Project RS4: Finding Lost Power
A Coke Habit

I’ve done around 10,000 miles since picking up Project RS4 last August last year, and to be fair it’s not skipped a single beat mechanically.

The Audi has been flawless at karting me and my inordinate amount of largely unnecessary camera kit up and down the country, as well as serving me well as both a fun weekend car and daily driver.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-1

In fact, not only am I not really missing my old Honda S2000, but I even went and sold my runaround – it’s been pretty good at everything.

Except fuel economy. It’s terrible at that, but hey, if I don’t have fun burning up all the dead dinosaur juice then someone else will, am I right?

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-1-2

Since fitting the KW Variant 3s a couple of months back I’ve been really pleased with how the car rides and handles. I’m yet to tweak the ride height to exactly where I want, but it feels superb on the road. There’s still a bit of the familiar Audi understeer when pushed hard, but that’s to be expected with a heavy car and heavy engine. Still, I’m looking into how I can dial a bit of that out possibly with the addition of an adjustable rear sway bar. I digress – that’s for another update.

One job that I knew I’d need to do, even back before I purchased the car, was get the engine decoked. While this particular V8 is an awesome piece of engineering on Audi’s behalf, it’s not without its flaws, and one in particular plagues RS4 owners around the world: carbon build up.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8197

Long story short, there’s not a stock RS4 out there that makes the 414hp book power figure after a few thousand miles. Some drop to the low 300s if left unattended, or worse if other issues are present. On these engines, decoking is essentially routine maintenance.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8069

There are countless tuners up and down the country that offer carbon cleaning, but significantly less that I’d trust to work on my own car. After seeing the work that Regal Autosport did on Paddy’s Project GTI last year, and the fact that he drove across three countries overnight just to use Regal, I knew where my first port of call was going to be.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7031

Having met up with the guys from Regal at a private track day at Goodwood the day before, introductions were out of the way and a plan of action was agreed upon for the following days. Rather than drop the car off and come back to pick it up later in the week, it made sense to set up shop at the workshop for a couple of days so I could document the work, along with other cool stuff that the guys have going on.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7059

Plus they have a workshop doggo, so I was never going to get bored.

Under The Knife

No sooner than the car had landed in Regal’s workshop, technician Ben had it on the ramp, undertray removed and was preparing it for its ‘before’ dyno run. This would give us a solid idea on how effective the work had been.

I’m breaking the convenience of chronology in doing so, but I’m saving the before/after dyno comparison for the next update…

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8211

With the ‘before’ run completed, Ben got to work on removing the inlet manifold. The V8 is pretty tightly packed into the B7’s engine bay, so what seemed like endless pipes, covers and components were soon being pulled out of the bay and placed to one side.

Rather than get in Ben’s way during what looked like a testing time, I took leave to have a wander around the premises and see what else was going on.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7064

The first day of my visit was a comparatively quiet one for the workshop, although there was still a steady stream of cars in and out for jobs. Regal’s own GT3 is the stuff of dreams and distracted me for longer than it should.

Much of Regal’s work originated in the world of Vauxhall tuning and race cars, and there was evidence of this scattered around the premises. Nowadays they’re busied with all manner of work, with a focus on German marques, both in terms of tuner and road cars as well as track day and race car building and prep.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8141

I also spent a good amount of time admiring this RS3 Sportback, which was in for a dyno run and geometry setup. It made good power for a stock engine, and with a full Milltek exhaust system fitted sounded pretty amazing on the dyno. It certainly made me want to look at how I can make the RS4 sound a bit more raw, without making it too loud at the same time.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8195
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7038
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8218

Meanwhile in the workshop, this E92 BMW M3 was receiving a fast road geometry setup, and Speedhunters’ own Ryan Stewart’s Alpina was propped up in the air awaiting an engine rebuild. Underneath something sleek, exotic and supercharged was tucked up out of view. There was always something going on to distract me!

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8102

Regal are UK distributors for Wavetrac differentials, and Regal’s marketing manager Ash Stewart must have seen me looking incredibly confused at the in-progress diff upgrade on the workbench, so walked over to explain. This particular diff is going into a customer’s Porsche race car. The crux is that it’s a PDK-equipped car, so upgrading the factory diff unit is complex work.

