2nd Generation Specific 1986-1992 Discussion

5th & 6th Ports?

Old 05-25-2004, 09:53 PM
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I just put an exhaust on my S4 n/a. I didn't realize the 5th and 6th port backpressure thing. So after I found this out I decided to check my backpressure, well to my surprize I have a WHOPPING ONE HALF POUND OF BACKPRESSURE. What can I do to get the optimal performance without plugging up my exhaust? I have heard of wiring them open, so I tried it. It felt pretty good once I got up to the power band but low end, I think I took a lot of life off of my clutch, cause the thing would stall so easy. Can I take them out? What are "pinnapple inserts"? PLEASE ANYONE, ANSWERS!!!



Thanks, Jack.
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Old 05-25-2004, 10:37 PM
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how did you measure the actual backpressure? I have an 88se, with the stock exh. mani, t2 downpipe, and straight pipe exh to the stock mufflers, and mine operate fine. You wont be able to see if they're opening like they should, since the engine needs load to activate them, rather than just revs. fc3s.org has a couple of options for getting them to open off of diff vacuum sources, like the airpump or a standalone air compressor and rpm switch.
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Old 05-26-2004, 09:42 AM
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Originally Posted by ambassador_josh' date='May 25 2004, 11:37 PM
how did you measure the actual backpressure? I have an 88se, with the stock exh. mani, t2 downpipe, and straight pipe exh to the stock mufflers, and mine operate fine. You wont be able to see if they're opening like they should, since the engine needs load to activate them, rather than just revs. fc3s.org has a couple of options for getting them to open off of diff vacuum sources, like the airpump or a standalone air compressor and rpm switch.
That's interesting about the T2 dp. I didn't know that would work on NA. How does the power feel? I was considering a switch back to the stock mani with a pipe to get more torque for autocross. My car has no low end.









Jack, don't forget the FAQ section in here, theres plenty of good posts about this. six port faq
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Old 05-26-2004, 02:19 PM
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why does the motor need a load to create the back pressure? i have 3" pipe off the stock manifold. to an empty cat housing to a high flow v-force muffler. 3" y-pipe into 3"tails and stainless tips.. i measure the backpressure from the downpipe right after the manifold. 1/2 #
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Old 05-26-2004, 05:26 PM
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with the t2 dp, theres no low end change that I've felt, but there is a bit of top end...its almost like a cat-delete pipe.
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