I've been an old-school 5-cylinder Audi enthusiast for awhile, but I always loved the idea of the RS6 Avant. The engineers at Audi (bless them) took an unassuming family station wagon and thought "but what if dad was REALLY late for soccer practice?" They calculated exactly much engine could possibly fit under the hood, decided that was not enough and extended the front to fit more. The resulting twin turbo V8 estate blended practicality and performance in a way I could only dream of, since Audi had also decided us Americans would be content simply knowing it exists. And with a 6-speed? HA! The RS6 has never been offered with a manual anywhere in the world.
Well, opportunity came a-knocking one pandemic-riddled year, when I found this storied oddity: an RS6 sedan, abandoned at a Quik Trip when its owner fled the state to evade the law. After sitting at a gas station for weeks, it was towed and received a salvage abandoned title, as well as a new key. The car was listed on Facebook marketplace, with a single grainy picture, fake RS6 badging, by a company who had no idea what it was or if it even ran. I called them up, not knowing if this was even a real car, and we struck a deal, sight unseen, from 9 hours away. I showed up with trailer in tow and found myself equally surprised that it was, indeed, a real RS6, and, despite being told it would not run, it fired right up with a jump pack and drove itself onto the trailer! What follows is the tale and details of the build that this fortuitous sequence enabled.
Let me start out by saying I am not the first to do this swap, nor is this a definitive guide. There are many possible ways you might accomplish a similar outcome, but I'd like to share my process, in the hopes that it may help inspire future builds
The biggest issue that I've found is that RS6 owners, historically, have been a lot more willing to shell out cash that I am. This means parts are expensive, and a lot of people had their car serviced by a garage, so DIY information is a little spotty - BIG shoutout to the players who did post up what they knew. I'd like to use this thread to fill in the gaps and pay it forward.Foreword
This swap is not for the faint of heart. The individual steps are not terribly difficult, but there are a lot of them. You will need a pretty thorough mechanical understanding, as well as basic to medium fabrication capabilities. Rather than documenting every single nut and bolt, I will be outlining the major steps as they relate to the changepoints only, with the assumption that you can fill in the gaps. I will, of course, answer any questions I can, but please do not expect a step-by-step instruction.
That said, yes, you could perform this as a capable backyard mechanic on jack stands alone, but a lift will make your life much easier. I built one of the cars on a lift and the other on the ground, so I got a taste of both.
You will need (at a minimum), the following:
- Jack/stands
- Engine hoist/stand
- Angle grinder
- Die grinder
- Welder
- Basic metric tool set, including wrenches, sockets, triple squares, etc
- Torque wrench(es)
- Wire strippers/crimpers
- Multimeter
- A/C manifold gauge / vacuum pump
- Paint gun and a GOOD respiration system
- 40v timing belt tools
- Cam tensioner tool
The Patients
I'm typically an opportunistic car buyer. A good deal and mechanical worthiness are far more important to me than paint and cosmetics, so my cars have always ended up being silver - not because I have any affinity for the color, but I guess no else does either. However, for this build, I decided I wanted something special and worthy of the swap. I really wanted an Amulet Red or Nemo Blue S6, and I held out for awhile just looking for the right candidate. After a few false starts, I finally came across the perfect spec: Amulet Red over black alcantara interior, solar sunroof, and it even had a third row! Body was straight and rust-free and the clear on the roof was starting to go, so I could actually afford it. I flew out to Colorado and drove it back to Ohio for its new life!
