Audi 2.0 TFSI Tuning

Test & Tune by BAR-TEK® Motorsport

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In 2013, the BAR-TEK fleet has welcomed a new addition: The latest member of the fleet is an Audi A3 Sportback quattro (8PA) 2.0 TFSI (AXX) with 200 HP. From 2004 to 2008, the same engine was used in the Golf Mk5 GTI. In comparison to the 1.8T, the 2.0 TFSI engine has a much higher compression ratio (10.5:1 vs. 9.0X:1). Basically, the AXX engine is not so good for tuning since it has a penchant for piston ring flutter at high speeds and low load due to the forged pistons. This is why cast pistons were used in the successor BWA engine, and the compression ratio was reduced to 10.3:1. In addition, we used a new software. Our AXX already had over 180,000 km on the clock, but, except for the usual teething troubles, there were no problems with the engine.

We initially eliminated these teething troubles. The error: “Boost control limit undercut” was stored in the error memory.

1. PCV ventilation for the crankcase

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The pressure control valve (PCV) of the crankcase ventilation ensures that the boost does not escape into the crankcase when the boost is reached. The PCV has a large diaphragm. This diaphragm becomes porous with time due to the crankcase vapors and will tear sooner or later. Then, when idle, air can get into to the intake system past the air mass sensor (false air). The result is an irregular idle, and boost can escape in charging mode. The increased boost in the crank drive damages the engine, and gaskets can be damaged. The increased pressure finds its way to the outside. The safe solution for these two problems is our PCV Fix with TÜV.

2. Blow-off valve

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The blow-off valve ensures that no boost builds up in front of the throttle when the valve is closed. This would cause the charger to be slowed down. When the throttle is re-opened, the turbocharger must initially build up pressure again. This phenomenon is also called turbo lag. When the blow-off valve is open, the air on the pressure side is directed to the intake side again, so the charger is not unnecessarily slowed down. The original blow-off valve of the first series has a rubber diaphragm that becomes porous and tears. A portion of the charge air permanently gets in front of the charger again, and not enough boost can be built up. As a result, VW modified the blow-off valve. Since then, a plastic sealing element has been used; for design reasons, it also doesn’t seal 100%, though. The solution is the conversion kit by GFB.

3. Carbon deposits in the induction channel

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A major disadvantage of direct injection is the formation of carbon deposits in the induction channel. The oil vapors from the crankcase are directed into the intake manifold and burned by the engine. But since the injection nozzles are in the cylinder head in the TFSI and inject directly on the piston, cleaning the intake valves with the injected fuel, as in the 1.8T engine, is not done. So-called long-life oils facilitate the carbon deposit effect. These contaminations on the valves and in the induction channel can be quite substantial. Not only do they slow down the filling (creeping power losses): in extreme cases, the valve might even tear off (severe engine damage)!

We recommend the following measures:

  1. Clean the induction channel with a special cleaner
  2. Change oil to Castrol Edge oil
  3. Installation of the PCV Fix (which means less oil vapors in the manifold)
  4. Conversion to external oil catch tank (not allowed in the StVZO [Road Traffic Licensing Regulations]), since oil vapors escape to the outside)

First 2.0L TFSI tuning project with the K03 standard (OEM) turbo:

Second 2.0L TFSI tuning project with conversion to K04 turbo

Next came the fuel supply. Here, too, Audi made many changes in comparison to the 1.8T: The TFSI engine is equipped with a high-pressure and low-pressure system. A mechanical fuel pressure control has been eliminated; likewise, the drainage line to the tank. Instead, there is a demand-controlled fuel pump in place, which is controlled electronically by means of a PWM (pulse width modulation) signal. This mechanism was invented so as to reduce the energy needs of the pump to a low level and thus save fuel. But since we are not saving fuel with tuning, the flow rate had to be increased both on the high-pressure and the low-pressure pump.

We recommend a stronger high-pressure pump starting from an engine output of 300 HP. An increase in the low pressure we recommend as of an engine output of 400 HP.

There are a number of suppliers for Upgrade high-pressure pumps or conversion kits. From experience, we know only Integrated offers a stable and durable high-pressure pump. A major problem with conventional TFSI high-pressure pumps is they use a piston that steps down to smaller diameter, which can result in greatly increased wear and thus fuel in the crankcase (oil dilution).

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It is not enough just to replace the high-pressure pump, though. In addition, the following parts must be replaced:

  • New pump tappet (we recommend our DLC tappets)
  • Upgrade valve in the fuel rail
  • The data status (chip) must be adapted to the changes

But let’s continue with the conversion to the K04 turbocharger as installed in the Audi S3. The K04-064 turbo differs in two main points when compared to the K03:

  1. Larger diameter at the turbo output (outlet to intercooler).
  2. The blow-off valve does not sit on the turbo itself but near the throttle valve.
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The conversion of the turbocharger is relatively easy. Alongside new gaskets and studs, we used our turbo nuts for fastening on the cylinder head. It is also advisable to replace the oil lines and water lines of the turbocharger. As mentioned above, the blow-off valve must be moved to the front. For this, you need the following components:

  • Pressure pipe from the intercooler to the throttle valve with connection for the blow-off valve (we used an Upgrade power pipe).
  • Mount for the blow-off valve
  • Extension cable for the blow-off valve
  • Connection hose for the blow-off valve (Forge Motorsport)
  • Pressure pipe kit for K04 turbo by SPULEN (connection between the turbocharger and the intercooler)
  • S3 injectors
  • SPULEN pressure pipe kit for K04 turbo (connection between the turbocharger and the intercooler)

You can find our complete plug & play turbo kit here or simply click on the picture:

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With our matching data status (chip), we were able to measure a performance of 355 HP (510 Nm). The boost was set to 1.5 bar in the overboost and to 1.2 bar in the holding pressure. Unfortunately, more boost is not possible with the AXX since the first turbo direct injection engine by Audi, with a compression ratio of 10.4:1, is more on the level of an aspirated engine. This high compression ratio has been made possible by the direct injection in the first place. Because the fuel is directly injected into the combustion chamber at very high pressure, the anti-knock properties are enormously improved. In addition, the fuel evaporates a lot faster on the hot cylinder bores, which in turn has a positive effect on the formation of the mix. Not for nothing was the 2.0L TFSI engine nominated for “Engine of the Year”.

Third 2.0L TFSI tuning project: What is the maximum performance possible with the K04 charger?

Let’s take our K04 Upgrade charger. It was furnished by us with a larger basic unit. Actuator and manifold have also been tuned to the higher boost. But first things first: After all, our engine base was the AXX. As you know, this engine does not have particularly stable con rods in comparison to the S3 (BHZ) or CDL engine. This is why we opted to build a new engine so the basis is also laid for the tuning projects yet to come.

The new engine was equipped with the following components:

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