Turning my A4 into an S4.

[b5quattro_man]

So the time has come to pull the trigger on my swap I have been thinking about. I am going to be swapping everything over from my s4 to my a4. I have given a lot of consideration to this and have decided it's going to be my best route at this point.

The a4 has been my daily driver for the last couple months and has been an amazing car for me. It has the 2.8 atq with an o1a. Bone stock. The body is near perfect condition and has aged really really well over the years. Had a broken TB when i bought it so I went and rebuilt the top end and cleaned up the engine. I have since put about 4k miles on it with no problems at all. But then after about 120 miles into a 500 mile road trip the bolt that holds the TB tensioner broke off into the block and let the TB slip. Now it's a brick. (Someone that was helping me out did the TB for me. When I asked him about it he said that he torqued the TB components all to about 35 ft/lbs! Which is why you don't let other people work on your car!!!) Just undid all my time and money I put into that car.



The first tear down.



I got a killer deal on an S4 locally that had blown turbos and a salvaged title. The car apears as if it was in a minor front end collision or was put into a ditch at some point. The front bumper was replaced with a hideous aftermarket rs4 style bumper and there is damage all down the passenger side. Nothing really too bad, car still drives straight. Allegedly has a stage 2 tune on it with supporting mods (i think). I know for sure that it has exhaust, clutch, intake, fuel pump and a short throw shifter. Other than these I can't 100% say that it has any other upgrades but the previous owner said it had a stage 2 ecu. Runs amazing but doesn't build boost at all and smokes out the tailpipe. I believe it just has stock ko3s on it right now but won't be able to tell until engine is pulled. I don't know much else about the car other than this.



Originally I was planning on just fixing up the s4 and keeping it for one of my fun cars and have the a4 as my daily driver. Unfortunately since my a4 gave out, I am stuck with two cars that are basically bricks right now. So, the way I see it, I can rebuild the top end on my a4 again or I can swap everything over from my s4 for less than a quarter of the cost. While the motor is out I am going to rebuild the turbos and fix any leaks I find. Another thing the s4 has that my a4 doesn't is heated seats, so I will be swapping over my dash harness and interior as well.

With Christmas coming up, I have a 1000 mile road trip I have to go on to see my family and am supposed to leave in about 5 days. I am going to attempt to have the car up and going for that trip.

This will be my first build thread I have done so any help/pointers are appreciated. Any info or tips are welcome. I am an experienced mechanic and spent years restoring cars and working on European imports. I know that this is not for the faint of heart and I would not suggest this swap to a novice mechanic but with enough patience it should go smoothly.

So far I have gotten the rear subframe out of the a4 and halfway with pulling the rear out of the s4. Along with starting on the interior pull and front clip removal.

[b5quattro_man]

By the end of the day my goal is to have the s4 rear subframe installed on the a4 and have the a4 front subframe and engine pulled at least and started on the s4.

Sent from my SM-G955U using Audizine mobile app

[BGB]

That's a lot of work, good luck!

[Nollywood]

Good stuff!

Out of interest, what’s actually wrong with the factory S4? Bad shell? I might have missed this bit.

[HumbleTurbo]

Hats off to you on this project!! Especially given the timeframe! Hopefully you can document build thoroughly but if not its totally understandable.

[kwnk]

Nice man! Stay focused! Gl with the project


Sent from my iPhone using Audizine

[b6Hate4]

Interesting thread. I did nearly the exact same thing, turned an A4 shell completely into an s4 last year. Still finishing up small things but everything transferred over very smoothly.

[GOODBYNAAIR]

Good luck, that's a lot of work !

[b5quattro_man]

Good stuff!

Out of interest, what’s actually wrong with the factory S4? Bad shell? I might have missed this bit.

Other than the damaged shell? It has a salvaged title, blown turbos and needs wheels is all really. But the body looks a little out of square and it has very obviously been messed with and half assed done. I feel more comfortable with the car if I'm able to go through literally everything on the car.

[b5quattro_man]

Hopefully you can document build thoroughly but if not its totally understandable.

Definitely going to try to. My problem is that I forget to stop halfway through what I'm doing to take pictures and what not haha.

[b5quattro_man]

Interesting thread. I did nearly the exact same thing, turned an A4 shell completely into an s4 last year. Still finishing up small things but everything transferred over very smoothly.

Didbyou use a donor car or did you just source the parts you needed? Also did you keep the A4 gauges or did you install an S4 one.