Donor #1: 200X Audi A6 sedan, seized 2.7T engine, 6-speed manual
(Knoxville, TN)
Donor #2: 2003 Audi RS6 sedan, Avus Silver over Black interior, 116k miles, Felonious History
(Kansas City, MO)
Recipient: Project Sauron: 2002 Audi S6 Avant, Amulet Red with Black alcantara interior, 204k miles
(Boulder, CO)
Donor RS6 Parts
You might be thinking "I'll just buy an engine and swap it," but I highly recommend you have access to a whole donor car. If you want a comprehensive RS6 conversion, the following parts are unique to the RS6 and must be swapped:
Powertrain:
- BCY engine and all accessories, including intercoolers, turbos, harness, exhaust, ECU etc
- Motor mount brackets bolted to engine
- Frame rail snub mount bracket (cut and re-welded)
- Rear differential
Battery
- The battery needs relocated to the rear
- Main fuse blocks
- Starter wire harness
Coolant System:
- Entire coolant system (except heater core), including pipes mounted to 2nd firewall and reservoir
- Core support and radiator, incl electric fans
- Radiator fan control unit
- Radiator fan control harness, unbroken from driver's frame rail, along the fender, terminating in driver's footwell
Brakes:
- All calipers/rotors (just leave these assembled with the whole suspension/subframe if you can)
- Rear spindles
- Brake booster + master cylinder combo
- Brake booster vacuum pump
- Brake booster pump relay and harness under the cluster
- Parking brake cables
Steering:
- Steering rack (shorter ratio)
- Lines to/from rack
- Heat shields over the steering rack
Air Conditioning
- Entire line set from the firewall to the compressor
- Drier and mounting bracket
Fueling
- Fuel injectors
- Entire fuel lines from engine bay to tank (RS6 is bigger diameter and routed a little differently in the engine bay)
- Fuel pump
- Auxiliary fuel pump and entire harness
- Auxiliary fuel pump controller
- Fuel tank (tanks are technically the same, but it was easier for me to swap the lines and pumps as one assembly with the tank when the subframes were off)
Suspension
- DRC control valves on the wheel well
- DRC lines under body to each knuckle
- Struts and springs
- Rear subframe (may be the same, depending on your S6)
- Front subframe (the same, but its just easier to swap the suspension, subframe and brakes all as one assembly)
Electronics:
- ABS controller (can be upbolted separately from pump)
- Cluster
- Auxiliary fuel pump controller
- Engine control unit
- Immobilizer "pill" in the key (paired to the cluster)
- Radiator fan control unit
- Horns
Exterior:
- Front (vented) fender liners for intercooler airflow
- Front bumper and crash shocks
- Grill
- Badges (if you're a poser like me)
- Front lock carrier
- Door blades
- Side skirts
- Side view mirrors
(RS6-Avant specific parts must be imported, including rear bumper, spoiler, and polished trim surrounding the windows)
Interior
- Seats front/rear - only the outer pieces of the seat backs are Avant/sedan specific, but fortunately, both my cars matched interior color
- Door cards (I did not swap these, as I liked the S6 Alcantara)
- Interior door handles, if whole door card is not swapped
- Steering wheel
- Door sills
- Carbon fiber interior trim
The following thread will cover the details of swapping all these parts over. Comments, feedback and corrections are most welcome!
- - - Updated - - -
Stage 0: General Maintenance
This is a personal preference, but I'd recommend getting the engine(s) well-sorted if you have the engines out and it's all accessible. Both my cars had a relatively unknown history. If you can do this ahead of the swap, even better. The idea here is to minimize the amount you need to focus on when it comes to the big swap, or for that matter, removing variables if you need to troubleshoot. My recommendations for the 4.2 and 4.2T:
- Timing belt, water pump, idlers, seals, etc
- Cam tensioner pad replacement + oil pickup screen removal if timing is serviced (The tensioners themselves don't typically fail in isolation, but the plastic pads get brittle and can fall apart. That or, the oil screen gets dislodged and sucked in, leading to failure)
- Front and rear main seals
- Accessory belt
- New spark plugs; check condition of coil packs and replace if necessary
- Oil change, filter, air filters
- Oil cooler coolant pipe, aka Bufkin pipe
- Knock sensors, injector O-rings, and intake manifold gaskets + (RS6) Suction jet pump and afterrun pump under the intake manifold. Save yourself the headache of these breaking when they are impossible to get at.
