Choosing Mods to make the best modified A4

"Tuning the A4 range of cars."

You can easily tune an A4, with remaps, turbo upgrades and tuning modifications much can be done to lift performance. We look at the best tuning mods and upgrades to enable you to achieve the ultimate modified A4 project car.

Let's look at the range and then we will dive into the tuning upgrades that work best on the A4

The A4 is the Audi take on the executive car - something which they have executed very well.

The A4 range from 1995 continuing the Audi range of high quality executive cars. Due to the modular nature of the VAG group designs the A4 shares much with the A3 and A5, including interior space.

The A4 badge gets you a larger boot/trunk space and the engine bay is also longer, so it adds weight to the A3 design, which is why fuel economy and performance are always down when compared like for like, so let's see what can be done to improve the performance of your A4.

The range includes a selection of body styles from the Saloon to the Estate model. Reliability is up to the usual high Audi standards and the huge range of engine choices ensure there is a model suitable for most drivers needs. (Although I would argue there was a drop in quality around 2007-2010 as was the case for many motor manufacturers during the financial crisis!)

Please watch our video which covers the top Audi A4 Tuning Mods. Be sure to keep up with our latest YouTube content and subscribe.

Best Engine Mods for your A4

  1. Engine Tunes - engine tuning/remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
  2. Fast road cams are one of the most significant mechanical changes, but they must be installed by someone who knows what they're doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft.
  3. Intake and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
  4. Upgrades to turbochargers and superchargers - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.
  5. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.

Audi A4 Tuning Stages

Typical stage 1 mods often include: Remaps/piggy back ECU, Intake manifolds, Fast road camshaft, drilled & smoothed airboxPanel air filters, Sports exhaust header/manifold, Suspension upgrade.

Typical stage 2 mods often include: Sports catalyst & performance exhaust, high flow fuel injectors, Fast road cam, Ported and polished head, induction kit, fuel pump upgrades,Sports gearbox.

Typical stage 3 mods often include: Internal engine upgrades (head flowing porting/bigger valves), Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Competition cam, Twin charging conversions.

Revisions to the A4 platform over the years with links to our tuning guides for each.

Please watch our video which covers all the principles of tuning your Audi.

A4 Power/Engine mods.

This list of the stages and sports tuning kits are usually fitted by our members, decide how far you want to push your car before you begin - this avoids you wasting money or wrecking your lovely A4 with the wrong tuning upgrades.

Getting the right motorsport inspired upgrade kits for your planned usage of the car is essential. Stage 3 competition upgrades just won't work well on the road making the car difficult to drive.

In a car used daily you need to match your engines power to your typical driving style.

A4 Quarter mile times after Mods

We are assuming an average 1610kgs kerb weight, & Manual transmission with Quattro in place for power levels exceeding 200hp.

Base power Quarter
118hp 18.96 130hp 1610kg 18.38
168hp 16.91 205hp 1610kg 15.86
225hp 15.39 240hp 1610kg 15.07
328hp 13.63 *735hp 1610kg 10.98
*635hp 1400kg 10.99

Looking at the stats and performance figures, the 118hp A4 takes 19 seconds to run a quarter mile, typical improvements to the engine power will drop this to 18.38 seconds.

Power figures of 250hp or more need to be put through the Quattro or rear wheel drive or the traction issues will make the car undrivable.

The best engines are the turbo versions, these can tolerate more tuning and produce more power from a tune/remap pushing quarter mile times into the 16 second range.

*If you wanted to build a 10 second A4 you'd need quite a lot of power as the last two figures show with a 210kg weight reduction effectively matching a 100hp power gain.

For most projects on a turbocharged A4 we see gains around 30-40% and this works quite well.

Cutting weight is always a good way to go with your project, so source lighter components and look to shave off all the weight you can.

Best Engine Mods for your A4 by power gains

  • Turbo Upgrades
  • Remapping
  • Fast road camshaft
  • Intercoolers
  • Air intake
  • Exhaust (catback & headers)
  • Slip differentials

A4 Remapping

So, what exactly is ECU remapping?

