The Narrow-Body RS4 Build - A Build Log

[KiwiRider]

I have always loved the B5 generation of Audis, especially with a 1.8T A4 B5 being my first car at age 18.
Over the years I have tried three times to buy an RS4 B5, my dream wagon. Unfortunately every time the seller pulled out. With only 35 here in New Zealand its a hard market!
I also knew only 77 S4 B5 were ever sold here, so when I found one in nice condition in late 2023 for $8000NZD ($4500 USD) I knew I had to have it!
Now I am building my own RS4, as I managed to purchase a freshly rebuild RS4 engine, for now in the normal S4 body - hence the Narrow Body RS4!

Here she is on the day I picked her up in the North Island in November of 2023 with 212k km in the clock. No mods other than wheels, a Remus catback exhaust and S4 B6 brakes and rotors



This is her sitting next to my MTM Stage 2 A4 I had at the time. Quite a few parts were taken off this to fix misc things like the climate control module, as well as the Audi Mudguards which I loved the look of.



First thing I did was put on new wheels and tires, a 034 Rear Sway Bar with Subframe Brackets, X34 Carbon Intake and Y-Pipe as well as Street Density Transmission mounts and the 034 Snub Mount and Bracket.





This is how she would sit while I drove her for the next year as a daily, even though I didn't really drive her as much as I should. Only did 2000km that year.

[KiwiRider]

After about a year of ownership I decided it was time to do some basic maintenance, like replace the leaking valve cover gaskets, repaint the valve covers and remove some of the systems I knew I wouldn't needs when I eventually went stage 2 (the plan at the time).
I was also going to fit some XS Power Decat Downpipes, as well as 034 Bi-Pipes and Throttle Body Boot and Spider Hose before getting a tune.

But then as I delved in and thought I'd have a look at the turbos I found disaster! my RHS turbo has eaten something at some point and was not in very good shape



What to do!? Well, if I was going to pull the engine to get at the turbos I knew I wouldn't bother with the K04's.

I decided on a basic K04 build and started looking for the required parts. Picked up some used and tested/cleaned 550cc injectors, but was shocked at the prices of turbos and decent clutches etc...
The New Zealand Dollar doesn't fare too well against the USD, shipping is a killer and we have to pay additional import tax on shipments over $1000NZD ($530USD).

I knew it had to be done, but it was going to cost at least as much as I had paid for the car, if not more...

I worked on other things on the car while trying to figure out my plan, such as repainting and installing an RS4 rear spoiler and getting a big brake kit sorted.





The rear spoiler makes the rear of the car much more cohesive, it is such a minor mod but really widens the look of the car. Especially when in combination with the factory mud guards.

In terms of brakes I got some 18Z callipers off a mate and started restoring these back to brand new. I also decided the forged 18x9 wheels off my TTRS 8J would be moving onto the S4 after a test fit with the new brakes.



The restore:





The final result. I went with the tried and tested ML55 AMG 345mm disks.
Here in New Zealand we have annoying certification laws for modifying cars. They recently changed it that you can no linger use nut and bolt options to fit aftermarket callipers to cars.
As a result I am going to get the stock bolts used for 18Z callipers on the SUVs and tap the M16 threads into my steel uprights. This will allow a factory looking fit and should pass cert or even without if the WOF (our MOT) inspector misses it.

[KiwiRider]

At this point I am still trying to decide what direction to take the S4 engine build.
Stick to the K04s and have a fun and reasonably quick daily?
Put rods in it while its out and go bigger to hybrids? That can quickly go out of control...

Then while thinking about this I got a message out of the blue from a mate.
"Hey, I've tracked down an RS4 motor locally if you want to go nuts?"

Oh... Oh Damn! I asked about the engine history, the parts that come with it and the price. Everything seemed too good to be true, but I knew this guy was for real. The price was a lot for me, but I also knew it was very cheap for what I was getting... Lo and behold there went all my saving...

And what did I get for all my money?
A freshly rebuilt - never run - ASJ RS4 engine. All the big boy parts were there, heads, intake manifold, throttle body, bi-pipes etc.
Yet it still came with much, much more too! The guy he got the car off planned an all out build, so it came with a lot of nice parts too!