While Ash tried to explain what I was seeing, complex numbers and equations swirled around above my head, but the long and short of it is that A.) Wavetrac diffs are the stuff of magic, B.) in the case of this job, the diff was awaiting some shims to be machined up so the guys at Regal could set the backlash correctly, and C.) Regal are some form of Wavetrac wizards. And thus my knowledge on the matter is disseminated.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8338

Ash also took time to show me some new brakes that Regal are testing. These whopping Sparta Triton Rs are destined for Regal’s E92 M3 track car, and measure 380mm (6-pot) up front and 355mm (4-pot) out back. There’s lots of cool touches going on here, such as castellated pistons for reduced heat transfer, and plenty of weight saving designs. Just 3.25kg on the front calipers? Me gusta.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8243

Back on the RS4, Ben was hauling the hefty inlet off and placing it to one side to assess the carbon build up.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8257

That is what 80,000 miles of carbon looks like. Peering down into each port the caked-on carbon is clear to see, with thick chunks clinging to each valve stem – not pleasant, and almost definitely the cause of any lost horsepower.

The carbon build up isn’t an issue unique to the RS4 either – it happens on almost all direct injected engines sooner or later, as the fuel is added directly into the cylinder rather than injected into the port past the valve. Without this fuel to help keep the valves clean, they are gradually coated with carbon deposits over time, which not only adds mass to each valve stem, it also coats the inside of the intake, inlet manifold and the ports, essentially reducing the amount of air reaching each cylinder. Neither of these qualities are conducive to delivering the most horsepower possible from the engine.

Being naturally aspirated, the problem is exacerbated as the airflow through the ports is slower than a forced induction engine too, so the carbon deposits fall out of suspension, coating the internals. The good news is that on this engine the problem is confined to the valves and ports, so isolating and cleaning this area is known to immediately restore the engine to factory power. The bad news? It’ll come back eventually, making the decoking process something that should be done as part of maintenance.

To help shift the build up with less elbow grease, Ben soaked each port and valve in fuel and let it sit overnight. With some manual cleaning, things would hopefully be looking a bit less coked up!

Coming Clean
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8284

Come the next day and Regal was bustling long before breakfast. Alongside Project RS4, the team also had a factory-fresh RS3 saloon in for some new KW suspension. With just 800 miles on the clock and already wearing a set of OZ Racing wheels, someone wasn’t hanging about.

The clever thing is that the KW system in question mates to the stock Audi dynamic suspension, and so retains all electronic control over damping modes, whilst closing the tyre-to-arch gap.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7100

I have to say I’m slightly envious of the tuning potential of newer RS models. Here we (I say we, I mean Ben) are trying to restore my car back to at least stock power, while one of these can be mapped to 500hp with a simple ECU flash. There are RS3s knocking on 700/800hp without breaking a sweat.

Still, it doesn’t have a massive V8 or make massive V8 noises, and mine does, so there.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8300

By this time, Ben had already started manually cleaning said V8’s ports. By turning the engine so that five ports are closed, and then sealing off the open ports, he was able to complete the job in two passes. First he manually cleaned the inlets with a cleaning solution, and then blasted each port with polymer beads via a pressurised airline, which removed any remaining carbon.

Any loose carbon was then removed before Ben turned the engine over and worked on the remaining ports in the same fashion.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8281

The result? Shiny and clean ports, along with unhindered valves – I couldn’t believe the difference!

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8263

With the head taken care of, the next port of call was the inlet manifold. The RS4 features vacuum-actuated flaps in each intake runner which alters the airflow at low revs, and while these help add a bit of low-end torque, the downside is that they inevitably affect airflow at high RPMs. They’re also yet another component for carbon to cling onto, and are activated by plastic actuator arms, which can become brittle and snap.

With the manifold already off, Regal advised me to take this chance to remove the flaps from the intake. At the cost of a few lb/ft of low down torque, the result would be an engine that produced more power and torque up high, and revved much more freely. This would require a re-map to stop a fault code from showing up when the flaps didn’t activate, but as part of this map Regal are able to compensate for the reduction in bottom end torque to retain drivability.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8319
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8326

This process is fairly simple (says the guy who can barely turn a spanner without assistance) and a far more competent Ben quickly removed the blanking plugs from the manifold, before unscrewing each flap and removing it from the manifold. The manifold was then cleaned to remove the light carbon build up inside.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8465

Refitting is the reverse of removal, and before long the engine was back together and Ben had the RS4 plugged in. He first backed up the existing map as a safeguard before loading on Regal’s Stage 2 software.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8448
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8456

While I was anxiously awaiting the next set of dyno runs to see what a difference the work had made, there were still a couple more jobs to do. First Ben ran an EDT oil treatment through the engine – this machine pulses warm mineral oil through the block, clearing out the oil galleries of any contaminants and sludge from the system. This was followed up with a fresh filter and oil change.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8500

Ben also checked the condition of the plugs – they’d seen better days for sure, so to be on the safe side we replaced these too.

Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-

After checking everything over twice, the V8 barked back to life and was left to warm up while Ben prepped the dyno for the ‘after’ runs. It was pretty nerve-racking time, but after seeing all the work that had gone in, I was pretty confident that the results would be worth it. Stay tuned for the verdict in the next update very soon…

Jordan Butters
Instagram: jordanbutters
jordan@speedhunters.com

Cutting Room Floor
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7029
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7041
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7044
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7066
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7082
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7087
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-7109
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8064
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8071
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8076
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8132
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8138
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8148
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8165
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8186
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8189
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8196
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8223
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8265
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8305
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8310
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8336
Project RS4 Carbon Clean Regal Autosport by Jordan Butters Speedhunters-8446-2
ADVERTISEMENT

Comments

Add comment

E-mail is already registered on the site. Please use the Login form or enter another.

You entered an incorrect username or password

Sorry, you must be logged in to post a comment.

39 comments

by Oldest
by Best by Newest by Oldest
1

The suspense is killing me....

2

For a sec, in that first picture, I thought Paddy went ahead and bought himself a Golf R or repainted Project GTi in a factory blue LOL but i wanna see some (possible) forced induction or maybe breathing mods.

3
Paddy McGrath

I'm pretty much married to my MK6 for another year yet, although the R is high on the list of potential replacements.

Author4
Jordan Butters

I’d love to go down the route of forced induction, but the options are very limited - there’s really no room for turbocharging; and a supercharger setup is incredibly expensive for these engines (circa £15k once installed and set up).

As for breathing mods - that’s exactly what is being done - in the last update we stripped out the air box flaps and vacuum system and installed a panel filter. Now we’ve removed the manifold flaps too, so the next step is an exhaust of sorts.

5

Jordan if you want to tame the understeer nature of these cars throw out the factory alignment specs!
Go for toe out front and rear (maybe 1mm F and 0.5mm R) to get the weight on the outside of the car as you initiate.
That and maximum caster are your friends :)
Love the work, Brian from NZ.

6

Audi makes such functionally-beautiful V8s.

7

WE WANT TO KNOW

8

Hey no oil catch can installed to preven oil/carbon buildup?

Author9
Jordan Butters

It’s been tried before with negligible effect on build up. PCV vapours are only one cause of carbon on these motors. There’s a lot of speculation online, but it’s believed that the internal EGR system is to blame much of the time.

10

Can you not get a EGR delete in your area? Worked wonders for me, although I have a Mk3 VW Jetta.

https://www.audi-sport.net/xf/threads/help-egr-delete-kit.159846/

11

Good job, Jordan. I scrolled down here to look for those three horrible little letters: EGR.

Obviously, that carbon wouldn't be there without the EGR system. I disabled it with an ECU upgrade on my MK3 Jetta. Also, I worked at a European Auto shop for a while, and the Audis routinely came in with this problem. So sad, because the engines really sound great, and the chassis are equally impressive, but then this one issue essentially destroys the long term value of the vehicle.

Hopefully, any enthusiasts can get the EGR delete for their motor. It was a big deal for mine, the manifold is much cleaner now, (along with a PCV external dump) and also it no longer drains back onto my air filter, which was really annoying, too.

These are all remedies in certain locations, but I'm not sure you can do that in CA, or any smog-nazi states.

https://www.audi-sport.net/xf/threads/help-egr-delete-kit.159846/

Author12
Jordan Butters

Joe – from my research the EGR system on this motor is mostly internal via valve overlap (the inlet valves opening before the exhaust valves have fully closed), so it's not as simple as that sadly.

13

Wow so if that is the case you and in order to do proper EGR delete you will need (if possible) to do camshafts swap, ECU tune and catch cans for PCV and valve cover breather.
So much effort and money thrown there to have a somewhat clean engine.

Author14
Jordan Butters

And for all that, you may as well just have the inlet off every couple/few years and give it a clean. Plus, the valve overlap has other benefits, such as the scavenging effect from the exhaust drawing air into the cylinders, and the inlet valves being open for longer.

15

Jordan don't be such a tease. The suspense will now have me refreshing the Speedhunters page every day and night.

16

Out of curiousity how much did that work set you back?

Author17
Jordan Butters

In total it worked out around £1600-1700, including service, oil treatment and so on. Obviously the big variable here is the decoking process as it depends how bad the problem is. Get in touch with Regal and I’m sure they’ll be able to give you a more accurate quote.

18

For the exhaust, a bypass valve equipped exhaust should do the work i think.

As an owner of a 2T engine motorcycle, we face the same problem with the valves (but on the exhaust side). Bonus note: if the valve system is broken or a valve got damaged somehow and the parts found the way inside the engine (believe me they will).... you can imagine what happens. So the best choice is canceling the disaster cause, but on a small bike engine you can feel the loss of torque on low RPM, did you try it before re-mapping to check the difference?

Author19
Jordan Butters

The stock exhaust is valved on these already, so you get two different sounds.