At popular highway speeds like 30 mph, 56 mph, and 70 mph, where the majority of automobiles spend the most of their time, electronic ignition enables the manufacturer to fine-tune the economy and meet emissions standards.

(In the 2016 cheat software scandal, some manufactures even wrote code to detect test circumstances and run ultra lean to meet emissions regulations.)

When we threw out the clunky carb fed engines, it is now possible to advance the timing when the throttle is wide open for more power or back down the timing while travelling at steady speed for better efficiency monitoring the throttle position, load and even the quality of the engine burn.

Why do OEM maps function so poorly? When a manufacturer prepares a timing map, they provide a large margin of error to account for local variances in fuel emission requirements, and operational weather circumstances typically need a compromise to construct a one-size-fits-all strategy.

Manufacturers do not want people to report their A4 has broken down, experiencing early component failure, or developing a reputation for uneconomical vehicles, thus they design in a broad margin of tolerance.

Since no two cars are exactly same, each time an A4 rolls off the assembly line, it's impossible to predict exactly how much power it will have when compared to what's listed in the specifications so they really dumb the map down to cover a worst case scenario.

Instead of subjecting each automobile to a one-of-a-kind evaluation and creating a custom timing map, they use a one-size-fits-all approach.

It's also true that manufacturers utilise tunes or remaps to create various power versions of the same engine, resulting in lower insurance cover ratings and improved fuel efficiency.

You can see the amazing possibilities for improvement, and when you consider that the typical TorqueCars reader will be adding higher performing components to the vehicle, you have a pretty good argument for a remap.

Remaps are also strongly advised for all current A4 turbocharged engines (diesel and gasolene), where they often offer 20-30% more power.

A4 Performance Camshafts

I'd be surprised if you have found a Motorsport camshaft is a pleasure to live with when driving around busy urban areas.

This is because a competition cam causes a very lumpy idle on the A4, and makes the car more prone to stall or jerk along in stop start traffic, sadly though many ignore this and end up ruining a perfectly good car and having to revert back to a fast road, or OEM cam profile.

Competition cams, raise the top end band but as a result, the car will not idle smoothly and low end power nearly always suffers.

Each engine responds better to extreme camshaft durations so set your engine up on a rolling road.

The ECU mapping and fuel pump and injectors also have a large bearing on the bhp gains you'll achieve.

Altering your A4's valve durations can alter the bhp band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

You really need to keep as much low end torque as possible and aim to get a long power band across the rev range rather than a narrow top end power spike.

Here are some of the Audi engines we've covered in more detail and most will make suitable engine swaps in your A4 (don't forget that some of these engines have transverse versions).

From a tuning point of view on the A4 range we would recommend the 1.8T power plant which really does stand out as the tuners choice.

This engine also came as a Quattro option, losing a bit of economy and acceleration but gaining so much extra traction. The 1.8T provides a good mix of economy and power.

This was later replaced with the superb 2.0 TFSi engine, which is very reliable and easily tunable. For example a tune/remap yields a power figure approaching 270bhp. Later Quattro models were released with a 220bhp engine (BUL code in the LeMans and Limited edition models - it's well worth tracking down one of these if you can).

Tuning tips and articles

Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

In the diesel line up we have a maximum power of 150bhp in the 2.5 TDi which provides plenty of scope for power gains when remapped. All other TDi models will benefit from a tune/remap although only the 2.5 TDi will get a large gain for a minimal outlay.

The best mods we recommend for your A4 are fast road camshaft, remap, induction and exhaust, suspension.

NA (naturally aspirated) engines do not achieve big power gains if you tune/remap them, unless you have done extensive modifications. With turbocharged engines this is another story. A tuned/remapped turbo will give impressive power gains and fully release the potential power of the engine.

Adding forced induction or adding a larger compressor will usually require a lower compression ratio or water injection.