- (Optional) Secondary air injection delete - if you won't get dinged for emissions compliance, this will free up some room in the engine bay and greatly simplify layout. The monitor can be disabled via the ECU.
- (RS6) Turbo rebuild
- (RS6) Replace/repair leaking intercoolers - I re-cored my intercoolers with Bell Intercooler cores A300090100 (3"x 9"x10")
- (RS6 Optional) Auxiliary radiators delete
- - - Updated - - -
Stage 1: Manual Swap
Since I was planning to swap both drivetrains, I actually manual-swapped both cars prior to the engine swap. It allowed me to spread the scope of the project out over time without an extended period of downtime. Each car was individually swapped while the other could still serve as a useable car. It should be noted, you don't *need* to remove the engine for this on the S6, but you will for the RS6.
Disclaimer: The RS6 engine does not directly mate to an 01E. The RS6 gearbox has a wider bellhousing pattern, as found on the later D3/C6 engines with the 6HP gearbox. This means several bolts don't line up, and crucially, the starter sits further out. There are a few excellent kits out there to get around this issue. I have no issue with them, but personally, I felt I could accomplish a similar result for a smaller cost. Some folks do not agree with this methodology, as it involves irreversible modification the engine block, and there are fewer bellhousing bolts securing engine to gearbox. I'll share the details below, but please understand this disclaimer.
There are a few manual swap guides out there, so I'll keep this short. This is another case where a donor car would be handy. The following parts were used, mostly from a 6MT 2.7T A6 sedan. And of course, if you're swapping both cars... you'll need double these parts.
- C5 A6 01E shift linkage from cabin to gearbox
- C5 A6 01E transmission mount brackets
- C5 S6/RS6 auto transmission mounts
- 2.7T 01E spacer for dual-mass flywheel (11mm)
- C5 A6 01E driveshaft OR Non-4.2 driveshaft + JHM driveshaft spacer (despite the info on their site, the 4.2 driveshaft is too short)
- B5/C5 manual pedal assembly
- B5/C5 01E clutch slave cylinder
- C5 01E clutch master cylinder
- B5/C5 clutch switch
- B5/C5 transmission alignment dowels for use with 01E spacer
S6 parts used:
- 2.7T flywheel (I used a Fidanza LWFW)
- B5 S4 clutch
- 01E throwout bearing
RS6 parts used
- TTV Racing 10-bolt flywheel for RS6
- Ringer Racing Stage 5 clutch + extended throwout bearing
Oil cooler
In the likely event that your RS6 oil cooler stripped the threads undoing them, there is a repair solution out there on the forums. However, I took the opportunity to increase the oil cooling capacity. I cut off the end tanks with the stripped threads and welded on a plate with -10AN male fittings on either end. In effect, I had combined the ATF and oil coolers into one, larger unified oil cooler. At the block, you can use an M22-> -10AN adapter fitting to then make AN lines to the cooler.
...and now I realize I don't have any pictures of this setup
Gearbox refresh
This would be an excellent opportunity to give the gearbox a little love. I rebuilt my 6-speed 01E with the JHM syncros and the updated 1-2 shift collar. There's a great video by JHM on Youtube guiding this process.
Block modifications
Your options when manual-swapping an RS6 are essentially one of three:
- Use an adapter kit (for example, SteveKen or Apikol)
- Swap internals (rods/pistons/crank) from RS6 engine block to N/A block. This would also allow you to use a much more common 8-bolt flywheel if you retained the N/A crank
- DIY adapt the engine block to mate to the 01E
For all of the above options, you will be throwing out your RS6 starter.
For option #3, you will need a D2/C5 4.2 starter. The first step is to adapt it to the block. The good news is that the holes for the alignment dowels on the engine are common between RS6 and S6 engines. This means you can comfortably bolt up the gearbox without worrying about misalignment. After fitting the dowels, you can throw on an 01E or just the spacer to serve as a template for drilling the holes for the new starter position, as well as a hole through the upper oil pan that gets tapped.
