The Lowdown on "QR25DD Modifications"

How to modify and upgrade the Nissan QR25DD

"Comprehensive guide to performance tuning the Nissan QR25DD engine!"

Sites like TorqueCars are frequently getting emails requesting information on how to improve the QR25DD from people wanting to know what are the things tuners are recommending when it comes to QR25DD modifications. So let us look into Nissan QR25DD upgrades and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Nissan QR25DD are popular tuning projects and with carefully chosen motorsport upgrades like remaps, turbo kits and camshafts you will certainly maximize your driving enjoyment.

In this article we review QR25DD tuning and outline the optimum mods that work.

Just because particular upgrades are popular with QR25DD owners it doesn't mean you should fit it, instead we'll focus on the greatest upgrades that will give your QR25DD the best power gain for you spend.

Without us subscribing to the common myth of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

Improving air intake on the QR25DD

You need air matched to fuel for an engine to work. If there is a lack of fuel then it will run lean, if there is too little air it runs rich sapping power which risks damage to the QR25DD. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Shoving more air into each cylinder is the main goal to any tuning task.

You'll commonly see there is a restriction in the air flow sensor MAF/MAP on the QR25DD when loads more air is being drawn into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting performance at a much lower level.

Headers take the air from the air cleaner and allow it to be pulled into the engine and mixed with fuel.

The shape and flow rate of the air Intake manifold can make a large difference to to fuel mixing and power on the QR25DD.

Commonly we find the intake manifold are begging for aftermarket tuning parts, although some OEM provide reasonably well designed intake manifold.

Increasing the QR25DD valve size, carrying out QR25DD port enlargement and head flowing will also raise bhp, and as an added benefit will afford you raising the bhp increase on other parts.

QR25DD performance cam tips.

Some QR25DD engines respond better to more aggressive camshaft durations than others.

The engine timing and injectors and fuel pump also have an effect on the bhp gains you'll hit.

Altering 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.

Altering your QR25DD cam will make a dramatic difference to the engine engines power. Choosing a higher performance cam profile raises the engines power accordingly.

NB: Fast road cams normally boost the performance through the rpm range, you may sacrifice a little bottom end power but your high end rpm power will improve.

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

A Motorsport and race camshaft is not great on the daily commute.

You should ideally optimize your bhp range to your driving style so for a road car stick with a shorter duration QR25DD camshaft

Stage 1, 2 and 3 mods for the QR25DD

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

1. Suspension Upgrades - always improve your cars handling
2. Brake Upgrades - Even before adding power improve those brakes
3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
6. Fuelling - when you've increased power you'll need to match this with more fuel
7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 QR25DD parts:

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

Stage 2 QR25DD parts:

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

Stage 3 QR25DD 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.

A remap helps fully realize the full potential of all the upgrades you've done to your QR25DD.

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 your results usually vary depending on the upgrades you've fitted and the condition of your engine.

Turbo modifications on the QR25DD

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 QR25DD.

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

If the engine is turbo charged modifications are giving better power gains and we find turbocharged engines are built using stronger components.

However every engines have weakspots

We recommend you find these restrictions and fit better pistons and crank to survive the power.

It's not unheard of guys spending a lots of money on turbo charger upgrades on the QR25DD only to experience the whole thing explode when it's been completed.

Large upgraded turbos will usually experience low end lag, and small turbos spool up really quickly but do not have the high rpm engines power gains.

In the last 10 years the selection of turbo chargers is always evolving and we now see variable vane turbo chargers, allowing the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust flow into 2 channels and flow these at differently designed vanes in the turbocharger. 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 bhp and torque gains, although more challenging to configure. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the QR25DD

You will need to ensure that the engine is not starved of fuel so will have to uprate the fuelling when you start going beyond 20% of a performance hike. It is important to over specify your injector capacity.

As a rule of thumb add another 20% when buying an injector, this accounts for injector deterioration and gives a bit of 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 QR25DD performance exhaust upgrades

You only need to to improve your exhaust system with an upgraded one is if your current exhaust is creating a restriction in flow.

On most factory exhausts you'll find the flow rate is good 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.

Don't go with the biggest exhaust you can get you'll reduce 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.

Typically exhaust restrictions come around the catalysts installed, so adding a faster flowing performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the QR25DD

Like most engines an QR25DD, 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 QR25DD, failure to do this will exacerbate engine wear, on a tuned QR25DD 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 QR25DD why not pop over to the forums at TorqueCars where you can chat about QR25DD tuning options and read about others projects who may be planning to do similar modifications on their QR25DD.

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This entry was posted under Makes and Models. Tags: engine, nissan
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