I've seen much debate on what is the best size for exhaust for an SR20DE (2 1/4 or 2 1/2). I'm just curious what size the collectors are on the popular headers for our cars (Hotshot, Stillen, etc). Anybody have an answer?

Thanks:)

You left out 3".

I know I left out 3" and 2 3/8" too. I'm trying to plan out my exhaust and header purchase... and would be interested in comparing collector sizes.

most headers are 2.5" downpipes into the stock 2.5" cat. Usuall for NA a 2.25" exhaust is plenty but if you run NOS then a 2.5" will help that out.

Brent

OEM cat has larger diameter than either Hotshot Gen IV secondary or Courtesy exhaust. I would measure it but I gave it away. Courtesy exhaust is 60mm.