Once that's done, it's time to clear away all that extra material for the starter. I had previously modelled the starter for another project, so I 3D-printed out a cross-section of the starter to use as a template and went to town with a die grinder. The goal, ultimately, is to remove material until it matches your N/A block.
Finally, we need a starter spacer. If you look at the mounting boss for the BCY starter versus the N/A motor, you'll see that the RS6 is a bit thinner. This is purely from memory 4 years ago, but I believe it's around 9mm different. I approximated this by using a plate of 5/16" 6061 aluminum cut to fit the starter profile. You can just take a hole saw (3 inch?) to the plate, then easily drop the starter on to trace the rest of the profile. At this point, you can technically be finished, by just sandwiching the spacer when the starter gets bolted. However, since the starter position is located precisely by the 3" hole in the spacer, and the spacer is free to move around a little, I wasn't happy with the potential variance you could have on install. As such, I carefully aligned it on the bench and welded the spacer to the block. Then I cut a small relief in the outer side of the spacer to allow the starter to be installed/uninstalled. Finally, I made a steel bracket to fix the back end of the starter to the block, like you see on the N/A application. *Slaps starter* "That ain't going nowhere"
Now we could actually be done. Many folks (including myself) have run this type of setup for many miles without issue at elevated power levels. You will have 7-8 bolts between the gearbox and engine, but there will be about 3 missing on the oil pan. These were obviously included by the engineers for a reason, but some might call it "good enough." However, if you simply cannot sleep at night with this omission, I believe there is a solution that hasn't been explored yet! Next time my engine comes out, I will be swapping the RS6 oil pan with an N/A oil pan that has been tapped to include turbo oil returns. They appear to be interchangeable and will complete the mating to the 01E.
And that's it! Bolt it all together like any clutch job at this point.
Manual Swap Wiring
Couldn't be easier!
Clutch switch
You'll need to wire a clutch switch that is opened when you depress the pedal. This is used by the ECU both for cruise control interrupt, and to adjust ignition timing for driveability. Without this switch, the engine will rev-hang between shifts. Wire one side of the switch to ECU pin #39. There's no wire there, but it is populated by an empty pin that you can pull out and crimp to using a barrel crimper. The other wire of the switch needs to go to switched 12V power, which is available if you splice into the equivalent line on the brake switch.
Starter interlock
Did you turn the key and nothing happened? It's time to bypass the function of the Park-Neutral safety switch from the automatic. There are three options here, actually
Reverse Switch
This will depend on whether you removed the automatic transmission harness or not. I simply left the harness in place and spliced into the reverse wiring on the 10-pin F125 connector. Extend these 2 wires and attach them to a 2-pin Bosch connector to plug into the 01E reverse switch. That's it! The reverse lights will work, and the backup sensors/camera tilt will automatically engage when you hit reverse.
You'll need to wire a clutch switch that is opened when you depress the pedal. This is used by the ECU both for cruise control interrupt, and to adjust ignition timing for driveability. Without this switch, the engine will rev-hang between shifts. Wire one side of the switch to ECU pin #39. There's no wire there, but it is populated by an empty pin that you can pull out and crimp to using a barrel crimper. The other wire of the switch needs to go to switched 12V power, which is available if you splice into the equivalent line on the brake switch.
Starter interlock
Did you turn the key and nothing happened? It's time to bypass the function of the Park-Neutral safety switch from the automatic. There are three options here, actually
- (OEM) Install a clutch switch that closes at the bottom of the pedal stroke (from B5/C5). Wire it with one pin to ground, and the other to the ground control side of the starter interlock relay
- Permanently trigger the starter interlock relay by grounding the control line - there's no clutch safety in this configuration
- Remove the starter interlock relay entirely and jump from the power supply to the load (30 to 87) - also no clutch safety in this configuration
Reverse Switch
This will depend on whether you removed the automatic transmission harness or not. I simply left the harness in place and spliced into the reverse wiring on the 10-pin F125 connector. Extend these 2 wires and attach them to a 2-pin Bosch connector to plug into the 01E reverse switch. That's it! The reverse lights will work, and the backup sensors/camera tilt will automatically engage when you hit reverse.