[WolfGanG13]

Nice. Thinking of doing the same since this will be easier then swapping my ABZ 4.2 over .


StreetDreaming

[b5quattro_man]

Ok so I got the rear subframe from the s4 bolted up to the a4 today.



I was stuck messing with trying to get the exhaust bolts off of the downpipe. What a PITA!! Whoever put this exhaust in previously had welded it all in one piece. I was hoping to pull it all out in one piece so that way I wouldn't need to weld anything back up when reinstalling. After an hour or so I got the exhaust unbolted and then realized that due to the trans tunnel and just the shape of the car, it can't come out in one piece. So I ended up cutting it anyways.

Also got a good jump in the interior pull today.



Tomorrow morning will be dedicated to the rest of the dash and harness pull. (Tape and a Sharpie will be my best friend). Also I am hoping to at least have the front subframe pulled out of the A4 by the end of the day. Hopefully get the one out of the s4 as well....

[b5quattro_man]

One thing I am curious about has to do with my key. My A4 has a working key fob and my S4 has a cheap eBay generic key. I really want to keep my fob and also don't want to change all the door locks over. I assume I can keep the whole a4 steering column with the original ignition lock.

I guess my question is that since I am changing the dash harness from the S4, is there a control module or something of the sort that I can keep in the A4 or am I going to have to run the S4 receiver and have my A4 fob recoded?

I am hoping that I can just keep the receiver from the A4 so that it will still work. Maybe it's wishful thinking haha. Maybe someone on here has some insight to this? I couldn't find any specifics on it but I will keep searching.

Update: I know how to reprogram the fob by turning on ignition and holding the unlock button. But will my A4 key sync up to the S4 reciever?

[b6Hate4]

Didbyou use a donor car or did you just source the parts you needed? Also did you keep the A4 gauges or did you install an S4 one.

I had gotten the entire interior from a donor car, engine came from another car, kept the 01A for now, porsche BBK ect... I used the S4 cluster. Plug and play.

[walky_talky20]

I'm pretty sure that the Central Locking is not S4-specific. It may be facelift-specific, but both of the cars are facelift, so you should be good.

One benefit I see with your swap is that you'll have an S4 with A4 insurance prices. Personally, I would leave the exterior and all badging as A4 spec for total sleeper status.

[b5quattro_man]

I'm pretty sure that the Central Locking is not S4-specific. It may be facelift-specific, but both of the cars are facelift, so you should be good.

One benefit I see with your swap is that you'll have an S4 with A4 insurance prices. Personally, I would leave the exterior and all badging as A4 spec for total sleeper status.

Ok cool. That's what I'm hoping.

The sleeper idea has really grown on me. I was planning on running the stock a4 front bumper for sure but was thinking of replacing my 2.8 badge with the 2.7 badge and leaving the a4 badge on the car as well.

[b5quattro_man]

So today it was raining off and on most of the day but I still worked through it even though it might have slowed me down a bit.

I managed to get the whole front subframe out of of the A4.




Also managed to get the dash pulled and start on the dash harness.




Tomorrow I am planning on having the dash harness out of the A4 and hopefully close to having the front subframe out of the S4. Hopefully weather permits. It's supposed to snow tomorrow! Normally I would welcome snow but im not looking forward to working in it at all.

[redline380]

One benefit I see with your swap is that you'll have an S4 with A4 insurance prices. Personally, I would leave the exterior and all badging as A4 spec for total sleeper status.

My S4 is a 2000, costs the same exact as my 2000 A4 Avant. My 01 A4 costs about $3/month more, but they don't know it has the power it does. They are all roughly $30/month for liability, but I have $250k/$500k coverage and a million dollar umbrella.

Kudos to OP for actually doing the swap. Many times it has been asked "Can I S4 swap my A4?" The correct answer is of course just go buy an S4. But considering the circumstances, this is a good project.

[HumbleTurbo]

It's supposed to snow tomorrow! Normally I would welcome snow but im not looking forward to working in it at all.[/QUOTE]

You can do it!! This is hella OG bro!

[b5quattro_man]

"Can I S4 swap my A4?" The correct answer is of course just go buy an S4

Every time I looked for something like that, that is all that people would say haha. So I stopped looking up s4/a4 swap threads.

[b5quattro_man]

Well thankfully no snow today!! I got a good amount of time in today and managed to get the dash core and harness out.I also pulled my carpet to expose the chassis harness. I couldn't believe the amount of wires under the carpet!!