As far as performance models go the early S4 Quattro and the recent RS4 put Audi back at the forefront as creators of a car which every driver wants.

Some may complain that the S4 and RS4 models are ordinary looking but this car appeals to the driver who doesn't want to draw attention to himself making the A4 range a car for the purists.

The car was updated in 2001, the floor pan was extended a little, and a whole selection of more powerful engine options were introduced.

The 2.0 FSi engine gives good power and economy ratio with the A4 Quattro hitting 220bhp by 2006, and Diesel tuners have a selection of 2.5TDi engines ranging from 163 to 180 bhp which are just begging for a remap.

A 3.0 NASP petrol engine gave a range topping 220bhp (until the reincarnation of the mighty S4) but is not particularly economical.

A4 Turbo Mods & Upgrades

Your K03 can get up to 180 horsepower with the right mods and upgrades (remap and intake mods)!

This is an easy power upgrade but if you push the turbo too hard, its life will be cut short. See our guide to Audi turbos.

KO3 vs K03s vs K04

The K03s is stronger than its brother, the K03. Most tuners won't want to push it more than 215 bhp with K03s, but if they do, they run into trouble and shorten the lifespan of the turbo. You can get up to 250 horsepower out of this turbo, but you should not expect it to last very long.

A K03s are generally 25 bhp more powerful than K03s. As long as you're willing to cut back on your turbos lifespan or do more maintenance, you can get even more out of your car making quite impressive power gains.

The K04 is in turn better than the K03s. It is bigger and does better work than the K03 and K03s.

In order to make the K04 run better, you need the right hardware. The safest power limit to retain factory reliability for the KO4 is 220 hp.

Turbo power limits

Safe figures should retain factory reliability and longevity, the Max however is pushing to the limits and will certainly shorten the turbos lifespan.

Turbo Safe Max Maximum
K03 190hp 220hp
K03s 215hp 250hp
K04 220hp 350hp

There are turbochargers from the newer generation of the VAG Group.

The IHI IS12, IS20, and IS38 turbochargers are the most recent generations of VAG turbochargers. They replace the K03, K03s, and K04 turbochargers, which were made by IHI.

Because Audi and VW make their own turbos, the IS12 and IS20 have been made to work with their 2.0t MQB engines.

A4 Intake and Exhaust Tuning Mods.

The next area for modification is the intake and exhaust. Air induction kits will only help to increase performance if the cars air intake is struggling! Adding an induction kit to most standard engines will see NO POWER GAIN AT ALL.

If you have heavily modified your engine and it's need for air INCREASES DRAMATICALLY then an induction kit is the answer and will help remove this restriction.

Derestricting the air feed into the engine is a primary goal of car tuners so get a better flowing air filter if you find that the car is running lean only if you find the car is running lean. Induction kits can sound great but due to the warm air in the engine bay they will not really increase power and often rob you of power.

Sports exhausts will certainly help air flow from the engine but avoid an exhaust that is too large or you could very well end up with a reduced flow rate. So generally speaking, keep to 1.5 to 2.5 inches as a rule of thumb.

Airflow through the head can be dramatically increased with some professional polishing and ported. These should match and be setup to take into account any other engine mods. When you start tuning your A4 you will often find that the standard clutch starts to suffer so get an uprated clutch.

A4 Handling/Suspension Upgrades

Improving the handling for car owners first priority in your A4 tuning project. If you set the toe out to 0.8 to 1.3 degrees on the front, and add some negative camber then cornering will radically improve.

On the track, quick turns are very important, and suspension plays an important role in this. Because the track is forgiving and well-maintained, you can make more drastic suspension settings and lower your car to make it more aerodynamic and less likely to roll over without problems. On the road we need to think about comfort and practicalities.

On the road, and particularly with worn suspension you'll get squeaks, rattles, and bumps because the rubber suspension bushings don't last as long as they used to. This makes the suspension sloppy and ruins the handling.

So, your first step should be to improve the basic setup, and replacing rubber bushings with polyurethane bushings.

