2.5 TFSi engine tuning

Guide to the VAG 2.5 TFSi engine

The 2.5 TFSi is the VAG Group 5 Cylinder turbo engine, as fitted to the TTRs RS3 TSQ3 and the Quattro concept.

Voted engine of the year 5 times in a row (2015) we start to see that this is a very special engine indeed. It is a chain driven DOHC, with variable valve timing.

The Block is aluminum Alloy or a DJV-450 vermicular graphite cast iron cylinder block depending on the application (for example the D8 GTO uses a stronger cast iron block). The firing order is 1-2-4-5-3 and it runs at a 10.0:1 compression ratio thanks to the knock resistant inlet design and direct fuel injection.

These blocks were designed to tolerate power figures in the region of 700bhp so make a great base for a tuning project.

This engine won awards every single year in the '2.0-litre 2.5-litre' category from 2010 to 2018 annual competition for International Engine of the Year!

FSi injection running at up to 1770psi on a common rail. The ECU is a Bosch Motronic MED unit and it uses two knock sensors, allowing it to manage each cylinder separately.

Currrent engine codes include CEPA, CEPB, CTSA, CZGA, CZGB, DAZA, DNWA

Engine Codes CEPA on the early engines, later engines from mid 2011 were CEPB.

CEPA in Aug 2010 had some revisions to the engine crankcase, new pistons, sealing flange and oil spray jets.

DAZA was launched in 2017 with further revisions pushing power to the 400bhp mark. Peak torque of 354lb-ft comes in at only 1700rpm!

CEPB came with the TTRS Plus offering 355bhp and 343lbft of torque in 2012.

Then in 2019 we had the DNWA engine block revision where peak torque came in at 1950rpm, interestingly this adds fuel economy and feels more powerful in everyday driving.

  • 335bhp 332lb-ft - TTRS
  • 355bhp 332lb-ft - RS3 TTRS
  • 355 bhp & 343 lb-ft TTRS plus
  • 306bhp 343lb-ft - RS Q3
  • 363bhp  343 lb-ft RS3 from 2015
  • 394bhp 354lb-ft TTRS & RS3 from 2017

Interestingly VAG managed to squeeze 402bhp and 354 lbf-ft from this engine in the Audi Quattro concept.

The engine timing and injectors and fuel pump used will also have an effect on the bhp gains you'll make.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen camshaft profile, so large torque gains are on offer for camshaft upgrades.

Fast road camshafts normally bump the bhp and torque throughout the rev band, you could sacrifice a little low down torque but your high end rpm power will be higher.

Motorsport and race camshafts, bump the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

Extending exhaust or intake 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.

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Best Engine Mods for your 2.5TFSi

  1. Engine Tunes - engine tuning/remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
  2. 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.
  3. 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.
  4. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.
  5. 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.

2.5 TFSi tuning stages

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

Typical stage 2 mods often include: Fuelling (fuel pump and port injectors), Ported and polished head, induction kit, fuel pump upgrades, Fast road cam, Sports catalyst & performance exhaust.

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

Many of our forum members report that gains of 70bhp are possible with just a tune/remap alone, combine this with a turbo upgrade and you'll have a potent engine.

2.5 TFSi  intake manifolds and exhaust mods

Upgrading the downpipe will allow the turbo to spool up more quickly and releases some extra HP. The GTX3576R works well on this engine, allowing you to see a 100bhp+ power gain on standard low octane fuel. There is an APR conversion around which wil realise 665bhp on 104RON fuel!


Intake Manifolds carry or channel the air from the air cleaner and allow it to be pulled into the engine and mixed with fuel.

The shape and flow rate of the Intake manifold can make a noticeable effect on fuel atomization and engine efficiency on the 2.5 TFSi R5.

It's not uncommon that intake manifolds are in desperate need of aftermarket tuning parts, although some manufacturers provide reasonably well designed intake manifolds.

Big valve conversions on the 2.5 TFSi R5, carrying out 2.5 TFSi R5 port enlargement and head flowing will also improve bhp, the fantastic side effect is it will afford you a better bhp increase on other parts.

2.5 TFSi remapping

Remappers are experts in performance tuning by adjusting the OEM map through the 2.5TFSi OBD port, as well as the installation of ECU chips or bench flashing in cases where the OBD port is not accessible or there are other issues.

