MENUTuning the Audi 2.5 R5 TDi
"All you need to know about performance tuning the Audi 2.5 R5 TDi engine!"
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The Audi 2.5 R5 TDi make a good tuning project and with the right parts like a remap, turbo improvements and camshafts you will really increase your driving fun.
Here we examine the options for your 2.5 R5 TDi tuning and show the premier upgrades.
We rely on our visitors to pass on tips and tell us about their projects and what worked on their car, and this article is the culmination of the feedback we have received. First let us look at the history and specs of this engine and then consider which tuning modifications work best on it.
History of the Engine
2.5 R5 SDI 40-55kW
- 55kw 74 bhp 160nm 118 lbft @2,250 rpm — Volkswagen LT LT28 & LT35 AGX: 05/96-04/01
2.5 R5 TDI 65-121kW
- 65kw 87 bhp 195nm 144 lbft @1,900 rpm — Volkswagen Transporter T4
- 75kw 101 bhp 250nm 184 lbft @1,900 rpm — Volkswagen Transporter T4
- 80kw 107 bhp 280nm 207 lbft @1,900 rpm — Volkswagen LT
- 85kw 114 bhp 265nm 195 lbft @1,900 rpm — Audi C4 100
- 88kw 118 bhp @3,250 rpm 275nm 203 lbft @2,500 rpm — Audi C3 100, ANG: 02/02-
- 103kw 138 bhp 290nm 214 lbft @1,900 rpm — 1994 Audi C4 100, Audi C4 A6, as Volvo D5252T: Volvo 850, Volvo S70, Volvo V70, early Volvo S80s
- 111kw 149 bhp 295nm 218 lbft @1,900 rpm — Volkswagen Transporter T4 AHY, AXG: 1998-2003
2.5 R5 TDI CR 65-120kW
- 65kw 87 bhp @3,500 rpm; 220nm 162 lbft @2,000 rpm — BJJ
- 80kw 107 bhp @3,500 rpm; 280nm 207 lbft @2,000 rpm — BJK
- 100kw 134 bhp @3,500 rpm; 320nm 236 lbft @2,000 rpm — BJL
- 120kw 161 bhp @3,500 rpm; 350nm 258 lbft @2,000 rpm — BJM
2.5 R5 TDI PD 96-128kW
- 96kw 129 bhp — Volkswagen Transporter T5 128kw 172 bhp @3,500 rpm; 400nm 295 lbft @2,000 rpm
Tuning the Audi 2.5 R5 TDi and best 2.5 R5 TDi performance parts.
What are the most effective 2.5 R5 TDi parts
The best 2.5 R5 TDi upgrades on an engine are in our opinion the ones that give the biggest return for your cash.
We won't be swayed by popular 2.5 R5 TDi upgrades, they need to be cost effective.
The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen camshaft profile, so large torque gains are on offer for camshaft upgrades.
Fast road camshafts tend to push up the power through the rev range, you might lose a little low end power but the higher rpm power will be higher.
Competition camshafts, push up 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 should ideally to match your engines power to your cars usage.
I would be surprised if you have ever thought a 2.5 R5 TDi Race cam is a pleasure to live with when on the daily commute.
Some 2.5 R5 TDi engines respond better to more aggressive cam durations than others.
The map and injectors and fuel pump also will make differences on the power gains you'll make.
Altering valve durations 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.
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How to tune your car
- Improve the handling
Focus on Suspension improvements, such as coilovers and make sure the bushings are in good order and that the alignment is correct. Then focus on improving the brakes, with a big disk brake conversion kit and fast road brake pads.
- Remove restrictions
Focus on the intake and exhaust with filters being the common point of restriction in a tuned car. Intercoolers may also become restrictive on turbo engines so this may also need to be uprated.
- Burn more fuel & air
Increase the fuelling so it matches the air coming into the engine. The ratio is important so you need to improve the fuel pump and injectors, so the head mods, big valve conversions, fast road camshafts and forced induction upgrades extra supply of air is adequately met.
