I'm currently stuffing (actually has more room on the sides than the 4.2) a W12 in my B7 A4 Avant with a 6spd manual transmission. I will be maintaining the AWD setup as well. The engine and transmission are mated finally and have a twin disc clutch setup between them. The engine wiring harness has been modified and rerouted to fit the B7 factory ecm box and harness boot. I had to pull the harness apart to move several sensors that went into the car and out a different location into the engine bay. I had to condense a lot of wiring. Getting the harness through the original harness boot was a job in itself. The boot didnt want all those wires ran through it and fought me the whole time but I finally got it done and the wiring fits and looks like it came that way from the factory. Next phase is removing the interior so I can start running all the necessary wiring inside for relays, fuel pumps, exhaust dumps, ect. I look forward to gathering information from the forum during this build.

My difficult project

Interior after removing fish scale trim and installing light birch trim from 3 different audi models. Wanted all black interior but Avants are hard to come by. I picked up this avant and the A8L W12 for 2500.00 total so this project is way under budget considering the cost of the engine alone through scrapper sites.

 

Oh my! This is great!!!!

 

Got most of the wiring done this week. Need to install gateway module, after-run pump relay and n115 wiring to rear of the car. Turned the key on and the throttle bodies started humming. No action with pedal movement though, just a bunch of clicking. need to triple check all of my work.

 

Car was completed and running fine. i told myself i wasn't going to beat up on the car but i couldn't help launching and doing awd burnouts. 3rd gear was my favorite gear to stretch out. I finally broke the car in June leaving a car show. Everyone was showing off leaving the show and i joined in and pushed the car a little harder than i had previously. As i was shifting from 2nd to 3rd, something popped and the whole car started vibrating horribly. Once i got the car home, i found the rear u-joint had one cap broken and thought....WOW, this will be an easy fix. It wasn't quite that simple, when i went to remove the driveshaft flange i noticed the rear diff felt loose. Turns out, I ripped the factory bushings out of the subframe, which most likely damaged the u-joint. i ended up machining some sleeves for the subframe since the bushings were press in style. The sleeves are 2 piece that slide in the front and back side of the subframe. I machined the sleeves to accept some old energy suspension bushings i had laying around that are still available to purchase. There's no chance of the rear diff coming out now unless i brake the bracket it is bolted to. Once everything was back together, i went to take it for a spin and quickly realized that my favorite gear in the transmission was gone so everything had to come out. i ended up purchasing a S4 (0A3) transmission and rear diff from someone in Va. Luckily the guy lived close to where i was driving to get a 72 Audi Super 90 Variant, so i picked everything up on the same trip. Finally got the transmission modified and installed but didn't have the bottom trans mount and the 02X mount isn't the same so I ordered some chromoly pipe and will be making a transmission x-member and using side mounts on the trans. I will be replacing the rear stabilizer as well. i noticed the the factory stabilizer was flexing bad enough to cause damage to the spare tire area under the car. Looks like it pushed in the wheel well about 3". Plan on upgrading to the ECS S4/RS4 rear stabilizer.