Manual Swap Coding
(Note: I need to double check these steps are accurate; they are based on my notes from two years ago)
You can now simply remove the TCU. I left the harness in place for convenience. Three units will need to be updated to play nice and not report faults for the missing TCU
ECU Coding:
The ECU will need to be remapped to utilize the clutch switch you've added. Your tuner should be able to add this function, as well as any monitors you want to disabled (SAI, rear O2, etc).
Once this is done, the soft coding needs to be set with VCDS. There is no login for this setting.
Set coding to 10712
ABS Coding
Auto S6 Coding: 06397 (06 = Audi A6, 3 = HP2 brakes (1LX), 9 = 6/8cyl, 7 = automatic)
Auto S6 Login: 07497 (07 = Audi A6, 4 = HP2 brakes (1LX), 9 = 6/8cyl, 7 = automatic)
Manual S6 Coding: 06395
Manual S6 Login: 07495
Auto RS6 Coding: 06697 (06 = Audi A6, 6 = 2FNR brakes (1LJ/1LP), 9 = 6/8cyl, 7 = automatic)
Auto RS6 Login: 07197 (07 = Audi A6, 1 = 2FNR brakes (1LJ/1LP), 9 = 6/8cyl, 7 = automatic)
Manual RS6 Coding: 06695
Manual RS6 Login: 07195
This one's easy to get wrong, and it won't take if you do. Use VCDS and follow these steps to get it to work:
Note: If your steering calibration has been lost, the ABS will forget its soft coding (00000). You will need to follow these steps to set the stock coding again.
Cluster
The ECU will need to be remapped to utilize the clutch switch you've added. Your tuner should be able to add this function, as well as any monitors you want to disabled (SAI, rear O2, etc).
Once this is done, the soft coding needs to be set with VCDS. There is no login for this setting.
Set coding to 10712
ABS Coding
Auto S6 Coding: 06397 (06 = Audi A6, 3 = HP2 brakes (1LX), 9 = 6/8cyl, 7 = automatic)
Auto S6 Login: 07497 (07 = Audi A6, 4 = HP2 brakes (1LX), 9 = 6/8cyl, 7 = automatic)
Manual S6 Coding: 06395
Manual S6 Login: 07495
Auto RS6 Coding: 06697 (06 = Audi A6, 6 = 2FNR brakes (1LJ/1LP), 9 = 6/8cyl, 7 = automatic)
Auto RS6 Login: 07197 (07 = Audi A6, 1 = 2FNR brakes (1LJ/1LP), 9 = 6/8cyl, 7 = automatic)
Manual RS6 Coding: 06695
Manual RS6 Login: 07195
This one's easy to get wrong, and it won't take if you do. Use VCDS and follow these steps to get it to work:
Note: If your steering calibration has been lost, the ABS will forget its soft coding (00000). You will need to follow these steps to set the stock coding again.
- IG-on, establish connection with VAGCOM
- Select ABS-Brakes module
- Login (11)
- Type generated login code for the current state of the controller (stock)
- Coding (07)
- Type generated target code; if workshop code is 00000, you must change it! (e.g. 12345)
- Login (11)
- Type 40168 (enable basic settings) -> Do it!
- Don't start engine; turn steering 90deg left, back straight (you can read out group 005; must be +/-5 deg of 0
- Click Basic Settings (04)
- Group 001 -> Go! This performs the calibration. Should say OK under "Alignment status"
- Done, Go back
- Check for faults; they should now be cleared.
