[amRam]

This should be a simple question.

Let's say I have a 2.0L 4 cylinder engine running a small turbo at 12 psi and putting out 150 horses. What happens to the powerband if I get a larger turbo and run it at 12 psi (the same pressure)? Is the engine making the exact same amount of power?

If so, what's the advantage in having a bigger turbo? Just to be able to run higher pressure which the smaller turbo isn't capable of?

Discuss.

 

[GungHo]

 

[Grant]

The larger turbo will (generally) be more effecient than the smaller one. It will have to spin at less RPMs to created the same boost pressure, so it will heat up the intake charge less. If you have a huge intercooler, this probably won't help that much.

But the larger turbo will also have a larger exhaust wheel, and will require less exhaust pressure to spin the turbo at those less RPMs. This means less exhaust backpressure on the engine, so there is less exhaust left behind in the cylinders after each exhaust stroke, allowing more air + fuel in. And its easier for the engine to remove the old exhaust since there is less backpressure.

So yes, all other things being equal a larger turbo will make more power, although usually at a later RPM.

 

[amRam]

Alright, that's about what I figured... but the question remains... at 10psi, will a big 16g turbo make more power than a small 14b?

Seems that running 10psi on any size turbo would yield the same results on a dyno... because both a big and a small turbo would be forcing 10psi of air into the engine, only difference being that one is spinning slower than the other.

 

[SlowEclipseGS-T]

You have to remember that the larger turbo will be moving more air at the same boost pressure. So a 16G will be a little more powerful than a 14B at the same boost pressure. It won't be much however, since neither turbo is "big" by any standards...