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Discussion Starter #1
Hello,

How can a 18g or any upgraded turbo give a wrx more power at the same boost.
example:
stock turbo at 15psi and lets say an 18g at 15psi.
The 18g should produce more power because its flowing more cfm right?


If CFM increases should the PSI increase?
Any info would be great!
Thanks
 

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This is the most misunderstood concept ever and here is the quick and easy answer :)

OK, the best example ever given to me was to consider a garden hose and a firehose both holding 16psi of pressure. When you allow the water to flow there is considerably more water coming out of the firehose right?

A smaller turbo Vs a bigger turbo mirrors this concept.

Now, an important distinction to make here is that the pressure is measured at the intake manifold, NOT actually in the engine. So, its simply a matter of thinking about what happens when your intake valves open.

With a smaller turbo running 16psi it will flow X amount of air into your cylinders, whereas with a larger turbo it will flow X + a heap more air into your cylinders once the valve opens.

Therefore a smaller turbo doesn't 'flow' as much air into your engine as a bigger turbo will. Your engine runs at a whole lot more than 16psi so its like trying to fill a bath tub with a firehose Vs the garden hose, the firehose will kick ass.

More air = higher density under compression = more power.
 
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