Introducing Project B6 420-TS Avant.

[Nollywood]

An interesting discussion arose yesterday, between myself and one of my buddies.


As many are aware, the C5 RS6 is the only 077-series V8 40V that runs a 10-bolt crank. It was designed strictly for automatic application, the RS6 uses the same huge torque converter as the W12 engines. The block is also pretty much RS6 / automatic-specific, with the rear mating flange being substantially larger than that of the N/A V8 077-series 40V.


My previous V8 swap (my 6th since I started these swaps in 2008) was with a 2004 D3 4.2 V8 40V. It was a massive learning curve for me, too. This block is again, automatic-specific, and the same issues when mating a C5 RS6 block to an 01E 6-speed manual gearbox, apply here, too. The BFM block is from the same cast as the C5 BCY block. I however had the rear of my BFM block drilled and machined to bolt up to an 01E...


Back to my current project. In the past, MTM have used the regular N/A 077-series V8 40V block, and it's 8-bolt crank to convert the C5 RS6 to manual. Before my last B5 V8 swap, I too would have taken this route. Indeed, this is what I suggested back in 2009, when folk realised how different the rear flange of a C5 RS6 block was to an 01E 6-speed manual gearbox...


So. last night, my buddy asked why I didn't simply build the C5 RS6 internals into a N/A 40V block, instead of just using the N/A 40V crank? After all, I do have a couple of 40V short engines, from C5's.


My answer is simple.


Torsional rigidity. It's a well known fact, that an engine block has to resist "twisting" whilst in service. The more torque an engine develops, especially from really low rpm, and the more load the crank and rods have to cope with (boost junkies, pay heed), the greater the stresses the block has to cope with. Manufacturers overcome this in different ways. Girdles, thicker block webbing, different block material.


The C5 RS6 block has thicker webbing than the N/A 40V block, making it substantially stiffer. The C5 RS6 bare block is also slightly heavier as a result. I will weigh both bare C5 RS6 and N/A blocks, and post the results.


Using a N/A 40V block will be easier, it's definitely a short cut to bolting on an 01E, but it's not for me. I do not wish to sacrifice torsional strength for ease of 01E fitment. So, BCY block will be retained. The C5 RS6 crank offers no strength advantage over a N/A 40V crank, which is great. I have a spare crank from a 2002 European C5 S6 (ANK) which I will be using.

[Nollywood]

I was lucky to get hold of a 2002 C5 S6 crankshaft this arvo. I say lucky, as most sellers wouldn't tear down an engine to sell internals.


This will replace the 10-bolt RS6 item in my C5 RS6 BCY engine.

[Nollywood]

Updated list - May 02nd, 2017:


B6 S4 front spindles.
B6 S4 front lower arms.
B6 S4 front upper arms.
B6 A4 / S4 front sway bar C-links.
B7 RS4 Wheels - 9.0" x 19" ET 29.
Built B6 3.0 / C5 2.5 V6 TDI 01E 6-speed gearbox.
B6 A4 3.0 Quattro (pre-2002) 4.11:1 rear differential.
B6 A4 3.0 Quattro (pre-2002) 01E shifter.
Brembo 6-piston front calipers, rotors TBC.
Brembo rear calipers, and Brembo parking brake calipers, rotors TBC.
B6 S4 KW V3 or Eibach Pro-Street adjustable coilovers.
B6 A4 2.5 V6 TDI Quattro front axles and 01E gearbox output flanges (130mm).
Vibratechnics aluminium Motorsport engine mounts (will work for my 3.0 V6, and the D3 4.2 V8 40V).
Custom V8 40V solid billet steel flywheel.
C5 RS6 BCY engine, complete.
C6 S6 (ANK) crankshaft.
B5 A4 Quattro front subframe.
B6 custom solid rear differential mounts.
B7 RS4 OEM complete exhaust (cat-back) with active rear mufflers.
B7 RS4 Avant rear bumper.
B6 RS4-style hood grille.
B7 RS4 Side Skirts.
B7 RS4 rear door, right-hand side.
B7 RS4 rear door, left-hand side.
B7 RS4 fender, right-hand side.
B7 RS4 fender, left-hand side.
B7 RS4 Avant rear quarter, right-hand side.
B7 RS4 Avant rear quarter, left-hand side.
B7 RS4 front bumper (as donor for the corners).
B6 S4 Xenon headlamps.
B7 RS4 front wheel arch liners.
B7 RS4 rear wheel arch liners.
B7 RS4 gas tank flap.
B7 RS4 Avant black headlining with all matching trims and sun visors.
B7 Seat Exeo dashboard.
B6 S4 Convertible instrument cluster.
B7 Seat Exeo glovebox.
B8 S4 aluminium mirrors, with integral LED side repeaters.

