Tuning Feature: Nissan QG18DD Modified

"Comprehensive guide to tuning the Nissan QG18DD engine!"

We are always getting posts asking about the best QG18DD upgrades. So let us look into Nissan QG18DD upgrades and outline the best mods that work on this great engine and point out some common pitfalls along the way.

The Nissan QG18DD make a good tuning project and with a few sensible modified parts like a remap, turbo upgrades and camshafts you will dramatically improve your driving pleasure.

Let us examine QG18DD tuning and summarise the best mods that work.

When talking about the top parts for your QG18DD engine, we are going to focus on the parts that give the biggest return for your cash.

The cam profile plays a big part in the engines power output so cam upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen cam profile, so large bhp gains are on offer for cam upgrades.

NB: Fast road cams normally increase the performance throughout the rev band, you may lose a little low down bhp but your higher rpm power will be better.

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

A Motorsport cam is not great in heavy traffic.

You should ideally optimize your engines power to your driving style so for a car used daily stick with a fast road QG18DD cam

Different QG18DD engines respond better to more or less aggressive cam durations so view each engine as unique.

The ECU mapping and injectors and fuel pump also have an effect on the bhp gains you'll get.

A longer valve duration 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.

QG18DD Tuning Stages

Stage 1 QG18DD modifications: Fast road camshaft, Sports exhaust manifold, Intake headers, Panel air filters, Drilled & smoothed airbox, Remaps/piggy back ECU.

Stage 2 QG18DD modifications: Fast road cam, Sports catalyst & performance exhaust, induction kit, high flow fuel injectors, fuel pump upgrades, Ported and polished head.

Stage 3 QG18DD modifications: Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Competition cam, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression.

ECU flashing allows a tuner to to establish the full potential of all the tuning mods you've done to your QG18DD.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your mileage will rely on the tuning mods you've fitted and the condition of your engine.

Shoving more air into the QG18DD engine is the whole point to any car tuning project.

Intake headers take the air during the suck phase from the intake filter and allow it to be drawn into the engine cylinders.

Structure and flow characteristics of the Air Intake manifolds can make a big difference to to fuel delivery on the QG18DD.

Many mass produced engine plenum chambers are needing motorsport parts, although a few makers provide reasonably well designed plenum chambers.

Fitting big valve kits, getting QG18DD port enlargement and head flowing will also raise bhp and torque, and as an added benefit will permit a better bhp and torque increase on other parts.

Turbo upgrades for the QG18DD

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 QG18DD

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.

When your motor has a turbocharger tuning parts are giving better power gains and turbocharged engines will have more solid components.

There are tuning limits for every engine, with some being incredibly solid and some only able to handle stock power

Research these limitations and fit higher quality crank and pistons to handle the power.

It's not unheard of car owners spending a loads of money on turbo charger upgrades on the QG18DD only to experience the engine block explode soon after it's completed.

Bigger upgraded turbos commonly suffer low end lag, and small turbos spool up quickly but do not have the peak rpm engines power gains.

Thanks to new tech the selection of turbos is always improving and we now see variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust gases into a couple of channels and feed these at differently angled vanes in the turbo charger. They also boost the scavenging effect of the engine.

You'll commonly see there is a limit in the air flow sensor AFM/MAP on the QG18DD when loads more air is being fed into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp and torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp gains, although more challenging to configure. We have this article on twincharging if you want to read more.

Uprating QG18DD fuel injectors

You will need to ensure that the engine is not starved of fuel so should increase the fuelling when you start exceeding 20% of a bhp and torque increase.It is important to be generous with your flow rate on the injectors.

As a rule of thumb add another 20% when buying an injector, this accounts for injector deterioration and gives a little 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.

Best QG18DD performance exhausts

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

On most factory exhausts you should find that the flow rate is still 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 from the engine but do not go too large or you may end up reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Typically exhaust restrictions can be located in the catalyst and filters installed, so adding a better flowing performance alternative will help avoid this restriction.

Problems and issues to look out for on the QG18DD

The QG18DD engines, if regularly serviced and maintained, are generally very reliable and have few issues. {But if neglected they can cost a small fortune|When neglected they get very expensive to run|They can however be quite expensive if neglected| }

Regular oil changes are vital on the QG18DD, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your QG18DD engine please join us in our friendly forum where you can discuss tuning options in more detail with our QG18DD owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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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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