Modding uprating the VAG D5252T engine!

All you need to know about "D5252T Modifications"

D5252T Modifications Guide

How to modify and upgrade the VAG D5252T

"Comprehensive guide to performance parts and tuning the VAG D5252T engine!"

Our friends at TorqueCars are regularly getting messages requesting information on how to improve the D5252T from people wanting to know what are the best D5252T mods that work. So let us look into VAG D5252T upgrades and outline the best mods that work on this great engine and point out some potential pitfalls along the way.

The VAG D5252T great bases for a tuning project and with the optimum parts like remaps, turbo upgrades and camshafts you will substantially enhance your driving fun.

Here we review D5252T tuning and report on the greatest modifications.

Just because particular mods are appear in lots of D5252T projects it doesn't mean its worth having, instead we'll concentrate on the greatest mods that will give your D5252T the best power gain for you money.

Without us subscribing to the popular mentality of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

D5252T induction kits

Improving air intake on the D5252T

You need fuel and air for an engine to work. If there is a lack of fuel then it will run lean, if there is a lack of air it runs rich resulting in lost power which risks damage to the D5252T. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the goal to any engine upgrade task to force fuel and air into your D5252T but this has a knock on effect with the air flow sensor.

It is not unusual that there is a restriction in the air flow sensor AFM/MAP on the D5252T when loads more air is being sucked into the engine.

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

Engines intake headers take the air from the filter and allow it to be drawn into the engine and mixed with fuel.

Design and rate of flow of the Plenum can make a large effect on to fuel delivery on the D5252T.

Commonly we find the air intake manifolds are in desperate need of aftermarket tuning parts, although some car makers provide reasonably good air intake manifolds.

Big valve conversions on the D5252T, carrying out port work and head flowing will also increase bhp and torque, & importantly will raise potential for a better bhp and torque increase on other modifications.

D5252T performance cam tips.

Each engine responds better to different camshaft durations than others.

The engine timing and fuel pump and injectors also will make differences on the power gains you'll make.

Extending exhaust or intake 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.

Significant air intake, and exhaust improvements on the D5252T can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road camshafts commonly increase the performance throughout the rev range, you might lose a little low down power but the high end rpm power will be lifted.

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

On a typical daily driver you should ideally to match your engines power to your usage of the car.

I'd never have found a D5252T Motorsport and race cam is a pleasure to live with when in heavy traffic.

Stage 1, 2 and 3 mods for the D5252T

Stage 1 D5252T parts:

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

Stage 2 D5252T parts:

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

Stage 3 D5252T parts:

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

Plan your options and then find your tuning parts and set yourself a power target to save yourself from expensive mistakes.
Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Mapping will help release the full potential of all the parts you've done to your D5252T.

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 figures achieved usually differs on the parts you've carried out and the condition of your engine.

Turbo modifications on the D5252T

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 D5252T.

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

When an engine has a turbocharger mods are going to make more power and most turbo engines will have uprated components.

There are common areas of failure for every engine, with some being very over engineered and some just sufficiently able to handle stock power

Discover these limitations and upgrade to better quality components to handle the power.

We see many people spending a loads on turbocharger upgrades on the D5252T only to suffer the humiliation of seeing the engine block throw a rod just after it's used in anger.

Large upgraded turbo chargers commonly suffer a bottom end lag, and low capacity turbo chargers spool up much more quickly but don't have the peak end torque gains.

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

Twin scroll turbo chargers divert the exhaust gases into two channels and direct these at differently designed vanes in the turbo. They also increase 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 harder to setup. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the D5252T

You will need to ensure that the engine is not starved of fuel so need to uprate the fuelling when you start going beyond 20% of a performance hike. We strongly recommend you to be generous with your flow rate on the injectors.

The rule of thumb is to add 15% to the flow rate when buying an injector, this accounts for injector deterioration and gives 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 D5252T performance exhaust upgrades

Only look to upgrade your exhaust system with an upgraded one is if the current exhaust is actually causing a restriction in flow.

On most factory exhausts you'll see the flow rate is still fine 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 usually air flow through the engine but avoid an exhaust that is too wide or you could will reduce the flow rate. Stick to one and a half to two and half inches for best results.

Usual exhaust restrictions come around the emissions filters installed, so adding a freer flowing sports alternative will help avoid this restriction.

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

Faults issues and things to look out for on the D5252T

Like most engines an D5252T, 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 D5252T, failure to do this will exacerbate engine wear, on a tuned D5252T 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 D5252T why not pop over to the forums at TorqueCars where you can chat about D5252T tuning options and read about others projects who may be planning to do similar modifications on their D5252T.

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