why 2.5" o2?
why 2.5" o2?
Why are all o2 housings 2.5 inches? Why not a nice smooth transition up to three inches? It would seem that dumping a 2.5 inch pipe directly into a 3 inch pipe within inches of the turbo is not only a restriction but creates unnecessary turbulence. What am I missing here?
2.5" o2 housings are typically made because of space in the engine bay.. sure if you wanted to delete your ac and p/s etc you could fit as large as you want.. but because of clearances, they are made this way.. and I'm not sure if it is THAT big of a restriction.. my o2 housing on my turbo kit starts out at 2.5" and transitions to 3" I believe.. not 100 percent sure though..
The factory Donut gasket has an inside diameter of 2.5 inches; the OEM Donut Gasket helps add flex to the exhaust system the 2.5. Every Downpipe Made except the Buschur Downpipe has this immediate transition at the front flange to accommodate the OEM Donut Gasket. (IMHO and 99% of engineers) thinks there needs to be some flex somewhere or the exhaust system would be too rigid throughout the entire length. The engine torques and flexes and without any flex in the exhaust piping there would be extreme stress and will eventually cause failure.
To answer your question most if not all O2 Housings have designed into them the re-use of the Factory/OEM Donut Gasket; hence the 2.5 inch pipe. Also you might think just how much flow is coming out of the stock turbo, it can't outflow most 2.5 inch pipes. Maybe a larger RED Turbo or an engine breathing more efficiently could outflow the 2.5 pipe. In this case any added volume flow will help, whether there is a transition or not.
To answer your question most if not all O2 Housings have designed into them the re-use of the Factory/OEM Donut Gasket; hence the 2.5 inch pipe. Also you might think just how much flow is coming out of the stock turbo, it can't outflow most 2.5 inch pipes. Maybe a larger RED Turbo or an engine breathing more efficiently could outflow the 2.5 pipe. In this case any added volume flow will help, whether there is a transition or not.
I believe the WORKS unit has a outlet bigger than the OEM 2.5 but it is very expensive and needs the WORKS downpipe. I did not go with it because it was like $450 and the ebay one is $125.
2.5" o2 housings are typically made because of space in the engine bay.. sure if you wanted to delete your ac and p/s etc you could fit as large as you want.. but because of clearances, they are made this way.. and I'm not sure if it is THAT big of a restriction.. my o2 housing on my turbo kit starts out at 2.5" and transitions to 3" I believe.. not 100 percent sure though..
R/TErnie and I are making a 3in o2 currently for my car. It's going to be a 3in 02 housing with a 1.75in external dump tube. FastFreddie has a recirc 3in with vband on his downpipe to rid the 2.5 donut, so that way you have a straight 3in right off the hotside. I'm going same setup but external dump. I expect good gains over my megan. I'll keep everyone up to speed on the build.
Last edited by BLKCarbonEVO; Aug 14, 2009 at 07:16 PM.
