Modding uprating the Renault K4J engine!

Car tuning tips:K4J Modifications"

K4J Modifications Guide

How to modify and upgrade the Renault K4J

"Comprehensive guide to tuning the Renault K4J engine!"

Our friends at TorqueCars are frequently seeing threads asking how to improve the K4J from people wanting to know what are the optimum K4J mods that work. So let us look into Renault K4J upgrades and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

Car Tuning Tips will review K4J tuning and summarise the optimum modifications. Renault K4J are popular engines and with the right tuning tuning mods like ECU maps, turbo kits and camshafts you will certainly maximize your driving fun.

When talking about the optimum parts for your K4J engine, we are going to focus on the tuning mods that give the best value for money.

K4J induction kits

Improving air intake on the K4J

You need air matched to fuel for an engine to work. If there is not enough fuel then it will run lean, if there is little flow of air it runs rich resulting in lost 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 Shoving more air and fuel into the K4J engine is vital to any car tuning project.

It is common that there's a limitation in the air flow sensor AFM/MAP on the K4J when loads 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 bhp and torque at a much lower level.

Intake manifolds transmit the during the engines suck phase from the filter and allow it to be fed into the engine and mixed with fuel.

Shape and flow rate of the Plenum can make a substantial change to fuel delivery on the K4J.

Most intake headers are begging for a performance upgrade, although a few manufacturers provide reasonably well designed intake headers.

Increasing the K4J valve size, carrying out port matching and head flowing will also increase performance, and importantly will give you increasing the performance increase on other upgrades.

K4J performance cam tips.

Different K4J engines respond better to more or less aggressive camshaft durations so set your engine up on a rolling road.

The ecu map and injectors and fuel pump also will make differences on the torque gains you'll achieve.

Extending exhaust or intake durations can alter the torque 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.

Altering your K4J camshaft will make a dramatic difference to the engine torque. Choosing a higher performance camshaft profile raises the torque accordingly.

NB: Fast road cams commonly raise the power across the rev range, you could drop a little bottom end bhp but your top end will be lifted.

Competition cams, raise the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport cam makes it harder when driving around busy urban areas.

You should ideally optimize your torque band to your usage of the car so for a typical daily driver stick with a fast road K4J cam

Stage 1, 2 and 3 mods for the K4J

Stage 1 K4J parts:

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

Stage 2 K4J parts:

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

Stage 3 K4J parts:

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

The K4J engines respond well to mods and we see that there is a lot of modifications and performance parts around.

ECU flashing should help to fully realize the full potential of all the upgrades you've done to your K4J.

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 the outcome usually differs on the upgrades you've carried out and the condition of your engine.

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

Turbo modifications on the K4J

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 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 major power gains.

When your car is fitted with a turbo upgrades are relatively easy and most turbo engines are made using uprated components.

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

Research these limits and upgrade to higher quality crank and pistons to utilize the power.

It's not unheard of people spending a lots of money on turbo upgrades on the K4J only to suffer the indignity of watching the whole thing literally blow up on it's first outing after it's been enthusiastically driven.

Bigger upgraded turbo units will usually suffer low end lag, and smaller turbo units spool up really quickly but don't have the peak end engines power gains.

Thanks to new tech the world of turbo chargers is always moving on and we now see variable vane turbo chargers, where the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbo chargers divert the exhaust flow into 2 channels and feed these at differently profiled vanes in the turbo. They also improve the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large torque gains, although more difficult to get working. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the K4J

When you boost the performance you will need to uprate to the fuel system.

More performance needs more fuel. It makes sense to be generous with your injector capacity.

The rule of thumb is to add 15% capacity when buying an injector, which takes into account injector deterioration and provides a little 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 K4J performance exhaust upgrades

You only need to to boost your exhaust system with an upgraded one is if your exhaust is actually creating a restriction.

On most factory exhausts you'll see the exhaust flow rate is 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.

Please dont run with the biggest exhaust you can buy you'll slow up the exhaust flow rate - the best for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

The usual suspects causing problems in your exhaust flow rate are traced to the emissions filters installed, so adding a better flowing sports alternative will help avoid this restriction.

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

Faults issues and things to look out for on the K4J

Like most engines an K4J, 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 K4J, failure to do this will exacerbate engine wear, on a tuned K4J 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 K4J why not pop over to the forums at TorqueCars where you can chat about K4J tuning options and read about others projects who may be planning to do similar modifications on their K4J.

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