All current U.S. Scions have 4 cylinder engines.
The Scion Xb/Xa both share the 1NZ-FE 1.5 liter engine, rated at 108 hp at 6000 rpm and 105 ft-lb of torque at 4200 rpm.
The Xb got a new 2.4 liter engine with the 2008 model year that it shares with the Tc and Toyota Camery.
The Xd is an all new model replacing the Xa in the 2008 MY and shares an 1.8 liter 2ZR-FE engine with the Toyota Corrolla.
The Scion Tc has the 2AZ-FE 2.4 liter engine, rated at 161 hp at 5,700 rpm and 163 ft·lb of torque at 4000 rpm.
The 2012 Scion xB has an inline 4 engine.
The 2014 Scion tC has an inline 4 engine.
The 2013 Scion xB has an inline 4 engine.
The 2008 Scion tC has an inline 4 engine.
The 2011 Scion xD has an inline 4 engine.
The 2014 Scion xB has an inline 4 engine.
The 2009 Scion tC has an inline 4 engine.
The 2004 Scion xB has an inline 4 engine.
The 2013 Scion xD has an inline 4 engine.
The 2008 Scion xD has an inline 4 engine.
The 2010 Scion tC has an inline 4 engine.
The 2012 Scion iQ has an inline 4 engine.