Are you aware that the manufacturer of the engine in your 2.5 TFSi has purposefully limited the engine's intended responsiveness and 2.5TFSi power output? This is owing to the fact that they must accommodate drivers who insist on using inferior gasoline or who refuse to follow service schedules.

They also need the car to be ultra reliable so they don't have to deal with warranty issues and set everything up very conservatively.

It's also often limited for marketing purposes, such as dropping an engine's power output into a certain category. The good news is that you are not required to adhere to these limitations. You just need to tune/remap your ECU chips if you want them to be deleted.

This is normally accomplished via your 2.5TFSi OBD port. Be wary of claims of increased power and off-the-shelf products. Many of which are little more than a generic slight improvement over the factory map.

Some firms overstate power increases in order to "sell" their goods by giving the client the impression that they are receiving more for their money!

In the maps shown above would you prefer the red 200hp map or the Green 175hp option? See how one looks better in the adverts but the other will clearly outperform it.

A decent distribution of power from tickover to peak rpm is required from a remap, with no unexpected surges of power from the turbo. It should be smooth, and the engine will be more energetic, pulling harder throughout the rev range.

When you push the power to its limits, you risk having reliability issues, such as injector leaks, hesitation, overboosting, and, in the worst-case scenario, a "blown" engine.

Remaps are often performed via the OBD port using a utility like "Genius."

The map is extracted from your ECU and a copy is made; yes, your vehicle can still be driven while this is being done. The map from your vehicle is then altered by the mapper to suit your needs, such as if you have installed a cat back exhaust system or an aftermarket filter, and then installed back into your vehicle.

2.5 TFSi R5 Turbo upgrades

The more air to get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes massive power gains.

When your car is turbo charged mods are going to net you a larger power gain and you'll see that turbo engines are made using stronger components.

VAG Groups line of turbochargers.

While the K03, K03s, and K04 were the previous generations of VAG turbochargers, the IHI IS12, IS20, and IS38 are the newer ones.

The IS12 is the turbo that comes with Audi and VW 1.8t MQB engines. The IS20 is the turbo that comes with the 2.0t MQB engines for example.

Why Is The IS38 Turbo So Great?

The IS38 is important because this turbo can make up to 370 hp (with the proper add-ons). It's a very popular turbo from IHI because it's very durable. This is why it's so popular.

They have a lot of benefits.

In many cars, this turbo has a big advantage because it's already built in. This includes the VW Golf R, the VW Arteon, the Audi S3 and the TTS.

As a result, the IS38 is a great choice for people who want a reliable option that can perform well and last a long time.

Other great things about the IS38 are:

An easy way to put on a turbo is because it's a bolt-on, so it's not very difficult to do.
There are a lot of hybrid models that have better housing and impeller designs that make them more efficient.

Replacement for the IS12 and IS20.

Several car enthusiasts have switched out the old IS12 turbo with the newer, more powerful one.

2.5 TFSi Turbo Swaps

Why should you buy a new turbo for your car?

We would recommend you do this for a number of reasons, but here are a few of them:

  • Upgrading the turbo is a good way to improve a car's performance. This is one of the most important methods to add power to a car.
  • Turbos lose their ability to work well over time, so they need to be replaced.
  • Newer turbos have more add-on options for car owners, and they use new technology to make their cars run better with faster spool up and longer power bands.

Choosing the Best Turbochargers to Buy for your 2.5TFSi

You need to figure out which part is best for your car because there are so many to choose from. We recommend that you check your supplier carefully because there are a lot of fake and low-quality turbo units out there.

Fit a cheap turbo upgrade, and we're sure you'll have to do it again in about 6 months.

It's also a good idea to choose a turbo that can offer the following upgraded performance features when you buy one:

  • A compressor wheel made of billet aluminum (light and strong)
  • An actuator for the wastegate (sharpens throttle response and maximizes your power gains)
  • A design with VNT Vanes (Maximizes the boost available)
  • Ball bearings or Ceramic bearings (these outperform the common thrust bearings)
  • Properly flowed and balanced internals - makes all the difference to reliability and power delivery

Keeping these small things in mind can make the difference between a successful project and money that was wasted.

After installing a turbo, you must tune/remap your 2.5TFSi.

