buy the RB header now, convert it later

https://www.rx8club.com/rx-8-racing-...rx-8-a-220741/

^^do not use a diverging collector like the OP did though


another one:

https://www.rx8club.com/series-i-aft...6/#post4374261

And another: https://www.rx8club.com/rx-8-racing-...2/#post4668544

Again, DO NOT use a diverging collector. The main gain comes from having a straight 3" outlet right into a 3" midpipe. A longer, smoother merge angle is better than short, steep angle, but if you have a cat then you are limited with what you can fit in there. The most gain comes from having 3" straight thru all the way to the back. It really has nothing to do with tube length, equal tube length, etc. Short tube can make same power as long tube if you do the above. There are a few other factors if you want to quibble over a 2 or 3 hp difference.




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