How the Turbocharger works
Exhaust gas spins an impeller which turns a compressor wheel that compresses air and force-feeds it into the intake under pressure. A wastegate is built into the system that vents the exhaust gases away from the impeller at the intended boost level. Generally therefore turbos hold fixed, stable boost at top rpm. Ikkunat
Turbocharging generally has the greatest relative power gain of all charging methods, since it uses energy otherwise lost out the exhaust. Turbos typically draw off 1.5% of engine power to operate (compared with 5% for centrifugals, and more with Roots).
They of course suffer from Turbo Lag, delivering little boost until the exhaust gases have spooled up the compressor. They become more efficient towards the higher end, gaining a reasonable adiabatic efficiency (see our Supercharger Heat page for a definition) in the range of 60% to 80% maximum.
Turbos are widely used in racing, where the lag at the low end while the system spools up is less of a hindrance than is the case in street applications. The lag generally extends through the first quarter to third of the rpm range before boost starts to take effect. The turbo works well with automatic transmissions because you can rev up against the brake to get boost started, similarly with drag racing. best online mba programs
Turbochargers are quite efficient
In general, turbo compressors are considered more efficient than supercharger compressors, and on diesels turbocharging can actually improve fuel economy and emissions. Because of the exhaust modifications required, and various others, turbocharging is a more complicated add-on at the aftermarket level, although this problem is less constraining at the OEM level. As a design issue the turbo is generally more compact than the supercharger, and it can fit wherever in the engine compartment there's room, although it wants to be close to the exhaust manifold (whereas the supercharger needs the space at the front of the block for the belt drive, an already crowded area). Quick payday loans - payday loans from best payday lenders.
Turbos spin at often more than 100,000 rpm, and yet they are mostly very quiet. They deliver large torque gains. Older model autos with turbos suffered from cold-weather starting and performance problems, in newer vehicles with fuel injection and modern computer engine controls these problems are now minimal. And some OEMs are trying to address the lag using twin-turbos or more (each smaller and thus quicker to spool up) running in combination.
The turbocharger spins much faster than the centrifugal supercharger, to build as much boost as possible at low rpm, with the wastegate to prevent overboost at higher rpm. Turbo fans prefer it over the centrifugal supercharger in this respect, because the centrifugal makes almost nothing at low rpm (the centrifugal is designed for power at the high end, see our Centrifugal Superchargers page).
|