We didn’t try the car before remapping after the intake flaps were removed - it didn’t make much sense to, and we were running short on time. I anticipate that low down torque would be lessened as that’s the function of the system.

20

sure it will theoretically and if taking numbers as reference, but just out of curiosity i had to ask if you made the test and how much difference did you feel (the human side not the technical side). Since you were short on time, and knowing the end result from the test, better to make the remapping instead of losing time on a "silly" test.

Author21
Jordan Butters

Not at all saying it was a silly idea - sadly we just didn’t have the luxury of time to try it. Still, I’ll be sharing the before/after dyno graphs next so everyone can see exactly the effect that all of the work has had.

22

Waiting for the dyno graphs.
I was referring to silly idea by making the test and leaving the remapping having the time against you and can't make both.

23

Carbon build up, I can hear all the R56 mini owners crying..

Looks like a good set of preventative maintenance / good old tune up, hope it feels much better after!

Also, that's an unassuming Corsa C with TD 1.2s and R888rs on the dyno!

Author24
Jordan Butters

And yes, that Corsa C is a bit of a wolf in sheep's clothing!

Author25
Jordan Butters

The R56 is a similarly afflicted platform for the same reasons definitely. The thing is, as long as you know the issue is there, and are aware that it WILL come back, you can then budget for maintenance cleans every so often. Also, doing things like changing the oil frequently, running high octane fuel and a good ol' fashioned throat clear every so often helps delay the build up too.

26

Fortunately the inlet valves on R56's are much more accessible for cleaning, plus a dual catch can setup combined with some good ol' fashioned Italian tuning can help keep them clear. Bit frustating there's no real preventative maintenance to avoid buildup on your RS4! Keep up the good work.

27
Sebastian Heck

I love to read these rs4 Project articles. <3

Can anyone name the wheels on this white rs3 sb?

Author28
Jordan Butters

They are made by Neuspeed, unsure of the model.

29

I would take a guise at 428hp

30

About the Sparta caliper weight... isn't the scale in the picture set (small black triangle on the right of the display) on "lb", rather than "kg"?
What are they made of if they weigh 3.25lb=1.5kg?

31

Sparta employee here, as much as we'd love to say the scale was in lbs, our 6P-A Triton R caliper weights 3.25kg (7.15lb) without pads.

Author32
Jordan Butters

I’m pretty sure that’s just the angle of the photo - that seems impossibly light.

33
Hunt Country European

I have solved several customer's carbon buildup issues on direct injected gasoline motors with water injection systems. Yes, even on the naturally aspirated RS4 and R8. It was a natural answer for the 2.0T motors, and some people doubted the effectiveness on an NA motor, but it works beautifully. For about the cost of one de-carbon job (and a full service, and a few other little things, just being honest), they will never have to worry about carbon buildup again and get a little more out of their engines on track days.

Author34
Jordan Butters

I've done some reading up on this and water/methanol injection does seem like it helps the issue. I'm not sure it's that much of a burden that I need to go down that route just yet.

35
Hunt Country European

Cost justification really depends on how much you drive the car (some RS4 owners only drive it once or twice a month!) and if you track the car, especially in a hot environment. Most of the RS4s and the one R8 I've installed systems in are nearly daily-driven and tracked quite a lot. Of course it also adds another thing to check and top up at every fill-up, but I've found that most RS4 owners are extremely detail-oriented to begin with.

36

Using high quality gasoline (shell v-power or similar) and running it hard often (maybe the PO didn't?) should mitigate intake valve deposits. Many petroleum companies are working hard to improve formulations to address this exact issue.

If you get to it before this point you can usually clean it up with a chemical cleaner fed through the intake track without disassembling the engine.

37
Hunt Country European

Unfortunately this is not the case with gasoline direct injected engines. Fresh fuel never passes over the head of the intake valves since the injectors spray directly into the combustion chamber (with one exception - Lexus engineers added a stream of fuel into the air intake tract of their GDI engines to help attenuate the issue). Factor in looser tolerances, lighter weight engine oils, higher engine operating temperatures, and tenacious PCV systems and you get nasty intake valves rather quickly.

The problem with adding a chemical cleaner into the intake is there are usually no ports in the individual runners to add the cleaner through, and a mist of solvent passing over the deposits for a brief period of time really has no effect. And even if you were able to clean the deposits off, those deposits have nowhere to go but into the combustion chamber where they have a good chance of wreaking havoc like scoring the cylinder walls. Tedious manual cleaning is really the only way to do it right.

38

You could add water injection at the throttle body that activates at WOT, should help keep the valves much cleaner.

39

Now that's a sad looking workshop doggo! ;-)) But out of my own experience I know these can be very joy- and playful so I don't really mean the afformentioned. They just do make me smile everytime I see one! :-D

OFFICIAL SPEEDHUNTERS SUPPLIERS