Modding upgrading and tuning the Renault K7J engine!

Car tuning tips:K7J Modifications"

K7J Modifications Guide

How to modify and upgrade the Renault K7J

"Comprehensive guide to tuning and performance parts on the Renault K7J engine!"

Forums like the one at TorqueCars are always getting emails requesting information on how to improve the K7J from people wanting to know what are the premier K7J mods that work. So let us look into Renault K7J modifications and outline the best upgrades on this great engine and point out some common pitfalls along the way.

Now we will examine the options for your K7J tuning and show the premier mods that work. Renault K7J are awesome to work on and with the ultimate uprated upgrades like remaps, turbo kits and camshafts you will positively maximise your driving opportunities.

Just because particular modifications are appear in lots of K7J projects it doesn't mean its worth having, instead we will concentrate on the ultimate modifications that will give your K7J the best power gain for you money.


Without us subscribing to the 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'.

K7J induction kits


Improving air intake on the K7J

You need air matched to fuel for an engine to work. If there is little supply of fuel then it will run lean, if there is too little 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 it's important to any engine modification task to force fuel and air into the K7J engine but this has a knock on effect with the air flow sensor.

You'll commonly see there is a limitation in the air flow sensor AFM/MAF on the K7J when loads more air is being drawn into the engine.

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

Engines intake headers transmit the air during the suck phase from the intake filter and allow it to be sucked into the engine cylinders.

The size of bore and shape and flow rate of the Air Intake manifolds can make a large difference to to fuel mixing and power on the K7J.

Most headers are improved through performance upgrades, although a few manufacturers provide reasonably well designed headers.

Larger K7J valves, doing a bit of port matching and head flowing will also boost performance, & importantly will give you raising the performance increase on other parts.

K7J performance cam tips.

Each engine responds better to more or less aggressive cam durations so view each engine as unique.

The map and fuel pump and injectors also have a large bearing on the bhp gains you'll hit.

A longer valve duration 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.

Significant air intake, and exhaust improvements on the K7J can be made from camshaft upgrades. Changing the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road camshafts commonly bump the torque over the rpm range, you could sacrifice a little low end power but your higher rpm power will be lifted.

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

A Motorsport cam won't do well if driving around busy urban areas.

You should ideally match your torque band to your usage of the car so for a daily driver stick with a fast road K7J cam

Stage 1, 2 and 3 mods for the K7J

Before we detail your best tuning upgrade options as stages of tune, let's list the most effective tuning upgrades for you.

  1. Tunes & remaps - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  2. Fuelling (injectors & pump) - when you've increased power you'll need to match this with more fuel
  3. 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).
  4. Suspension Upgrades - always improve your cars handling
  5. Brake Upgrades - Even before adding power improve those brakes
  6. Intake - make sure your cars intake isn't restricted, use performance filters and intake upgrades to improve this
  7. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 K7J parts:

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

Stage 2 K7J parts:

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

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 3 K7J parts:

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


Carefully think through your options and then source your tuning parts and set yourself a power target to avoid costly mistakes.


Remaps helps release the full potential of all the parts you've done to your K7J.

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 your mileage usually depend much on the parts you've carried out and the condition of your engine.

Turbo modifications on the K7J

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 K7J.

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

When your car is fitted with a turbocharger parts are going to make more power and you will discover turbo engines will have many forged and stronger components.

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

We recommend you find these limits and fit higher quality crank and pistons to handle the power.

There are many drivers spending a loads on turbo charger upgrades on the K7J only to see the K7J throw a rod soon after it's completed.

Large capacity turbo chargers commonly suffer a bottom end lag, and low capacity turbo chargers spool up more quickly but won't have the top end engines power gains.

Thanks to new tech the choice of turbo chargers is always developing and we commonly find variable vane turbo chargers, where the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

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

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large power gains, although harder to install. We have this in depth look at twinchargers if you want to read more.

Tips about fuel supply on the K7J

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

The rule of thumb is to add 15% to the flow rate when fitting an injector, this allows for injector deterioration and allows 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 K7J performance exhaust upgrades

You should look to boost your exhaust system with an upgraded one is if the existing exhaust is actually creating a restriction.

On most factory exhausts you should find that your 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 large, ie: over two and a half inches diameter, you will lose a great deal of your flow rate and end up lacking power and torque.

The usual suspects causing problems in your exhaust flow rate are in the catalysts installed, so adding a freer flowing high performance 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 K7J

Like most engines an K7J, 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 K7J, failure to do this will exacerbate engine wear, on a tuned K7J 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 K7J why not pop over to the forums at TorqueCars where you can chat about K7J tuning options and read about others projects who may be planning to do similar modifications on their K7J.

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