These included:
- SRM Exhaust Manifolds
- SRM Inlets
- SRM V2 Intercoolers
- 034 Fuel Rails
- Bosch 1000cc Injectors
- R8 Coils
- 034 Spider Hose
- 034 Motorsport Billet Engine Mounts
- 034 LWFW
- Sachs RS4 Clutch
- 3" Downpipes
- Early JHM RS6-R Turbos
- RS4 Wiring Harness with all the deletes
- Old Style 034 Carbon Y-Pipe
- 034 Big Bore Lobsters
- 034 DVs
- More smaller misc upgrades like SAI Delete etc

So there you go, off goes my money to him plus another chunk for delivery on a pallet. I was nervous. Did I just spend all my saving on an RS4 engine, knowing there were a few small parts missing... Yeah... Sure did!

He did inform me that the pervious guy how build it didn't seem too clued up, and that some sensors may be missing... This turned out to be very, very true... More on that later.

But for now! Here she was... A slightly shabby looking but fully rebuilt ASJ RS4 motor, with all the brand new upgrade parts coming with her!

[KiwiRider]

Now that the engine had arrived it was time to give it a good look over and make sure it was assembled correctly...
Well, that didn't go well. She looked pretty shabby, with a lot of surface corrosion on the exhaust housing and manifolds, and even most of the aluminum parts like the heads, engine mount brackets and valve covers had oxidized and pitted a bit.

For such a special engine, this wasn't going to do! We will get into the mechanical bits that were missing and wrong in the next post.

For now, much had to be done to make the engine look as pretty and special as it was. So I stated taking everything off until I was left with almost a bare short block, noting down missing parts and problems along the way.
Fortunately I have a sandblaster and full paint booth at work, so made the most of it getting things restored.

Starting with the valve covers. The paint was flaking off and lots of oxidation underneath. But came up as new after a good blast!



Then onto paint. I used the same colour as the brake calipers to give it a nice flow throughout the car. Plus, red makes more power right??



For anyone wondering, the valve covers on an RS4 are the same part number as an S4 and A6. Nothing special here.
With these back on with new valve cover gaskets with sealant in the correct places, it was already looking miles better!



Now I wanted to tackle the SRM exhaust manifolds. These are fantastic parts, but even tough they were brand new they were looking very sad! So off to the blaster and then painted with a 650 Celsius high temp paint to try protect them.





I also made sure to get the RS4 intake manifold and bi-pipe fitting blasted and gave it a repaint with some 2K silver to protect them from any oil or grease in there over time.







I also did my shifter surround in the same lovely silver at the same time to freshen up the interior, as well as the oil vapor housing in the centre of the V. It will never be seen but I can't leave all that corrosion in there!

Last off I tackled some of the oxidation on the heads. These beautiful Cosworth heads shouldn't look all sad like this, especially with everything inside them being brand new.
So out came the wire brush and scotch wheel on the dremel. Lovely improvement!

All sad before:



Much better after!

[ShelbyM3]

Now that the engine had arrived it was time to give it a good look over and make sure it was assembled correctly...
Well, that didn't go well. She looked pretty shabby, with a lot of surface corrosion on the exhaust housing and manifolds, and even most of the aluminum parts like the heads, engine mount brackets and valve covers had oxidized and pitted a bit.

For such a special engine, this wasn't going to do! We will get into the mechanical bits that were missing and wrong in the next post.

For now, much had to be done to make the engine look as pretty and special as it was. So I stated taking everything off until I was left with almost a bare short block, noting down missing parts and problems along the way.
Fortunately I have a sandblaster and full paint booth at work, so made the most of it getting things restored.

Starting with the valve covers. The paint was flaking off and lots of oxidation underneath. But came up as new after a good blast!



Then onto paint. I used the same colour as the brake calipers to give it a nice flow throughout the car. Plus, red makes more power right??



For anyone wondering, the valve covers on an RS4 are the same part number as an S4 and A6. Nothing special here.
With these back on with new valve cover gaskets with sealant in the correct places, it was already looking miles better!



Now I wanted to tackle the SRM exhaust manifolds. These are fantastic parts, but even tough they were brand new they were looking very sad! So off to the blaster and then painted with a 650 Celsius high temp paint to try protect them.





I also made sure to get the RS4 intake manifold and bi-pipe fitting blasted and gave it a repaint with some 2K silver to protect them from any oil or grease in there over time.







