[Dean]

I think one of the common things that confuses people is the use of the word fan. They often think of their radiator or house fans. Most people have little or no experience with turbines or even cetrifugal fans.

This is why you often get questions like, why not use electric fans for blowers...

Ok, this is oversimplified, but...

Lets do some math... a 2L engine running at 4000RPM sucks in about 4000L or 141 Cubic Feet of air per minute. This is an incrediable amount of air. Baically, a box of air 5 feet x 5 feet and just over 5.5 feet tall.

The turbo compressor not only moves this volume of air, but can maintain a positive pressure of 15PSI or so in the intake manifold while the engine gobles up this air.

This doesn't sound like a big deal, but maintaing this level of pressure would be like trying to blow up an air matress with a hole in it the size of your fist.... Not that it is the same technology, but it takes a big 50lb shop air compressor to move 17CFM @ 90PSI

So what does this mean? Well, if the cylinders on a NA engine are normally filled with air at say 5-10PSI, and the turbo can fill them with air at 15 PSI, in theory, you could see 50 to 100% more air and fuel to burn. Is there a corresponding 50-100% more power? Here are some VW specs, you be the Judge...

2.0L 115 horsepower, 122 lbs-ft torque, 4 cylinder, in-line, gas

1.8T 150 horsepower, 162 lbs-ft torque, 4 cylinder, in-line, 5V, turbocharged, gas

1.8T 180 horsepower, 173 lbs-ft torque, 4 cylinder, in-line, 5V, turbocharged, gas.

Not sure if that helps, but it might...