Cluster
- Using VCDS, go to Instruments
- Adaptation
- Channel 60
- Set to 1025
- Done
- - - Updated - - -
Stage 2: Cosmetics and Body Work
Following the manual conversion, I decided to pull off the body parts that would need paintwork. This way, I could prep and paint the parts without disabling the cars.
DANGER Automotive paint is no joke. You can develop lifelong lung issues from improper ventilation or respiration, even from a single session from some clear coats. Most home respirators are not up to the task. I invested in a supplied air respirator that could port fresh air from elsewhere and provide positive pressure of fresh breathable air to my mask, no matter how hazy the air I was in got.
Disclaimer: I don't really know what I'm doing with paint, but it's quite expensive to outsource, so I decided I'd try anyways.
Painted parts include:
- Front bumper cover
- Side skirts
- Lower door blades
- Rear spoiler (RS6 Avant specific - it'll have to come from a real one in Europe, but I just bought a stick-on approximation on eBay that I'm happy enough with)
- Rear bumper (RS6 Avant specific - this part has a real RS tax, and I frankly don't care enough to pay it purely for cosmetics. It is omitted from my build unless I come across a cheap one)
At this point, you can also install the bodyparts you've painted, as well as the non-painted bits like the grill and side-view mirrors.
The interior is also primed for swapping!
- Front seats (direct interchange)
- Rear seats (direct interchange, except the outer bolster that is Avant/sedan specific. If you're lucky like me, the two cars have matching interior colors, so they could be left)
- Carbon trim, if you have it
- Black RS6 interior door handles (you could swap the whole door card, but I wanted to keep the S6 alcantara cards). Good to do this step with the side-view mirrors
- Door sills - Have fun with these! They are very difficult to pull up without damaging them, but meticulous prying, gentle heat, and solvents like goo-gone can get you there eventually. I cleared off the old adhesive from the sills and applied new strips of 3M trim adhesive strips
- Steering wheel
Cluster is omitted for now due to immobilizer function. This will be swapped with the engine.
- - - Updated - - -
Stage 3: Battery Relocation
WORK IN PROGRESS. Need to gather pictures and more details. Will edit and update when available
Due to the tight layout of the RS6 engine bay, the cooling system occupies the space where the C5 battery conventionally lies. As a result, you'll have to move the battery elsewhere.
In the RS6 sedan (USA), the battery has a "bread box" that occupies a large portion of the trunk area. This was absolutely unacceptable to me to swap over, as it defeats practical space of an Avant. In the rest of the world, both the RS6 sedan and the Avant got their battery located in the spare wheel well. This is better, but I like to carry a spare, and I consider it a practical essential of using the car as a daily. Therefore, the only real solution left, in my eyes, is to put the battery in one of the two side storage areas in the hatch area. Based on the space available, I elected to use the driver's side pocket.
I ordered 20 feet of 1/0 welding wire and went to town tucking it away in a way that was hidden, yet minimally invasive. From the new battery compartment (behind the interior panels), it went up and over the rear drivers wheel wheel and down behind the fixed piece of the rear seatback. It then travels under the rear seat over towards the passenger side, where you can tuck into the carpet. There is a corner where it can tuck in without getting pinched or kinked. Some trim needs to be removed to lift the carpet sufficiently, but you can run it all the way forward along the side of the floor to the box where the TCU is kept, just in front of the passenger seat. Here you can center the wire a little more and run it the rest of the way up the passenger footwell to the end of the carpet.
Look at the sedan donor car and note where the battery cable passes through. You can drill a hole in the Avant in the exact same spot. You'll want to include a good grommet to keep the battery from shorting to the body here. Pass the battery cable through the hole and fit the grommet, then cut the cable to length to mate with the RS6 fuse block that is now mounted to the area. I crimped a ring terminal at both ends of the cable to finish it out.
WORK IN PROGRESS. Need to gather pictures and more details. Will edit and update when available
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Originally Posted by Aktapod
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