How to Make a Stock Engine Turbo Readyby Alexander Eliot
Turbocharging your car's stock engine will substantially increase the engine's horsepower potential. Turbochargers pressurize and force air into the engine's cylinder head, allowing for a much more powerful combustion process than is possible on naturally aspirated engine setups. Many of the turbo system's components, such as the intake and exhaust manifold, will replace the engine's stock parts. However, there are many upgrades you can perform on your stock engine that can be utilized when installing a turbo system in the future, allowing for maximum turbocharged horsepower potential.
Replace the engine's stock header-back exhaust system with an upgraded, larger-diameter version. This includes the after-cat exhaust system and high-flow catalytic converters. Increasing the engine's exhaust flow potential will assist the turbocharger in spooling. An upgraded exhaust also increases the engine's efficiency and horsepower, especially on high-power turbo setups. The stock exhaust manifold should not be replaced; you will replace that with a turbo-exhaust manifold when installing your turbo system.
Upgrade the stock clutch to a higher-horsepower unit. The increased engine torque generated by a turbocharger greatly increase the likelihood that the stock clutch will slip under acceleration. Depending on your vehicle, the stock clutch may be adequate for low-boost turbo applications. For higher-horsepower applications and/or to ensure drivetrain reliability, an upgraded clutch kit is a must.
Install an engine-management system on your vehicle. These include stand-alone systems, which entirely replace the stock engine control unit (ECU), as well as piggyback systems, which plug into the stock ECU, allowing you to custom tune the engine's fuel curves. An engine-management system will increase the horsepower and efficiency of any modified engine. However, once a turbo system is installed, engine-tuning capability is a must, since the stock ECU's fuel (consumption) curves will no longer be adequate for the increased airflow of the turbocharger.
Upgrade the engine's stock fuel system if you plan to make substantial horsepower gains with your turbo system. The stock fuel pump and injectors often are incapable of flowing a large amount of fuel beyond the stock level. This limits your engine's tuning potential and, ultimately, the amount of boost you'll be able to get. Upgrading the fuel pump and injectors to higher-flow units will allow you to compensate for the turbo's increased airflow via tuning, maximizing horsepower and reliability.
Upgrade the engine internals for maximum horsepower turbo applications. This includes turbo camshafts as well as forged rods and pistons. It's also a good idea to go with a lower-compression piston setup, to allow for the most reliable high-boost performance. Some stock engines are able to reliably make 100 or more horsepower when turbocharged on the stock internals. However, for engines with weak internals --- and/or if you're looking for the maximum possible horsepower out of your engine --- replace the engine internals with high-strength, turbo-specific units so that the engine can handle substantially increased turbo boost levels.