Tips when choosing A4 suspension

It's important to think about these things when setting up and choosing the suspension for your everyday driver.

In the process of making a car's suspension, engineers have to think about speed bumps, uneven ground, passenger comfort, and road noise.

Most factory-built cars, including the A4, have soft, comfortable suspensions that make it difficult to drive and less fun to drive. Because track cars are set up to fit the driver's preferences and style, the best configuration is not only a matter of personal preference but also a matter of how the circuit is set up.

A good suspension system keeps the tires at the right angle on the road for the most contact with the ground. There must be little body roll and the centre of gravity of the car must be low. There should be a 30mm drop for A4s with S line suspension and a 40mm drop for those with stock springs.

A4 Suspension Mistakes and Myths.

No, don't buy a suspension package that lowers the car by 30mm and think that it will work perfectly there is much more to setting up suspension than that, the geometry and way it responds to load has much to do with your A4's handling.

There are a lot of kits that are very general, and many of them say that they can be used on any or many types of cars. Is it true that the same suspension can be used for all A4 models, no matter what kind of engine, wheel, or weight they have?

Sadly not, in reality diesel engines that are very heavy, and the newer 1.4 Turbos are very light, and this dramatically affects the suspension settings required.

There could be problems with the drive shaft and gearbox if they aren't at the right angle. When the suspension drops, this could make the problems worse.

A different ride height also changes how the suspension moves when it's stressed, which can cause scrubbing and early tire wear.

To buy less springs and use standard dampers, or to buy more dampers and use standard springs, is another bad idea. There should be a look at the suspension system as a whole. This is how it should be done:

TorqueCars says that for most A4 road cars, you should drop your car about 40mm. There are some people who say that for cars with better suspension, you should lower your car about 30mm (sporty versions which already have lower suspension).

People who drive regular cars with 17-inch wheels may have a lot less room for error when the car is on the ground and the wheels are on. Then, it could cause a lot of problems especially on larger alloys.

Ideally, you should get a suspension package that you can easily and quickly adjust on your A4 to match your driving style. Adjustable coilover kits fit the bill nicely  on the A4.

A good set of well-made coilovers will help because you can change them to fit your driving style. Some of the A4 kits made by Koni, Bilstein, Eibach, and KW aren't bad at all.

A4 Alloy Wheel Upgrades.

Due to the fact that alloys are less heavy they improve performance and they can help to cool the brake disks.

If you are serious about performance then you will need to carefully choose your tires - ideally with a directional tread pattern tire.

The drawback to large alloys on your A4 is that you're altering your final drive ratio and adding unsprung weight, so this will have a detrimental effect on performance.

Because of this endeavor to keep the overall rolling diameter of the wheel the OEM setup.

On the A4 we suggest sticking with 18 inch wheels, although the 19's look nice they do suffer from tram lining and are quite heavy. The wheel size can be adjusted via an OBD menu option to ensure the speedo is accurate, so when you change wheels consult your dealer and ensure that the studs used are correct.

When it comes to tire choices, I found Dunlop Sport Maxx, Goodyear Eagle F1's, Michelin Pilot sport and Continental Premium contacts all worked really well on my A4.

I didn't like Pirelli P6000's at all the wet grip and general feel was so bad I pulled them off after 4 months. I will be trying the Pirelli P Zero nero's next though so will keep this article updated.

If you would like to know more, or just get some friendly advice on Tuning your car please join us in our friendly forum where you can discuss A4 options in more detail with our A4 owners. It would also be worth reading our unbiased Audi tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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A4 Tuning

A4 Buyers Guide and Weakspots.

When buying an A4 avoid the low spec basic models as these are hard to resell, get the S line or limited edition models with leather seats.

There are a few problems and issues to look out for on these, but I've split these off into other articles if you want more information.

