S8 exhaust on A8L Success! Need Flap Actuator Vacuum Advice.
08-26-2016, 09:12 AM
#1
AudiWorld Super User
Thread Starter
Join Date: Feb 2012
Location: Moronville, Tennessee (Middle TN)
Posts: 2,223
Received 83 Likes
on
69 Posts
S8 exhaust on A8L Success! Need Flap Actuator Vacuum Advice.
I replaced a 7 foot- 7 inch section of the A8L exhaust with one unbolted from a 2005(?) S8, including the rear mufflers with their variable flow flaps. Miraculously, they are the same length! It connects from about where the front doors end . There are big band clamps there, and the S8 system bolts right up, same diameter pipe (60mm OD), the rubber hangers line up, and the rear (muffler) ones are pretty close. Of course, the rear valance has to be modified, but I've temporarily coat-hangered the rearmost mount points with their respective rubber mounts. It sounds far better but isn't loud, and I've gained so many HP 
that I only got 10 MPG on the last tankful, haha - mainly from keeping it in sport mode and enjoying the engine's high-rev sounds as I bullet away from every stop.
I've fixed the flaps in the open position against the rather strong pull of the solenoids' springs, and would like to find a rear vacuum source (I know there is a line going to the leak test pump in the right rear fender, but don't know if it's always on) to enable adjusting the sound, just because I can (can't envision a scenario where the car would be too loud as it is).
This would require a solenoid with the switch in the car.
Alternatively, I could run a vacuum line from a valve in the cabin to the rear. (I wonder if there is a vacuum source easily accessible in the cabin to avoid having to pass through the firewall?)
Anyway, HTH in case anyone's contemplating this "mod", and thanks for any input.
-Tom
that I only got 10 MPG on the last tankful, haha - mainly from keeping it in sport mode and enjoying the engine's high-rev sounds as I bullet away from every stop. I've fixed the flaps in the open position against the rather strong pull of the solenoids' springs, and would like to find a rear vacuum source (I know there is a line going to the leak test pump in the right rear fender, but don't know if it's always on) to enable adjusting the sound, just because I can (can't envision a scenario where the car would be too loud as it is).
This would require a solenoid with the switch in the car.
Alternatively, I could run a vacuum line from a valve in the cabin to the rear. (I wonder if there is a vacuum source easily accessible in the cabin to avoid having to pass through the firewall?)
Anyway, HTH in case anyone's contemplating this "mod", and thanks for any input.
-Tom
08-26-2016, 01:59 PM
#4
AudiWorld Super User
Thread Starter
Join Date: Feb 2012
Location: Moronville, Tennessee (Middle TN)
Posts: 2,223
Received 83 Likes
on
69 Posts
Oh, I got videos out the wazoo! I just have to edit out the illegal parts and "PID" ... My brother did a couple full-throttle runs in a nearby subdivision and he's says "shiste, I had to let off in second because I was going 80!". I just wanted some outside the car video.
This is My wife who was instructed to nail it... but i doubt she did. With the new setup, in "S". Sorry for the filthy-looking front wheels, but I've been driving it "in a spirited fashion" for a week... will wash soon.
Also, that's my retard neighbor's lawn; I don't think she took the shipping blocks out from her mower. Scalp-a-thon. No weed eating; (Tom will do that). She rides it DAILY (for pleasure, she told me it's "relaxing"). I told her she's got a blade out of balance. Offered to fix both problems but she likes her lawn the height of the greens on the nearby golf course.
This is My wife who was instructed to nail it... but i doubt she did. With the new setup, in "S". Sorry for the filthy-looking front wheels, but I've been driving it "in a spirited fashion" for a week... will wash soon.
Also, that's my retard neighbor's lawn; I don't think she took the shipping blocks out from her mower. Scalp-a-thon. No weed eating; (Tom will do that). She rides it DAILY (for pleasure, she told me it's "relaxing"). I told her she's got a blade out of balance. Offered to fix both problems but she likes her lawn the height of the greens on the nearby golf course.
Last edited by aTOMic; 08-26-2016 at 02:02 PM.
