All you need to know about "QG18DE Modifications"

How to modify and upgrade the Nissan QG18DE

"Comprehensive guide to tuning the Nissan QG18DE engine!"

Forums like the one at TorqueCars are frequently seeing threads asking about how to improve the QG18DE from people wanting to know what are the best QG18DE upgrades. So let us look into Nissan QG18DE modifications and outline the best modifications on this great engine and point out some problems along the way.

Now we shall review QG18DE tuning and provide tips on the optimum mods that work. Nissan QG18DE have loads of potential and with carefully picked modified upgrades like remaps, turbo kits and camshafts you will positively maximize your driving pleasure.

Just because particular tuning parts are are common on QG18DE it doesn't mean its worth having, instead we will concentrate on the ultimate tuning parts that will give your QG18DE the best value for money to power increase.

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 QG18DE

You need fuel and air for an engine to work. If there is a lack of fuel then it will run lean, if there is not enough air it runs rich resulting in lost power which risks damage to the QG18DE. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the whole point to any engine modification project to pull more air and fuel into each cylinder but this has a knock on effect with the air flow sensor.

It is not unusual that there is a limitation in the air flow sensor AFM/MAF on the QG18DE when loads more air is being fed into the engine.

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

Engines intake headers transmit 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.

The size of bore and shape and rate of flow of the Plenum can make a substantial improvement to fuel delivery on the QG18DE.

It's not uncommon that plenum chambers are in dire need of performance upgrades, although a few makers provide reasonably good plenum chambers.

Fitting big valve kits, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also lift power, and as an added benefit will give you increasing the power increase on other tuning parts.

QG18DE performance cam tips.

Different QG18DE engines respond better to different cam durations check your engine on a rolling road.

The engine timing and fuelling also will say much on the bhp gains you'll make.

Extending exhaust or intake 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 QG18DE camshaft will make a dramatic difference to the engine power band. Choosing a higher performance camshaft profile raises the power band accordingly.

NB: Fast road camshafts commonly boost the power across the rpm band, you might lose a little bottom end bhp but the high end rpm power will be better.

Motorsport camshafts, 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 cam makes it harder when driving in heavy traffic.

You should ideally match your bhp range to your driving style so for a car driven daily stick with a fast road QG18DE cam

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:

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

Stage 2 QG18DE parts:

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

Stage 3 QG18DE parts:

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

ECU mapping helps unlock the full potential of all the 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 your results may vary depending on the parts you've done 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 massive power gains.

When your motor is fitted with a turbocharger mods are relatively easy and turbo engines use better components.

However you'll find engines will have power limits

We recommend you find these limitations and install better quality components to cope with the power.

It's not unheard of people spending a a stack of money on turbo charger upgrades on the QG18DE only to suffer the humiliation of seeing the whole thing throw a rod just after it's been enthusiastically driven.

Big upgraded turbo units often suffer low end lag, and smaller turbo units spool up much more quickly but don't have the high rpm bhp gains.

In recent times the selection of turbo chargers is always moving on and we now see variable vane turbo chargers, allowing the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbo chargers divert the exhaust flow into 2 channels and flow these at differently profiled 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 gains, although more difficult to setup. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the QG18DE

You will need to ensure that the engine is not starved of fuel so will need to look at the fuelling when you start going beyond 20% of a power hike. Experienced tuners recommend to be generous with your injectors flow rate.

The accepted safe increase is to add 15% to the flow rate when fitting an injector, this takes into account injector deterioration and provides some 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 QG18DE performance exhaust upgrades

Only look to boost your exhaust system with an upgraded one is if your exhaust is creating a restriction.

On most factory exhausts you'll find the exhaust 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.

Please dont run with the widest exhaust you can get you'll slow the exhaust rate - the best exhausts 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.

The usual suspects causing problems in your exhaust flow rate can be traced to the catalysts installed, so adding a higher flowing performance alternative will help avoid this restriction.

Decatting (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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