What is the stock factory exhaust diameter for a 5th gen civic dx? And if you know, what is it for the 97 GSR (b18c1)? I'm puting a b18c1 into my EG and I want to know if I should change my exhaust. I am planning on installing i/h/e. Is there a good exhaust diameter that will provide more more than stock?
I know it can't be too big so that the vacuum can pull more exhaust out. Thanks a bunch for the info Honda Gurus! (insert: imoticon that kisses ass here)

2inch or 2.5 inch would be fine for a I/H/E combo.. that's the best power area for small engines, unless you're boosted or plan on more than 300 HP.. which you won't get on pump gas w/o hundreds of hours of tuning and rebuilding..

IIRC, the stock diameters of most honda's is like 1 3/8 ID.. they have a aluminized heatshield pipe on the outside of the actual pipe that makes it look bigger.. and provides a inner shield to keep heat in the exhaust pipe for the scavenging effect. (Higher heat == Higher ehxaust pressure == more flow due to added pressure == more "pull" in the exhaust flow for scavenging and "pulling" exhaust from the engine.)