Modding upgrading and tuning the Volkswagen 2.5 Tdi (R5) engine!

Modifying and improving: "2.5 Tdi (R5) Modifications"

2.5 Tdi (R5) Modifications Guide

How to modify and upgrade the Volkswagen 2.5 Tdi (R5)

"Comprehensive guide to tuning the Volkswagen 2.5 Tdi (R5) engine!"

Our friends at TorqueCars often are seeing threads requesting info on how to improve the 2.5 Tdi (R5) from people wanting to know what are the best 2.5 Tdi (R5) upgrades. So let us look into Volkswagen 2.5 Tdi (R5) tuning mods and outline the best upgrades on this great engine and point out some common pitfalls along the way.

Now we will review and look at 2.5 Tdi (R5) tuning and outline the best mods that work. Volkswagen 2.5 Tdi (R5) offer good returns when tuned and with a few sensible uprated parts like a remap, turbo kits and camshafts you will dramatically maximise your driving pleasure.

The top 2.5 Tdi (R5) mods on an engine are typically the ones that give the best power gain for your hard earned cash.

We won't be swayed by popular 2.5 Tdi (R5) mods, they need to be cost effective.

2.5 Tdi (R5) induction kits

Improving air intake on the 2.5 Tdi (R5)

You need air and fuel for an engine to work. If there is too little fuel then it will run lean, if there is not enough air it runs rich resulting in lost power which risks damage to the 2.5 Tdi (R5). We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the primary aim to any engine tuning project to pull more air and fuel into each cylinder but this has a knock on effect with the air flow sensor.

It is common that there is a limitation in the air flow sensor AFM/MAP on the 2.5 Tdi (R5) when considerably more air is being drawn into the engine.

When tuning you may well find you need to get an air sensor or flow meter capable of upto 4 bars to cope with quite large power gains, whereas the OEM air sensor was restricting bhp at a much lower level.

The intake plenum take the air from the intake filter and allow it to be sucked into the engine and mixed with fuel.

The bore size, shape and flow characteristics of the Air Intake manifolds can make a noticeable improvement to fuel mixing and power on the 2.5 Tdi (R5).

On popular production engines headers are begging for performance upgrades, although a few manufacturers provide fairly well optimized headers.

Fitting big valve kits, doing some port work and head flowing will also improve power, & more importantly will make space for a greater power increase on other upgrades.

2.5 Tdi (R5) performance cam tips.

Different 2.5 Tdi (R5) engines respond better to more aggressive cam durations than others.

The ECU mapping and fuelling also have a large bearing on the power gains you'll achieve.

A longer valve duration can alter the power 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.

Altering your 2.5 Tdi (R5) camshaft will make a dramatic difference to the engine torque. Choosing a higher performance camshaft profile raises the torque accordingly.

NB: Fast road camshafts usually increase the bhp and torque through the rev range, you could sacrifice a little low end bhp but the higher rpm power will be better.

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

For a car used daily you must carefully try to match your engines power to your driving style.

You'll never have found a 2.5 Tdi (R5) Race cam is a pleasure to live with when driving around busy urban areas.

Stage 1, 2 and 3 mods for the 2.5 Tdi (R5)

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 2.5 Tdi (R5) parts:

Drilled & smoothed airbox, Fast road camshaft, Sports exhaust manifold, Intake headers, Remaps/piggy back ECU, Panel air filters.

Stage 2 2.5 Tdi (R5) parts:

fuel pump upgrades, Ported and polished head, Fast road cam, high flow fuel injectors, induction kit, Sports catalyst & performance exhaust.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 3 2.5 Tdi (R5) parts:

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

Review your options and then acquire your parts and set yourself a power target to avoid costly mistakes.

Remapping helps unlock the full potential of all the tuning parts you've done to your 2.5 Tdi (R5).

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your results will vary depending on the tuning parts you've done and the condition of your engine.

Turbo modifications on the 2.5 Tdi (R5)

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 2.5 Tdi (R5).

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

When your motor is fitted with a turbo parts are simpler to install and you will discover turbo engines are made using many forged and stronger components.

However you'll find engines have weakspots

Discover these limitations and upgrade to better pistons and crank to cope with the power.

It's not unheard of people spending a lots of money on turbo charger upgrades on the 2.5 Tdi (R5) only to experience the whole thing throw a rod on it's first outing after it's completed.

Big capacity turbo chargers commonly suffer a bottom end lag, and low capacity turbo chargers spool up much more quickly but won't have the top end power band gains.

In recent times the choice of turbo chargers is always developing and we are seeing variable vane turbo chargers, permitting the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust gases into a couple of channels and direct these at differently angled vanes in the turbocharger. They also help the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large bhp gains, although more complex to install. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the 2.5 Tdi (R5)

When you lift the power you will need to pay attention to to the fuel system.

More power needs more fuel. It is important to be generous with your flow rate on the injectors.

The accepted safe increase is to add another 20% when specifying an injector, which takes into account injector deterioration and affords you some spare capacity should the engine require more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended 2.5 Tdi (R5) performance exhaust upgrades

You only need to to improve your exhaust system with an upgraded one is if the current exhaust is actually creating a flow problem.

On most factory exhausts you'll see the exhaust flow rate is ok even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts can help equal out the flow of air through the engine.

But if the exhaust is too big, ie: it's over two and a half inches diameter, you will lose much of your flow rate and end up sapping power and torque.

Usual exhaust restrictions are in the catalyst and filters installed, so adding a higher flowing performance alternative will help avoid this restriction.

Cat bypassing (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the 2.5 Tdi (R5)

Like most engines an 2.5 Tdi (R5), should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the 2.5 Tdi (R5), failure to do this will exacerbate engine wear, on a tuned 2.5 Tdi (R5) this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your 2.5 Tdi (R5) why not pop over to the forums at TorqueCars where you can chat about 2.5 Tdi (R5) tuning options and read about others projects who may be planning to do similar modifications on their 2.5 Tdi (R5).

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with upgrades on your 2.5 Tdi (R5), it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...

Feedback

Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article