Nissan VQ25HR Tuning

"All you need to know about tuning the Nissan VQ25HR engine!"

We get emailed and see posted questions for some tips on improving the VQ25HR and which tuning modifications we rate as the most optimal, so we've created an article goes over what we feel are the primary areas and methods of modifying and tuning on the VQ25HR engine.

The Nissan VQ25HR really good project engines and with the optimum motorsport enhancements like remaps, turbo kits and camshafts you will positively improve your driving pleasure.

Our aim here is to review and look at VQ25HR tuning and report on the ultimate modifications.

History, Power & Specs of the VQ25HR Engine

The V6 VQ platform cc capacity ranged from 2.0 to 4.0 and engines were adopted by Renault and even formed the basis for Nissan's race engines - the VQ30DETT

  • 2006–2012 Nissan Skyline V6 250GT Sedan
    229 PS (168 kW; 226 hp)
  • 2006–2012 Nissan Fuga 250GT
    223 PS (164 kW; 220 hp)
  • 2006–2012 Infiniti M V6 M25 Sedan
    218 hp (163 kW; 221 PS)
  • 2010–2012 Infiniti EX J50 EX25 Crossover SUV
    222 PS (163 kW; 219 hp)
  • 2011–2012 Infiniti G25 Sedan
    218 hp (163 kW; 221 PS)
  • 2012 Mitsubishi Proudia 250 VIP
    223 PS (164 kW; 220 hp)

Tuning the Nissan VQ25HR and best VQ25HR performance parts.

Best VQ25HR upgrades

Just because particular modifications are appear in lots of VQ25HR projects it doesn't mean it is good, instead we'll focus on the greatest modifications that will give your VQ25HR the best power gain for you spend.

Altering your VQ25HR camshaft will make a dramatic difference to the engine torque. Choosing a higher performance camshaft profile raises the torque accordingly.

Fast road cams usually boost the power throughout the rpm band, you could sacrifice a little low end torque but the top end will be higher.

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

A Competition cam won't do well if driving around busy urban areas. This is because a competition cam causes a very lumpy idle, and makes the car more prone to stall or jerk along in stop start traffic, sadly though many ignore this and end up ruining a perfectly good car and having to revert back to a fast road, or OEM cam profile.

You should ideally match your power band to your typical driving style so for a car driven daily stick with a shorter duration VQ25HR cam

Some VQ25HR engines respond better to more or less aggressive camshaft durations check your engine on a rolling road.

The ecu map and fuel pump and injectors also have a large bearing on the torque gains you'll make.

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

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

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

    Plan your options and then acquire your upgrades and set yourself a power target to void expensive mistakes.

    Mapping helps unlock the full potential of all the upgrades you've done to your VQ25HR.

    (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 the outcome may vary depending on the upgrades you've applied and the condition of your engine.

    It is the aim to any car tuning job to feed fuel and air into each cylinder

    Intake manifolds carry the air during the suck phase from the air filter and allow it to be fed into the engine cylinders with fuel for the squish phase.

    Structure and flow rate of the Intake manifold can make a noticeable improvement to fuel atomisation on the VQ25HR.

    On popular production engines intake are in desperate need of performance upgrades, although a few manufacturers provide reasonably well designed intake.

    Big valve conversions on the VQ25HR, doing some port work and head flowing will also raise torque, and as an added benefit will allow you to get raising the torque increase on other tuning mods.

    VQ25HR 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 VQ25HR

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

    When an engine has a turbo already fitted tuning mods are simpler to install and we find turbocharged engines are made using more solid components.

    There are weak spots for every engine, with some being extremely strong and some only able to handle stock powerIt is important to find these restrictions and install higher quality components to utilize the power.

    There are many drivers spending a loads on turbo charger upgrades on the VQ25HR only to suffer the indignity of watching the whole thing throw a rod when it's first rolling road session.

    Bigger turbo units often suffer no power at low rpm, and low capacity turbo units spool up much more quickly but don't have the peak end torque gains.

    In the last 10 years the world of turbochargers is always moving on and we commonly find variable vane turbochargers, where the vane angle is altered according to speed to lower lag and increase top end performance.

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

    It is common that there is a limitation in the air flow sensor (AFM/MAF/MAP) on the VQ25HR 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 performance at a much lower level.

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

    Fuelling

    Don't omit to pay attention to the fuel delivery when you are increasing the performance - it makes the car more thirsty. It is important to be generous with your injectors flow rate.

    The accepted safe increase is to add 20% to the flow rate when fitting an injector, which takes into account injector deterioration and affords some 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

    VQ25HR Performance Exhausts

    You only need to increase your exhaust if your current exhaust is creating a flow problem.

    On most factory exhausts you'll find the exhaust flow rate is good 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 usually air flow through the engine but avoid an exhaust that is too wide 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.

    Common exhaust restrictions come around the catalysts installed, so adding a higher 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 VQ25HR

    The VQ25HR 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.

    Keep an eye on the oil consumption, piston ring and cylinder wear is exacerbated by poor quality fuel resulting in blow by.

    Exhaust cam cover wear and failure can result in rough idling.

    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 VQ25HR, 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 VQ25HR engine please join us in our car forums where you can discuss with our VQ25HR owners. It would also be worth reading our unbiased articles to get a full grasp of the benefits and drawbacks of each modification.

    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 upgrades 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 VQ25HR tuning guides which get regular updates and revisions.

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