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kellcats521 kellcats521 is offline
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Join Date: Feb 2005
Location: Atlanta Metro
Posts: 219
Originally posted by WydRyd
OK, would there be any adverse effects using headers with 1 1/2" primaries on heads which have 1 5/8" exhaust ports?
Without having a smooth transition down to the smaller primaries, you'll have really poor exhaust flow since there's a lip that the gasses are slamming into, and the temp of your heads will also increase (this can't ever be a good thing in a Porsche).

If you bought or made some spigots and used them to make a transition down to the header primaries, they would work much better.

Also remember, most turbo experts want the least resistance as possible on the exhaust side. Typically, the scavanging ability of a faster exhaust flow rate (helping to fill the cylinder during the intake stroke) is not relevant in a turbo motor, as the compressor force feeds it. But too much exhaust volume slows low RPM flow, and it will increase lag - everything is a tradeoff of sorts.....

Pat K
Old 03-30-2007, 03:41 AM
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