Tuners tips on "XU Modifications"

How to modify and upgrade the PSA XU

"Comprehensive guide to performance parts and tuning the PSA XU engine!"

Our friends at TorqueCars are regularly getting posts about how to improve the XU from people inquiring about getting more power from the XU and wanting to know what are the greatest XU modifications. So let us look into PSA XU upgrades and outline the best modifications on this great engine and point out some common pitfalls along the way.

The PSA XU have loads of potential and with carefully picked sports upgrades like remaps, turbo improvements and camshafts you will noticeably improve your driving experience.

In this article we outline options for your XU tuning and summarise the best modifications for your car.

Just because particular modifications are are common on XU it doesn't mean you should fit it, instead we will concentrate on the best modifications that will give your XU the best power gain for you spend.

Without us subscribing to the common myth 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'.

Improving air intake on the XU

You need air and fuel for an engine to work. If there is little supply of fuel then it will run lean, if there is not enough air it runs rich sapping power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Forcing more air and fuel into your XU is the primary aim to any engine modification job.

It is not unusual that there's a limitation in the air flow sensor MAF/MAP on the XU when considerably more air is being sucked 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.

Intake manifolds flow the during the engines suck phase from the filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

The bore size, shape and flow rate of the Air Intake manifolds can make a substantial difference to to fuel atomisation on the XU.

We often see air intake manifolds are in dire need of an upgrade, although a few makers provide decently flowing air intake manifolds.

Adding a XU larger valve kit, carrying out port matching and head flowing will also raise power, this will allow you to get a greater power increase on other mods.

XU performance cam tips.

Different XU engines respond better to different camshaft durations so view each engine as unique.

The ECU mapping and injectors and fuel pump also will make differences on the bhp gains you'll hit.

Altering valve 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.

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

NB: Fast road camshafts normally boost the bhp and torque throughout the rev range, you may sacrifice a little low down power but higher rpm power will be better.

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

For a road car you must carefully try to match your bhp range to your driving style.

I'd be shocked if you have found a XU Motorsport camshaft is a pleasure to live with when on the daily commute.

Stage 1, 2 and 3 mods for the XU

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 XU parts:

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

Stage 2 XU parts:

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

Stage 3 XU parts:

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

ECU flashing will help to establish the full potential of all the upgrades you've done to your XU.

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 vary depending on the upgrades you've carried out and the condition of your engine.

Turbo modifications on the XU

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 XU.

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 a car is turbocharged, tuning mods are giving better power gains and most turbo engines are made using stronger components.

However engines will need better parts at higher power limits

See where you'll find these limitations and upgrade to better quality crank and pistons to utilize the power.

It's not unheard of guys spending a lots of money on turbo upgrades on the XU only to suffer the indignity of watching the engine literally blow up on it's first outing after it's been enthusiastically driven.

Large turbochargers often suffer low end lag, and small turbochargers spool up really quickly but won't have the top end engines power gains.

Thankfully the market of turbo units is always improving and we are seeing variable vane turbo units, where the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbo units divert the exhaust gases into two channels and push 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 and torque gains, although more difficult to get working. We have this guide to twinchargers if you want to read more.

Tips about fuel supply on the XU

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

The accepted safe increase is to add 20% when specifying an injector, this allows for injector deterioration and gives a bit of spare capacity should the engine need 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 XU performance exhaust upgrades

You should look to replace your exhaust system with an upgraded one is if your exhaust is creating a restriction in flow.

On most factory exhausts you'll see the flow rate is still good 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 gases through the engine.

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

The usual suspects causing problems in your exhaust flow rate can be traced to the catalyst and filters installed, so adding a freer flowing sports alternative will help avoid this restriction.

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

Faults issues and things to look out for on the XU

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

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This entry was posted under Makes and Models. Tags: engine, PSA
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