Renault H4B Tuning

"All you need to know about performance parts and tuning the Renault H4B engine!"

Herein we look into H4B tuning and provide tips on the best modifications. Renault H4B make a good tuning project and with the ultimate uprated mods like ECU maps, turbo improvements and camshafts you will noticeably improve your driving enjoyment.

History, Power & Specs of the H4Bt Engine

H4Bt, 898 cc, turbo-charged petrol - small but powerful

  • 90hp @5000 (66kW) 100 lb ft @2000-3500 (135 N m)

You can find the H4Bt in the following models

  • Dacia Sandero II
  • Dacia Logan II
  • Nissan Micra
  • Renault Clio IV
  • Renault Captur
  • Renault Twingo III
  • Smart ForTwo
  • Smart ForFour

Tuning the Renault H4Bt and best H4B performance parts.

Best H4Bt modifications

The top H4B upgrades on an engine are in our opinion the ones that give the best power gain for you spend.

We won't be swayed by popular H4B upgrades, they need to be cost effective.

Significant gains on the H4B 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 commonly raise the bhp across the rev band, you could drop a little low end torque but your higher rpm power will improve.

Motorsport and race cams, 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 road car should ideally to optimize your power band to your typical driving style.

I'd be amazed if you have found a H4B Competition cam 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.

Different H4B engines respond better to less aggressive cam durations so set your engine up on a rolling road.

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

Longer valve 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.

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Best mods for your H4Bt

  1. ECU Tunes - H4Bt remapping provides the most power for the money, replacement ECUs, and piggyback ECUs are all alternatives.
  2. Fast road Camshafts are generally the biggest mechanical mod upgrade, but they must be setup 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. Intake Mods and Performance Exhausts - NB: 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.
  4. H4Bt Handling Mods (suspension) - Fitting a more sporty Suspension kit dramatically improves H4Bt handling Coilovers and Bushings are the usual go to mods
  5. Brake Upgrades - Improve your H4Bt's stopping power should be near the top of your Mods list.
  6. Turbo upgrades - Adding a turbocharger is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. Although one of the most costly upgrades it offers big gains.
  7. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.

H4Bt Tuning Stages

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

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

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

The H4B engines respond well to upgrades and we're happy to report there is a growing number of upgrades and performance parts about.

A remap should help to release the full potential of all the parts you've done to your H4B.

(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 your results often vary depending on the parts you've done and the condition of your engine.

Pulling air into your H4B is the main goal to any engine upgrade task.

Intake manifold take the air during the suck phase from the filter and allow it to be sucked into the engine cylinders.

The shape and rate of flow of the Intake can make a noticeable effect on to fuel delivery on the H4B.

Many mass produced engine manifolds are in desperate need of performance upgrades, although some OEM provide fairly well optimized headers.

Increasing the H4B valve size, doing some 3 or 5 angle valve jobs and porting and head flowing will also increase performance, & more importantly will give you an improved performance increase on other upgrades.

H4B Turbo upgrades

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.

If your motor has a turbocharger modifications are going to make more power and most turbocharged engines already contain many forged and stronger components.

However most engines will need better parts at higher power limits. It is important to find these restrictions and fit better quality crank and pistons to survive the power.

We've seen tuners spending a loads of money on turbocharger upgrades on the H4Bt only to watch the H4Bt go up in smoke when it's first rolling road session.

Larger capacity turbo units commonly experience no power at low rpm, and low capacity turbo units spool up much more quickly but don't have the peak end power band gains.

Over the last 20 years the market of turbochargers is always improving and we are seeing variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end power.

Twin scroll turbochargers divert the exhaust flow into 2 channels and direct these at differently designed vanes in the turbo charger. They also boost the scavenging effect of the engine.

You'll commonly see there is a limitation in the air flow sensor MAP/MAF/AFM on the H4Bt when loads more air is being pulled into the engine.

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

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


Don't omit to increase the fuelling when you are increasing the bhp and torque - it makes the car more thirsty. Most tuners we speak with say to be generous with your injectors flow rate.

The rule of thumb is to add 20% capacity when fitting an injector, which takes into account injector deterioration and affords a bit of 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.

H4Bt Performance Exhausts

You should look to uprate your exhaust if the existing exhaust is actually creating a flow problem.

On most factory exhausts you'll see the exhaust flow rate is fine 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 will certainly help air flow out of the engine but do not go too large or you could very well end up with a reduced flow rate. So generally speaking, keep to 1.5 to 2.5 inches as a rule of thumb.

Usual exhaust restrictions can be located the catalyst and filters installed, so adding a faster flowing performance catalyst removes the restriction. We note that performance cats perform similarly to decats and have the added benefit of keeping your car street legal, as decats or catalyst removal is illegal in most territories for road going cars.

Weak spots, Issues & problem areas on the H4Bt

The H4B 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 H4B, 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 H4B engine please join us in our car forums where you can discuss H4B tuning options in more detail with our H4B 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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