- Test and replace any weak parts
Weak areas are commonly the clutch, the turbocharger and pistons and crankshaft in a highly tuned engine. Makes sure these components will cope with your power aspirations.
- The Tune or Remap
A cars ECU controls the fuel, timing, spark and even the turbo in some cases, so to fully extract your gains you should remap the car last and this will fully release the power. Some cars are easy to map, and others require piggyback ECU's or aftermarket ECU's but this is the most vital step of your tuning project.
Modifying to Stage 1:
Intake headers, Remaps/piggy back ECU, Fast road camshaft, Panel air filters, Sports exhaust manifold, Drilled & smoothed airbox.
Modifying to Stage 2:
Ported and polished head, Sports catalyst & performance exhaust, Fast road cam, fuel pump upgrades, induction kit, high flow fuel injectors.
Modifying to Stage 3:
Competition cam, Crank and Piston upgrades to alter compression, Twin charging conversions, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Internal engine upgrades (head flowing porting/bigger valves).
ECU mapping helps release the full potential of all the tuning mods you've done to your 2.5 R5 TDi.
It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the end result will depend much on the tuning mods you've done and the condition of your engine.
It is vital to any tuning job to force fuel and air into your 2.5 R5 TDi
The intake plenum transmit the air from the filter and allow it to be sucked into the engine and mixed with fuel.
Shape and flow characteristics of the Headers can make a substantial improvement to fuel atomisation and engine efficiency on the 2.5 R5 TDi.
On popular production engines intake are ripe for an upgrade, although a few car makers provide decently flowing intake.
Fitting big valve kits, doing some 3 or 5 angle valve jobs and porting and head flowing will also increase bhp and torque, and as an added benefit will raise potential for a greater bhp and torque increase on other upgrades.
Which turbo upgrades are best?
There are many mechanics spending a lot of money on turbocharger upgrades on the 2.5 R5 TDi only to suffer the indignity of watching the motor throw a rod just after it's first rolling road session.
Big turbochargers will usually experience low end lag, and little turbochargers spool up much more quickly but won't have the high rpm bhp gains.
In recent times the choice of turbo chargers is always developing and we now see variable vane turbo chargers, permitting the vane angle is altered according to speed to lower lag and increase top end performance.
Twin scroll turbo chargers divert the exhaust gases into two channels and push these at differently profiled vanes in the turbo charger. They also improve the scavenging effect of the engine.
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.
You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp and torque at a much lower level.
Adding a supercharger or additional turbo will make large power gains, although harder to configure. We have this article covering twinchargers if you want to read more.
Fuelling
You will need to ensure that the engine is not starved of fuel so need to uprate the fuelling when you start exceeding 20% of a bhp increase.
It makes sense to over specify your flow rate on the injectors.
As a rule of thumb add 20% to the flow rate when specifying an injector, this accounts for injector deterioration and affords you some spare capacity should the engine require more fuel.
Choosing the right performance exhaust
One of the most common mistakes and problems we see in tuning projects is usually down to the exhaust, or rather a poorly chosen exhaust for your engine.
You only need to to improve your exhaust if the current exhaust is actually creating a restriction.
On most factory exhausts you should find that your flow rate is ok even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.
Note that with the largest exhaust you can source you'll reduce the exhaust flow rate - the best exhausts for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.
Usual exhaust restrictions can be located the catalyst installed, so adding a higher flowing high performance alternative will help avoid this restriction.
Weak spots Issues & problem areas on the 2.5 R5 TDi
The 2.5 R5 TDi engines are generally reliable and solid as long as they are regularly serviced and maintained.
Regular oil changes are vital on the 2.5 R5 TDi, especially when tuned and will help extend the life and reliability of the engine.
For more information on Tuning your 2.5 R5 TDi engine please join us in our friendly forum where you can discuss tuning options in more detail with our 2.5 R5 TDi owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.
Please help us improve these tips by sending us your feedback in the comments box below.
We love to hear what our visitors have got up to and which tuning mods work best for them on each model of car. Comments are used to improve the accuracy of these 2.5 R5 TDi articles which are continually updated.
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