* 2.5i: A 2.5-liter inline-6 engine producing 184 horsepower.
* 3.0i: A 3.0-liter inline-6 engine producing 225 horsepower.
It's important to note that these are the standard engine options. There might have been other versions available in different markets, or special editions with modified engines.
To know the specific engine size of a particular 2005 BMW Z4, you'll need more information, such as the trim level or VIN.
