The new turbo I'm installing will have 4" tubing for the intake side (vs. the stock 3" tubing). If I put a 4" air filter on the end of the tubing, it will end up being placed where the AFM is, right next to the radiator, sucking in all that hot air. On the other hand, I can run a reducer on it to make it 3" tubing again and be able to put the filter in front of the radiator, where there's significantly cooler air.

So the question is, which method would perform better, the larger filter that sucks in hot air, or a more restrictive diameter filter that sucks in cool air?

 

Enlarge the hole in the radiator support by 1". Hot air sucks!

 

does the ZXT have the stock filterbox in the same position as mine, infront of the radiator? I just hacksawed the box off of the assembly and used the existing metal hard tubing to hold my cone filter

 

The stock airbox is only a 3" dia, so that doesn't solve the question of 3" filter in front of the radiator vs. a 4" filter that sucks up hot air.

 

I'd think it wouldn't matter. Hot air is hot air, and cooler air is always going to be better going through your intake than hot air.