Renault H4Jt Tuning

"All you need to know about tuning the Renault H4Jt engine!"

Our aim here is to examine the options for your H4Jt tuning and outline the premier mods that work. Renault H4Jt are popular tuning projects and with carefully picked sports parts like remaps, turbo upgrades and camshafts you will greatly maximize your driving enjoyment.

History, Power & Specs of the H4Jt Engine

This was produced under collaboration with Nissan where the engine is badged as HR14DET (Renault H4Jt)

1397 cc, 96 kW at 5500 rpm, 190 Nm at 2250 rpm.

• 2009–2013 Renault Megane III
• 2009-2013 Renault Scénic III

Tuning the Renault H4Jt and best H4Jt performance parts.

Best H4Jt parts

Just because particular mods are appear in lots of H4Jt projects it doesn't mean you should fit it, we will concentrate on the optimum mods that will give your H4Jt the best power gain for you spend.

Significant gains on the H4Jt 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 cams tend to increase the performance throughout the rev band, you might lose a little low end bhp but high end rpm power will improve.

Motorsport and race cams, increase the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

On a daily driver must carefully try to optimize your engines power to your usage of the car.

I'd be amazed to hear from any driver that a H4Jt Motorsport camshaft is a pleasure to live with when in heavy traffic because low end power will be very lumpy. Competition cams are designed for maximum power at the top end of the RPM range, a place that most daily commutes will not permit!

Different H4Jt engines respond better to extreme cam durations so view each engine as unique.

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

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 H4Jt

1. ECU Tunes - A tune/remap provides the most advantage compared to cost, replacment ECUs, and piggyback ECUs are all alternatives.
2. Fast road Camshafts are one of the most significant mechanical changes, but they must be fitted 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.
3. Internal engine mods - crank, pistons, conrods & compression ratio including balancing and blueprinting
4. Intake Upgrades and Sports Exhausts - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
5. Turbo 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 but provides the best gains.

H4Jt Tuning Stages

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

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

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

Mapping should help to unlock the full potential of all the modifications you've done to your H4Jt.

(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 power output will vary depending on the modifications you've done and the condition of your engine.

Shoving more air into your H4Jt is the main goal to any engine modification task.

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

The bore size, shape and flow characteristics of the Intake manifold can make a noticeable change to fuel mixing and power on the H4Jt.

On popular production engines air intake manifolds are needing a performance upgrade, although a few makers provide reasonably well designed air intake manifolds.

Adding a H4Jt larger valve kit, carrying out port matching and head flowing will also increase torque, and importantly will allow you to get increasing the torque increase on other parts.

H4Jt 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 H4Jt

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.

If your motor has forced induction upgrades are giving better power gains and you'll see that turbo engines already contain better components.

There are reliable limits for every engine, with some being extremely strong and some only just able to handle stock powerSee where you'll find these limits and upgrade to better quality components to handle the power.

There are many guys spending a loads on turbo upgrades on the H4Jt only to suffer the humiliation of seeing the motor go up in smoke on it's first outing after it's been finished.

Big upgraded turbo units often experience low end lag, and small turbo units spool up much more quickly but do not have the high rpm torque gains.

Thanks to progress the world of turbo chargers is always developing and we commonly find variable vane turbo chargers, where the vane angle is altered according to speed to lower lag and increase top end performance.

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

It is common that there's a limit in the air flow sensor (AFM/MAF/MAP) on the H4Jt when loads more air is being drawn into the engine.

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

Adding a supercharger or additional turbo will make large bhp gains, although more difficult to install. We have this guide to twinchargers if you want to read more.

Fuelling

When you raise the bhp you will need to look at to the fuel system.

More bhp needs more fuel. Don't forget to over specify your injector capacity.

The accepted safe increase is to add 20% when specifying an injector, this takes into account injector deterioration and gives a little spare capacity should the engine need 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.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder turbocharged engines

1. 1. • 58 PSI 340cc/min 200hp
      • 58 PSI 511cc/min 300hp

4 Cylinder supercharged engines

1. 1. • 58 PSI 312cc/min 200hp
      • 58 PSI 468cc/min 300hp

H4Jt Performance Exhausts

You may need to improve your exhaust if your current exhaust is actually causing 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 pipe is too large, ie: over 2.5 inches bore, you will lose a great deal of the flow rate and end up sapping power and torque.

Common exhaust restrictions can be traced to the filters installed, so adding a freer flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots, Issues & problem areas on the H4Jt

The H4Jt 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 H4Jt, 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 H4Jt engine please join us in our car forums where you can discuss H4Jt tuning options in more detail with our H4Jt 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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