Well I cant say for sure because I didnt measure the stock exhaust diameter, but I would say it is about 1 3/4" but dont quote me on it. A 2.5" I think would be to big it would be like putting a 4" on your RSX in the end it will hurt you. You can throw a 3" on your RSX with out a problem and you will make power at a Lower RPM and all the way threw the power band.looks good! i can't wait for the vid!
question though, im just wondering if the stock piping is less than 2", wouldn't there be a loss of TOO MUCH backpressure if trying to push towards the 2.5" mark? making this 2.25" axleback (with hopefully a matching midpipe) perfect for our cars? i know on my rsx, stock piping was 2.25" and aftermarket had a couple 2.36" and predominantly 2.5", leaving 3" diameters for turbo. im not a motorhead or anything like that, i was just asking based on the diameter discrepancies from stock. i know more flow means more power, but is there such a thing as too much flow?