Nissan RB25DE Tuning

"All you need to know about tuning the Nissan RB25DE engine!"

The Nissan RB25DE are popular engines and with the optimum performance upgrades like remaps, turbo improvements and camshafts you will noticeably improve your driving enjoyment.

It's big brother RB25DET takes all the limelight as the project engine with it's turbo and high power figures, but bear in mind that it shares much design wise with the RB25DE so there is a wide array of parts and options out there for this engine block.

This pages aim is examine RB25DE tuning and report on the ultimate mods that work.

History, Power & Specs of the RB25DE Engine

  • RB25DE NON-TURBO twin-cam 180 - 200 hp @ 6000 rpm
  • RB25DE NEO- NON-TURBO twin-cam 219 hp @ 6000 rpm

The RB25DET takes all the limelight as the project engine, but it shares much design wise with the RB25DE and that in itself shows the potential of this engine.

Tuning the Nissan RB25DE and best RB25DE performance parts.

Best RB25DE tuning mods

When talking about the greatest modifications for your RB25DE engine, we are going to focus on the modifications that give the best power gain for you money.

Altering your RB25DE camshaft will make a dramatic difference to the engine torque. Choosing a higher performance camshaft profile raises the torque accordingly.

Fast road cams usually push up the power throughout the rev range, you could sacrifice a little bottom end torque but the top end will be better.

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

The variable valve timing works really well but can get in the way on higher power builds.

Just adding an adjustable Vernier pulley to the exhaust cam will allow a fair bit of fine tuning and adjustment.

In a daily driver one must carefully try to optimize your torque band to your driving style.

I'd be surprised if you find a RB25DE Race 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!

Each engine responds better to more or less aggressive cam durations so set your engine up on a rolling road.

The engine timing and fuelling also will say much on the torque gains you'll hit.

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.

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Best Engine Mods for your car

  1. Mapping - remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
  2. Fast road cams are one of the most significant mechanical changes, but they must be installed by someone who knows what they're doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft.
  3. Intake and Exhaust - 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.
  4. Upgrades to turbochargers and superchargers - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.
  5. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.
  6. Typical stage 1 mods often include:
    Panel air filters, Fast road camshaft, Intake manifolds, drilled & smoothed airbox, Sports exhaust header/manifold, Remaps/piggy back ECU.

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

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

    The RB25DE power trains respond well to mods and thankfully there is a growing number of modifications and tuning parts out there.
    Adding some decent spec plugs like the iridium BKR5EIX-11 will avoid problems associated with a weak spark and should give good long term reliability.

    ECU mapping helps fully realize the full potential of all the upgrades you've done to your RB25DE.

    (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 mileage may differs on the upgrades you've fitted and the condition of your engine.

    It is the aim to any engine upgrade job to shove more air into your RB25DE

    Intake manifold carry the air from the filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

    The bore size, shape and flow rate of the Intake manifolds can make a noticeable effect on to fuel engine efficiency on the RB25DE.

    Commonly we find the plenum chambers are crying out for aftermarket tuning parts, although a few OEM provide well optimised plenum chambers.

    Fitting big valve kits, doing a bit of port matching and head flowing will also lift power, & more importantly will raise potential for raising the power increase on other upgrades.

    RB25DE 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 RB25DE

    Although we admire your ambition, adding a turbo to the RB25DE is a challenge and swapping in the RB25DET makes so much more sense, economically and time wise.

    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.

    When your car is fitted with a turbo tuning parts are simpler to install and most turbocharged engines are built using strengthened components.

    However you'll find engines have weak spots. See where you'll find these limits and fit better pistons and crank to utilize the power.

    There are many people spending a fortune on turbo upgrades on the RB25DE only to experience the motor catastrophically fail on it's first outing after it's used in anger.

    Big capacity turbo units often experience a bottom end lag, and low capacity turbo units spool up quickly but won't have the top end torque gains.

    Thanks to new tech the market of turbochargers is always moving on and we now see variable vane turbochargers, permitting the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

    Twin scroll turbochargers divert the exhaust gases into 2 channels and push these at differently profiled vanes in the turbo. They also increase the scavenging effect of the engine.

    You'll commonly see there is a limit in the air flow sensor MAF/MAP on the RB25DE 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 limited power at a much lower level.

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

    Fuelling

    When you boost the performance you will need to look at to the fuelling.

    More performance needs more fuel. Most tuners we speak with say to over specify your injectors flow rate.

    As a rule of thumb add another 20% when fitting an injector, this takes into account injector deterioration and allows 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.

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

    6 Cylinder NA (naturally aspirated) engines

    • 58 PSI 189cc/min 200hp
    • 58 PSI 284cc/min 300hp
    • 58 PSI 378cc/min 400hp
    • 58 PSI 568cc/min 600hp

    6 Cylinder turbocharged engines

    • 58 PSI 227cc/min 200hp
    • 58 PSI 341cc/min 300hp
    • 58 PSI 454cc/min 400hp
    • 58 PSI 682cc/min 600hp

    RB25DE Performance Exhausts

    Only look to uprate your exhaust if the existing exhaust is actually causing a restriction.

    On most factory exhausts you'll see your flow rate is still 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 generally help improve air flow from the engine but avoid an exhaust that is 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 for best results.

    Usual exhaust restrictions can be traced to the catalyst and filters installed, so adding a faster flowing sports alternative is the answer. This keeps the car road legal and will flow much better due to it's higher internal surface area and design, so has the added benefit of keeping your car road legal. The alternative decat should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars..

    Weak spots, Issues & problem areas on the RB25DE

    The RB25DE 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 RB25DE, 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 RB25DE engine please join us in our car forums where you can discuss RB25DE tuning options in more detail with our RB25DE owners. It would also be worth reading our unbiased Nissan tuning articles to get insights into each modification and how effective they will be for your car.

    Please help us improve these tips by sending us your feedback in the comments box below.

    We love to hear what our visitors have got up to and which tuning parts work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these RB25DE tuning guides which get regular updates and revisions.

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