Quad Exhaust fitted.
05-05-2008, 03:28 AM
#13
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The x-pipe removes the raspy tone that normally results from the uneven firing order of a V-8.
The exhaust note also becomes both slightly quieter and higher pitched. I had a video link (now broken) to the first NASCAR race where only one car uses an x-pipe. Surprise surprise, the x-pipe results in a slight HP increase, and the car won with a huge lead. Since they race without mufflers, the difference between and x-pipe and h-pipe was easy to hear.
On a more technical note ... Most V8's use what's called a "dual-plane crankshaft". V8's from Ferrari, Lotus, TVR, and a few others use a "flat crankshaft". The main difference is in the firing order.
CYLINDER NUMBERING SYSTEM:
1 2 3 4
8 7 6 5
Ferrari V8 flat crank firing order
1 - 5 - 3 - 7 - 4 - 8 - 2 - 6
Audi V8 dual-plane crank firing order
1 - 5 - 4 - 8 - 6 - 3 - 7 - 2
A 4-cycle motor takes two complete revolutions (or 720 deg) to complete one cycle; and with eight cylinders, one fires every 90 deg. Note that the firing of the Ferrari's cylinders alternates back-and-forth between banks. With the Audi motor, twice every 720 deg (once each bank), two of the cylinders in a bank fire in succession.
With an H-Pipe or no crossover, the pulses resulting from the uneven firing order carry all the way to the exhaust tips. The X-pipe crossover distributes the flow from each bank evenly thru both exhausts, and the raspy sound resulting from the uneven firing order is not apparent at the exhaust tips. The result does seem to have a higher pitch, just like a Ferrari V8 :-)
The dual-plane crank in a Ford GT40 uses another solution, the bundle of snakes headers. Note that two of the primaries from each side cross over to the other side!
<img src="http://home.comcast.net/~lemanswinner/mar03/Mar16_013.jpg">
On a more technical note ... Most V8's use what's called a "dual-plane crankshaft". V8's from Ferrari, Lotus, TVR, and a few others use a "flat crankshaft". The main difference is in the firing order.
CYLINDER NUMBERING SYSTEM:
1 2 3 4
8 7 6 5
Ferrari V8 flat crank firing order
1 - 5 - 3 - 7 - 4 - 8 - 2 - 6
Audi V8 dual-plane crank firing order
1 - 5 - 4 - 8 - 6 - 3 - 7 - 2
A 4-cycle motor takes two complete revolutions (or 720 deg) to complete one cycle; and with eight cylinders, one fires every 90 deg. Note that the firing of the Ferrari's cylinders alternates back-and-forth between banks. With the Audi motor, twice every 720 deg (once each bank), two of the cylinders in a bank fire in succession.
With an H-Pipe or no crossover, the pulses resulting from the uneven firing order carry all the way to the exhaust tips. The X-pipe crossover distributes the flow from each bank evenly thru both exhausts, and the raspy sound resulting from the uneven firing order is not apparent at the exhaust tips. The result does seem to have a higher pitch, just like a Ferrari V8 :-)
The dual-plane crank in a Ford GT40 uses another solution, the bundle of snakes headers. Note that two of the primaries from each side cross over to the other side!
<img src="http://home.comcast.net/~lemanswinner/mar03/Mar16_013.jpg">
05-05-2008, 04:05 AM
#14
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B6 S4 V8 YouTube comparison of custom exhausts
It's not the same car, but ...
<a href="http://www.youtube.com/watch?v=r2HxjG7jbdo&NR=1">H-pipe</a>
<a href="http://www.youtube.com/watch?v=ENVwLlOZ-d4">X-pipe</a>
The former sounds more like an American muscle car, I prefer the latter.
<a href="http://www.youtube.com/watch?v=r2HxjG7jbdo&NR=1">H-pipe</a>
<a href="http://www.youtube.com/watch?v=ENVwLlOZ-d4">X-pipe</a>
The former sounds more like an American muscle car, I prefer the latter.
05-05-2008, 05:17 AM
#15
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OKOKOKOK...I spend more time moving that sucker around the garage than anything so...
I'll try and get on "that" again here. Wayway back I'd shot the "before" portion of the vid, dunno if I have a clue where "that" is now and if not no time to shoot again.
I'll see what I can come up with here tho for time / place to hack it in.
Stay tooned.
I'll see what I can come up with here tho for time / place to hack it in.
Stay tooned.
05-05-2008, 06:30 AM
#17
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I'll try and get some motivation to log some AC-22 runs before and after if I can...
...finagle an install soon and see what if any power gains are had.
Don't bother fabbing one, I got mine off fleabay for like $66 or some crap.
Lordy. All the exhaust talk has exhausted my will power - now I'm looking into a system for der 930 - dammit! I'll try and give new meaning to the word "Stimulous check" heh heh...
Don't bother fabbing one, I got mine off fleabay for like $66 or some crap.
Lordy. All the exhaust talk has exhausted my will power - now I'm looking into a system for der 930 - dammit! I'll try and give new meaning to the word "Stimulous check" heh heh...
05-05-2008, 06:59 AM
#18
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Heh, I've heard Zork Tube'd cars and they're SINISTER loud - criminal even! Tho the sound of...
...the turbo whining and wailing *is* nut tickling sure.
Waaaaay too obvious 'what you're doing' for me heh heh heh.
I'd keep it nice and simple. I'm toying with the one on the lower left <a href="http://www.rarlyl8.com/">here</a> (click on Turbo, scroll down). Not sure if I like the protruding tips on left better or the flush / tucked ones on right. Dunno. We'll see. WG def. being dumped to atmosphere tho!
Waaaaay too obvious 'what you're doing' for me heh heh heh.
I'd keep it nice and simple. I'm toying with the one on the lower left <a href="http://www.rarlyl8.com/">here</a> (click on Turbo, scroll down). Not sure if I like the protruding tips on left better or the flush / tucked ones on right. Dunno. We'll see. WG def. being dumped to atmosphere tho!
05-05-2008, 07:23 AM
#19
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Re: Cheers on the great DIY ! Sounds fierce. Now all you need to do is fix..
LOL,
Hmmmm; damned colonials, I think I'll have to round up some Redcoats and teach you a driving leson!!!
:P
Mike
Hmmmm; damned colonials, I think I'll have to round up some Redcoats and teach you a driving leson!!!
:P
Mike
