OK guys for those of you wishing to carry out the above this will hopefully give you the info required to help you on the way.
On the face of it it seems like a big job but when its broken down into sections it really is not that bad to do.
So I went about the job by first trawling through ELSA, ETKA and Bentley manuals to see what parts are needed to complete.
The key components to working ACC are (Note the S8 related parts)
[]S8 Instrument Cluster 4E0 920 981 FX
[]Distance regulation control stalk 4E0 953 521 C 4PK
[]Gateway with extended CAN 4E0 907 468 F or 4E0 907 468 H
[]Radar unit 4E0 907 561 F
[]Plug housing for radar 4E0 972 713
[]Terminals for radar Plug housing can be found here
[]Plug seals for housing here
[]Wire seals for housing here
[]S8 Grill suitable for ACC 4E0 853 651 AM 1RR Grill comes with no number plate surround or fasteners but does include radar cover.
[]licence plate holder 4E0 807 285 AD 1RR
[]4 x Panel Screws N 104 055 02
[]4 x Speed Nuts N 900 942 01
[]1 x Repair wire for Gateway extra wiring 000 979 010 E
[]1 x Repair wire for Mini Fuse fitment 000 979 021 E
[*]3 x M6 x 16mm bolts for mounting radar N 104 492 02 (Specially coated to prevent corrosion don’t cheap out and use normal ones)
You will also need to source the following if you don’t have it already
[]0.5mm2 max wire in suitable colours or a way to clearly identify your wires
[]Good tool kit This is what I used
[]Soldering Iron
[]Heat shrink
[]Crimping pliers for the terminals Like these
[]Crimping pliers for Normal electrical crimps
[]Multimeter for testing
[]Tyraps
[]Dielectric grease
[]Coroplast loom tape
[*]Plenty of time
Before starting work do a full Auto scan and be sure to save the results.
I recommend you have at least a radar, gateway, and the parts for wiring that are needed so you can test the radar before removing the bumper etc and having a disappointment.
Begin by making a harness for the radar to the Gateway and fuse box, I made mine starting at the Radar end so it would be an unbroken loom without joints on the outside of the car.
Pace out the length needed from front centre, across the front to passenger headlight, over the top of the wing and onwards to the inside giving yourself plenty extra so you can terminate inside the car.
Using two separate coloured wires mount them in a drill and fasten other ends in vice or have assistant help, twist the wires together to form a twisted pair of fairly tight lay up <20mm
http://forum.a8parts.co.uk/attachment.php?attachmentid=11622&stc=1&d=1439560231
http://forum.a8parts.co.uk/attachment.php?attachmentid=11623&stc=1&d=1439560231
Then cut and terminate the other wires ready not forgetting to place the wire seals on first
Insert the terminals in the housing after unlocking the pink locking strips by pushing them across the housing, with the locking tang facing outwards of the housing until you feel it snap into place.
Do not push in the wire seals yet!!!
Once you have done that check the continuity of the harness with a multimeter by back probing the housing before proceeding any further, once happy tape the harness together using the coroplast tape. (Sorry no pictures)
Still don’t insert the seals yet!!!
The wire numbers and my colours are as follows
1-Ground (Blue)
2-Can-H (Orange)
4-Can-L (Yellow)
12-!2v Positive feed (Red)
http://forum.a8parts.co.uk/attachment.php?attachmentid=11624&stc=1&d=1439560409
http://forum.a8parts.co.uk/attachment.php?attachmentid=11625&stc=1&d=1439560409
This is the wiring diagram
http://forum.a8parts.co.uk/attachment.php?attachmentid=11640&stc=1&d=1439567880
Next would be the replacement of the Gateway and inserting extra wires to gateway harness and test the radar.
The Gateway is at the heart of the system changing it will not create any problems with the car while you are using it prior to fitting the other parts, you will however get a fault logged saying there is no comms with radar which is to be expected.
I am of the understanding that the Q7 gateways can be used in the A8/S8 but there is a chance that Component Protection will kick in if fitted.
I chose to stick to A8/S8 part numbers that were relevant to the systems I wanted in the car and I did not encounter CP on the fitment of the Gateway.
To gain access to the Gateway it requires the removal of the glovebox
You can take a little shortcut here like I did and drop the glovebox with the AMI/CD changer still in it or take them out like in the photo’s below.
I also find it easier if you remove the sill trim, pull it up nearest the seat and work forward and finally pull it away from dash.
http://forum.a8parts.co.uk/attachment.php?attachmentid=7834&d=1397685173
http://forum.a8parts.co.uk/attachment.php?attachmentid=7831&d=1397685173
http://forum.a8parts.co.uk/attachment.php?attachmentid=7833&d=1397685173
http://forum.a8parts.co.uk/attachment.php?attachmentid=7832&d=1397685173
http://forum.a8parts.co.uk/attachment.php?attachmentid=7830&d=1397685173
http://forum.a8parts.co.uk/attachment.php?attachmentid=7829&d=1397685059
So in the centre of the last picture above you can see the gateway next to the control head for the mmi
Replacement is really a matter of unclip the two connectors one electrical and one optical and two torx bolts.
