If I have a 8psi external wastegate spring...
Turbo A is a small T25
Turbo B is a big T3

If both use the same external wastegate... will the wastegate open at exactly the same pressure's in the manifold? Is it as simple as - just that the larger turbo makes more horsepower at the same pressure?

I don't quite understand

thanks

 

If everything is correct otherwise, yes. Internal gates can be picky. Usually mechanical problems, not the can.

Boost is a measure of resistance. Might be the cylinders didn't clear because you have a small turbo and lots of exhaust pressure. This will show as more boost and will have a lower VE, or less power.

A bigger turbo has less exhaust pressure because the turbine is bigger. The engine clears the exhaust out much better. 8PSI in the manifold there means a lot more burnable **** made it into the cylinder, so it makes more power. Turbo is probably also spinning slower making less heat, too. Still pumps more air and air is power.

 

Yes, as deezums said. I swapped from a Garrett 2560 to a 2871R and kept the same external wastegate and spring. The new turbo made a LOT more power at 12psi, but spooled slower (obviously).