Choosing an A4 for tuning

"Tuning the A4 range of cars."

The A4 range from 1995 continuing the Audi range of high quality executive cars. In the A4 Audi had a car which rivals the BMW 3 series, albeit without the image. 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.

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

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 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).

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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 remap although only the 2.5 TDi will get a large gain for a minimal outlay.

Audi A4 tuning

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 Tuning

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.

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.

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 manufacturers 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.

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. 

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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