Quote:
Originally Posted by Reaper
well most turbo kits have a 2.5 outlet unless you're running a gtx30. I know my GTX2867r is 2.5 but feeds into a 3 inch DP then has a 2.5 flange on the bottom like most kits. But what everyone seems to forget is even though most kits have a 3 inch DP they have 2.5 inch flanges on to mate with just about every overpipe on the market. Fullblown made 605whp on a factory overpipe! (I think that's 2.2), and I made 461whp with a 2.5 perrin op matted to a 3 inch fullblown exhaust. Now exhaust gasses slow down as they cool down so a 2.5 op matted to a 3 inch exhaust can make a great difference in spool. This is also why stepped headers work. Which is probably why fullblown was able to make good power on the factory OP with a 3 inch exhaust. As the exhaust pulse moves away from the turbo it cools and effectively expands as it slows. So fatory OP to 2.5 works, or 2.5op to 3 inch exhaust works. Will you be limited on power? A little with the 60r. I think king tut made 280wtq on a 2.5 perrin exhaust but you'd have to ask him yourself. Will it hurt spool? Yes but you may not notice it until you put a bigger exhaust on later. Over 350whp the turbo will work a little harder to make the same power as something with a 3 inch exhaust. For reference fullblown made 300whp on a factory exhaust on 93. swapped it all out and made I think 320whp+.
in short, the 60r is small but the 80r is pretty damn big for the street and very loud. fullblown and perrin make some nice 3 inch exhausts but they have zero ground clearance. Perrin, nameless and abunch others make nice 2.5's. if you want next weekend I can have video of the fullblown dual 3 inch.
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Exhaust gases expand as they heat and contract as they cool. Gases contracting during travel through a constant piping size is what will cause a decrease in velocity, and is why stepped headers/exhaust components are effective in maintaining velocity.