Tuning the Nissan QR20 / QR25

"Comprehensive guide to performance parts and tuning the Nissan QR20 / QR25 engine!"

Let us outline options for your QR20 / QR25 tuning and provide tips on the ultimate mods that work. Nissan QR20 / QR25 have loads of potential and with a few sensible motorsport parts like remaps, turbo upgrades and camshafts you will definitely improve your driving opportunities.

Just because particular upgrades are appear in lots of QR20 / QR25 projects it doesn't mean it is good, instead we will optimum upgrades that will give your QR20 / QR25 the best value for money to power increase.

Altering your QR20 / QR25 cam will make a dramatic difference to the engine torque. Choosing a higher performance cam profile raises the torque accordingly.

NB: Fast road camshafts tend to bump the bhp throughout the rpm range, you might lose a little bottom end power but your high end rpm power will be higher.

Motorsport camshafts, bump 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 cam won't do well if in heavy traffic.

You should ideally match your power band to your preferences so for a car driven daily stick with a mild fast road QR20 / QR25 cam

Each engine responds better to mild camshaft durations so view each engine as unique.

The ecu map and injectors and fuel pump also have an effect on the torque gains you'll achieve.

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.

Stage 1 modifications: Fast road camshaft, Sports exhaust manifold, Intake headers, Panel air filters, Remaps/piggy back ECU, Drilled & smoothed airbox.

Stage 2 modifications: fuel pump upgrades, high flow fuel injectors, Fast road cam, induction kit, Sports catalyst & performance exhaust, Ported and polished head.

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

ECU mapping allows a tuner to fully realize the full potential of all the modifications you've fitted to your QR20 / QR25.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output usually differs on the modifications you've done and the condition of your engine.

Feeding more air into each cylinder is the aim to any engine upgrade project.

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

Design and rate of flow of the Plenum can make a substantial effect on to fuel atomisation on the QR20 / QR25.

On popular production engines intake are ripe for aftermarket tuning parts, although a few car makers provide reasonably good intake.

Big valve conversions on the QR20 / QR25, getting QR20 / QR25 port enlargement and head flowing will also lift torque, this will allow you to get increasing the torque increase on other tuning mods.

Turbo upgrades

NASP 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 QR20 / QR25

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

When your car is turbo charged upgrades are going to make more power and we find turbocharged engines are made using better components.

There are reliable limits for every engine, with some being over specified and some only just able to handle stock power

See where you'll find these limitations and fit better quality crank and pistons to survive the power.

There are many people spending a loads of money on turbo charger upgrades on the QR20 / QR25 only to watch the motor explode when it's been enthusiastically driven.

Large capacity turbos commonly suffer low end lag, and low capacity turbos spool up quickly but don't have the peak rpm engines power gains.

We are pleased that the world of turbo units is always evolving and we commonly find variable vane turbo units, allowing the vane profile is altered according to speed to lower lag and increase top end torque.

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

It is common that there is a limit in the air flow sensor AFM/MAP on the QR20 / QR25 when considerably more air is being drawn into the engine.

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

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

Fuelling upgrades and mods

Don't overlook the need to boost the fuelling when you are increasing the performance - it makes the car more thirsty. It is important to be generous with your flow rate on the injectors.

The rule of thumb is to add another 20% when specifying an injector, which takes into account injector deterioration and provides 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.

Exhaust upgrades and mods

You should look to upgrade your exhaust if the existing exhaust is actually causing a restriction in flow.

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 through the engine but avoid an exhaust that is too big or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Common exhaust restrictions are traced to the filters installed, so adding a freer flowing high performance alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the QR20 / QR25

The QR engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Valve clearances need to be checked and reset on all engines without hydraulic lifters.

Overheating can cause major issues so check the cooling system is in good condition especially the water pump.

Regular oil changes are vital on the QR, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

History of the Engine

Configuration Inline-four with a capacity ranging between 2.0–2.5 L (1,998–2,488 cc)

Cylinder bore: 89 mm (3.5 in)
Piston stroke: 80.3 mm (3.16 in) OR 100 mm (3.94 in)

QR20 Engines

• QR20DE 148 hp at 6000 rpm 148 lbft at 4000 rpm
• QR20DD 148 hp at 6000 rpm 148 lbft at 4400 rpm

QR25 Engines

• QR25DE 175 hp at 6000 rpm  180 lbft of torque at 4000 rpm
• QR25DE  170 hp at 6000 rpm and 175 lbft at 4000
• QR25DD 168 hp at 5600 rpm 181 lbft at 4000 rpm
• QR25DER supercharged & 20hp electric motor 250 hp at 5600 rpm and 243 lbft at 3600 rpm

The QR25DE was revised in 2007 quite extensively with reduction in friction, higher red line and revised cam profile and relocation of the balancer.

For more information on Tuning your QR engine please join us in our friendly forum where you can discuss tuning options in more detail with our tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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We really like hearing from our readers, and hearing about which parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our QR guides and tips are kept up to date.

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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under Nissan. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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