I was also able to get the engine harness completely out of the S4 and got the front subframe ready to come out. It was very apparent that someone has had this motor out a few times and didn't care how it went back together. I haven't seen so many zipties in one engine bay before! I am really glad that I am going through everything.

[Joe Jr.]

dang that's a big job....cool to see you doing this.

[V70R]

Great thread, and even better to see that you found a matching Santorin parts car. If you need anything from just north of ya don't hesitate to ask or shoot me a PM.

[b5quattro_man]

If you need anything from just north of ya don't hesitate to ask or shoot me a PM.

Most definitely! I'm planning a trip to discount import parts next week after Christmas on my way through portland for some driveline bolts and a few other small parts I need. I love that place! Haha

[V70R]

For sure! I've been going there since the early 2000's and know the crew pretty well (and stayed I contact with most as some have moved to other careers) but Dave is good people and still there at the East side location.

[BGB]

Any updates on your progress?

[b5quattro_man]

Hello everybody!! I'm back from traveling for holidays.

Let me start this post off with saying that I originally wanted to have this swap done by Christmas. There are a few things that stopped me from doing so. The main issue was that by the time I went to order the turbo rebuild kits, the expected delivery day was December 27th. Two days too late. Also at this point I really didn't want to rush anything and accidentally miss something. This s4 is showing more and more signs of being half-assed by previous owners and I want to do it justice by making sure everything is done and put together the way it goes. So from here on out I am taking my time and checking everything I can.

I got a few hours of work in yesterday and am working on it today. So far I have the dash and core pulled plus the heater assembly and almost the main harness. Only a couple things to do before the assembly starts on the a4!!

[b5quattro_man]

It turned out to be quite the productive day! I managed to swap over the heater assembly, dash harness, dash core, heated seat harness and the cooling fan harness that goes to the main relay center.

The main reason for me to even swap the dash harness is because I really want heated seats. After looking at the main loom I figured out that the heating function of the seat is it's own harness from the main junction to the seats. There was only one wire that I had to cut and splice. Otherwise it was pretty straight forward (comparetively lol).

Complete s4 dash harness with heated seats.



Had to pull the heated seat harness out of the main chassis loom.



Harness for heated seats.



What it looked like after I got it all back together.



By the end of the day I was able to install the dash core, heater assembly and the dash harness.



Hopefully tomorrow I will be able to finish the interior swap and then it's on the the front subframe/motor transfer to the a4. I am just waiting for me to get the rebuild kits for the turbos. But I finally feel like I am well over halfway done!! Starting to get excited to be driving this car.

[b5quattro_man]

Looking for a wiring guru to help me out. I found an extra harness on the s4 that isn't on my a4. It goes from the dash harness to the driver kick panel junction and then into the driver door to an electrical box inside the driver door. In the a4, this harness is not there or the box in the door. Does anyone have an idea what it is for? I am thinking it has something to do with the side curtain airbags. Hopefully someone can verify. It's two wires, a red w/ black stripe and an all brown wire. I am not swapping over the side curtain airbags or the esp system so if it has to do with either, I don't have to worry about it.

[Rodgman15]

Looks like heated door locks according to the part #.

https://shop.autewo.de/Elektrik---Sc...43737195_u341/

[b5quattro_man]

Looks like heated door locks according to the part #.

https://shop.autewo.de/Elektrik---Sc...43737195_u341/

I think you're right. It seems to keep going to the lock mechanism and it would make sense because the s4 has the cold weather package and my a4 doesn't. I tried to Google the PN from the tag but couldn't find anything. I must have had a digit or two wrong.

Thanks for the help.

[b5quattro_man]

One thing I noticed recently is that one of the previous owners of the s4 has deleted the after run coolant pump under the intake. They didn't relocate it, just deleted it. When I look up how other people have relocated it, they moved it to the front of the motor. This one has nothing there, but when I look at my 2.8 on the front of the motor there seems to be a pump. Did the 2.8 run an after run pump? It looks just like it and is inline on a coolant line by the alternator. Could I maybe use the one off my 2.8 to relocate the one off the 2.7? I see the importance for something like this and would really like to have it installed for safekeeping but I also don't want to spend the money on a new one if I don't need to.

The missing spot on the 2. 7



This is the pump on my 2.8.

[walky_talky20]

The 2.7 really has a terrible location for the pump, originally. So terrible, in fact, that Audi issued a TSB (for some model years) to relocate the pump if it ever fails. This is the OEM relocation kit for that TSB:

https://www.ecstuning.com/b-genuine-...kit/078998998/


It looks like it may even use some of the same parts as the 2.8 side-located pump does. As long as you plumbed stuff correctly, I see no reason why you couldn't use at least some of the 2.8 parts.

