I just wanted some opinions from people regaurding the relevence of higher displacement in a turbo application. Will an 84mm B series necesarily make more power than an 81mm with all other things created equal? Is the displacement going to increase the power or just help to spool a larger turbo and make more of a powerband.

 

with all other things equal yes the 84mm bore will make more power over the 81mm.....

 

I assume that by more power, you mean at any given rev point at all points below a certain small percentage at the very very top end, the 84mm will make more power than the 81mm. Things get a little more complicated when you get closer and closer to some limitation... flow efficiencies of various components (cylinder head, 4 ports of entry/exit on the turbo, etc.)

 

a bigger bore motor will always make more ftq not always alot more whp

 

All any engine is doing is filling a cylinder with air and fuel and combusting it. So by having a bigger cylinder you can naturally put in more air and fuel.

But like mentioned previosuly, if your head and manifolds and piping are close to the max by filling 1.8L, then you will realize "less" gains by going to 2.0L than if your system had plenty of headroom over 1.8L.