Turbo's an pressue and power increase

[gaara]

Hello,

 

to put simply.

 

i have an engine and a small sized turbo that allows 9psi of air into the engine. an where the pressure is read from is a 2 inch pipe(lets say) that thereafter goes straight into the piston.

 

ok so the system is EXACTLY the same.. but we change the size of the turbo to a bigger one.. an still have it at 9psi.....

 

my friend reckons that the car goes faster with the bigger turbo... but i dont see how that is possible....

 

can someone please rectify this problem thank yohu.

[Ndi]

The size has to do with the quantity of air delivered. A bigger turbo that has the same pressure (limited) is able to drive an engine of a larger displacement, but the relative boost would be the same.

 

The system is simple. For a one-litre engine, one litre of air is sucked in every cycle (note this means every two rotations for a 4-stage engine). The air is at 1 atmosphere. Raise pressure to 1.3 atm and you get 1.3 liters of air in. Add 1.3 x gasoline and you have yourself a 1.3 liter engine.

 

As a result, pressure determines power, not flow. If your turbo is too small, it will not be able to deliver the same pressure because the engine is sucking up more than the turbo delivers. Add a bigger turbo and you have the ability to build up more pressure. If you limit the pressure (via wastegate/blow-off/pop-off) then excess air will be vented.

 

You can only get more power if you get more pressure in. As a sidenote, this can be hazardous to the engine.

 

As another sidenote, a bigger turbo is, well, bigger and it needs more power from exhaust gases to turn at the same rate. Make it too big and you get LESS pressure. If you overdo it you might have the turbo not spin at all and the power decreases.