  1. 2.0 TFSi carbon problems - direct injection engines require an intake clean 25,000 miles.
  2. 2.0 TFSi problems - high oil consumption, N75 and N249, Cam Follower wear, Water Pump failure, and Turbo issues
  3. 2.0 TDi problems - Oil pump, Flywheel, Lumpy Idling

I would argue there was a drop in quality around 2007-2010 as was the case for many motor manufacturers during the financial crisis with many silly electrical relay issues and switch problems.

The Quattro models and Avant models hold their value better and are the most sought after.

There are some minor weak spots on the 2.0 TFSi and DPF equipped engines to look out for. Firstly you must use the correct oil specification, failing to do so is just asking for trouble.

DPF equipped diesel engines: If you only drive short distances and the engine doesn't warm up the DPF filters are known to clog. Even motorway runs are sometimes not enough to clear it all out.

Running the car at high RPM for 15 minutes will generally do the trick, it also pays to drive it fairly hard.

Cars that are driven carefully and at the lower RPM band tend to suffer more from soot build up. We have written a DPF cleaning guide to help.

The 2.0 TFSi engines are very strong and provide excellent power to economy but you need to watch out for 2 things that will eventually go wrong. If you catch this early enough you will avoid problems and should regard these as service items. (Later engines address these issues to a large degree.)

Firstly the cam follower that drives the mechanical fuel pump has a special dark low friction coating on it. It looks a bit like a thimble that sits on the bottom of the fuel pump.

Check this every 30,000 miles for wear. If the coating has worn down and exposes a metal surface this will quite quickly wear through the follower and the cam shaft will become worn resulting in lost fuel pump pressure. It is a simple check and as long as you are careful about the extremely high fuel pump pressures is a simple DIY job, little more complex than doing a set of spark plugs.

Secondly the direct injection engine suffers from carbon build up on the valves. The fuel is not being injected over the valves so there is effectively no cleaning taking place.

Most direct injection engines suffer from this and after 70,000 miles a decoke is recommended.

The RS4 engine with direct injection is even more prone to carbon build up. The carbon build up will rob you of power rather than do any major damage but cleaning out the head will dramatically increase the performance.

We have seen no evidence to suggest that water/alcohol injection sufficiently cleans the intake valves. Running fuel cleaner also does very little as the fuel does not get sprayed on the intake.

They say prevention is better than cure so what can be done to prevent this carbon build up issue. Using good quality clean burn fuel free of bio elements, the higher octane fuels also tend to burn cleaner.

Get the engine up to temperature as soon as you can (don't idle it but just drive it steadily at around 2000rpm till it warms up) and keep the engine operating at 3000rpm for 15 minutes per week. At this RPM range the engine is designed to run hotter and this can help burn off some of the carbon deposits.

Keep an eye on the recirculation valve, the oil this sprays into the intake when it goes is cited as a major cause of the carbon build up. If you notice high oil consumption then get this valve checked ASAP.

Cleaning the head is usually done by removal and refitting but we have seen some excellent results from intake cleaners that are sprayed at high pressure into the intake.

An inspection probe through the intake or via the spark plugs will give an indication on the state of carbon build up.

The DIY spray cans of carbon cleaner do at best a minor job, the trick is delivering the cleaner evenly to all of the valves. For best results take off the intake manifold and spray the cleaner directly onto the problem area and leave it to soak. (Always follow the manufacturer's instructions though, I don't doubt that some formulations should not be left on for long periods of time.)

The VAG group are researching self cleaning valves with catalytic coatings, small amounts of fuel sprayed in the intake and "leaking valves" to help burn off the deposits.

To read our tuning tips, engine tuning tips see our tuning articles and please join our forum where you can chat and swap ideas and tips with other enthusiastic Audi A4 owners.

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2 Responses to “A4 tuning”

  1. brad says:

    what do I start with to tune my2007 Audi A4 Quattro

  2. Marty says:

    I have a 2001 Audi A4 B6 1.8t avj 110kw

    K04/015 turbo and front mount intercooler cold air intake pod filter what is the cheapest tune you have
    Could I get a tune for 550cc injectors or is it cheaper to stick with stock injector ?

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