While you are in here its a good time to prep the Gateway harness to accept the wiring from the radar and also to test the radar.
Start by sliding the locking tab on the end of the removed gateway electrical connector housing and then sliding out the internal part with the wires in.
Cut the repair wire 000 979 010 E in half and insert into 13 and 26 like the pictures below, mark the one in 13 with a sharpie pen or something so you know which one is CAN-H, then twist together.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11627&stc=1&d=1439562667
http://forum.a8parts.co.uk/attachment.php?attachmentid=11628&stc=1&d=1439562116
http://forum.a8parts.co.uk/attachment.php?attachmentid=11629&stc=1&d=1439562116
Now temporarily join the pin 13 gateway to pin 2 radar, and 26 to 4 using choc block or similar and check again for correct connection and continuity.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11630&stc=1&d=1439562714
Once you are happy you have wired the CAN connections correctly, connect the gateway harness back together and code the gateway to suit the options on your car (easy way is to copy the coding from your VCDS scan that you took prior to starting this, then using the long coding helper add ACC as well.
Also code module 7 for ACC
Once happy connect the radar to a fused supply, I used a cigar lighter adaptor connection thing and temp wired it to that.
Then you should now have the extra menu appear in the MMI under car/systems/adaptive cruise control
This is a quick visual way to tell you have comms with the radar, the other way is with vcds and look for module (13)
http://forum.a8parts.co.uk/attachment.php?attachmentid=11631&stc=1&d=1439564633
http://forum.a8parts.co.uk/attachment.php?attachmentid=11632&stc=1&d=1439564633
Now you can inserts the seals and plugs into the Connector housing for the radar.
Now you need to prep the fuse box for the connections that feed the radar or you could do this first before testing the radar, either way.
You need to remove the two bolts that hold the passenger side fuse box in place from the end of the dash and unclip the fuse box from the dash frame.
The pics are the opposite side but the same applies.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11633&stc=1&d=1439565955
http://forum.a8parts.co.uk/attachment.php?attachmentid=11634&stc=1&d=1439565404
Now open the back of the fuse box and release the pink locking bar by sliding it over, so you may insert the fuse terminal repair wires 000 979 021 E into both side of slot 17
This is 17
http://forum.a8parts.co.uk/attachment.php?attachmentid=11639&stc=1&d=1439565763
Locking bar in locked position
http://forum.a8parts.co.uk/attachment.php?attachmentid=11636&stc=1&d=1439565654
Lever point to open the locking bar
http://forum.a8parts.co.uk/attachment.php?attachmentid=11635&stc=1&d=1439565654
Locking bar in open postion
http://forum.a8parts.co.uk/attachment.php?attachmentid=11637&stc=1&d=1439565654
Yellow repair wire inserted
http://forum.a8parts.co.uk/attachment.php?attachmentid=11638&stc=1&d=1439565654
Now I apologise I have no pictures of the connections in the back of the fuse box because I was pushed for time that day.
However you will see when you open the passenger side fuse box that slot 17 has no terminals so yo must fit both, using the repair wire cut in half, fit both terminals and lock the bar once done.
If you look at the wiring in the fuse box there is a few solid black wires, choose one of the wires and cut it in a suitable place to allow you to splice in the repair wire and join both sides of the black wire together using solder and heat-shrink or a butt crimp if you don’t like soldering but I prefer solder over crimps.
The reason for using the black wire is it is a switched live and is only on with ignition on. Study the electrical diagrams and you will see the radar is also fed from a black wire which originates from the same relay.
Now once you have done that and happy the unterminated wire ends from gateway are going to come to no trouble you can put the glovebox back together for a while like I did or continue with the bumper removal and fitment of radar.
To fit the radar, the bumper needs to be removed along with the passenger side wheel arch liners and wheel, if you have axle stands or access to a ramp you may as well go ahead and remove the drivers side wheel too just to make life easier.
The instructions here are a bit vague IMO and I really struggled first time round on the bumper removal, so tips from me are
[]Pull out the foglight cover drivers side and remove the fog light
[]Disconnect the headlight washer pipe from the t piece carefully
[]Remove the fixings around the bottom of the wing
[]Drop the belly pan away from rear edge of bumper
[]Remove the front half of wheel arch liner completely on passenger side
[]Peel back the drivers side arch liner enough for access to the three nuts holding the bumper to the wing
[]Remove the three nuts both sides
[]Pull out the black trim that runs along the top of the grill
[]Dig out the two pieces of sponge hiding two bolts
[]pull out both side of the bumper at the bottom of the wings
[*]Finally remove the fixings along the top of the bumper 7 in total
You can now carefully pull bumper clear of the car and be careful as there are two electrical connectors attached to the bumper on passenger side, release them and you should be clear to put it to one side.
