Tuning the Citroen TU

"Comprehensive guide to performance parts and tuning the Citroen TU engine!"

We are always getting posts requesting information on the ultimate TU modifications. So let us look into Citroen TU upgrades and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Citroen TU offer good returns when tuned and with carefully chosen performance enhancements like remapping, turbo upgrades and camshafts you will definitely enhance your driving pleasure.

We shall consider TU tuning and report on the optimum modifications for your car.

When talking about the greatest parts for your TU engine, we are going to focus on the ones that give the best value for money.

Significant gains on the TU can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the engines power and power output.

NB: Fast road camshafts tend to raise the power across the rev range, you may lose a little low end torque but your higher rpm power will be higher.

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

In a car used daily you need to match your torque band to your cars usage.

You will never find a TU Competition camshaft is a pleasure to live with when in heavy traffic.

Each engine responds better to more or less aggressive camshaft durations than others.

The ECU mapping and injectors and fuel pump also will say much on the bhp gains you'll get.

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.

TU Tuning Stages

Stage 1 TU modifications: Panel air filters, Sports exhaust manifold, Drilled & smoothed airbox, Intake headers, Remaps/piggy back ECU, Fast road camshaft.

Stage 2 TU modifications: high flow fuel injectors, Sports catalyst & performance exhaust, Ported and polished head, fuel pump upgrades, Fast road cam, induction kit.

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

Mapping should help to release the full potential of all the upgrades you've done to your TU.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output usually vary depending on the upgrades you've carried out and the condition of your engine.

Shoving more fuel and air into the TU engine is the aim to any engine performance tuning job.

The intake plenum carry the air during the suck phase from the filter and allow it to be drawn into the engine and mixed with fuel.

The bore size, shape and flow characteristics of the Headers can make a substantial change to fuel atomisation on the TU.

It's not uncommon that intake manifold are improved through an upgrade, although a few car makers provide reasonably well designed intake manifold.

Adding a TU larger valve kit, doing some port work and head flowing will also improve bhp, and importantly will permit a better bhp increase on other modifications.

Turbo upgrades for the TU

NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your TU

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

When your car is fitted with a turbo tuning parts are more reliable and we find turbo engines already contain strengthened components.

However you will find an engines will need better parts at higher power limits

Discover these restrictions and fit better quality components to cope with the power.

We see many drivers spending a fortune on turbocharger upgrades on the TU only to suffer the humiliation of seeing the car explode when it's finished.

Big upgraded turbo chargers tend to suffer a bottom end lag, and low capacity turbo chargers spool up much more quickly but do not have the peak end torque gains.

Thankfully the world of turbo units is always improving and we commonly find variable vane turbo units, allowing the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo units divert the exhaust gases into two channels and direct these at differently profiled vanes in the turbocharger. They also help the scavenging effect of the engine.

You'll commonly see there's a restriction in the air flow sensor AFM/MAF on the TU when a lot more air is being sucked into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although harder to get working. We have this article on twincharging if you want to read more.

Uprating TU fuel injectors

You will need to ensure that the engine is not starved of fuel so will need to uprate the fuelling when you start exceeding 20% of a bhp increase.Most tuners we speak with say to over specify your injector capacity.

The accepted safe increase is to add another 20% when specifying an injector, this allows for injector deterioration and provides some spare capacity should the engine require more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Best TU performance exhausts

You should look to boost your exhaust if your current exhaust is actually creating a restriction in flow.

On most factory exhausts you'll find the exhaust 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.

Sports exhausts can help increase the flow of air through the engine.

But if the exhaust is too large, ie: over 2.5 inches bore, you will lose a lot of the flow rate and end up sapping power and torque.

Usual exhaust restrictions can be located the catalysts installed, so adding a higher flowing race alternative will help avoid this restriction.

Problems and issues to look out for on the TU

The TU engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the TU, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your TU engine please join us in our friendly forum where you can discuss tuning options in more detail with our TU owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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

We really like hearing from our readers, and hearing about which parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our TU guides and tips are kept up to date.

Please Check out my YouTube channel, we're regularly adding new content...

Click to accept YouTube Cookies & Play.

This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under Citroen. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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.