A turbocharger is basiclly an air pump that is driven by the engines exhaust gases. it pressurizes the intake to allow more air to go to the cylinder. more air and fuel means more horsepower. there are two sides to a turbocharger, the turbine side which is spun by the exhaust gases leaving the engine, and the compressor side which is spun up by the turbine side and this in turn sucks in and compresses air before entering the engine.
the size of the turbine and compressor wheels and the size and shape of their housings effects the efficient range of the turbo.
the turbine size has an impact on how much power the engine can produce. a large turbine wheel pose little resistence to outgoing exhaust gases, so the engine will be able to make more horsepower, but a large turbine wheel will spin up much more slowly.
a small turbine wheel will spool up quickly, but will choke down the exhaust and limit horsepower.
the compressor side has less of an effect on spool up, but generally a larger compressor will produce cooler compressed air, and will be able to generate more turbo boost, but will take a little longer to spin up to speed.
the moral of the story is that there is no free lunch. a larger, more efficient turbo can produce more boost but will spin up more slowly and will not work as well at low speeds. a smaller turbo will spin up faster but be weaker at high rpm horsepower.
what does this mean? factory turbos are usually sized for ‘around town’ driving, and not for ‘track days’, so they tend to be smaller with low lag and modest boost levels. increasingly, modern turbochargers are sized for fast response and minimal lag, which makes hefty torque but a fall off in high rpm power.
we hope this all makes sense to you all, but if you would like to discuss further you can call us on 01253 933794 or visit our website www.turborepairs.com