# Cataylic converter question? **URL:** \ **Category:** SON240sx Automotive\ **Created:** [December 13, 2008, 5:53am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556 "2008-12-13T05:53:35Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![JDM-KID](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/jdm-kid/32/5640_2.png) [@JDM-KID](https://forums.speedlife.net/u/JDM-KID)\ **Post date:** [December 13, 2008, 5:53am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/1 "2008-12-13T05:53:35Z")
Hey guys I have a question about a high flow cat for an s13. I need a cat with a 2.5" inlet and a 3" outlet is there such thing? I’ve checked Google but had no luck. The reason why I need one with that sizing is because aftermarket headers have a 2.5" inlet and the exhaust I could get for free has 3" so now you see the problem. I know I could just buy a 2.5" catback but I’m trying to save money.lol Or I could custom fab the header outlet flange to a 3" flange since I’m a welder:) what do you guys think. Thanks ---
**Author:** ![87s15lt1](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/87s15lt1/32/5706_2.png) [@87s15lt1](https://forums.speedlife.net/u/87s15lt1)\ **Post date:** [December 13, 2008, 5:57am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/2 "2008-12-13T05:57:04Z")
or just buy/make a 2 1/2" pipe fit inside a 3" pipe. just need to bump it up. easy as pie. do it all the time. could proably buy an adapter. ---
**Author:** ![UNDEAD\_S14](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/undead_s14/32/5735_2.png) [@UNDEAD\_S14](https://forums.speedlife.net/u/UNDEAD_S14)\ **Post date:** [December 13, 2008, 5:58am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/3 "2008-12-13T05:58:25Z")
i’m haveing this same problem at the moment with my s13 ---
**Author:** ![87s15lt1](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/87s15lt1/32/5706_2.png) [@87s15lt1](https://forums.speedlife.net/u/87s15lt1)\ **Post date:** [December 13, 2008, 6:00am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/4 "2008-12-13T06:00:15Z")
^^^ post intro son. in new members section. this is not new members section ---
**Author:** ![sidewayz240](https://avatars.discourse-cdn.com/v4/letter/s/e99b99/32.png) [@sidewayz240](https://forums.speedlife.net/u/sidewayz240)\ **Post date:** [December 13, 2008, 6:07am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/5 "2008-12-13T06:07:01Z")
Meh, I’ve been using a 3" highflow on a hotshot header (2.5") for a long time now, works fine just get a good gasket. Its when you go from bigger diameter to smaller that you’ll run into problems. ---
**Author:** ![JDM-KID](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/jdm-kid/32/5640_2.png) [@JDM-KID](https://forums.speedlife.net/u/JDM-KID)\ **Post date:** [December 13, 2008, 6:08am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/6 "2008-12-13T06:08:57Z")
^ true thanks man:) ---
**Author:** ![alesserfate](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@alesserfate](https://forums.speedlife.net/u/alesserfate)\ **Post date:** [December 14, 2008, 10:30pm UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/7 "2008-12-14T22:30:55Z")
I bought a magnaflow high-flow cat that is 3" inlet and outlet from PDM racing a couple of years ago. One side of it is bolted to my 3" downpipe and the other side is bolted to the stock exhaust which isnt 3". Maybe that one is compatible with all ? Good luck. ---
**Author:** ![KoukiS14](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/koukis14/32/5522_2.png) [@KoukiS14](https://forums.speedlife.net/u/KoukiS14)\ **Post date:** [December 15, 2008, 7:40am UTC](https://forums.speedlife.net/t/cataylic-converter-question/120556/8 "2008-12-15T07:40:34Z")
Simply use a 3-inch cat and either weld a 2.5 flange onto the side that attaches to the header or just use all 3-inch. The 2.5 will seal to a 3 no problem. I ran this setup on my brothers car. Had DC headers to a 3inch cat which had a 2.5 flange welded onto it.