It is important to point out that if you want to change the stock turbo with a more powerful aftermarket one, the car's software may need to be updated. You might get away with the OEM map but you'll be missing out on lots of extra performance.

Make sure you don't forget to run a full engine diagnostic as well as mapping it. If you don't, your engine could run lean or go into limp home mode with error codes. Using a new ECU is also how you can get the most out of your upgrade. If you use a stock ECU, you'll only be able to slightly change the fueling and you'll be wasting your time.

However you will find an engines will need better parts at higher power limits and thankfully the 2.5 TFSi is very well build and the block can handle around 400bhp in standard form, and most owners say around 500bhp is the peak power level you hit on a stock block before the rods start to fail.

It is important to find these restrictions and upgrade to better pistons and crank to cope with the power.

Bigger turbo chargers commonly suffer low end lag, and small turbo chargers spool up more quickly but do not have the top end power band gains.

We are pleased that the world of turbos is always evolving and we now see variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end performance.

It is not unusual that there is a restriction in the air flow sensor MAF/MAP on these engines when loads more air is being drawn into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited bhp and torque at a much lower level.

When upgrading to the GTX3576R turbo you should add a higher pressure fuel pump, uprate the intercooler and we would also recommend some exhaust upgrades namely a high flow downpipe and sports catalyst. There may be additional pipe/mounting point work required to site this turbo depending on whether you purchase it in a kit for the 2.5TFSi.

2.5 TFSi Fuelling upgrades

When you boost the power you will need to uprate to the fuel system.

More power needs more fuel. This is the simple basic fact of tuning a car.

Most tuners we speak with say to be generous with your injectors flow rate. The TFSI high-pressure injection pump supplying up to 122 bars or 1,770 psi gives quite a bit of headroom but you might need to add more capacity for larger power increases.

Port injection kits are available which can help mitigate the carbon build up and provide more fuel when you need it.

The accepted safe increase is to add 20% when specifying an injector, helps cope with injector deterioration and gives a little spare capacity should the engine need more fuel.

These engines really do appreciate high octane fuel, timing, fuelling etc are adjusted to fully realize the potential of the higher octane and you will see more power and greater economy. For most drivers the extra miles per tank will cover the cost of the higher price of the fuel.

2.5 TFSi Problems and issues

The 2.5 TFSi R5 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

2.5TFSi carbon build up problems

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines.

When there is significant carbon build up you'll lose power and a full intake clean will restore this lost power immediately.

We have tips on removing carbon build up.  Carbon build up is still an issue on these engines, although significant improvements have been made and later engines now feature port injection  on warm up which removes the issue completely.

Avoid  Carbon build up problems by using good quality fuel, adding a good quality cleaner to your fuel like BG44K and run the engine hot and use the full RPM range when warm. You should get over 70,000 miles on an engine before carbon build up can cause a problem on these although if you only do short runs this will happen much sooner.

Belt and timing chain tensioners failures

There are reports of failing tensioners that will cause quite a bit of damage if not addressed. Just replacing a belt and using the old tensioner is a bad philosophy that is just asking for trouble.

So try to change belts/timing chains at shorter intervals than the manufacturer recommends and do the tensioners at the same time.

We would also recommend water and oil pump replacements during this service item, as they are quite costly to fit on their own, but much easier to do when swapping the timing chain.

Problems after tuning mods

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Keeping your 2.5TFSi in good order

Regular oil changes are vital on the 2.5 TFSi R5, especially when tuned and will help extend the life and reliability of the engine.

Please submit your tuning tips, comments and details of common faults below so we can update this article and keep it current.

To discuss tuning these and the full range of VAG engines in more detail please join our very friendly international car forums.

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3 Responses to “2.5 TFSi Tuning”

  1. Torn says:

    “The Block is aluminum Alloy with a DJV-450 vermicular graphite cast iron cylinder block”
    Block can be aluminum or castiron it can’t be both.

  2. TorqueCars says:

    It can be both, the engine was around in two versions, aluminum and cast iron, the D8 GTO for example uses a cast iron 2.5 TFSi block which is heavier but much stronger. I have reworded the article to clarify this point for you .

  3. Jbo says:

    “However you will find an engines will need better parts at higher power limits and thankfully the 2.5 TFSi is very well build and the block can handle around 400bhp”

    DAZA is 400bhp stock. The block can handle way more, rods typically go first at 500ish wtq.

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