ok so i'm in the process of tunning up my hatchback w/b18. obviously i'm going to have to go with custom exhaust. it's got one on there right now, but i think its too big. whats the proper size piping for this engine with dc sport headers, and j's intake. i'm sure theres some internal mods as well as minor bolt ons. i think it has a zex FPR, so i know there was nitrous on the setup. but i really need a n/a piping size. thanx in advance

 

2.5'' should do you right.

 

2.25 mandrel bent, 2.5 crush bent.

 

 

2.25 down the middle, 2.5 after the first bend

 

2.5 is too large at any point in the exhaist system for a naturally aspirated b18a/b, mandrel or crimp bent in my opinion. 2.25 will be fine. You won't be flowing enough air to make proper use of the larger size. You will only lose power.