I also did my shifter surround in the same lovely silver at the same time to freshen up the interior, as well as the oil vapor housing in the centre of the V. It will never be seen but I can't leave all that corrosion in there!

Last off I tackled some of the oxidation on the heads. These beautiful Cosworth heads shouldn't look all sad like this, especially with everything inside them being brand new.
So out came the wire brush and scotch wheel on the dremel. Lovely improvement!

All sad before:



Much better after!

I really enjoy reading this and following along. A man after my own heart, making everything clean and functional. I love it! Keep up the great work!


Sent from my iPhone using Audizine Forum

[KiwiRider]

In the last post I mentioned that there was a lot more missing and wrong with this engine for something that was said to be "plug and play".
Some are minor things that didn't worry me too much. Some just make me wonder what the hell was going on in the fellas head who assembled the engine (to clarify, not the friend I bought the engine through).

Lets start with minor things I would steal off my normal S4 engine:
- The intake air temp sensor that sits in the bottom of the intake manifold was missing
- Both cam position sensors were missing

Then I found some significantly more major parts missing that I would have to steal off the S4 engine:
- Coolant hardpipe that feeds into the back of the thermostat housing under the intake manifold. Would have caused a hell of a leak if I didn't see that!
- However, that leak would have been pretty insignificant compared to this one...



The entire thermostat housing and thermostat was just... Not there! And the crazy part is this can't be installed with the cam belt in place (at least from what I found removing the housing off my S4 engine to fit to this one. So the previous assembler just... Forgot?? To install the thermostat and housing?

Luckily my S4 engine recently had a new housing installed so it is the updated aluminum one. Gave this a quick sandblast and a bit of clear coat to keep it looking pretty! Question for those who have a higher power build, should I install a new low temp thermostat or run the normal temp one? Don't want to use the old one out of the S4 on such a cheap part, rather replace with a new one.

But that's not all. Here are some more smaller but equally crappy assembly problems I found:
- Brand new EGT probe cross threaded, both exhaust manifold thread and the sensor threads buggered. Will need to retap the manifold and hope I can save it. EGT was just spinning in place so would have been an exhaust leak too.
- Self tapping screws holding in the MAP sensor into the bi-pipe aluminum manifold, also destroyed these threads.
- No gaskets between the intake manifold and the plenum spacer, or the spacer and the head. So just metal on plastic on both heads... Nice leak waiting to happen.
- No gasket on throttle body to intake manifold, just sealant. Another possible leak.
- Wastegate lines hardened and dryrotted.
- Alternator ground cable not connected.
- All fuel lines and fittings on the fuel rails loose. One AN fitting was in backwards so the flared hose couldn't seal. Very happy I checked all these as I'd have had at leak 5 fuel leaks!
- AUX water pump brackets snapped off the mount, no issue as I have a delete hose for this.
- Oil fittings on R/H turbo loose.

So with all of those found and noted/fixed, its now time to get onto some fun stuff! Porting the intake components and inspecting the turbos... Some magic to happen with those while I'm in there too

[KiwiRider]

Well that last post was rather sad and frustrating... Lets cheer up the mood with some fun stuff and eventually reassembly of some sexy parts!

Let this act as a trigger warning to those Audi purists who don't like expensive rare parts modified... That's not how I like to do things

Today I will be focusing on the intake system post turbos for the RS4 engine. As we know already I have the OEM RS4 intake manifold, throttle body and bi-pipe manifold, as well as oversized stainless 3" bi-pipes.
I like to optimize where I can and with everything apart there is no better time than the present!

I started with the intake manifold. I didn't see the point of major porting and polishing here as it already flows massively well stock. I got out my digital calipers and did some measuring of the ports on the head, the plenum spacers and the intake manifold outlets. The spacers are bang on to the heads (56mm x 28mm) but there was a little to be removed from the manifold to have a nice clean port match. This measured around 51mm x 26mm.
Not a massive amount to be had, but if I can improve the flow efficiency I definitely will! The inside casting is interesting and the inboard side has some very sharp protrusions which definitely hamper flow. I smoothed these out as much as I was comfortable.

Note that in the manifold I am not polishing anything extra, as I want good fuel mixing and turbulence when flowing over the injectors. In the next picture you can see the small black outline of what I will be removing to port match. Not much, but may as well optimize!