[MetalMan]

One thing I noticed recently is that one of the previous owners of the s4 has deleted the after run coolant pump under the intake. They didn't relocate it, just deleted it. When I look up how other people have relocated it, they moved it to the front of the motor. This one has nothing there, but when I look at my 2.8 on the front of the motor there seems to be a pump. Did the 2.8 run an after run pump? It looks just like it and is inline on a coolant line by the alternator. Could I maybe use the one off my 2.8 to relocate the one off the 2.7? I see the importance for something like this and would really like to have it installed for safekeeping but I also don't want to spend the money on a new one if I don't need to.

The missing spot on the 2. 7


This is the pump on my 2.8.

Just last night I deleted/bypassed the afterrun coolant pump on my S4.
From everything I researched, it sounds like under normal conditions the pump doesn't generally turn on because the temperature switch has a relatively high set point. So in the off chance that high temperature is reached, the pump may fail since it's been heat-cycling on top of the engine for who knows how long.

My pump wasn't leaking, so bypassing it was more of a preventative thing. I'll just make sure that the engine isn't ran hard and shut off right away.

Now, there is a "blue" temperature switch which has a lower set point:
http://etspec.com/index.php?route=pr...product_id=120
With this switch, the afterrun pump is much more likely to run under normal operating conditions. If I were to keep the pump, I'd definitely buy this switch.


Also with the pump on your 2.8, based off of my scouring ETKA, it looks like those should be the correct parts to relocate the pump on your 2.7. Go for it!

[b5quattro_man]

Well.... managed to get the front subframe and motor out of the s4.



Pulled my bank 1 turbo and found that the small nut that goes on the intake side had fallen off and was sitting in the inlet housing.





I haven't even attempted to pull the bank 2 turbo yet. It's covered in like an inch of oil build-up.

So now I am in search of a set of ko3s. Maybe ko4s if I find the right deal. If I put ko4s on it will I need to upgrade the ecu or is that something I can do later down the road?

Also managed to get my dash top installed in the a4. I am waiting to put the steering column in until I have the subframe in so that I can make sure the wheel is straight.

[HumbleTurbo]

Jumping up to ko4's would be cool, but ill be disappointed at not seeing those turbos rebuilt which I think you mentioned doing before. I feel like its a simple fix that most people dont attempt for some reason. Just did my ko3 this summer, only being a moderately skilled backyard mechanic I was nervous but it went well and full boost has been holding. Not to mention only 60 bucks for the kit off rockauto... But anyway this build is sweet and the time your doing it in I'm impressed with. Loving the frequent updates.

[b5quattro_man]

Jumping up to ko4's would be cool, but ill be disappointed at not seeing those turbos rebuilt which I think you mentioned doing before. I feel like its a simple fix that most people dont attempt for some reason. Just did my ko3 this summer, only being a moderately skilled backyard mechanic I was nervous but it went well and full boost has been holding. Not to mention only 60 bucks for the kit off rockauto... But anyway this build is sweet and the time your doing it in I'm impressed with. Loving the frequent updates.

I am still rolling ideas around about what to do. I am pretty sure that the one turbo is not rebuildable. I think the shaft snapped. I might be able to get a rebuilt core and use that... I am not sure right now but funds are a little tight for now. The Next few days I think I am just going to concentrate on cleanup and organization (engine bay and minor parts to swap over) until I figure out what to do.

[b5quattro_man]

So today I am concentrating on swapping all of the smaller stuff over to the a4. So far I have swapped over the radiator fan harness since it runs two fans on the s4. I also found a vacuum reservoir (I think?) Tucked inside the driver fender.



Next I need to swap over the high pressure power steering line under the intake because now the fittings don't match up. Should be a pretty easy thing.

What it looks like in the a4


What is in the s4


Other things I can think of that will need to be swapped is the SMIC mounts, SAI delete and the purge valve piping by the air box.

If anyone can think of anything else that I'll have to swap over, please let me know. I don't want to miss anything that's going to have to make me go back in and do it again.

[b5quattro_man]

Oh and I forgot to mention that I did get the 2.7 front subframe into the a4. I wanted to put it in now so that I can mock up everything else other than the motor. Once I get my turbo situation figured out, the motor and trans are coming out so that I can do some detailing and fixes on the motor itself before it goes back in for the final time.