Thursday, December 13, 2007

Pros and Cons of Turbocharger

Advantages
More specific power over naturally aspirated engine. This means a turbocharged engine can achieve more power from same engine volume.

Better thermal efficiency over both naturally aspirated and supercharged engine when under full load (i.e. on boost). This is because the excess exhaust heat and pressure, which would normally be wasted, contributes some of the work required to compress the air.

Weight/Packaging. Smaller and lighter than alternative forced induction systems and may be more easily fitted in an engine bay.

Fuel Economy. Although adding a turbocharger itself does not save fuel, it will allow a vehicle to use a smaller engine while achieving power levels of a much larger engine, while attaining near normal fuel economy while off boost/cruising. This is because without boost, only the normal amount of fuel and air are combusted.

Disadvantages
Lack of responsiveness if an incorrectly sized turbocharger is used. If a turbocharger that is too large is used it reduces throttle response as it builds up boost slowly. However, doing this may result in more peak power.

Boost threshold. Turbocharger starts producing boost only above a certain rpm due to a lack of exhaust gas volume to overcome inertia of rest of turbo propeller. This results in a rapid and unlinear rise in torque, and will reduce the usable power band of the engine. The sudden surge of power could overwhelm the tires and result in loss of grip, which could lead to understeer/oversteer, depending on the drivetrain and suspension setup of the vehicle. Lag can be disadvantageous in racing. If throttle is applied in a turn, power may unexpectedly increase when the turbo winds up, which can induce wheelspin.

Cost.
Turbocharger parts are costly to add to naturally aspirated engines. Heavily modifying OEM turbocharger systems also require extensive upgrades that in most cases requires most (if not all) of the original components to be replaced.

Complexity. Further to cost, turbochargers require numerous additional systems if they are not to damage an engine. Even an engine under only light boost requires a system for properly routing (and sometimes cooling) the lubricating oil, turbo-specific exhaust manifold, application specific downpipe, boost regulation, and proper gauges (not intrinsically necessary, but very highly recommended). In addition inter-cooled turbo engines require additional plumbing, whilst highly tuned turbocharged engines will require extensive upgrades to their lubrication, cooling, and breathing systems; while reinforcing internal engine and transmission parts.

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