You can reach the three nuts securing the bumper to the wing (driver side) by reaching around through the opening but its easier through the wheel arch with liner peeled back.
You can see the studs where the three nuts are and the washer hose t piece in this photo
http://forum.a8parts.co.uk/attachment.php?attachmentid=11641&stc=1&d=1439572047
With the bumper off you can now continue and peel back the rear wheel arch liner on the passenger side to reveal the route in for the wiring.
This shows the rear liner pulled down enough for clearance
http://forum.a8parts.co.uk/attachment.php?attachmentid=11642&stc=1&d=1439572467
Now go ahead and mount the Radar to the bumper beam, it can be done with it in place but for all the time it took to remove it, I chose to do it that way.
Its just two 18mm bolts either end and remove the horn bracket from the mounting giving you easy access to the three mounting holes for the radar bracket.
Mounted to bar and cable following existing wiring
http://forum.a8parts.co.uk/attachment.php?attachmentid=11648&stc=1&d=1439572467
Harness follows the original wiring past headlight like below see white tyraps for route
http://forum.a8parts.co.uk/attachment.php?attachmentid=11646&stc=1&d=1439572467
http://forum.a8parts.co.uk/attachment.php?attachmentid=11647&stc=1&d=1439572467
The harness continues through into area at the top of the wing and follows the original wiring back to the rear of the wing next to the Valve block for the Suspension.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11645&stc=1&d=1439572467
http://forum.a8parts.co.uk/attachment.php?attachmentid=11643&stc=1&d=1439572467
Once you have reached the area of the Valve block you need to release the metal clamp holding the loom in place and cut off the tyrap around the neck of the rubber boot.
Then using a coat hanger or cable fishing device feed the harness from one side of the rubber boot to the other side inside the car.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11644&stc=1&d=1439572467
You can see the new harness inside the rubber boot now.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11649&stc=1&d=1439573216
Refit the cable clamp to the loom and you can now go ahead and finish the wiring for the radar inside the car.
Cut back the harness to a sensible length now and remove the loom tape far enough back to allow you to join the required wires together.
You will have already put in the repair wires to the fuse box, so go ahead and solder or crimp them together and insulate
Join the two can wires in the same way to the tails you have from before ensuring to keep the twist as tight as possible to avoid interference.
Fit the ground wire crimp and bolt to the chassis of the car just inside the door at the base of the pillar.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11650&stc=1&d=1439574072
http://forum.a8parts.co.uk/attachment.php?attachmentid=11651&stc=1&d=1439574072
You can now fit the fuse in position 17 and confirm that you have comms to the radar again, if all is good then proceed to put the new grill in the bumper and rebuild the car.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11652&stc=1&d=1439574795
http://forum.a8parts.co.uk/attachment.php?attachmentid=11653&stc=1&d=1439574795
Only hardware items remaining are the stalk for cruise control and the cluster.
To remove the stalk the Steering wheel needs to be removed.
But in order to do so the Airbag needs to be removed and its easier done with the engine running.
Start the car and rotate the wheel round 90 degrees and remove the cap covering the securing bolt for the airbag, turn to the opposite way and repeat, make sure once you have undone the bolts to prevent the airbag falling out of the wheel while you re-centre the steering.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11662&stc=1&d=1439634518
Now Disconnect the battery with the ignition on but not with engine running to dissipate energy from the electrical systems and prior to unplugging the airbag be sure to ground yourself first by touching the door latch loop or other point of chassis.
Pull the airbag forward carefully and disconnect the wiring harness and put aside, remove the securing bolt from the centre and mark the alignment of the wheel then remove it.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11663&stc=1&d=1439634815
http://forum.a8parts.co.uk/attachment.php?attachmentid=11664&stc=1&d=1439634815
http://forum.a8parts.co.uk/attachment.php?attachmentid=11665&stc=1&d=1439634815
You need to drop the dash below the steering wheel and to do that remove the trim both sides like in the pictures.
Start by opening the coin holder the slide the front part to the left so it unclips, then close it again.
You can now remove the trim piece by starting at the end nearest the door pry outward with a trim tool working along towards the steering wheel.
http://forum.a8parts.co.uk/attachment.php?attachmentid=11656&stc=1&d=1439633903
http://forum.a8parts.co.uk/attachment.php?attachmentid=11657&stc=1&d=1439633903
http://forum.a8parts.co.uk/attachment.php?attachmentid=11658&stc=1&d=1439633903
Do the same process for the short trim on the other side
http://forum.a8parts.co.uk/attachment.php?attachmentid=11659&stc=1&d=1439633903