[Nollywood]

My C5 S6 crank turned up today, well packed and oiled.


It's quite a substantial piece, I suppose it could be lightened, but while it would aid quicker spool up, it would hurt drivability, and make for a slightly snatchy on/off throttle characteristic.

[Nollywood]

Some pictures of my BCY motor, B6 420-TS's new heart. These are pre-delivery pictures, as the seller sent to me, so they're poor quality, really, might have as well used a pin-hole camera. It's going to be transported down next week, so I'll take my usual high-resolution shots.

[Nollywood]

So, I've been looking at flywheel and clutch options for the C5 RS6 motor.


As I have opted to run a regular 077-series V8 40V engine, I have more flywheel options open to me (8-bolt fitment to crank). I was considering the popular B7 RS4 flywheel and clutch, but having spoken to TTV Racing, as well as quite a few respected tuners in the UK, Europe and the United States, there's no proven benefit in running the B7 RS4 clutch over a B5 RS4 item.


If anything, the B5 RS4 pressure plate has been tested in different rigs, and it has more clamping force than the B7's. Torque wise, both the B5 and B7 RS4 engines produce similar torque outputs - 440 and 430Nm respectively. The B5 RS4 however produces its torque much lower down the rev range, which loads the clutch up more. Put it this way, 450Nm produced at 2,000 rpm is more destructive to a clutch than 500Nm produced at 6500. One of the reasons why it's popular to run diesel flywheels and clutches in big power gasoline motors.


The RS6 4.2 V8 BiTurbo (BCY) engine produces 580Nm between 1,950 and 5600 rpm. A very wide, and useful power band. It almost doesn't matter what gear you're in, it'll pull strong. Very different from a highly-strung, properly built 1.8T making 550hp. The power band really matters to me.


Engine will be with me by Wednesday, and I'll be ordering my flywheel sometime next week.

[Nollywood]

The heart of this creation is a C5 RS6 (BCY) motor. I am tearing it down, and rebuilding it, retaining just the oil pump. I am using the crank out of a 2002 C5 S6, (ANK) which gives more flywheel options, due to its 8-bolt fitment. It seems a waste to start off with a built motor, and not go to stage 3.


What turbos would I need to go stage 3? I will not be running the original RS6 exhaust manifolds, with their low-slung, rear-mounted snails. My manifolds will locate both turbos above the frame rails, for ease of replacement, and close proximity to the frames, and transmission (01E 6-speed).


Camshafts? I'm aware the lumpy sticks in a C5 4.2 V8 have more lift, and duration (not S6). Are these a better option?


I would really appreciate some direction here.

[Nollywood]

So today, my C5 RS6 engine turned up.


I've done 6 V8 swaps till date, but still, I'm always startled by how big it is. Within the confines of an engine bay, it looks pretty compact. Sitting on a pallet, it's massive.


It's complete with the ECU and harness, but no snails. Since I'm mounting them differently, with different manifolds and looking to go stage III, there seemed little point in the added expense. I got xxx off the final price. I also didn't bother having the alternator, as I've got a built 190A unit.


Once all the build parts are with me, I'll begin the strip down for rebuild. The crank, cams and rods will be cryogenically treated, while the rotating assembly - crank, rods with pistons, flywheel and clutch attached, will be balanced before being refitted to the block.


Pictures to follow.

[Nollywood]

C5 RS6 BCY motor, shortly after it was unloaded from the delivery truck:























Stock C5 RS6 exhaust manifolds - I won't be using them, though:





C5 S6 (ANK) crankshaft:





C5 RS6 harness and ECU:





C5 RS6 (BCY) data sticker on timing belt cover:

[Nollywood]

One issue that C5 RS6 owners often come up against, when doing manual swaps, is ABS and ESP. Not being able to code the BCY ECU for manual, the ABS controller get's really unhappy. To a lesser degree - I say lesser, because it's not really an essential. Cruise Control.


I've been trawling through wiring diagrams, the ABS controller, and what data it needs to see, and via which pin / pins. I think I've got it worked out, and I know exactly what I need to do. [up]