Looking for a performance exhaust system for a 01 S8 ?
03-08-2007, 03:29 PM
#4
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Custom dual exhaust with x-pipe
Swen undoubtedly has the best S8 exhaust on two continents.
<a href="https://forums.audiworld.com/a8/msgs/56520.phtml">Stage 1</a>: dual exhaust
<img src="http://www.tyresmoke.net/attachments/133820-IMG_3974s.jpg">
<a href="http://www.tyresmoke.net/ubbthreads/showflat.php?Cat=1,20,22,25,27,3&Number=246410&pag e=1&view=collapsed&sb=5&o=&fpart=1">Stage 2</a>: x-pipe installed (note the 292 g/sec <a href="https://forums.audiworld.com/a8/msgs/114304.phtml">MAF</a>, the highest ever seen on any A8/S8)
<img src="http://www.tyresmoke.net/attachments/246388-173_7311s.jpg">
Several have used a <a href="https://forums.audiworld.com/a8/msgs/99080.phtml">Magnaflow x-pipe</a>.
<img src="http://www.tonypai.com/2005_0707Image0009.JPG">
<a href="https://forums.audiworld.com/a8/msgs/56520.phtml">Stage 1</a>: dual exhaust
<img src="http://www.tyresmoke.net/attachments/133820-IMG_3974s.jpg">
<a href="http://www.tyresmoke.net/ubbthreads/showflat.php?Cat=1,20,22,25,27,3&Number=246410&pag e=1&view=collapsed&sb=5&o=&fpart=1">Stage 2</a>: x-pipe installed (note the 292 g/sec <a href="https://forums.audiworld.com/a8/msgs/114304.phtml">MAF</a>, the highest ever seen on any A8/S8)
<img src="http://www.tyresmoke.net/attachments/246388-173_7311s.jpg">
Several have used a <a href="https://forums.audiworld.com/a8/msgs/99080.phtml">Magnaflow x-pipe</a>.
<img src="http://www.tonypai.com/2005_0707Image0009.JPG">
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03-09-2007, 05:54 AM
#8
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Great post Randy... as a...
...NEWB to this forum last fall I'd missed such gems!
I feel enlightened by the Tyresmoke chatter, great data.
I'm intrigued by this X-pipe. If I understood it all correctly it gives a slightly more muted yet refined tone, showed a measurable increase to MAF performance, and gives slightly better WOT power?
I got a good local bender who could bang that out for me. I'll try to scrounge together a few clams come spring maybe and have at it.
Any benefit from buying that $75 or whatever Magnaflow'er vs. the DIY fab'd "X"?
Thanks again for the enlightenment, always appreciated.
I feel enlightened by the Tyresmoke chatter, great data.
I'm intrigued by this X-pipe. If I understood it all correctly it gives a slightly more muted yet refined tone, showed a measurable increase to MAF performance, and gives slightly better WOT power?
I got a good local bender who could bang that out for me. I'll try to scrounge together a few clams come spring maybe and have at it.
Any benefit from buying that $75 or whatever Magnaflow'er vs. the DIY fab'd "X"?
Thanks again for the enlightenment, always appreciated.
03-09-2007, 07:14 AM
#9
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The X-pipe better handles the uneven firing order of the Audi V8.
With the following physical motor layout,
1 .. 5
2 .. 6
3 .. 7
4 .. 8
The flat crankshaft of a Ferrari V8 has a 1-8-3-6-4-5-7-2 firing order. Note that cylinders take turns firing in each bank. Even if the exhaust system had no crossover at all, the pulses from each bank of headers would be evenly spaced. Lotus and TVR V8's also use flat cranks.
The 90-degree crank of Audi's V8 has a 1-5-4-8-6-3-7-2 firing order. Note that the 8-6 and the 2-1 (wrap-around) are firing cylinders consecutively in the same bank. This is what's causing the back pressure with an H-pipe crossover, especially at high rpm's, and the more raucous exhaust note. Relieving that back pressure with the X-pipe is what allows the HP gains. An X-pipe exhaust system is also noticeably quieter than an H-pipe exhaust (allowing the removal of one of our mufflers?), and since the pulses are equalized thru each of the dual exhaust pipes, the sound is more like that of the Ferrari, especially at high rpm :-)
And then there's the brute force solution as used in the original Ford GT40. Note that some of the primary headers in the "bundle-of-snakes" cross over before they reach the collectors.
<img src="http://xtremeclassics.com/images/1stdrive12-640.jpg">
Re: A Magnaflow vs DIY X-pipe ... Their's probably no performance advantage one way or the other. However, I believe the Magnaflow X-pipe is mild steel; a DIY X-pipe could be stainless.
1 .. 5
2 .. 6
3 .. 7
4 .. 8
The flat crankshaft of a Ferrari V8 has a 1-8-3-6-4-5-7-2 firing order. Note that cylinders take turns firing in each bank. Even if the exhaust system had no crossover at all, the pulses from each bank of headers would be evenly spaced. Lotus and TVR V8's also use flat cranks.
The 90-degree crank of Audi's V8 has a 1-5-4-8-6-3-7-2 firing order. Note that the 8-6 and the 2-1 (wrap-around) are firing cylinders consecutively in the same bank. This is what's causing the back pressure with an H-pipe crossover, especially at high rpm's, and the more raucous exhaust note. Relieving that back pressure with the X-pipe is what allows the HP gains. An X-pipe exhaust system is also noticeably quieter than an H-pipe exhaust (allowing the removal of one of our mufflers?), and since the pulses are equalized thru each of the dual exhaust pipes, the sound is more like that of the Ferrari, especially at high rpm :-)
And then there's the brute force solution as used in the original Ford GT40. Note that some of the primary headers in the "bundle-of-snakes" cross over before they reach the collectors.
<img src="http://xtremeclassics.com/images/1stdrive12-640.jpg">
Re: A Magnaflow vs DIY X-pipe ... Their's probably no performance advantage one way or the other. However, I believe the Magnaflow X-pipe is mild steel; a DIY X-pipe could be stainless.
03-09-2007, 07:29 AM
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Neat stuff, good reading as always from you Randy. Now...
...it was noted somewhere previously the mid muffler is doing the majority of the muffling. Your thought on an X pipe being quieter may translate into possibly being able to (acceptably) run sans rear box then? Odd as that's contrary to what I ran on me E28 ///M5 - removing the resonator was the key there, as well as on a 300E I had. But I'll take yous guys word on that of course!
The key is on the "acceptably" part - I don't want an IROC certainly. Hmmm... I have to play guinea pig I guess. I'll chew on that with the bender when the time comes, maybe spring / summer, and see what I come up with. Whereas I want 'some' more sound I don't want much, esp. too much.
I gotta spend some more time outside of the car during WOT driveby's and try and listen to what it's asking for 8-). Always fun!
The key is on the "acceptably" part - I don't want an IROC certainly. Hmmm... I have to play guinea pig I guess. I'll chew on that with the bender when the time comes, maybe spring / summer, and see what I come up with. Whereas I want 'some' more sound I don't want much, esp. too much.
I gotta spend some more time outside of the car during WOT driveby's and try and listen to what it's asking for 8-). Always fun!