Renault K4J Tuning

"All you need to know about performance parts and tuning the Renault K4J engine!"

The Renault K4J great bases for a tuning project and with the right tuning parts like ECU maps, turbo improvements and camshafts you will maximise your driving fun.

This pages aim is review K4J tuning and show the best mods that work.

History, Power & Specs of the K4J Engine

K4J 700/K4J 714/K4J 750

70 to 72 kW 95 to 98 PS 94 to 97 hp @ 6000 rpm

Renault Clio II
Renault Megane
Renault Scenic
Renault Scénic II

K4J 730/ K4J732/ K4J740

60 to 72 kW 82 to 98 PS 80 to 97 hp @ 6000 rpm

Renault Megane II
Renault Scénic II

K4J 712/K4J 713

70 kW 95 PS 94 hp @ 6000 rpm

Renault Clio II
Renault Thalia II

K4J 770/K4J 780

72 kW 98 PS 97 hp @ 6000 rpm

Renault Clio III
Renault Modus
Renault Grand Modus

K4J 730

Renault Scenic I

Tuning the Renault K4J and best K4J performance parts.

Best K4J modifications

The optimum K4J tuning mods on an engine are obviously the ones that give the best power gain for you spend.

We won't be swayed by popular K4J tuning mods, they need to be cost effective.

Significant gains on the K4J can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

Fast road camshafts commonly raise the power through the rpm range, you may sacrifice a little low end power but the higher rpm power will be lifted.

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.

For a car driven daily you need to match your engines power to your usage of the car.

I'd be shocked if you'd find a K4J Motorsport camshaft is a pleasure to live with when on the daily commute, because the lumpy idle will make the car prone to stall and smooth driving at low rpm becomes impossible. If you are developing a track car this doesn't matter as you are in the high end of your RPM range anyway and that is where you want the power to be.

Some K4J engines respond better to extreme cam durations than others.

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

Longer 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.

Please watch our video which covers the 5 principles of tuning your car. Be sure to keep up with our latest YouTube content and subscribe.

Best mods for your K4J

  1. Engine Tunes - A tune/remap provides the most power in terms of cost, aftermarket ECUs, and inline Tuning boxes are all alternatives.
  2. Air Induction and Exhaust - Note that on their own these mods won't ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
  3. Fast road cams are one of the most significant mechanical changes, but they must be installed by someone who knows what they are doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft.
  4. Forced induction upgrades - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. Typically one of the most costly upgrades you'll see massive gains.
  5. Flowing and porting the engine head - for larger gains, you will get better flow and make a more efficient engine if you do this to support your other mods.

K4J Tuning Stages

Typical stage 1 mods often include:
Fast road camshaft, Remaps/piggy back ECU, Intake manifolds, Sports exhaust header/manifold, drilled & smoothed airbox, Panel air filters.

Typical stage 2 mods often include:
fuel pump upgrades, Ported and polished head, high flow fuel injectors, induction kit, Fast road cam, Sports catalyst & performance exhaust.

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

The K4J engines respond well to mods and we're finding that there are increasing numbers of modifications and performance parts around.

Mapping allows a tuner to release the full potential of all the mods you've done to your K4J.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but figures achieved may depend much on the mods you've done and the condition of your engine.

Pulling fuel and air into the K4J engine is the main goal to any engine modification task.

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

Shape and flow characteristics of the Air Intake manifolds can make a substantial effect on to fuel delivery on the K4J.

Most plenum chambers are begging for aftermarket tuning parts, although a few manufacturers provide reasonably well designed plenum chambers.

Fitting big valve kits, carrying out port work and head flowing will also increase power, this will permit increasing the power increase on other parts.

K4J Turbo upgrades

NA (naturally aspirated) 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 K4J

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

If a car has a turbo already fitted parts are simpler to install and you will discover turbocharged engines are made using stronger components.

There are tuning limits for every engine, with some being over specified and some only just able to handle stock powerWe recommend you find these limitations and upgrade to stronger pistons, crank and engine components to survive the power.

We've seen tuners spending a loads on turbo upgrades on the K4J only to suffer the indignity of watching the whole thing catastrophically fail soon after it's completed.

Large turbos tend to experience no power at low rpm, and low capacity turbos spool up much more quickly but don't have the peak end power band gains.

Over the last 20 years the range of turbos is always moving on and we commonly find variable vane turbos, where the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust gases into a couple of channels and flow these at differently angled vanes in the turbo. They also boost the scavenging effect of the engine.

It is not unusual that there's a limit in the air flow sensor MAP/MAF/AFM on the K4J when a lot 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 torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although more challenging to install. We have this article covering twinchargers if you want to read more.


Don't miss you'll need to increase the fuel delivery when you are increasing the bhp - it makes the car more thirsty. Most tuners we speak with say to over specify your flow rate on the injectors.

As a rule of thumb add another 20% when buying an injector, this allows for injector deterioration and provides a bit of 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.

K4J Performance Exhausts

You may need to uprate your exhaust if your current exhaust is actually creating a restriction in flow.

On most factory exhausts you'll find the flow rate is still good even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Don't go with the largest exhaust you can find this will reduce the exhaust flow rate - the best 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 come around the filters installed, so adding a freer flowing high performance aftermarket one will improve air flow, and rather than doing an illegal decat, will keep the car road legal.

Weak spots, Issues & problem areas on the K4J

The K4J engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the K4J, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your K4J engine please join us in our car forums where you can discuss K4J tuning options in more detail with our K4J owners. It would also be worth reading our unbiased Renault tuning articles to get insights into each modification and how effective they will be for your car.

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One Response to “K4J Tuning”

  1. pete says:

    i have a k4m800 engine i want to remove the vvt from it. by replacing the head with a head from a K4J780. do you know if this will bolt right on? i will then get ecu remapped this time i have an k4m800 that is running on a ecu from the k4j780 engine that does not have vvt. works just fine.

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