines is a matter of increasing the amount of air that can safely be pumped into the engine, which can be achieved by using a few simple bolt-on parts.
To limit the amount of air going into the engine, the boost controller opens a bypass valve called a wastegate. The later the valve opens, the more pressure there is in the intake manifold, and that means more air and more power. There are three types of controllers:
- An adjustable bleed valve works with the stock controller, relieving pressure to delay the opening of the wastegate. This is the cheapest option, but it can only be adjusted from under the hood.
- A manual controller has normal and high pressure modes. The latter mode is accessed by hitting a switch that’s usually mounted under the gas pedal. This way, the car operates normally, increasing boost only when the pedal is floored.
- An electronic controller gets information from the ECU, allowing it to vary pressure based on factors like the current gear, engine knock and throttle position. This offers the best all-around performance and drivability.
Compressing a gas heats it up, and that makes it less dense. An intercooler cools the air coming out of the turbo, either directly or through fluid transfer like the car’s radiator. Although pressure might go down slightly, the greater density increases the total amount of air going into the engine while also lowering combustion temperatures to resist pinging. Most stock systems include a small intercooler, but switching to a larger unit, especially when running more boost, can increase overall performance.
Stock turbos are designed for low-end grunt, letting the engine run at lower speeds for better fuel economy. A bigger turbo takes longer to spool up, but this provides more boost at higher RPM for better peak performance. Although expensive, this is a relatively simple modification since the supporting equipment is already built into the engine design. Turbos with ball bearings have less resistance and, therefore, less lag than traditional sleeve-bearing turbos, reducing the trade-off in drivability with a bigger turbo.
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