The Lowdown on "QG18DE Modifications"

How to modify and upgrade the Nissan QG18DE

"Comprehensive guide to tuning the Nissan QG18DE engine!"

Our friends at TorqueCars are always seeing threads requesting information on how to improve the QG18DE from people wanting to know what are the ultimate QG18DE modifications. So let us look into Nissan QG18DE upgrades and outline the best modifications on this great engine and point out some problems along the way.

The Nissan QG18DE have loads of potential and with carefully picked motorsport upgrades like remapping, turbo kits and camshafts you will certainly enhance your driving pleasure.

This pages aim is outline options for your QG18DE tuning and highlight the premier upgrades.

Just because particular mods are popular with QG18DE owners it doesn't mean it is good, instead we'll focus on the ultimate mods that will give your QG18DE the best power gain for you spend.

Without us subscribing to the popular mentality 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 QG18DE

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 little flow of air it runs rich sapping power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Pushing air into the QG18DE engine is the primary aim to any tuning job.

It is common that there is a limitation in the air flow sensor (AFM/MAF/MAP) on the QG18DE when considerably more air is being drawn into the engine.

When tuning you may well find you need to get an air sensor or flow meter capable of upto 4 bars to cope with quite large power gains, whereas the OEM air sensor limited power at a much lower level.

Air Intake manifolds transmit the on the suck phase from the intake filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

The shape and flow characteristics of the Intake headers can make a substantial improvement to fuel atomisation on the QG18DE.

I usually find headers are in desperate need of an upgrade, although a few makers provide reasonably good headers.

Increasing the QG18DE valve size, carrying out port work and head flowing will also improve bhp and torque, and importantly will allow you to get increasing the bhp and torque increase on other parts.

QG18DE performance cam tips.

Each engine responds better to less aggressive camshaft durations check your engine on a rolling road.

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

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.

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

NB: Fast road camshafts tend to boost the bhp and torque across the rpm band, you could sacrifice a little low end power but your higher rpm power will be lifted.

Competition camshafts, boost the higher 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 will just annoy you whilst driving around busy urban areas.

You should ideally optimize your torque band to your usage of the car so for a daily driver stick with a fast road QG18DE camshaft

Stage 1, 2 and 3 mods for the QG18DE

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 QG18DE parts:

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

Stage 2 QG18DE parts:

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

Stage 3 QG18DE parts:

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

ECU mapping will help fully realize the full potential of all the tuning parts you've done to your QG18DE.

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 figures achieved will vary depending on the tuning parts you've carried out and the condition of your engine.

Turbo modifications on the QG18DE

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 QG18DE.

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.

If a car is fitted with a turbo parts are relatively easy and you will discover turbo charged engines are built using more solid components.

However engines have limits

See where you'll find these restrictions and upgrade to better quality components to utilize the power.

There are many car owners spending a lots of money on turbo upgrades on the QG18DE only to have the engine block explode when it's been completed.

Large capacity turbo chargers tend to suffer a bottom end lag, and low capacity turbo chargers spool up really quickly but do not have the peak end bhp gains.

Thankfully the world of turbo chargers is always increasing and we now see variable vane turbo chargers, where 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 direct these at differently designed vanes in the turbo. 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 install. We have this article on twincharging if you want to read more.

Tips about fuel supply on the QG18DE

Don't forget to look at the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. It is important to over specify your injectors flow rate.

As a rule of thumb add another 20% when buying an injector, which takes into account injector deterioration and affords you some spare capacity should the engine need 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 QG18DE performance exhaust upgrades

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

On most factory exhausts you should find that your flow rate is still fine 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.

Sports exhausts can usually air flow from the engine but do not go too big or you could will reduce the flow rate. Stick to one and a half to two and half inches as a rule of thumb.

The usual suspects causing problems in your exhaust flow rate can be located the emissions filters installed, so adding a faster flowing performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the QG18DE

Like most engines an QG18DE, 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 QG18DE, failure to do this will exacerbate engine wear, on a tuned QG18DE 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 QG18DE why not pop over to the forums at TorqueCars where you can chat about QG18DE tuning options and read about others projects who may be planning to do similar modifications on their QG18DE.

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