08-26-2016, 03:13 PM
#5
AudiWorld Senior Member
Go manual
I replaced a 7 foot- 7 inch section of the A8L exhaust with one unbolted from a 2005(?) S8, including the rear mufflers with their variable flow flaps. Miraculously, they are the same length! It connects from about where the front doors end . There are big band clamps there, and the S8 system bolts right up, same diameter pipe (60mm OD), the rubber hangers line up, and the rear (muffler) ones are pretty close. Of course, the rear valance has to be modified, but I've temporarily coat-hangered the rearmost mount points with their respective rubber mounts. It sounds far better but isn't loud, and I've gained so many HP that I only got 10 MPG on the last tankful, haha - mainly from keeping it in sport mode and enjoying the engine's high-rev sounds as I bullet away from every stop.
I've fixed the flaps in the open position against the rather strong pull of the solenoids' springs, and would like to find a rear vacuum source (I know there is a line going to the leak test pump in the right rear fender, but don't know if it's always on) to enable adjusting the sound, just because I can (can't envision a scenario where the car would be too loud as it is).
This would require a solenoid with the switch in the car.
Alternatively, I could run a vacuum line from a valve in the cabin to the rear. (I wonder if there is a vacuum source easily accessible in the cabin to avoid having to pass through the firewall?)
Anyway, HTH in case anyone's contemplating this "mod", and thanks for any input.
-Tom
that I only got 10 MPG on the last tankful, haha - mainly from keeping it in sport mode and enjoying the engine's high-rev sounds as I bullet away from every stop. I've fixed the flaps in the open position against the rather strong pull of the solenoids' springs, and would like to find a rear vacuum source (I know there is a line going to the leak test pump in the right rear fender, but don't know if it's always on) to enable adjusting the sound, just because I can (can't envision a scenario where the car would be too loud as it is).
This would require a solenoid with the switch in the car.
Alternatively, I could run a vacuum line from a valve in the cabin to the rear. (I wonder if there is a vacuum source easily accessible in the cabin to avoid having to pass through the firewall?)
Anyway, HTH in case anyone's contemplating this "mod", and thanks for any input.
-Tom
It was a real muscle car, not sure it was faster with the headers open. It sure sounded and felt faster.
Sad to say it was not any faster than an A8. Low 14's in the quarter and maybe 6.5-7.0 zero to 60. But it felt like a rocket ship.
Trending Topics
08-27-2016, 05:21 AM
#8
AudiWorld Wiseguy
If you want auto flaps, there's a vacuum line to a flap in the Airbox that only opens under wider throttle openings and higher Rpms. Not sure what controls it, but it's there. It wouldn't surprise me if the S8 uses this same line for the exhausts.
08-27-2016, 06:41 AM
#9
AudiWorld Super User
Thread Starter
Join Date: Feb 2012
Location: Moronville, Tennessee (Middle TN)
Posts: 2,223
Received 83 Likes
on
69 Posts
Great idea, Dave! That'd work. But I want it "Loud" all the time. It's barely audible inside the car unless you really "get on it". The greatest improvement is at idle; I can hear the rumble from inside the house whereas before the wife could drive up & park and I'd only hear the doors close.
As for pics, it's not cut yet... Hopefully today. We're still down one car and "Mine" (the one we're talking about) hardly sits still. I want to take my time doing this job. I started to do it but the dremel-type tool I had was totally inadequate, so I have bought another one. I have the pipes hanging below the valance, It doesn't look horrible to normal people (doubt they even notice) but for an "A8 Guy" it does look odd. Not as bad as I thought, though.
George, do you know if the 442's exhaust was stock or an exhaust cut-out?
I agree, it's funny how much faster cars seem when they're louder.
As for pics, it's not cut yet... Hopefully today. We're still down one car and "Mine" (the one we're talking about) hardly sits still. I want to take my time doing this job. I started to do it but the dremel-type tool I had was totally inadequate, so I have bought another one. I have the pipes hanging below the valance, It doesn't look horrible to normal people (doubt they even notice) but for an "A8 Guy" it does look odd. Not as bad as I thought, though.
George, do you know if the 442's exhaust was stock or an exhaust cut-out?
I agree, it's funny how much faster cars seem when they're louder.
08-27-2016, 09:09 AM
#10
AudiWorld Senior Member
Yes pics please!! Great post thank you. 
I've been investigating doing something very similar to what you did.
I'm confused... why do you need vacuum source. I thought these valves were spring pressure operated.
I've been investigating doing something very similar to what you did.
I'm confused... why do you need vacuum source. I thought these valves were spring pressure operated.