BETTER FLOW from a full 3" 02 housing or 2.5" to 3" for EVO3 16g?

[91 GSX]

I'm trying to find out if an all the way through 3" 02 housing, or a 2.5" inlet to 3" outlet 02 housing would have better flow when mated to an Evo3 16g turbo. I don't know what size exhaust exit that particular turbo has, but I do know I want a 3" exit from 02 housing. I wish to spend the money on a stainless steel tubular housing, preferably one which would match up to a 3" Apexi N1 turbo back exhaust on a 1G AWD. Any thoughts to FLOW QUESTION??????? Basically, in regards to exhaust flow, if you have let's say a 2" tube flowing into a 3" tube, would having a gradual sloping increase in size to the 3" be better, or not. Thanks in advance

 

[sergiosdsm]

most aftermarket 02 housings exit at 2.5 inch. A 3 inch one is not needed unless you have a downpipe that starts at 3 inch anyway and the apexi n1 downpipe starts at 2.5 and after the flex section goes to 3 inch. I think you would be waisting money buying a 3 inch one, just get a external dump 02 housing from punishmentracing.com and call it a day.

 

[ivanr4g63]

the 2g O2 housing flows good enough even for the e316g turbo, porting helps alot, specially since this turbo loves to creep alot on high flow exhaust. If you're worried about best flow/performance of your setup get a basic 2.5" to 3" downpipe most vendors have and 3" thereafter madrel bent of course, then make sure you have a ported wastegate on your turbine housing, and ported 02 housing, I don't think you'll ever need a 3" 02 housing for a 16g, hell unless you have a full race car, you'll probably won't need it even with a bigger turbo.

3" Cat-Back exhaust flows pretty good, and you will not see much difference from a 2.5" to a 3" downpipe, if anything your torque curve will move a little higher up in the rpm but not by much. matter of fact the bigger the exhaust on your 16g turbo setup the harder is going to be to control your boost if you decide not to have a porting job on it.
(believe me, I have a full 3" turboback mandrel bent, no cat, and an Evo316g turbo, and boost creep was real bad until I ported the turbine housing)