And here we have the after result. Nothing world changing but worth the time especially for the much improved internal flow. This is in the shadow area of the intake ports in the picture.



Now lets look at the bi-pipe to throttle body manifold. My theory here is due to it being pre-throttle body, I am more focused on creating as much linear flow as possible and removing as much of the slow moving boundary layer near the rough casting surface (can you tell I'm an aircraft engineer by trade? Lol). Fuel mixing isn't a main concern in this area, and I believe the intake manifold has enough design and rough casting elements to achieve proper mixing.

I notice quite a significant lip on the sides connecting to the bipipes which would restrict some flow, so ported these to a nice bell mouth like shape to improve flow. I also completely removing all casting marks on the tubes, but left it in the central section around the MAP sensor. The below images show a great comparison of the difference, even though I had gone through the rough right hand side already with a scotch wheel.





I'm pretty happy with these minor changes. Will they make a noticeable difference? Most likely not! Did I enjoy the process and know that I've done as much as I'm comfortable with to improve flow and efficiency? Absolutely! And that is a big part of the enjoyment I get from working on stuff!

Now that these intake parts are where I want them, its finally time to actually reassemble something for a change!
Starting with the beautiful intake manifold, I assembled the Bosch 1000cc injectors (I believe these are 550ccs that have been modified by ET Spec) into the 034 rails. These are great as the spacer flip to accompany both long and short injectors, so I didn't have to run injectors hat spacers. I installed these onto the manifold and then remembered my problem with the self tapped screws that damaged the bi-pipe MAP sensor screws. I tapped these out to accept a normal M6 thread, but one went through all the way into the manifold. When installing the MAP sensor I made sure the add tread sealant to this one to not chance a small boost leak.

Finally, the cleaned throttle body was fitted to the intake manifold WITH A GASKET this time, and the bipipe manifold also got installed. I am trying to use new stainless fasteners where possible to keep a clean and rust free look!



Now, to finish it off I fitted the huge bi-pipes for a final look at the finished intake setup. And boy is it a pretty thing to behold!



With that section of the engine ready and just waiting for some new intake manifold gaskets to arrive, lets move on to looking at the turbo situation!

[zatch_303]

Nice progress! Didn't realize they were so rare over there. Only 77 ever sold!? That's wild. Pretty cool you'll be running the RS4 engine.

[KiwiRider]

All things in life should be balanced... Work life balance, nutrition and of course brake size front to rear!

After upgrading to lovely 345mm x 32mm front rotors, with a great colour and Audi emblem, the rear only having a 255mm x 22mm rotor looked very out of balance!
So I delved into upgrade options. I wanted to keep it OEM+ like the 18z fronts, while maintaining bolt on ease of upgrading and no extra brackets to space things out.

I came upon the upgrade to a B6 S4 rear brake setup, which uses a similar caliper but larger 300mm x 22mm rotors, as well a much larger pads for more contact area! Best part? It bolts right on with just lines required, as well as retaining the OEM park brake setup.

A reminder of the sad state of the stock rear brakes:



I gathered all the parts needed, which are the 300mm rotors, I picked up some as new EBC slotted and dimpled ones cheap!
Gave these a quick sandblast and paint protection. Lovely!



They make the old stock disks look like brakes off a bicycle



The other main component needed is the B6 S4 rear caliper and carrier. These use a different brake line, so make sure to either get that too, or order some braided M12 banjo to 1mm female lines.

My calipers looked very sad, but as per usual the sandblaster makes short work of this!



Some primer and paint later:





And new have the sexy final product!



To get these to bolt up you will need some 9mm thick spacers as the B6 uses a different rear hub. This places the caliper squarely over the new disk. I machined these out of billet aluminum, yes very overkill.
Here you get a great sense of the increased pad contact area of the new pads:



Now, time to fit them up! You will need 10mm longer bolts to make up for the spacer you are using. The hand brake cable takes a lot of tugging to get to fit up, but it does work!
Very happy with the final result, gives much more balance to the look with the front rotors, and reports say a much better rear end feel under braking.



Much more still to come... Currently waiting on shipments to arrive. Tackling suspension, clutch and a lot of bushings next... Also keep tuned for some great OEM+ suspension weight reduction!