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Originally Posted by jspeedm
just so you know. a 3" exhaust is not the best for a na ka. 2.5 is the largest you want to go.
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For what NA KA? For YOUR application, 2.5" did yield better performance gains, but don's jump to conclusions and say a built NA motor should run the same exhaust as your stock motor. On a KA that is even mildly built NA (little bit more than just intake/exhaust), a larger diameter pipe will be more beneficial...
A higher HP motor needs to push that gas out faster. A higher comp motor has more gasses to get out and needs them out faster, especially if valve lift/duration have been modified. Too much back pressure is lack of win and there needs to be a happy balance between flow restriction and velocity. You want the exhaust to exit the combustion chamber and speed along at the highest velocity possible - you want a FAST exhaust flow.
On the NA KA I am building (full rebuild, overbore/high comp pistons, dual exhaust cams, dual valve springs, titanium valves, port/polish head and intake manifold, fuel system upgrades) I'm sure as hell not gonna run a 2.5" inch exhaust when I'm done. I'll be running a custom 3" mandrel bend full exhaust with a custom header as well.
I doubt this guy is gonna be running a 2.5 exhaust any time soon...
Quote:
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Originally Posted by Greaser_
Its an insane drive. Spins 275's out back like a turbo car.
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